Journal articles on the topic 'Concrete, fines, recycling, heat'

Waste concrete is the most predominant constituent material among construction and demolition waste. Current waste concrete recycling is limited to the use of recycled concrete aggregates as a road-base material and less as aggregates in new concrete mixes. Further, the production of recycled concrete aggregates results in the generation of a high amount of fines, consisting mainly of cement paste particles. Hence, this study aims to produce the cement mortars using the upgraded recycled concrete aggregates (sand granulometry) for the total replacement of natural aggregates and recycled concrete fines activated through a thermal treatment method as a partial cement substitution material. Cement mortar specimens were tested for their compressive and flexural strength, density and water absorption performance. The results showed that the combined usage of upgraded recycled concrete sand for total replacement of primary crushed sand and recycled concrete fines as partial cement replacement material is a promising option to produce cement mortars.

Used tyre rubber wastes present a serious environmental problem of pollution and storage. The recycling of this waste in the industry of construction could be an appropriate solution to produce an eco-concrete and could contribute to the improvement of some of its properties. This paper aims to study the possibility of using tyre rubber waste as fine aggregate replacement in self-compacting concrete (SCC). Fines rubber particles of 0-2 mm of waste tyres were added SCC mixtures as a partial substitution of the total volume of sand at different percentages (5, 10, 15, 20 and 30%). The influence of fines rubber of used tyres on fresh and hardened properties of the SCC was investigated. The fresh properties of SCC were performed by using slump-flow, T50 flow time, L-box, V-funnel and segregation resistance tests. Characteristics of the hardened state were obtained by compressive strength and thermal conductivity. The experimental results showed that the inclusion of fines rubber in SCC decreases the workability, reduced its passing capacity and increases the possibility of blocking. A decrease in compressive strength is observed with the increase in rubber content. On the other hand, the incorporation of the rubber fines aggregates enhances in a remarkably way the thermal conductivity.

The disposal and further recycling of concrete is being investigated worldwide, because the issue of complete recycling has not yet been fully resolved. A fundamental difficulty faced by researchers is the reuse of the recycled concrete fines which are very small (< 1 mm). Currently, full recycling of such waste fine fractions is highly energy intensive and resulting in production of CO₂. Because of this, the only recycling methods that can be considered as sustainable and environmentally friendly are those which involve recycled concrete powder (RCP) in its raw form. This article investigates the performance of RCP with the grain size < 0.25 mm as a potential binder replacement, and also as a microfiller in cement-based composites. Here, the RCP properties are assessed, including how mechanical properties and the microstructure are influenced by increasing the amount of the RCP in a cement paste (≤ 25 wt%).

Concrete is the largest amount of artificial building materials in the world today. According to incomplete statistics, the construction waste produced in china each year can reach about one hundred million tons, and it can reach hundreds of millions of tons due to the long accumulation, which has become a serious social and environmental issues. In this paper, the technology of separation and recycle of waste concrete is studied, and the components of waste concrete are separated effectively, which provides a technical guarantee for the recycling of waste concrete. The waste concrete is disposed through the process of crushing, shelling and sieving and so on, the coarse aggregate and fine aggregate are separated effectively, the properties of coarse aggregate are nearly the same as natural aggregate. When the shelled fines is milled into ultrafine powder and used as concrete admixture, the performance of concrete can be improved. These all provide a new effective way for the recycling of waste concrete.

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and other low value-added applications. For their use as coarse aggregate in structural concretes, construction and demolition waste must exhibit high densities and regularity of the material. This material usually is presented in demolished concretes. About 20% of the particles from demolished concretes can be used as coarse aggregates substituting part of natural aggregates in structural concretes. This article presents studies of demolished concretes recycling by the use of a pneumatic jig. All jigging tests were carried out with three different concretes produced in three strength classes: C16/20, ordinary concrete; C50/60, high strength concrete; and C70/85, very high strength concrete. Based on density distribution of the three concretes, there are reasonable masses with densities over 2.7 g cm−3, particle density considered appropriate to the used as coarse aggregate for structural concretes. The concretes present different mass recoveries of the denser particles (different liberation). Coarse aggregates can be recovered with reasonable masses by the use of air jigs: About 65% for high strength concretes and about 75% for the low strength concrete. The jigging concentration efficiency depends on the concrete liberation, density and size distribution.

The waste produced from ready-mixed concrete (RMC) industries poses an environmental challenge regarding recycling. Three different waste products form RMC plants were investigated for use as recycled aggregates in construction applications. Crushed hardened concrete from test specimens of at least 40 MPa compressive strength (HR) and crushed hardened concrete from returned concrete (CR) were tested for their suitability as concrete aggregates and then used as fine and coarse aggregate in new concrete mixtures. In addition, cement sludge fines (CSF) originating from the washing of concrete trucks were tested for their properties as filler for construction applications. Then, CSF was used at 10% and 20% replacement rates as a cement replacement for mortar production and as an additive for soil stabilization. The results show that, although there is some reduction in the properties of the resulting concrete, both HR and CR can be considered good-quality recycled aggregates, especially when the coarse fraction is used. Furthermore, HR performs considerably better than CR both as coarse and as fine aggregate. CSF seems to be a fine material with good properties as a filler, provided that it is properly crushed and sieved through a 75 μm sieve.

This contribution discusses the carbon capture and utilization (CCU) approach based on CO2 mineralization of cement paste from recycled concrete as new approach to capture CO2 and significantly contribute to the reduction in CO2 emissions associated with cement production. The current literature suggests that all CO2 released from the decomposition of limestone during clinker production can be sequestered by carbonation of the end-of-life cement paste. This carbonation can be achieved in a few hours at ambient temperature and pressure and with a relatively low CO2 concentration (< 10 %) in the gas. The carbonation of cement paste produces calcite and an amorphous alumina-silica gel, the latter being a pozzolanic material that can be utilized as a supplementary cementitious material. The pozzolanic reaction of the alumina-silica gel is very rapid as a result of its high specific surface and amorphous structure. Thus, composite cements containing carbonated cement paste are characterized by a rapid strength gain. The successful implementation of this CCU approach relies also on improved concrete recycling techniques and methods currently under development to separate out the cement paste fines and such. Full concrete recycling will further improve the circular utilization of cement and concrete by using recycled aggregates instead of natural deposits of aggregates. Although the feasibility of the process has already been demonstrated at the industrial scale, there are still several open questions related to optimum carbonation conditions and the performance of carbonated material in novel composite cements.

The article shows a case study as to whether the thermal and mechanical recycling of concrete is suitable for concrete debris from the demolition of structural elements of a 30-year-old industrial hall. The experiment included 10 series of new composites made from heated recycled concrete aggregate (HRCA) subjected to different variants of heat treatment and one additional control series with only natural aggregate (NA). The compressive strength of the new concretes has been determined. The microscopic observations of HRCA have also been made. The test results revealed that proper heat treatment of concrete rubble makes it possible to obtain a high-quality recycled coarse aggregate, which can be used as a 100% replacement for natural coarse aggregates in new concretes.

Concrete is a building material commonly used for ages. Therefore, in the result of repairs or demolition of building structures, large amounts of concrete rubble are created, which requires appropriate management. The aim of the realized research was to determine the influence of heat and mechanical treatment of concrete rubble on the properties of recycled aggregate concrete. The research experiment included 12 series, with three variables: X1—roasting temperature (300, 600, 900 °C), X2—time of mechanical treatment (5, 10, 15 min), X3—content of coarse recycled aggregates (20, 40, 60% by volume). Two additional series containing recycled aggregate without treatment and natural aggregate were also prepared. Established properties of individual aggregates have confirmed a positive effect of thermo-mechanical treatment. Then, based on the results of compressive strength, flexural strength, Young’s modulus, volumetric density, water absorption, water permeability and capillarity, the most favourable parameters of heat and mechanical treatment of concrete were determined. The test results showed that appropriate treatment of concrete rubble allows to obtain high-quality coarse aggregate and valuable fine fraction. This was also confirmed by the macro- and microscopic observations of the aggregate and separated cement paste. Works realized on the concrete recycling method resulted in obtaining a patent PAT.229887.

The paper presents an analytical review of materials recycling for pavement dressing. Recycling or repeated usage of pavement dressing materials while making reconstruction and repair of road pavements is not considered as a new conception and it has been realized in various countries of the world since 20th century. Recycling (hot, cold) is based on methods of its execution, properties of pavement dressing materials which are subjected to processing and which influence on the quality of final material, technical and operational indices, specific economic efficiency. Investigations on the processes of structure formation, thermo-physical properties in components based on granulates of transformed pavement dressings during recycling demonstrate that regeneration makes it possible to attain 100 % recovery of material properties for road pavement base. The paper describes other factors which represent a complex of challenges concerning exterior and internal problems. These problems have arisen due to actual processes of heat and mass transfer in one layer, multi-layer systems of pavement dressings. At known coefficients of heat conductivity, steam- and mass permeability, diffusion, filtration, temperature conductivity, density of material layers etc. initial and boundary conditions it is possible to carry out optimization of heat- and mass transfer problems from bottom surface of road layer to its base (sand, bulk materials, ground). In addition to it, while taking into account development of scientific prospective direction that concerns nano-technology and creation of nano-materials for higher reliability of road dressings it is necessary to consider nanomaterial science in road-construction industry as the most actual one because when we study problems pertaining to fractional composition of all road dressing components including transfer to nanomaterials, for example, application of modified water-reducing agent based on nanostructured carbon it is possible significantly to increase physical and technological properties of asphalt concrete and concrete road dressings. The paper reveals that it is necessary to continue and expand study of physical and technical and thermophysical properties of new materials on the basis of nano-technologies with application of modified, nanostructured carbon-based plasticizer for construction-road industry because especially these additives significantly increase cement activity that leads to improvement of strength, reliability and longevity for the obtained materials.

The article suggests recycling aluminium and pipe industry wastes in the production of refractory materials. New compositions of light fibrous concrete are developed, compared to the known structures they have improved physical and mechanical properties and a low cost. This is achieved due to the lack of heat treatment and utilization of industrial waste. Aluminous slag and sulphate sludge are stored in open landfills. Recycling of slag and sludge helps to improve the ecological state of environment. This article describes the chemical composition of the waste and suggests the optimal ratio of the mixture components. The properties of refractory fibrous concretes were defined at hardening of mixture in the natural conditions in the absence of heat treatment.

ABSTRACTAsphalt concrete is the most common material for highway and motorway construction. The quality of asphalt is determined, to a large extent, by properties of asphalt binder. Fillers, which are mineral powders from carbonate rocks and aggregates fines, such as limestone and dolomite, are often used in the composition of bitumen mastics affecting the performance of asphalt.This article explores the feasibility of using the fines of aluminosilicate sedimentary rocks as fillers. These materials are composed of clay minerals, which change their properties upon the contact with water. Normally, the use of such fillers is restricted because of poor water resistance and swelling of asphalt concrete. In order to improve the performance of these fillers, the thermal modification at moderate temperatures of 500–600 °C has been proposed. Such treatment provides sufficient structural stability of obtained materials and results in the reduction of water absorption of asphalt, improved water resistance (up to 2.5 times) and also, in reduced swelling (up to 9 times).It has been demonstrated that improvement in the filler performance can be achieved by a heat treatment. Such treatment induces changes in the mineral composition and converts the structure of clay minerals into the frame structure of zeolite, as confirmed by X-ray diffraction and infrared spectroscopy. Due to thermal treatment, there is a change in the acid-base properties of the surface of the filler, which is reflected in the profiles of the main adsorption centers. As a result, due to chemisorption, the modified aluminosilicate fillers are able to interact with bitumen. The application of new filler materials in asphalt concrete enables to enhance the performance.

Due to the benefits of pollution reduction, energy saving, and recycling of resources associated with the recycled concrete, together with the apparent thermal storage thermal insulation yield of expandable polystyrene (EPS) template, the heat transfer dynamics of their combination has become a contemporary study topic. In this research work, an investigation of the heat transfer coefficient (U) of EPS template recycled-concrete shear wall has been carried out. Four different concrete mixtures shear wall samples having different insulation types were developed for the purpose of quantifying their thermal outputs. Both temperature (T) and humidity (H) affection to thermal conductivity coefficient (λ) of reinforced concrete and the EPS template were investigated, correspondingly. The λ0°C (relative variation for a 0°C of temperature variation in T) of cement mortar, recycled-concrete shear wall, and ordinary concrete shear wall were measured being 0.7526, 1.2463, and 1.3750 W·m−1·K−1, respectively. And the λ calculation of EPS was carried out being 0.0396 W·m−1·K−1. A corrected calculation method was put forward to application in practical work that could reflect the real U value in a more precise manner. These results brought to light the fact that the heat preservation output of recycled-concrete shear wall posed to be comparatively more improved than that of ordinary concrete shear wall. We put forth the suggestion for the use of corrected calculation method in the calculation and analysis of U of EPS template recycled-concrete composite shear wall in the climatic conditions of Beijing. The results revealed the fact that the U of EPS template recycled-concrete shear wall was dominantly controlled by the change of thermal conductivity changes of EPS template. The monthly mean U increased with increasing Tout and decreased with decreasing Tout. The smaller the U of the enclosure wall was, the better the thermal stability of the wall was experienced.

Abstract For both environmental and economic reasons, there is a continuing broad based interest in recycling of scrap rubber and development of recycling technologies. The use of post- industrial scrap is established as a systematic business. However, the disposal and reuse of scrap tires remains a serious environmental concern and a business opportunity. The method for reclaiming rubber utilizing aqueous alkaline solutions has been abandoned in North America because of environmental pollution hazards. The focus of more recent research is to apply processes that do not generate disposal hazards and that might be carried out directly in the product manufacturer's factory. The major process at the present time is to utilize the scrap rubber as a very finely ground crumb. Crumb is produced either by ambient temperature mechanical grinding or by cryogenic shattering. In general, the crumb rubber is combined with virgin elastomer compounds to reduce cost. However, there is some loss in physical properties and performance. This factor has motivated the search for cost effective in-situ regeneration or devulcanization of the scrap rubber to provide superior properties. Some progress has been achieved utilizing mechanical shear, heat and other energy input, and a combination of chemicals such as oils, accelerators, amines, etc. to reduce the concentration of sulfur crosslinks in the vulcanized rubber. The major application of scrap rubber, particularly as crumb, is outside the conventional rubber industry. More than half of the scrap is burned for its fuel value for generation of electricity and as a component in cement production. The utilization in extension of asphalt in road construction is now recognized to provide superior road performance and reduced cost. The simple use of crumb rubber as a component in artificial turf is developing into a significant industry. Rubber crumb is now widely utilized in rubber products such as mats, floor tiles, carpet undercushion, etc., where the crumb is rebonded using polyurethane or latex adhesives. Other applications, such as in landfill, concrete, thermoplastic blends, pyrolysis to generate carbon black and chemicals, are discussed. The tire industry does utilize a significant proportion of fine crumb rubber in tire compounds. This is likely to not increase much due to the concern about tire performance and safety. However, there is a serious interest by tire manufacturers to increase the use of scrap tire rubber, if the recycled rubber could be regenerated to improve compatibility and performance in tire compounds.

The paper presents a fragment of on-going investigations directed on creation of optimal information environment that ensures an access to the R&D publications from the known scientific journals and other scientific serials which are necessary for qualitative execution of scientific and technological activities on priority areas in highway engineering. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific publications which are necessary for execution of investigations on heat and mass transfer in road dressings. Their deformations occur under various climatic conditions due to heat and mass transfer processes, interaction of transport flows and road surface that leads to crack formation in depth and on the surface of road dressings. Structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-, reinforced concrete, concrete, brick scrap and products of their recycling, various wastes of production etc.) exerts an influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to viscosity, air velocity, geometric characteristics, permeability, capillary pressures in materials. It has been shown that calculations based on principles of complex number usage have specific features in engineering practice: it is required to observe their accuracy in approaches, calculation reduction due to some accuracy degradation as a consequence of transition from complex numbers to their modules with exclusion of phase shift account and related with propagation of thermal waves. In this respect calculations of heat resistance without phase shifts are considered as rather important if they are in agreement with principles based on the fact that a complexity is characterized by thermal absorptivity of the material in a great number of calculations. The investigations have been supported by Henan Center for Outstanding Overseas Scientists, Grant Number GZS 2018006 (People’s Republic of China, Henan Province).

Aerated concrete is a new type of wall material with beneficial features like light weight, heat insulation, fire prevention and low energy consumption. As a key milestone in wall materials innovation and energy-saving of building system, it has been proven to be an ideal wall material which can replace traditional clay brick through years of application and practice. This study calculated the CO2 emissions in all the stages of life cycle of aerated concrete production. Compared with clay brick, the life cycle CO2 intensity of aerated concrete block will be decreased by 67.4% with the same insulation effect. Study on the environmental loads of aerated concrete industry will provide theoretical base for the carry out of energy-saving and emission reduction, the formulation of clean production and the development of recycling economy.

<p>The growth in the consumption of industrialized products has implied a considerable increase in the generation of urban solid waste, among which stand out the glass waste. The great technological advantage of glass is its high recycling potential, as well as the possibility of being molded into the desired shape, which contributes to various applications. In this sense, this work aims to analyze the efficiency of the heat treatments applied to green-soda-glass vitreous samples from the recycling of filling bottles, and compare with the hardness of the base glass. Initially the bottles were benefited and manually crushed for later sieving. Then, the vitreous residues were accommodated in an autoclaved cellular concrete (CCA) mold and subjected to heat treatments, which resulted in the melting and annealing of the pieces. Four distinct heat treatments were tested, with melting temperatures of 800ºC (20 min), 820ºC (20 min), 840ºC (15 min) and 840ºC (30 min). The obtained samples were analyzed by X-ray diffraction (XRD) and Vickers microhardness test. The results indicated that the fourth heat treatment (840ºC - 30min.) Gave higher hardness than the base glass and higher degree of crystallinity.</p>

The paper presents a fragment of on-going investigations directed on creation of optimum data environment that ensures an access to world scientific journals and other publications which are necessary for qualitative implementation of works on priority directions of R&D in the field of road-construction industry in the period of 2016–2020. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific serial publiccations which are necessary for execution of investigations on heat and mass transfer in road dressings. The road dressings are considered as open heterogeneous thermodynamic systems. Their deformations occur under various climatic conditions due to heat and mass transfer processes and interaction of transport flows and road surface. Crack formation takes place in depth of the road dressings and on road surfaces as a result of temperature, mass transfer processes. As it is known material structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-concrete, concrete, reinforced concrete scrap and products of its recycling, brick rubble, various wastes of production etc.) influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to air viscosity, velocity of geometric permeability characteristics, capillary pressures in road pavements.

This study covers an in-depth investigation into the properties and practicality of the utilization of up to 40% Alumina Waste Filler (AWF) as a partial Portland Cement (PC) replacement material. AWF is a by-product from the recycling of aluminium, produced when salt slag is smelted and cleaned. Its use in concrete will lessen the landfill requirements for AWF disposal, and reduce the strain of the growing requirements and cost of PC. The results obtained from this study showed that the addition of AWF to the concrete mix caused a reduction in the compressive and tensile splitting strength values, and a less-workable concrete was achieved for every increase in the quantity of AWF added to each mix. The addition of AWF influenced the hydration reaction process and reduced the cumulative production of the heat of hydration over time, whilst the permeability of the concrete decreased.

The possibility of recycling large-tonnage waste of heat power engineer-ing and mining industry in road construction is shown. Compositions of road-building materials were researched, containing siftings of rock grinding, fly ash, Portland cement, modified with a stabilizing additive of polymeric nature. X-ray phase analysis showed availability of quartz in fly ash, calcite, feldspars, goethite and X-ray amorphous phase, what is consistent with the data of infrared spectroscopy. By atomic emission spectrometry with inductively coupled plasma it was revealed that fly ash is latent-active and can be disposed in compositions in the presence of a stabilizing additive. The X-ray phase analysis of grinding siftings showed that it contains quartz, feldspars, chlorite, calcite and dolomite. The specific activity of natural radionuclides (226Ra, 232Th, 40К) of fly ash and grinding siftings was 248 and 110 Bq/kg, which allows using such waste in construction without restrictions. It was revealed that the initial mineral raw materials belong to multiphase polymineral systems; therefore, when modifying them with stabilizing additives, binding of finely divided particles should be taken into account. It was revealed that the optimal content of Portland cement and fly ash in samples is 8 and 10 wt.%. It was found that an increase in the mass fraction of fly ash in the composition of soil-concrete up to 30 wt.% leads to softening of the samples and a decrease in their strength characteristics.

Polymer composites have been identified as the most innovative and selective materials known in the 21st century. Presently, polymer concrete composites (PCC) made from industrial or agricultural waste are becoming more popular as the demand for high-strength concrete for various applications is increasing. Polymer concrete composites not only provide high strength properties but also provide specific characteristics, such as high durability, decreased drying shrinkage, reduced permeability, and chemical or heat resistance. This paper provides a detailed review of the utilization of polymer composites in the construction industry based on the circular economy model. This paper provides an updated and detailed report on the effects of polymer composites in concrete as supplementary cementitious materials and a comprehensive analysis of the existing literature on their utilization and the production of polymer composites. A detailed review of a variety of polymers, their qualities, performance, and classification, and various polymer composite production methods is given to select the best polymer composite materials for specific applications. PCCs have become a promising alternative for the reuse of waste materials due to their exceptional performance. Based on the findings of the studies evaluated, it can be concluded that more research is needed to provide a foundation for a regulatory structure for the acceptance of polymer composites.

Fine recycled aggregates (FRA) (0/4 mm) are up to now not valorized on a high enough level because of characteristics like an elevated water absorption, higher fines content, and the presence of contaminations. Leftover gypsum residues from the construction site can cause internal sulfate attack when FRA are incorporated into new structures. Concern about this deteriorating reaction plays an important role in the rejection of FRA. In this study, samples of FRA from different recycling centers were characterized and incorporated into mortars. They were then subjected to swelling tests in order to evaluate the development of sulfate attack. Reference materials with different amounts of sulfates were used as a comparison. Results showed a variable sulfate content in industrial FRA, depending heavily on the source of the materials. In all but one case, the total amounts surpassed the acceptable sulfate contents specified in the European standard EN 206, meaning the FRA would be rejected for reuse in concrete. Nevertheless, swelling tests demonstrated that these contamination levels did not pose a risk for sulfate attack. These results indicated that the incorporation of FRA leads to acceptable mechanical performances and that the sulfate limit could be reviewed to be less strict.

The increased requirements for the treatment of wastewater, coupled with industrial growth, have created a need to treat and dispose of an over-proportional sludge volume. At the same time increasingly stringent regulations have resulted in limitations on the ultimate sludge disposal options. In highly urbanized municipalities, scarcity of landfill sites and increasing environmental awareness pose major public concern on the disposal of sludge. This situation has prompted the interest in recycling and reuse of sludge into building and construction materials as means of alleviating sludge disposal problems. This paper presents the results of the use of wastewater sludge to produce lightweight aggregates and cementitious binder as non-conventional construction materials. Lightweight coarse aggregates were produced from the incineration of sludge-clay mixture. Test results of porosity, specific gravity, bulk density, ten percent fines, water absorption and concrete strength, indicate that clay-blended sludge could be used to produce lightweight aggregates. The feasibility of using dried sludge mixed with lime as a cementitious binder after incineration was also studied. Evaluation of the mortar cube strengths shows that it is possible to produce masonry binder from sludge that will satisfy the strength requirements in the ASTM standard for masonry cement.

Different types of materials are used in hydraulic structures and coast protection constructions. These materials can be of natural (e.g. stone) and artificial origin (concrete, metal). The main trends typical for building construction now are as follows: cutting a share of natural materials and reusing waste products of dismantling construction objects. As a result of recycling it is possible to produce building materials that look like and have properties characteristic of natural stone materials, gravel, in particular. While gravel is being processed, it is possible to predict that it would obtain such characteristics as grade, frost resistance and strength. Reuse of recycled construction materials is a challenge, because this type of waste can hardly be reduced in volume and requires considerable space for burial. We propose to use gravel produced by processing in hydraulic engineering objects, i.e. in coast protection constructions. For that, we analyzed waste materials characteristics to justify their use in hydraulic structures. The research proved that strength of gravel produced by processing was sufficient enough. On the other hand, its frost resistance and fineness did not satisfy the requirements to materials used in coast protective structures. Besides, the construction of such structures causes water pollution as inert materials placed in waterbodies increase water turbidity. As a large part of the structure is located directly in the waterbody, during the period of the construction inert materials are supposed to be dumped. In this period the water body is filled with a significant amount of fine particles, which leads to an increase in turbidity at the construction site. Thus, we come to the conclusion that it is possible to reuse recycled construction materials in hydraulic engineering structures only on condition of their additional after-treatment processing. We offer to mix gravel produced by processing with cement mortal. As a result we obtain no-fines concrete, which is further processed by hot procedure (with bituminous materials). No-fines concrete can be produced in the form of precast units of 1,4×1,4×0,5 m. The use of prefabricated units will allow to avoid waterbody pollution and protect it from fine particles. Further processing by bituminous materials will enhance its frost resistance and reliability, which in turn will prevent contamination of the water body in the period of coast protection constructions usage.

Madagascar undergoes, like all countries in the world, the effects of climate change. in fact, since the last 5 years, in the coastal regions and the basins, the temperature has raised from 2 to 2.5 ° and varies between 34 to 36 ° in the shadow during the rainy season and on the high hills, the temperature diminishes from 2 to 2.5 ° during the dry period and varies from 4 ° to 8 °. However, the structure of lodging of 60% of the people are not adapted to this temperature change. Particularly, in the coastal regions, the walls of the houses are made of sheet iron. The inside of these houses is very hot when the weather is hot and very cold when it is cold. The inhabitants can’t afford the houses made in bricks or breeze block and the natural sources of aggregates are in the process of exhaustion. In the other part, we have seen that tons of paper are ready to be burned at the administrative services (public treasury, public financing, universities, ...) and the newspaper publishers. So, it becomes a must to find another way to the construction materials, justifying in that case our research axis. This study aims at the developing of construction material based on recycled paper, binder and aggregate. It deals of picking up or gathering all waste of papers and outdates newspapers and transforming them into brick for building constructions. What’s more, papers have prominent thermal insulating properties. Our work is focused on the study of variants on the different manufacturing processes, the choice of binder, the preparation of the specimens with different binders and different dosages, the mechanical compression tests for different binders, the evaluation of thermal conductivity for different binders and the numerical simulation of the thermo mechanical behavior of samples. The result is a lightweight brick with good thermal insulation. Tests have also made it possible to declare that the material has acceptable mechanical properties : the compressive strength is 1.56 [N/mm2], higher than the value prescribed by the standard for lightweight concrete blocks for construction of 1.1 [N/mm2], the value of thermal conductivity is 0.114 [W/mK], ten times less conductive heat than concrete and it can replace glass wool for a double its thickness. The specific weight is 57.5 [kg/m2].The practical results were confirmed by finite element simulations.

This article demonstrates the possibility of producing alkali-activated materials (AAM) from a mixture of mechanically processed concrete, ceramic, masonry, and mortar wastes, as a sustainable alternative for recycling construction and demolition wastes (CDWs) under real conditions. The addition of 10% Portland cement allowed the materials to cure at room temperature (25 °C). CDW binder achieved a compressive strength of up to 43.9 MPa and it was classified as a general use and low heat of hydration cement according to ASTM C1157. The concrete produced with this cement and the crushed aggregates also from CDW reported a compressive strength of 33.9 MPa at 28 days of curing and it was possible to produce a high-class structural block with 26.1 MPa according to ASTM C90. These results are considered one option in making full use of CDWs as binder and aggregates, using alkaline activation technology thereby meeting the zero-waste objective within the concept of the circular economy.

As the world population continues to increase, so does the demand for raw materials to produce basic needs of the human race. One of the areas where this pressing demand for means of production is evident is in the production of concrete materials for building construction and infrastructure. The source of constitutive materials for concrete production, such as cement and aggregates are fast shrinking across the nations of the earth, and there is an urgent need for substitutes that will guarantee the availability of this essential material to the built environment sector of the economy. One of the trending approaches is the adoption of waste materials as a replacement for some of the constitutive materials of concrete. This research reviews past works on the use of recycled plastic waste and periwinkle shells for the production of lightweight aggregate concrete. The results of this review showed that the adoption of a reduced percentage of waste plastic in concrete leads to acceptable strengths for lightweight concrete, economy, efficient energy and excellent crack resistance. The use of periwinkle shell is beneficial for satisfactory strengths for normal aggregate concrete and for lightweight aggregate concrete, excellent resistance to heat and economy. This approach is sustainable as a means of recycling and will facilitate the actualization of the sustainable development goal “Responsible Production and Consumption”, (SDGs 12). There is a perspective that combining these two waste materials will lead to improvement towards achieving sustainable concrete.

Breathing Walls are building structures based on porous materials crossed by an airflow, which act both as building envelopes and ventilation system components. In climates where both heating and cooling are needed, a pro-flux configuration (heat and air mass both flowing in the same direction) might be alternated with a contra-flux configuration (heat and air mass flowing in opposite directions) during the year or even on a day. Understanding and modelling the Breathing Walls' stationary and dynamic behaviour is thus fundamental, in order to optimize their design and to fully exploit their energy-saving potential. In this experimental study, a small-scale no-fines concrete Breathing Wall was investigated. The steady-state contra-flux tests performed in a Dual Air-Vented Thermal Box laboratory apparatus were used to derive the heat recovery efficiency of the sample as a function of the cross airflow velocity. The effectiveness of this technology was then evaluated in a virtual case study. An optimal airflow velocity across the Breathing Wall was found, leading to energy savings between 9% and 14%. Dynamic tests were performed assuming a sinusoidal variation of the operative temperature on one side of the sample. They showed how airflow velocity affected the Breathing Wall inertia and dynamic behaviour.

Zusammenfassung Beton-3D-Druck nach dem CONPrint3D-Verfahren ist eine kontinuierliche und schalungsfreie Bautechnologie, die die wirtschaftliche Errichtung von Betonbauteilen und Bauwerksstrukturen unter Baustellenbedingungen ermöglicht. Im vorliegenden Aufsatz wird eine Erweiterung dieses Verfahrens auf Schaumbeton vorgestellt. Schaumbeton zeichnet sich durch eine geringe Dichte und hohe Wärmedämmfähigkeit bei gleichzeitig für die tragende Funktion ausreichender Druckfestigkeit aus. Bei hinreichender monolithischer Stärke von Wänden aus Schaumbeton kann auf eine zusätzliche Wärmedämmung im Hochbau verzichtet werden. Dies beschleunigt nicht nur die vollständige Herstellung von Wänden, sondern vereinfacht auch das Recycling nach dem Nutzungsende des Bauwerks. Im Artikel werden baustofftechnologische, maschinentechnische und baubetriebliche Aspekte der neuen Technologie näher erläutert.

A steel slag has been treated by air granulation, in order to enhance cementitious properties of the slag. Two samples with sizes ranged 1.68-2.38mm and 212-297μm and coded as Slag A and Slag B, respectively, were chosen from the granulated slag for investigations. A sample of the original steel slag was also studied. XRD analyses indicated the formations of α-C2S, β-C2S, C2F, C2MS2, f-MgO and α-C2S, C2F, f-MgO in Slag A and Slag B, respectively. The phases in the two slag samples were quite different from the phases found in steel slag. The SEM results show a reduction of C2S sizes from 10-20μm for the steel slag to nano-scales by air quenching for Slag B. This treatment of air quenching has increased the cumulative heat of hydration to 105.35J/g measured for Slag B, almost two times greater than that of the steel slag. The study results demonstrate a high potential for utilizations of the steel slag in cement and concrete applications after the slag treatment by air quenching. The treatment may thus lead to an environmental friendly and cost-effective recycling for the steel slag. This can also contribute to the sustainable developments in the steel and cement/concrete industries.

An increasing amount of red mud (RM) is being generated globally due to the growth in aluminum production. To avoid RM pollution, low-cost methods for effectively recycling RM are being investigated. We propose a method for recycling RM as a construction material. Liquefied RM (LRM) was neutralized by nitric acid and added to cement paste, and the hydration heat, compressive strength, and hydration products were investigated. The cement paste with neutralized LRM had a higher compressive strength than that of plain cement paste and cement paste with LRM without neutralization at 1 day of aging; this indicates that nitric acid neutralization increases the early-age strength. Furthermore, the cement paste with 10% neutralized LRM showed 28 days-compressive strength and hydration heating curves similar to the plain mixture, indicating the positive impact of LRM neutralization on the strength. It was noted that a greater quantity of portlandite was produced earlier in cement paste with neutralized LRM than in that without. Therefore, the proposed method of using RM as a concrete additive has the potential to reduce the cost and environmental impact of both construction materials and RM waste management.

The paper discusses the important issues concerning recycling of industrial sulfur waste and bottom ash. The process flow diagram was designed to form protective coatings on cement concrete by impregnation with molten sulfur, which featured high strength, performance properties and corrosion resistance. The process parameters were specified. The addition of bottom ash slag to cement concrete not only offers a means for recovering waste from thermal power stations, but also increases the material strength. Besides, the impregnation process provides low thermal conductivity for concrete while giving the material high heat insulation. A higher strength of the samples containing bottom ash slag results from a high dispersity and reactive surface of bottom ash slag. The paper investigates the influence of the electrophilic agent (aluminum chloride) on the properties of sulfur binder. It was shown that addition of aluminum chloride encouraged the formation of a more effective protective coating that gave the samples of cement concrete higher strength, density, water resistance. The electrophilic agent stimulated the synthesis process for inorganic sulfides and composite materials based on them. It was found that addition of the electrophilic agent (aluminum chloride) reduced the viscosity of molten sulfur significantly, which was attributed to the formed short-chain sulfur radicals. Such a melt has a relatively high penetration capability to ensure the formation of a high-quality protective coating.

Cement is an extremely energy consuming material and its production leads to the emission of a vast amount of greenhouse gases. Cementitious concrete is a universal building material, which is used for the production of various structural elements. The paper describes the problem of cement production and its impact on the environment. This research deals with application of aluminous cement as binder component for the manufacture of refractory composites and with possibilities of further utilization of environmentally friendly materials with pozzolanic properties as a partial replacement of used aluminous cement. These materials are originating as waste in the building industry or by the recycling of cast-off materials. To reduce the costs and adverse effects on the environment was the binder system modified by finely ground ceramic powder and metakaolin. The experimental results present the values of flexural and compressive strength investigated on a series of composite specimens with dimensions of 40×40×160 mm3 and 10, 20 and 30 % of cement replacement. The aim of the present work is to apply the mentioned pozzolanic materials and reach the suitable composite with the sufficient heat resistance and residual mechanical parameters after gradual temperature loading.

AbstractRoad embankments, especially their slopes’ surfaces, must fulfil all the requirements concerning the exploitation criteria after the completion of construction works. This is very important while constructing or modernizing the embankments, based on the substrate including low-strength soils as well as in simple ground conditions (most convenient). The last dozen or so years of intensive construction of transport infrastructure have shown how big is the problem of ensuring the required volumes of qualified soil material for the construction of road embankments or the modernization of railway embankments. The depleting deposits of natural and easily accessible soils for the construction of embankments result in the need to use anthropogenic soils, for example, in the form of aggregates from the recycling of construction waste and other locally available waste materials, usually in the form of slag and ashes from the combined heat and power plants. In such cases, there’s a need to treat transportation earth structures individually in the scope of designing and quality control, because there are no applicable standard provisions in this scope.This work indicates some of these important contemporary problems of transport engineering, occurring in newly built and modernized road objects, such as the stability of road embankments based on a low-strength substrate, use of anthropogenic soils and materials originating from the recycling of concrete surfaces for the construction of road embankments.

The raw material mixture from the silicon-like technogenic component the ash-removal of thermal power plants and the preparation methods of waterproof porous heat-insulated materials wide usage for raw mass hot foaming powdered two-stage technology are developed. The development uses the polyfunctional properties of liquid glass as a) the binder component; c) breeder; c) the speed regulator of the clamping mass hardenin. Its optimized version begins to solidify at its usual temperature from the moment its "reproduction" is soluble glass and forms a paste-shaped cake with a set of properties necessary for the next fragmentation. The proposed formulation allows compositions processing in various ways, with the formation of granular heat-insulating fillers, materials for thermal insulation in complex structures, slab and shell-like types of thermal insulation materials. The task is set, depending on the goals and features of the tasks being solved; it is possible to conduct several different methods at the final stages of their obtaining. Two stages of the recycling process determine the character and behavior of the rare-glass composite systems constituent components during heat treatment, their strong adhesion to most structural materials and the need to solve billets easy removal problem from the molding unit. Study results can be used in the field of building materials production, in particular porous artificial products, in obtaining granular insulating material and light aggregate for concrete industrial and civil construction, in thermal engineering as thermal insulation, etc.

The field of Civil Engineering Materials has found a use for a range of industrial waste products as substitutes, that are as effective as standard construction materials but which have the bonus of providing an ecologically sound alternative for materials that would otherwise become an environmental concern. The use of waste materials in polymer composites is a prime example of this practice. These composites display excellent mechanical properties but must be adapted to the combustibility properties. This study aimed to produce polymer concrete composites using waste alumina from metallurgic industrial processing. The composites have an ortophtalic polyester resin as a binder, river sand as aggregates and fly ash as filler. Two kinds of flame retardants were used: a residue, polishing alumina and the other virgin, commercial alumina which were used in four different percentages 15, 30, 45 and 60% in mass in relation to the resin. The samples were subjected to testing of flexural strength, temperature changes of 125, 225 and 325°C and porosity by mercury addition. The results received statistical treatment in order to evaluate the variable significance in relation to the studied properties. In this study the composites displayed flexural strength values around 30 MPa. The statistical analysis showed that the factors temperature changes, addition percentage and the interaction among these factors posed great influence on the studied compositions in relation to the heat resistance testing. In general terms, it can be said that the flame retardant waste, polishing alumina, is an efficient alternative to substitute the trihydrated commercial alumina in the polymer concrete composites with the other components proposed in this study.Key words: polishing alumina, recycling, polymer concrete, fly ash, combustibility

Ceramic fibers are characterized by their light weight, high degree of purity, low heat storage, low thermal conductivity, thermal shock resistance and superior corrosion resistance in high-temperature environments. In addition, they can be produced extensively in substitution to all materials used in the coating of almost all heating equipment as well as contributing to the reduction of energy consumption. Such characteristics make them ideal in the coating of distributors, mufflers, heating ovens, among others, as highly demanded by the mining and metallurgical industries, among others. After use in the process of industrial production, generated waste will lose their insulation capacity and thus require safe disposal. The present work focuses specifically on ceramic and glass wools aiming at an evaluation of their recycling prospect of incorporation into cement mortars and concrete. This residues were pulverized and displayed ~30µm average particle size. The scan electronic microscopy (SEM) presented elongated, thin and straight particles, which is very different than flocular structure of cement. The X-rays diffraction revealed amorphous structure for glass wool and crystalline structure for ceramics wool. The chemical analysis showed high concentrations of Al2O3 and silica in both residues, with higher percentage of calcium oxide in glass wool.

AbstractWind power produces more electricity than any other form of renewable energy in the United Kingdom (UK) and plays a key role in decarbonisation of the grid. Although wind energy is seen as a sustainable alternative to fossil fuels, there are still several environmental impacts associated with all stages of the lifecycle of a wind farm. This study determined the material composition for wind turbines for various sizes and designs and the prevalence of such turbines over time, to accurately quantify waste generation following wind turbine decommissioning in the UK. The end of life stage is becoming increasingly important as a rapid rise in installation rates suggests an equally rapid rise in decommissioning rates can be expected as wind turbines reach the end of their 20–25-year operational lifetime. Waste data analytics were applied in this study for the UK in 5-year intervals, stemming from 2000 to 2039. Current practices for end of life waste management procedures have been analysed to create baseline scenarios. These scenarios have been used to explore potential waste management mitigation options for various materials and components such as reuse, remanufacture, recycling, and heat recovery from incineration. Six scenarios were then developed based on these waste management options, which have demonstrated the significant environmental benefits of such practices through quantification of waste reduction and greenhouse gas (GHG) emissions savings. For the 2015–2019 time period, over 35 kilotonnes of waste are expected to be generated annually. Overall waste is expected to increase over time to more than 1200 kilotonnes annually by 2039. Concrete is expected to account for the majority of waste associated with wind turbine decommissioning initially due to foundations for onshore turbines accounting for approximately 80% of their total weight. By 2035–2039, steel waste is expected to account for almost 50% of overall waste due to the emergence of offshore turbines, the foundations of which are predominantly made of steel.

By the time you read this, it will be wrong. Things seemed to be moving so fast in these first days after airplanes crashed into the World Trade Center, the Pentagon, and the Pennsylvania earth. Each certainty is as carelessly dropped as it was once carelessly assumed. The sounds of lower Manhattan that used to serve as white noise for residents—sirens, screeches, screams—are no longer signs without a referent. Instead, they make folks stare and stop, hurry and hustle, wondering whether the noises we know so well are in fact, this time, coefficients of a new reality. At the time of writing, the events themselves are also signs without referents—there has been no direct claim of responsibility, and little proof offered by accusers since the 11th. But it has been assumed that there is a link to US foreign policy, its military and economic presence in the Arab world, and opposition to it that seeks revenge. In the intervening weeks the US media and the war planners have supplied their own narrow frameworks, making New York’s “ground zero” into the starting point for a new escalation of global violence. We want to write here about the combination of sources and sensations that came that day, and the jumble of knowledges and emotions that filled our minds. Working late the night before, Toby was awoken in the morning by one of the planes right overhead. That happens sometimes. I have long expected a crash when I’ve heard the roar of jet engines so close—but I didn’t this time. Often when that sound hits me, I get up and go for a run down by the water, just near Wall Street. Something kept me back that day. Instead, I headed for my laptop. Because I cannot rely on local media to tell me very much about the role of the US in world affairs, I was reading the British newspaper The Guardian on-line when it flashed a two-line report about the planes. I looked up at the calendar above my desk to see whether it was April 1st. Truly. Then I got off-line and turned on the TV to watch CNN. That second, the phone rang. My quasi-ex-girlfriend I’m still in love with called from the mid-West. She was due to leave that day for the Bay Area. Was I alright? We spoke for a bit. She said my cell phone was out, and indeed it was for the remainder of the day. As I hung up from her, my friend Ana rang, tearful and concerned. Her husband, Patrick, had left an hour before for work in New Jersey, and it seemed like a dangerous separation. All separations were potentially fatal that day. You wanted to know where everyone was, every minute. She told me she had been trying to contact Palestinian friends who worked and attended school near the event—their ethnic, religious, and national backgrounds made for real poignancy, as we both thought of the prejudice they would (probably) face, regardless of the eventual who/what/when/where/how of these events. We agreed to meet at Bruno’s, a bakery on La Guardia Place. For some reason I really took my time, though, before getting to Ana. I shampooed and shaved under the shower. This was a horror, and I needed to look my best, even as men and women were losing and risking their lives. I can only interpret what I did as an attempt to impose normalcy and control on the situation, on my environment. When I finally made it down there, she’d located our friends. They were safe. We stood in the street and watched the Towers. Horrified by the sight of human beings tumbling to their deaths, we turned to buy a tea/coffee—again some ludicrous normalization—but were drawn back by chilling screams from the street. Racing outside, we saw the second Tower collapse, and clutched at each other. People were streaming towards us from further downtown. We decided to be with our Palestinian friends in their apartment. When we arrived, we learnt that Mark had been four minutes away from the WTC when the first plane hit. I tried to call my daughter in London and my father in Canberra, but to no avail. I rang the mid-West, and asked my maybe-former novia to call England and Australia to report in on me. Our friend Jenine got through to relatives on the West Bank. Israeli tanks had commenced a bombardment there, right after the planes had struck New York. Family members spoke to her from under the kitchen table, where they were taking refuge from the shelling of their house. Then we gave ourselves over to television, like so many others around the world, even though these events were happening only a mile away. We wanted to hear official word, but there was just a huge absence—Bush was busy learning to read in Florida, then leading from the front in Louisiana and Nebraska. As the day wore on, we split up and regrouped, meeting folks. One guy was in the subway when smoke filled the car. Noone could breathe properly, people were screaming, and his only thought was for his dog DeNiro back in Brooklyn. From the panic of the train, he managed to call his mom on a cell to ask her to feed “DeNiro” that night, because it looked like he wouldn’t get home. A pregnant woman feared for her unborn as she fled the blasts, pushing the stroller with her baby in it as she did so. Away from these heart-rending tales from strangers, there was the fear: good grief, what horrible price would the US Government extract for this, and who would be the overt and covert agents and targets of that suffering? What blood-lust would this generate? What would be the pattern of retaliation and counter-retaliation? What would become of civil rights and cultural inclusiveness? So a jumble of emotions came forward, I assume in all of us. Anger was not there for me, just intense sorrow, shock, and fear, and the desire for intimacy. Network television appeared to offer me that, but in an ultimately unsatisfactory way. For I think I saw the end-result of reality TV that day. I have since decided to call this ‘emotionalization’—network TV’s tendency to substitute analysis of US politics and economics with a stress on feelings. Of course, powerful emotions have been engaged by this horror, and there is value in addressing that fact and letting out the pain. I certainly needed to do so. But on that day and subsequent ones, I looked to the networks, traditional sources of current-affairs knowledge, for just that—informed, multi-perspectival journalism that would allow me to make sense of my feelings, and come to a just and reasoned decision about how the US should respond. I waited in vain. No such commentary came forward. Just a lot of asinine inquiries from reporters that were identical to those they pose to basketballers after a game: Question—‘How do you feel now?’ Answer—‘God was with me today.’ For the networks were insistent on asking everyone in sight how they felt about the end of las torres gemelas. In this case, we heard the feelings of survivors, firefighters, viewers, media mavens, Republican and Democrat hacks, and vacuous Beltway state-of-the-nation pundits. But learning of the military-political economy, global inequality, and ideologies and organizations that made for our grief and loss—for that, there was no space. TV had forgotten how to do it. My principal feeling soon became one of frustration. So I headed back to where I began the day—The Guardian web site, where I was given insightful analysis of the messy factors of history, religion, economics, and politics that had created this situation. As I dealt with the tragedy of folks whose lives had been so cruelly lost, I pondered what it would take for this to stop. Or whether this was just the beginning. I knew one thing—the answers wouldn’t come from mainstream US television, no matter how full of feelings it was. And that made Toby anxious. And afraid. He still is. And so the dreams come. In one, I am suddenly furloughed from my job with an orchestra, as audience numbers tumble. I make my evening-wear way to my locker along with the other players, emptying it of bubble gum and instrument. The next night, I see a gigantic, fifty-feet high wave heading for the city beach where I’ve come to swim. Somehow I am sheltered behind a huge wall, as all the people around me die. Dripping, I turn to find myself in a media-stereotype “crack house” of the early ’90s—desperate-looking black men, endless doorways, sudden police arrival, and my earnest search for a passport that will explain away my presence. I awake in horror, to the realization that the passport was already open and stamped—racialization at work for Toby, every day and in every way, as a white man in New York City. Ana’s husband, Patrick, was at work ten miles from Manhattan when “it” happened. In the hallway, I overheard some talk about two planes crashing, but went to teach anyway in my usual morning stupor. This was just the usual chatter of disaster junkies. I didn’t hear the words, “World Trade Center” until ten thirty, at the end of the class at the college I teach at in New Jersey, across the Hudson river. A friend and colleague walked in and told me the news of the attack, to which I replied “You must be fucking joking.” He was a little offended. Students were milling haphazardly on the campus in the late summer weather, some looking panicked like me. My first thought was of some general failure of the air-traffic control system. There must be planes falling out of the sky all over the country. Then the height of the towers: how far towards our apartment in Greenwich Village would the towers fall? Neither of us worked in the financial district a mile downtown, but was Ana safe? Where on the college campus could I see what was happening? I recognized the same physical sensation I had felt the morning after Hurricane Andrew in Miami seeing at a distance the wreckage of our shattered apartment across a suburban golf course strewn with debris and flattened power lines. Now I was trapped in the suburbs again at an unbridgeable distance from my wife and friends who were witnessing the attacks first hand. Were they safe? What on earth was going on? This feeling of being cut off, my path to the familiar places of home blocked, remained for weeks my dominant experience of the disaster. In my office, phone calls to the city didn’t work. There were six voice-mail messages from my teenaged brother Alex in small-town England giving a running commentary on the attack and its aftermath that he was witnessing live on television while I dutifully taught my writing class. “Hello, Patrick, where are you? Oh my god, another plane just hit the towers. Where are you?” The web was choked: no access to newspapers online. Email worked, but no one was wasting time writing. My office window looked out over a soccer field to the still woodlands of western New Jersey: behind me to the east the disaster must be unfolding. Finally I found a website with a live stream from ABC television, which I watched flickering and stilted on the tiny screen. It had all already happened: both towers already collapsed, the Pentagon attacked, another plane shot down over Pennsylvania, unconfirmed reports said, there were other hijacked aircraft still out there unaccounted for. Manhattan was sealed off. George Washington Bridge, Lincoln and Holland tunnels, all the bridges and tunnels from New Jersey I used to mock shut down. Police actions sealed off the highways into “the city.” The city I liked to think of as the capital of the world was cut off completely from the outside, suddenly vulnerable and under siege. There was no way to get home. The phone rang abruptly and Alex, three thousand miles away, told me he had spoken to Ana earlier and she was safe. After a dozen tries, I managed to get through and spoke to her, learning that she and Toby had seen people jumping and then the second tower fall. Other friends had been even closer. Everyone was safe, we thought. I sat for another couple of hours in my office uselessly. The news was incoherent, stories contradictory, loops of the planes hitting the towers only just ready for recycling. The attacks were already being transformed into “the World Trade Center Disaster,” not yet the ahistorical singularity of the emergency “nine one one.” Stranded, I had to spend the night in New Jersey at my boss’s house, reminded again of the boundless generosity of Americans to relative strangers. In an effort to protect his young son from the as yet unfiltered images saturating cable and Internet, my friend’s TV set was turned off and we did our best to reassure. We listened surreptitiously to news bulletins on AM radio, hoping that the roads would open. Walking the dog with my friend’s wife and son we crossed a park on the ridge on which Upper Montclair sits. Ten miles away a huge column of smoke was rising from lower Manhattan, where the stunning absence of the towers was clearly visible. The summer evening was unnervingly still. We kicked a soccer ball around on the front lawn and a woman walked distracted by, shocked and pale up the tree-lined suburban street, suffering her own wordless trauma. I remembered that though most of my students were ordinary working people, Montclair is a well-off dormitory for the financial sector and high rises of Wall Street and Midtown. For the time being, this was a white-collar disaster. I slept a short night in my friend’s house, waking to hope I had dreamed it all, and took the commuter train in with shell-shocked bankers and corporate types. All men, all looking nervously across the river toward glimpses of the Manhattan skyline as the train neared Hoboken. “I can’t believe they’re making us go in,” one guy had repeated on the station platform. He had watched the attacks from his office in Midtown, “The whole thing.” Inside the train we all sat in silence. Up from the PATH train station on 9th street I came onto a carless 6th Avenue. At 14th street barricades now sealed off downtown from the rest of the world. I walked down the middle of the avenue to a newspaper stand; the Indian proprietor shrugged “No deliveries below 14th.” I had not realized that the closer to the disaster you came, the less information would be available. Except, I assumed, for the evidence of my senses. But at 8 am the Village was eerily still, few people about, nothing in the sky, including the twin towers. I walked to Houston Street, which was full of trucks and police vehicles. Tractor trailers sat carrying concrete barriers. Below Houston, each street into Soho was barricaded and manned by huddles of cops. I had walked effortlessly up into the “lockdown,” but this was the “frozen zone.” There was no going further south towards the towers. I walked the few blocks home, found my wife sleeping, and climbed into bed, still in my clothes from the day before. “Your heart is racing,” she said. I realized that I hadn’t known if I would get back, and now I never wanted to leave again; it was still only eight thirty am. Lying there, I felt the terrible wonder of a distant bystander for the first-hand witness. Ana’s face couldn’t tell me what she had seen. I felt I needed to know more, to see and understand. Even though I knew the effort was useless: I could never bridge that gap that had trapped me ten miles away, my back turned to the unfolding disaster. The television was useless: we don’t have cable, and the mast on top of the North Tower, which Ana had watched fall, had relayed all the network channels. I knew I had to go down and see the wreckage. Later I would realize how lucky I had been not to suffer from “disaster envy.” Unbelievably, in retrospect, I commuted into work the second day after the attack, dogged by the same unnerving sensation that I would not get back—to the wounded, humbled former center of the world. My students were uneasy, all talked out. I was a novelty, a New Yorker living in the Village a mile from the towers, but I was forty-eight hours late. Out of place in both places. I felt torn up, but not angry. Back in the city at night, people were eating and drinking with a vengeance, the air filled with acrid sicklysweet smoke from the burning wreckage. Eyes stang and nose ran with a bitter acrid taste. Who knows what we’re breathing in, we joked nervously. A friend’s wife had fallen out with him for refusing to wear a protective mask in the house. He shrugged a wordlessly reassuring smile. What could any of us do? I walked with Ana down to the top of West Broadway from where the towers had commanded the skyline over SoHo; downtown dense smoke blocked the view to the disaster. A crowd of onlookers pushed up against the barricades all day, some weeping, others gawping. A tall guy was filming the grieving faces with a video camera, which was somehow the worst thing of all, the first sign of the disaster tourism that was already mushrooming downtown. Across the street an Asian artist sat painting the street scene in streaky black and white; he had scrubbed out two white columns where the towers would have been. “That’s the first thing I’ve seen that’s made me feel any better,” Ana said. We thanked him, but he shrugged blankly, still in shock I supposed. On the Friday, the clampdown. I watched the Mayor and Police Chief hold a press conference in which they angrily told the stream of volunteers to “ground zero” that they weren’t needed. “We can handle this ourselves. We thank you. But we don’t need your help,” Commissioner Kerik said. After the free-for-all of the first couple of days, with its amazing spontaneities and common gestures of goodwill, the clampdown was going into effect. I decided to go down to Canal Street and see if it was true that no one was welcome anymore. So many paths through the city were blocked now. “Lock down, frozen zone, war zone, the site, combat zone, ground zero, state troopers, secured perimeter, national guard, humvees, family center”: a disturbing new vocabulary that seemed to stamp the logic of Giuliani’s sanitized and over-policed Manhattan onto the wounded hulk of the city. The Mayor had been magnificent in the heat of the crisis; Churchillian, many were saying—and indeed, Giuliani quickly appeared on the cover of Cigar Afficionado, complete with wing collar and the misquotation from Kipling, “Captain Courageous.” Churchill had not believed in peacetime politics either, and he never got over losing his empire. Now the regime of command and control over New York’s citizens and its economy was being stabilized and reimposed. The sealed-off, disfigured, and newly militarized spaces of the New York through which I have always loved to wander at all hours seemed to have been put beyond reach for the duration. And, in the new post-“9/11” post-history, the duration could last forever. The violence of the attacks seemed to have elicited a heavy-handed official reaction that sought to contain and constrict the best qualities of New York. I felt more anger at the clampdown than I did at the demolition of the towers. I knew this was unreasonable, but I feared the reaction, the spread of the racial harassment and racial profiling that I had already heard of from my students in New Jersey. This militarizing of the urban landscape seemed to negate the sprawling, freewheeling, boundless largesse and tolerance on which New York had complacently claimed a monopoly. For many the towers stood for that as well, not just as the monumental outposts of global finance that had been attacked. Could the American flag mean something different? For a few days, perhaps—on the helmets of firemen and construction workers. But not for long. On the Saturday, I found an unmanned barricade way east along Canal Street and rode my bike past throngs of Chinatown residents, by the Federal jail block where prisoners from the first World Trade Center bombing were still being held. I headed south and west towards Tribeca; below the barricades in the frozen zone, you could roam freely, the cops and soldiers assuming you belonged there. I felt uneasy, doubting my own motives for being there, feeling the blood drain from my head in the same numbing shock I’d felt every time I headed downtown towards the site. I looped towards Greenwich Avenue, passing an abandoned bank full of emergency supplies and boxes of protective masks. Crushed cars still smeared with pulverized concrete and encrusted with paperwork strewn by the blast sat on the street near the disabled telephone exchange. On one side of the avenue stood a horde of onlookers, on the other television crews, all looking two blocks south towards a colossal pile of twisted and smoking steel, seven stories high. We were told to stay off the street by long-suffering national guardsmen and women with southern accents, kids. Nothing happening, just the aftermath. The TV crews were interviewing worn-out, dust-covered volunteers and firemen who sat quietly leaning against the railings of a park filled with scraps of paper. Out on the West Side highway, a high-tech truck was offering free cellular phone calls. The six lanes by the river were full of construction machinery and military vehicles. Ambulances rolled slowly uptown, bodies inside? I locked my bike redundantly to a lamppost and crossed under the hostile gaze of plainclothes police to another media encampment. On the path by the river, two camera crews were complaining bitterly in the heat. “After five days of this I’ve had enough.” They weren’t talking about the trauma, bodies, or the wreckage, but censorship. “Any blue light special gets to roll right down there, but they see your press pass and it’s get outta here. I’ve had enough.” I fronted out the surly cops and ducked under the tape onto the path, walking onto a Pier on which we’d spent many lazy afternoons watching the river at sunset. Dust everywhere, police boats docked and waiting, a crane ominously dredging mud into a barge. I walked back past the camera operators onto the highway and walked up to an interview in process. Perfectly composed, a fire chief and his crew from some small town in upstate New York were politely declining to give details about what they’d seen at “ground zero.” The men’s faces were dust streaked, their eyes slightly dazed with the shock of a horror previously unimaginable to most Americans. They were here to help the best they could, now they’d done as much as anyone could. “It’s time for us to go home.” The chief was eloquent, almost rehearsed in his precision. It was like a Magnum press photo. But he was refusing to cooperate with the media’s obsessive emotionalism. I walked down the highway, joining construction workers, volunteers, police, and firemen in their hundreds at Chambers Street. No one paid me any attention; it was absurd. I joined several other watchers on the stairs by Stuyvesant High School, which was now the headquarters for the recovery crews. Just two or three blocks away, the huge jagged teeth of the towers’ beautiful tracery lurched out onto the highway above huge mounds of debris. The TV images of the shattered scene made sense as I placed them into what was left of a familiar Sunday afternoon geography of bike rides and walks by the river, picnics in the park lying on the grass and gazing up at the infinite solidity of the towers. Demolished. It was breathtaking. If “they” could do that, they could do anything. Across the street at tables military policeman were checking credentials of the milling volunteers and issuing the pink and orange tags that gave access to ground zero. Without warning, there was a sudden stampede running full pelt up from the disaster site, men and women in fatigues, burly construction workers, firemen in bunker gear. I ran a few yards then stopped. Other people milled around idly, ignoring the panic, smoking and talking in low voices. It was a mainly white, blue-collar scene. All these men wearing flags and carrying crowbars and flashlights. In their company, the intolerance and rage I associated with flags and construction sites was nowhere to be seen. They were dealing with a torn and twisted otherness that dwarfed machismo or bigotry. I talked to a moustachioed, pony-tailed construction worker who’d hitched a ride from the mid-west to “come and help out.” He was staying at the Y, he said, it was kind of rough. “Have you been down there?” he asked, pointing towards the wreckage. “You’re British, you weren’t in World War Two were you?” I replied in the negative. “It’s worse ’n that. I went down last night and you can’t imagine it. You don’t want to see it if you don’t have to.” Did I know any welcoming ladies? he asked. The Y was kind of tough. When I saw TV images of President Bush speaking to the recovery crews and steelworkers at “ground zero” a couple of days later, shouting through a bullhorn to chants of “USA, USA” I knew nothing had changed. New York’s suffering was subject to a second hijacking by the brokers of national unity. New York had never been America, and now its terrible human loss and its great humanity were redesignated in the name of the nation, of the coming war. The signs without a referent were being forcibly appropriated, locked into an impoverished patriotic framework, interpreted for “us” by a compliant media and an opportunistic regime eager to reign in civil liberties, to unloose its war machine and tighten its grip on the Muslim world. That day, drawn to the river again, I had watched F18 fighter jets flying patterns over Manhattan as Bush’s helicopters came in across the river. Otherwise empty of air traffic, “our” skies were being torn up by the military jets: it was somehow the worst sight yet, worse than the wreckage or the bands of disaster tourists on Canal Street, a sign of further violence yet to come. There was a carrier out there beyond New York harbor, there to protect us: the bruising, blustering city once open to all comers. That felt worst of all. In the intervening weeks, we have seen other, more unstable ways of interpreting the signs of September 11 and its aftermath. Many have circulated on the Internet, past the blockages and blockades placed on urban spaces and intellectual life. Karl-Heinz Stockhausen’s work was banished (at least temporarily) from the canon of avant-garde electronic music when he described the attack on las torres gemelas as akin to a work of art. If Jacques Derrida had described it as an act of deconstruction (turning technological modernity literally in on itself), or Jean Baudrillard had announced that the event was so thick with mediation it had not truly taken place, something similar would have happened to them (and still may). This is because, as Don DeLillo so eloquently put it in implicit reaction to the plaintive cry “Why do they hate us?”: “it is the power of American culture to penetrate every wall, home, life and mind”—whether via military action or cultural iconography. All these positions are correct, however grisly and annoying they may be. What GK Chesterton called the “flints and tiles” of nineteenth-century European urban existence were rent asunder like so many victims of high-altitude US bombing raids. As a First-World disaster, it became knowable as the first-ever US “ground zero” such precisely through the high premium immediately set on the lives of Manhattan residents and the rarefied discussion of how to commemorate the high-altitude towers. When, a few weeks later, an American Airlines plane crashed on take-off from Queens, that borough was left open to all comers. Manhattan was locked down, flown over by “friendly” bombers. In stark contrast to the open if desperate faces on the street of 11 September, people went about their business with heads bowed even lower than is customary. Contradictory deconstructions and valuations of Manhattan lives mean that September 11 will live in infamy and hyper-knowability. The vengeful United States government and population continue on their way. Local residents must ponder insurance claims, real-estate values, children’s terrors, and their own roles in something beyond their ken. New York had been forced beyond being the center of the financial world. It had become a military target, a place that was receiving as well as dispatching the slings and arrows of global fortune. Citation reference for this article MLA Style Deer, Patrick and Miller, Toby. "A Day That Will Live In … ?" M/C: A Journal of Media and Culture 5.1 (2002). [your date of access] < http://www.media-culture.org.au/0203/adaythat.php>. Chicago Style Deer, Patrick and Miller, Toby, "A Day That Will Live In … ?" M/C: A Journal of Media and Culture 5, no. 1 (2002), < http://www.media-culture.org.au/0203/adaythat.php> ([your date of access]). APA Style Deer, Patrick and Miller, Toby. (2002) A Day That Will Live In … ?. M/C: A Journal of Media and Culture 5(1). < http://www.media-culture.org.au/0203/adaythat.php> ([your date of access]).