Reuse of waste iron as a partial replacement of sand in concrete

One of the major environmental issues in Iraq is the large quantity of waste iron resulting from the industrial sector which is deposited in domestic waste and in landfills. A series of 109 experiments and 586 tests were carried out in this study to examine the feasibility of reusing this waste iron in concrete. Overall, 130 kg of waste iron were reused to partially replace sand at 10%, 15%, and 20% in a total of 1703 kg concrete mixtures. The tests performed to evaluate waste-iron concrete quality included slump, fresh density, dry density, compressive strength, and flexural strength tests: 115 cubes of concrete were molded for the compressive strength and dry density tests, and 87 prisms were cast for the flexural strength tests. This work applied 3, 7, 14, and 28 days curing ages for the concrete mixes. The results confirm that reuse of solid waste material offers an approach to solving the pollution problems that arise from an accumulation of waste in a production site; in the meantime modified properties are added to the concrete. The results show that the concrete mixes made with waste iron had higher compressive strengths and flexural strengths than the plain concrete mixes.     

Recycling of waste glass as a partial replacement for fine aggregate in concrete

Waste glass creates serious environmental problems, mainly due to the inconsistency of waste glass streams. With increasing environmental pressure to reduce solid waste and to recycle as much as possible, the concrete industry has adopted a number of methods to achieve this goal. The properties of concretes containing waste glass as fine aggregate were investigated in this study. The strength properties and ASR expansion were analyzed in terms of waste glass content. An overall quantity of 80 kg of crushed waste glass was used as a partial replacement for sand at 10%, 15%, and 20% with 900 kg of concrete mixes. The results proved 80% pozzolanic strength activity given by waste glass after 28 days. The flexural strength and compressive strength of specimens with 20% waste glass content were 10.99% and 4.23%, respectively, higher than those of the control specimen at 28 days. The mortar bar tests demonstrated that the finely crushed waste glass helped reduce expansion by 66% as compared with the control mix.     

Use of waste plastic in concrete mixture as aggregate replacement

Industrial activities in Iraq are associated with significant amounts of non-biodegradable solid waste, waste plastic being among the most prominent. This study involved 86 experiments and 254 tests to determine the efficiency of reusing waste plastic in the production of concrete. Thirty kilograms of waste plastic of fabriform shapes was used as a partial replacement for sand by 0%, 10%, 15%, and 20% with 800 kg of concrete mixtures. All of the concrete mixtures were tested at room temperature. These tests include performing slump, fresh density, dry density, compressive strength, flexural strength, and toughness indices. Seventy cubes were molded for compressive strength and dry density tests, and 54 prisms were cast for flexural strength and toughness indices tests. Curing ages of 3, 7, 14, and 28 days for the concrete mixtures were applied in this work. The results proved the arrest of the propagation of micro cracks by introducing waste plastic of fabriform shapes to concrete mixtures. This study insures that reusing waste plastic as a sand-substitution aggregate in concrete gives a good approach to reduce the cost of materials and solve some of the solid waste problems posed by plastics.     

Use of Brazilian sugarcane bagasse ash in concrete as sand replacement

Sugarcane today plays a major role in the worldwide economy, and Brazil is the leading producer of sugar and alcohol, which are important international commodities. The production process generates bagasse as a waste, which is used as fuel to stoke boilers that produce steam for electricity cogeneration. The final product of this burning is residual sugarcane bagasse ash (SBA), which is normally used as fertilizer in sugarcane plantations. Ash stands out among agroindustrial wastes because it results from energy generating processes. Many types of ash do not have hydraulic or pozzolanic reactivity, but can be used in civil construction as inert materials. The present study used ash collected from four sugar mills in the region of São Carlos, SP, Brazil, which is one of the world’s largest producers of sugarcane. The ash samples were subjected to chemical characterization, sieve analysis, determination of specific gravity, X-ray diffraction, scanning electron microscopy, and solubilization and leaching tests. Mortars and concretes with SBA as sand replacement were produced and tests were carried out: compressive strength, tensile strength and elastic modulus. The results indicated that the SBA samples presented physical properties similar to those of natural sand. Several heavy metals were found in the SBA samples, indicating the need to restrict its use as a fertilizer. The mortars produced with SBA in place of sand showed better mechanical results than the reference samples. SBA can be used as a partial substitute of sand in concretes made with cement slag-modified Portland cement.     

Sustainable alkali-activated binders with municipal solid waste incineration ashes as sand or fly ash replacement

The present study investigates the feasibility of using two types of municipality solid wastes incineration ashes, namely, fly ash and bottom ash in the production of sustainable alkali-activated binder. The ashes are collected from the incineration plant and characterized to determine their particle size distribution, specific gravity, chemical composition, and heavy metals content. The ashes are then used as either fly ash or sand replacement with five replacement ratios 0%, 5%, 10%, 15%, and 20% to produce the binder. The produced binder are characterized in terms of strength, workability, density, water absorption, thermal conductivity and stability, chemical composition, and heavy metals content. The results reflect the ability of producing sustainable alkali-activated binder with small dosage of MSWI ashes as either fly ash or sand replacement without negatively affecting its strength, workability, density, and water absorption. The ashes enhance the thermal insulation capability of the binder.

     

Use of waste brick as a partial replacement of cement in mortar

The aim of this study is to investigate the use of waste brick as a partial replacement for cement in the production of cement mortar. Clinker was replaced by waste brick in different proportions (0%, 5%, 10%, 15% and 20%) by weight for cement. The physico-chemical properties of cement at anhydrous state and the hydrated state, thus the mechanical strengths (flexural and compressive strengths after 7, 28 and 90 days) for the mortar were studied. The microstructure of the mortar was investigated using scanning electron microscopy (SEM), the mineralogical composition (mineral phases) of the artificial pozzolan was investigated by the X-ray diffraction (XRD) and the particle size distributions was obtained from laser granulometry (LG) of cements powders used in this study. The results obtained show that the addition of artificial pozzolan improves the grinding time and setting times of the cement, thus the mechanical characteristics of mortar. A substitution of cement by 10% of waste brick increased mechanical strengths of mortar. The results of the investigation confirmed the potential use of this waste material to produce pozzolanic cement.     

Re-usage of waste foundry sand in high-strength concrete

In this study, the potential re-use of waste foundry sand in high-strength concrete production was investigated. The natural fine sand is replaced with waste foundry sand (0%, 5%, 10%, and 15%). The findings from a series of test program has shown reduction in compressive and tensile strengths, and the elasticity modulus which is directly related to waste foundry inclusion in concrete. Nevertheless the concrete with 10% waste foundry sand exhibits almost similar results to that of the control one. The slump and the workability of the fresh concrete decreases with the increase of the waste foundry sand ratio. Although the freezing and thawing significantly reduces the mechanical and physical properties of the concrete. The obtained results satisfies the acceptable limits set by the American Concrete Institute (ACI).     

Evaluation of concrete incorporating bottom ash as a natural aggregates replacement

A study on the incorporation of coal bottom ash from thermoelectric power stations as a substitute material for natural sand in the production of concrete is here presented. The normally coarse, fused, glassy texture of bottom ash makes it an ideal substitute for natural aggregates. The use of bottom ash in concrete presents several technical challenges: the physical and mineralogical characteristics of the bottom ash; the effect on water demand and the participation on cements hydratation. In the production of the concrete, substitutions in volume were used. Two different ways to employ bottom ash were used to make up the mix proportions: one considering the natural humidity present in the porous particles and the other not considering it, seeking to maintain the same strength. These considerations are fundamental given that the process of bottom ash extraction is carried out through moisture. Mechanical tests by compressive strength were performed and the elastic modulus was determined. An analysis of the influence of bottom ash in the formation of pores was carried out through tests for the water loss by air drying and water uptake by capillary absorption. The results show that the higher the bottom ash contents in the concrete, the worse the performance regarding moisture transport. However, for one bottom ash concrete type, the mechanical properties were maintained.     

An investigation of waste foundry sand in asphalt concrete mixtures.

A laboratory study regarding the reuse of waste foundry sand in asphalt concrete production by replacing a certain portion of aggregate with WFS was undertaken. The results showed that replacement of 10% aggregates with waste foundry sand was found to be the most suitable for asphalt concrete mixtures. Furthermore, the chemical and physical properties of waste foundry sand were analysed in the laboratory to determine the potential effect on the environment. The results indicated that the investigated waste foundry sand did not significantly affect the environment around the deposition     

Mechanical and toxicological evaluation of concrete artifacts containing waste foundry sand

The creation of metal parts via casting uses molds that are generally made from sand and phenolic resin. The waste generated after the casting process is called waste foundry sand (WFS). Depending on the mold composition and the casting process, WFS can contain substances that prevent its direct emission to the environment. In Brazil, this waste is classified according to the Standard ABNT NBR 10004:2004 as a waste Class II (Non-Inert). The recycling of this waste is limited because its characteristics change significantly after use. Although the use (or reuse) of this byproduct in civil construction is a technically feasible alternative, its effects must be evaluated, especially from mechanical and environmental points of view. Thus, the objective of this study is to investigate the effect of the use of WFS in the manufacture of cement artifacts, such as masonry blocks for walls, structural masonry blocks, and paving blocks. Blocks containing different concentrations of WFS (up to 75% by weight) were produced and evaluated using compressive strength tests (35 MPa at 28 days) and toxicity tests on Daphnia magna, Allium cepa (onion root), and Eisenia foetida (earthworm). The results showed that there was not a considerable reduction in the compressive strength, with values of 35 ± 2 MPa at 28 days. The toxicity study with the material obtained from leaching did not significantly interfere with the development of D. magna and E. foetida, but the growth of the A. cepa species was reduced. The study showed that the use of this waste in the production of concrete blocks is feasible from both mechanical and environmental points of view.     

Use of plastic waste (poly-ethylene terephthalate) in asphalt concrete mixture as aggregate replacement.

One of the environmental issues in most regions of Iran is the large number of bottles made from poly-ethylene terephthalate (PET) deposited in domestic wastes and landfills. Due to the high volume of these bottles, more than 1 million m3 landfill space is needed for disposal every year. The purpose of this experimental study was to investigate the possibility of using PET waste in asphalt concrete mixes as aggregate replacement (Plastiphalt) to reduce the environmental effects of PET disposal. For this purpose the mechanical properties of plastiphalt mixes were compared with control samples. This study focused on the parameters of Marshall stability, flow, Marshall quotient (stability-to-flow ratio) and density. The waste PET used in this study was in the form of granules of about 3 mm diameter which would replace (by volume) a portion of the mineral coarse aggregates of an equal size (2.36-4.75 mm). In all prepared mixes the determined 6.6% optimum bitumen content was used. In this investigation, five different percentages of coarse aggregate replacement were used. The results showed that the aggregate replacement of 20% by volume with PET granules would result in a reduction of 2.8% in bulk compacted mix density. The value of flow in the plastiphalt mix was lower than that of the control samples. The results also showed that when PET was used as partial aggregate replacement, the corresponding Marshall stability and Marshall quotient were almost the same as for the control samples. According to most of specification requirement, these results introduce an asphalt mix that has properties that makes it suitable for practical use and furthermore, the recycling of PET for asphalt concrete roads helps alleviate an environmental problem and saves energy.     

Valorization of titanium metal wastes as tanning agent used in leather industry

The development of new tanning agents and new technologies in the leather sector is required to cope with the increasingly higher environmental pressure on the current tanning materials and processes such as tanning with chromium salts. In this paper, the use of titanium wastes (cuttings) resulting from the process of obtaining highly pure titanium (ingots), for the synthesis of new tanning agent and tanning bovine hides with new tanning agent, as alternative to tanning with chromium salts are investigated. For this purpose, Ti waste and Ti-based tanning agent were characterized for metal content by inductively coupled plasma mass spectrometry (ICP-MS) and chemical analysis; the tanned leather (wet white leather) was characterized by Scanning Electron Microscope/Energy Dispersive Using X-ray (Analysis). SEM/EDX analysis for metal content; Differential scanning calorimetric (DSC), Micro-Hot-Table and standard shrinkage temperature showing a hydrothermal stability (ranged from 75.3 to 77 °C) and chemical analysis showing the leather is tanned and can be processed through the subsequent mechanical operations (splitting, shaving). On the other hand, an analysis of major minor trace substances from Ti-end waste (especially vanadium content) in new tanning agent and wet white leather (not detected) and residue stream was performed and showed that leachability of vanadium is acceptable. The results obtained show that new tanning agent obtained from Ti end waste can be used for tanning bovine hides, as eco-friendly alternative for chrome tanning.     

Use of waste rubber as concrete additive.

For resource reutilization, scrap tyres have long been investigated as an additive to concrete to form 'Rubcrete' for various applications and have shown promising results. However, the addition of rubber particles leads to the degradation of physical properties, particularly, the compressive strength of the concrete. In this study, a theoretical model was proposed to shed light on the mechanisms of decrease in compressive strength due to the addition of rubber particles as well as improvement in compressive strength through modification of particle surfaces. The literature suggests that the compressive strength can be improved by soaking the rubber particles in alkaline solution first to increase the inter-phase bonding between the rubber particles and cement. Instead, we discovered that the loss in compressive strength was due to local imperfections in the hydration of cement, induced by the addition of heterogeneous and hydrophobic rubber particles. Microscopic studies showed that the rubber particles disturbed the water transfer to create channels, which were prone to cracking and led to a loss in the compressive strength. Unexpectedly, no cracking was found along the surfaces of the rubber particles, indicating that the bonding strength between the rubber particles and cement phases was not the critical factor in determining the compressive strength. Therefore, a theoretical model was proposed to describe the water transfer in the Rubcrete specimens to explain the experimental data. In the model, the local water available for hydration (Q) is: Q = -A(slv)/6piv, where Q, A(slv), and v are mass flow rate (kg s(-1)), Hamaker constant (J), and dynamic viscosity (m2 s(-1)), respectively. By maximizing the quantity Q and, in turn, the Hamaker constant A(slv), the compressive strength could be improved. The Hamaker constant A(slv) for water film on rubber particle surfaces was smaller than that for the hydrated cement particles; the water transfer rate was lower in the presence of rubber particles because the Hamaker constant A(slv) for water film on rubber particle surfaces was smaller than that on the hydrated cement particles. Thus, the compressive strength of Rubcrete could be improved by increasing the Hamaker constant of the system. This was achieved by increasing the refractive indices of the solids (n(s)). The refractive indices of materials increase with increases in functional groups, such as OH and SH on the surface. The model provided a possible mechanism for the efficacy of treating rubber particles with NaOH in improving the compressive strength. By using NaOH solution treatment, an oxygen-containing OH group was formed on the rubber surface to increase the Hamaker constant of the system, leading to higher compressive strength. Based on this mechanism, a novel method for modification of the rubber particles was also proposed. In this process, the rubber particles were partially oxidized with hot air/steam in a fluidized bed reactor to produce the hydrophilic groups on the surface of the particles. Preliminary results obtained so far are promising in accordance with the theory.     

Finished leather waste chromium acid extraction and anaerobic biodegradation of the products

Due to the amounts of chromium in the leachate resulting from leather leaching tests, chromium sulfate tanned leather wastes are very often considered hazardous wastes. To overcome this problem, one option could be recovering the chromium and, consequently, lowering its content in the leather scrap. With this objective, chromium leather scrap was leached with sulfuric acid solutions at low temperature also aiming at maximizing chromium removal with minimum attack of the leather matrix. The effects of leather scrap dimension, sulfuric acid and sodium sulfate concentration in the solutions, as well as extraction time and temperature on chromium recovery were studied, and, additionally, organic matrix degradation was evaluated. The best conditions found for chromium recovery were leather scrap conditioning using 25 mL of concentrated H₂SO₄/L solution at 293 or 313 K during 3 or 6 days. Under such conditions, 30–60 ± 5% of chromium was recovered and as low as 3–6 ± 1% of the leather total organic carbon (TOC) was dissolved. Using such treatment, the leather scrap area and volume are reduced and the residue is a more brittle material showing enhanced anaerobic biodegradability. Although good recovery results were achieved, due to the fact that the amount of chromium in eluate exceeded the threshold value this waste was still hazardous. Thus, it needs to be methodically washed in order to remove all the chromium de-linked from collagen.     

Transesterification reaction of the fat originated from solid waste of the leather industry

The leather industry is an industry which generates a large amount of solid and liquid wastes. Most of the solid wastes originate from the pre-tanning processes while half of it comes from the fleshing step. Raw fleshing wastes which mainly consist of protein and fat have almost no recovery option and the disposal is costly. This study outlines the possibility of using the fleshing waste as an oil source for transesterification reaction. The effect of oil/alcohol molar ratio, the amount of catalyst and temperature on ester production was individually investigated and optimum reaction conditions were determined. The fuel properties of the ester product were also studied according to the EN 14214 standard. Cold filter plugging point and oxidation stability have to be improved in order to use the ester product as an alternative fuel candidate. Besides, this product can be used as a feedstock in lubricant production or cosmetic industry.     

Utilization of limestone dust waste as filler in natural rubber

The possibility of using limestone dust waste (LDW) as a filler in natural rubber (NR) was investigated. First, the basic properties of LDW were characterized; LDW was then incorporated into NR and the compound properties were determined. Comparison of the reinforcing effect of LDW and other commercial fillers such as light-precipitated calcium carbonate (PCC) and nanoprecipitated calcium carbonate (NPCC) was made. The results revealed that even though the addition of LDW has little effect on compound processability, it has a negative effect on most mechanical properties, e.g., tensile strength, tear strength, and abrasion resistance, of the vulcanizate. Among the three fillers, the degree of reinforcement could be placed in the following order: NPCC > PCC > LDW. Due to their relatively low specific surface area and thus low reinforcement ability, both LDW and PCC can be grouped as nonreinforcing fillers, whereas NPCC, the specific surface area of which is relatively high, could be grouped as a semi-reinforcing filler for rubber.     

铸造废砂/废地膜/粘附土三元复合体系的研究

通过X射线衍射分析、红外光谱分析、热分析、电镜及能谱分析、图像分析,可以判断废旧地膜上粘附土的主要矿物质是结晶二氧化硅（粉粒级石英）,它们与聚合物基废弃物复合材料中作为填料的铸造石英砂的性状类同。废旧地膜可以不经清洗,直接与铸造废砂制备复合材料,这可大大降低复合材料的加工成本。这种复合材料实际上是由基体PE、粘附土中大量的SiO2和铸造石英砂SiO2组成的三元复合体系。     

Sustainability of recycling plastic waste as fibers for concrete: a review

Journal of Material Cycles and Waste Management - Plastic waste management is of global concern while construction industry keeps searching for innovations to become more sustainable. In this...     

An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete

In this work, the utilization of shredded waste Poly-ethylene Terephthalate (PET) bottle granules as a lightweight aggregate in mortar was investigated. Investigation was carried out on two groups of mortar samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionally, blast-furnace slag was also used as the replacement of cement on mass basis at the replacement ratio of 50% to reduce the amount of cement used and provide savings. The water–binder (w/b) ratio and PET–binder (PET/b) ratio used in the mixtures were 0.45 and 0.50, respectively. The size of shredded PET granules used in the preparation of mortar mixtures were between 0 and 4 mm. The results of the laboratory study and testing carried out showed that mortar containing only PET aggregate, mortar containing PET and sand aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category in terms of unit weight and strength properties. Therefore, it was concluded that there is a potential for the use of shredded waste PET granules as aggregate in the production of structural lightweight concrete. The use of shredded waste PET granules due to its low unit weight reduces the unit weight of concrete which results in a reduction in the death weight of a structural concrete member of a building. Reduction in the death weight of a building will help to reduce the seismic risk of the building since the earthquake forces linearly dependant on the dead-weight. Furthermore, it was also concluded that the use of industrial wastes such as PET granules and blast-furnace slag in concrete provides some advantages, i.e., reduction in the use of natural resources, disposal of wastes, prevention of environmental pollution, and energy saving.