Bricks made of coal fly-ash and slag, cured in the open air

Volume mass, compressive strength, water uptake and water absorption of pressed test samples made of a mixture of coal fly-ash, slag and sodium silicate solution (water-glass) were determined. It was found that such mixtures can solidify in the open air and form water-stable materials. The composition and structure of new formations for the binder and cured material itself were established using X-ray diffraction and a scanning electron microscope. The material has a high water uptake, which may be reduced using a number of different methods, the best of which is short-term impregnation with a hydrophobic material of the siloxane group. The water uptake and water absorption of compressed samples impregnated with such materials are similar to those of comparable building materials, such as lime-sand bricks, clay bricks or concrete blocks.     

Feasibility study of using brick made from municipal solid waste incinerator fly ash slag

This study deals with the effect of MSWI slag on fired clay bricks. Brick samples were heated to temperatures which varied from 800 to 1,000 degrees C for 6h, with a heating rate of 10 degrees C/min. The material properties of the resultant material then determined, including speciation variation, loss on ignition, shrinkage, bulk density, 24-h absorption rate and compressive strength. Toxicity Characteristic Leaching Procedure tests were also conducted. The results indicate that the heavy metal concentrations in the leachates met the current regulatory thresholds. Increasing the amount of MSWI slag resulted in a decrease in the water absorption rate and an increase in the compressive strength of the MSWI-slag bricks. The 24-h absorption rate and compressive strength of the MSWI-slag brick made from samples containing slag sintered at 1,000 degrees C all met the Chinese National Standard (CNS) building requirements for second-class brick. The addition of MSWI slag to the mixture reduced the degree of firing shrinkage. This indicates that MSWI slag is indeed suitable for the partial replacement of clay in bricks.     

New Approach for the Application of Functional Ceramic Material in Carbon Bonded Doloma Refractories to Reduce Emissions

Doloma carbon bricks with graphite contents of approximately 2 wt% are widely used in the production of stainless steels in argon oxygen decarburisation (AOD) or in vacuum oxygen decarburisation (VOD) vessels as lining material. The application of doloma refractories is connected with metallurgical benefits such as high oxidic stability of its oxides, and the ability to bond sulphur from the hot metal. The production and application of carbon bonded refractories is linked with environmental harmful emissions in the broadest sense. Amongst the aspect of environmental friendly refractory systems this work has observed and shown the interaction of functional ceramic material TiO₂ with the organic binder system. In the centre of this work is the aspect of increased residual carbon content of the binder resin due to TiO₂ addition. The increased residual carbon content of the binder resin connected with improved mechanical, physical and thermomechanical properties due to sub‐micro scaled TiO₂ addition offers the feasibility to reduce the total carbon content without downgrading the brick properties. This aspect has not been observed yet and is of high interest with respect to reduced emissions and environmental friendly refractories. Previous works have investigated the influence of TiO₂ on other carbon bonded refractory systems such as alumina carbon and magnesia carbon. As illustrated in this work and previous work, TiO₂ is working completely different in the Doloma Carbon system from other systems.     

Mechanical and cementitious characteristics of ground granulated blast furnace slag and basic oxygen furnace slag blended mortar

Reusing waste materials and reducing carbon emissions are crucial environmental concerns. Ground granulated basic oxygen furnace slag (GGBOS) and ground granulated blast furnace slag (GGBS) are the by-products of the steel industry and has positive effects on the environment because it reduces the problems associated waste disposal. This study reused these two products to completely replace cementitious materials, thus contributing to waste recycling, reducing the production demand for cement, and mitigating carbon emissions. Twelve mixture proportions were designed in this study, including an ordinary Portland mortar (OPM) as the control group and 11 steel/iron slag blended mortar (SISBM) experimental groups for the mechanical and cementitious characteristic experiments. The optimal mixing ratio for SISBM compressive strength ranged from GGBOS (steel slag): GGBS (iron slag) = 3:7 to 5:5 (by weight). At the age of 91 days, the compressive strength of SISBM reached 80–90% compared with that of the control group. Based on the pH values, free-CaO, and microanalysis results, the cementitious characteristics were mainly generated because the GGBOS increased the free-CaO or Ca(OH)₂ concentrations in the SISBM curing water and provided alkaline environments for Ca(OH)₂ to engage in the pozzolanic reaction with the SiO₂ and Al₂O₃ in GGBS, forming crystals such as calcium aluminum silicate hydrate, (C–A–S–H), calcium silicate hydrate (C–S–H), and calcium–magnesium–alumina–silicate (C–M–A–S), which generated strength and strengthened microstructure.     

压蒸条件下钢渣的碳化过程

将钢渣压制成一定形状的试块,分别在60℃、90℃及120℃下采用CO_2对试块进行了碳化处理。对碳化后试块的质量、体积、抗压强度的变化进行了测试。采用X射线能谱仪(XRD)、热重-差热分析仪(TG-DSC)分析了碳化过程中的物相变化。用扫描电子显微镜(SEM)观察了碳化后产物的微观形貌。研究结果表明,在60℃、90℃、120℃碳化温度下碳化7d后,试块的质量分别增加15.30%、17.48%、23.84%;试块的体积分别增加5.9%、6.5%、11.44%;试块的抗压强度分别达到32.87 MPa、39.62 MPa、42.38 MPa。钢渣碳化后产物主要为CaCO_3。从碳化后试块的力学强度和节能两方面综合考虑,碳化的最佳温度为90℃。     

The legacy of monazite processing in Brazil

The exploitation of natural resources containing naturally occurring radionuclides may lead to enhanced levels of radioactive isotope and enhanced potential for exposure to naturally occurring radionuclides in products, by-products, residues or wastes. Such resources include, for instance, monazite, the processing of which, in Brazil, generated a great amount of radioactive residues, being stored in buried concrete tanks, in temporary storage buildings and in sealed trenches. In addition, during the 1980s there were no radiological protection rules concerning the storage and transportation of these kinds of residues. Mineral radioactive residues were used as landfills and the residues of chemical processes contaminated floors and buildings. The decommissioning process and cleaning of old plants have generated tons of wastes that has been added to previously produced wastes. This paper reports and discusses the cycle of monazite in Brazil and its consequences in terms of site remediation and amount of wastes and residues generated and stored.     

钢渣细度和掺量对钢渣复合水泥力学性能的影响

为找出在钢渣复合水泥中钢渣的最佳细度和最佳掺量,从钢渣的粉磨时间、掺量、不同助磨剂的作用和水泥配比等方面研究钢渣细度及掺量对复合水泥力学性能的影响,分析各个影响因素的作用。结果表明,随着磨细钢渣粒度的减小,钢渣复合水泥的抗折、抗压强度会有不同程度的提高;磨细钢渣的掺量为10%和20%时,钢渣复合水泥的力学性能较好,抗折、抗压强度甚至超过纯水泥;当掺量为30%和40%时,复合水泥力学强度下降幅度较大,3 d抗折强度不符合国家标准规定。     

Binding properties of ferromagnesian slags after mechanical activation with alkaline-earth carbonates

We have studied the feasibility of improving the reactivity of ferromagnesian slag through the mechanical activation of the slag with small additions of carbonate minerals in a centrifugal planetary mill. The results demonstrate that, like in the case of the mechanical activation of the slag in a carbon dioxide atmosphere, the process leads to a similar carbonization product, which is considerably more capable of hydraulic hardening than is the slag mechanically activated in air. The highest strength is offered by slag-carbonate materials containing 0.25–1 wt % carbonate (in terms of CO₂).     

钢渣超微粉/橡胶复合材料的性能及补强-阻燃机制

以磁选热闷渣、未磁选热闷渣、电炉渣和风淬渣作为研究对象,以乙二醇、三乙醇胺和无水乙醇制备钢渣助磨剂,钢渣助磨剂与钢渣进行复合获得钢渣超微粉。将钢渣超微粉与炭黑N220、促进剂、硫磺、 ZnO、硬脂酸、天然橡胶进行复合,制备钢渣超微粉/橡胶复合材料。研究钢渣种类和钢渣助磨剂用量对钢渣超微粉/橡胶复合材料力学性能和阻燃性能的影响。利用XRF、 XRD、 LPSA和FTIR对化学成分、矿物组成、粒度分布和组成结构进行测试。结果表明,以电炉渣制备的钢渣超微粉/橡胶复合材料的力学性能最佳,以磁选热闷渣或未磁选热闷渣制备的钢渣超微粉/橡胶复合材料的阻燃性能最佳。钢渣助磨剂可以减小钢渣超微粉的粒度尺寸,改善钢渣超微粉的粒度分布均匀程度。随着钢渣助磨剂用量的增加,钢渣超微粉的粒度分布均匀程度改善,钢渣超微粉/橡胶复合材料的力学性能提高,阻燃性能降低。     

Steel slag waste combined with melamine pyrophosphate as a flame retardant for rigid polyurethane foams

To explore the potential application of industrial waste, steel slag powder in combination with melamine pyrophosphate (MPP) was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The incorporation of steel slag slightly reduced the thermal conductivity of the resulting flame-retardant RPUF samples. The addition of MPP and/or steel slag did not significantly alter the thermal stability in terms of T_-10% and T_max but did obviously increase the T_-50% value, suggesting the improved thermal resistance of the residues. The coaddition of MPP and steel slag into RPUF resulted in higher LOI values and lower peak heat release rates than the samples incorporating either MPP or steel slag alone. The superior flame retardancy could be attributed to MPP promoting char formation, which then acted as a barrier at the beginning of RPUF thermal decomposition; simultaneously, the thermally stable inorganics in the steel slag powder strengthened the thermal resistance of this char layer.     

Using mathematical methods for designing optimal mixtures for building bricks prepared by solid industrial waste

This study evaluates the use of solid industrial waste generated by a water treatment plant (WTP) at a pulp mill in Brazil for manufacturing building bricks. The sludge from the WTP was mixed with three different wastes generated by the same factory (dregs, grits, and lime mud) and other wastes generated from crushing and grinding granite rock (granite fines). Mathematical and statistical methods are proposed for designing mixtures that satisfy the material properties for ceramic processing and the mechanical properties for the end product. A method for solving a linear system of equations using fewer equations than variables was required, as the number of materials exceeded the number of reference grain size distributions. This type of system is generally compatible and indeterminate. To obtain feasible solutions, a combination-of-variables method is proposed to optimize the mixture design. The formulation of the mixtures was based on the grain size distribution of the residues and the proportions of calcium, sodium, and potassium oxides in the mixtures. The nonparametric Kruskal–Wallis test and the median test were applied for all mixtures, followed by a multiple comparison test of classes. The mechanical properties of the specimens were evaluated after drying (linear shrinkage and flexural strength) and firing (ignition loss, linear shrinkage, and flexural strength) according to the Brazilian Association of Technical Standards and Brazilian Standards for red ceramics.     

Unusual water transport properties of some traditional Scottish shale bricks

Sorptivity, porosity and pore size distribution have been measured for five types of pressed fired-clay bricks recovered from a Second World War airfield in East Lothian, Scotland. It was found that the bricks, all manufactured locally from colliery shale, had similar porosities but significantly different compositions, leading to differences in pore structure and transport properties. Unusually high concentrations of organic carbon were found by analysis. In imbibition tests using water and n-decane, capillary absorption generally did not scale with time^1/2, indicating material non-uniformity in the flow direction. A sharp front n-layer model was used to estimate the variation of sorptivity and permeability in drilled cores taken through bed and stretcher faces. A surface skin of lower sorptivity was found in some materials. This is attributed to compression of the green clay in the brick mould during manufacture. Comparison of water and decane imbibition showed that water sorptivity is reduced throughout by partial wettability. This hydrophobicity of these shale bricks is tentatively related to their high organic carbon content, which is incompletely burned out during firing. We show how the partial wettability may be expressed in terms of a wetting index derived from imbibition data.     

Long-term progressive deterioration following fire exposure of OPC versus slag blended cement pastes

The normal practice of repairing fire-damaged concrete structures is to remove the visibly damaged portions and restore them with new concrete. However, little attention has been given to the long-term performance of fire exposed concrete which is not removed from the structure. This paper addresses this issue. Ordinary Portland cement (OPC) pastes, when exposed to a critical temperature of 400°C, undergo complete breakdown. This behaviour was attributed to the dehydration of Ca(OH)₂, followed by the expansive rehydration of CaO. In contrast, partial replacement of the OPC binder with slag, had a beneficial effect in the mechanical properties of the paste after exposure to high temperatures, as slag significantly reduces the amount of available Ca(OH)₂ in the cement paste. The present work provides new data regarding the long-term (after the exposure event) effect of CaO rehydration in the OPC and OPC/slag pastes. After 1 year the ongoing effect of the CaO rehydration was severe in the OPC paste while OPC/slag blends were not affected by rehydration. Compressive strength and thermogravimetric results are presented to explain this behaviour.     

Briques silico-calcaires autoclavées: influence de l’addition de laitier de haut fourneau sur la formation des phases

The mechanical properties of sand-lime bricks produced by autoclaving under different conditions and incorporation of granulated slag have been investigated previously. In this study, the relationship is established between the structure, the phases formed and the strength. Based lime and granulated slag a new binder is developed. This is cured at saturated vapour pressures of 1.0 and 1.8 MPa. The results showed a decrease in compressive strength due to the substitution. The microstructure analysis showed that reaction products consist mainly of 11 Å tobermorite and xonotlite. Also, when increasing the autoclave temperature, it results in an increase in xonotlite relative to tobermorite. The X-ray diffractions of these phases are very low, hardly visible; they are masked by the presence of quartz. Their intensities increase with the presence of slag. The slag seems more reactive with lime than quartz. Observations with the scanning electron microscope allow better to appreciate these phases. By its composition to amorphous structure, the granulated slag does not release new distinct phases of hydrates.     

Investigation of C/Si3N4 Nanocomposites

Nanocrystalline carbon black and graphite micrograins have been added to silicon nitride starting powder and sintering additives (Al₂O₃ and Y₂O₃). These mixtures were mechanochemically activated several hours in a planetary type alumina ball‐mill in order to achieve a homogenous mass. As an alternative to nano‐ and micrograins, carbon fibres have been added to carbon free silicon nitride batches. Sinter‐HIP has been applied to rectangular bars which were earlier dry pressed. Structural and morphological analysis were performed on as‐prepared samples. Bending strength and elastic modulus have been found to be influenced by amount of carbon black and graphite introduced in silicon nitride matrix.     

Innovative method for removing bromine in waste printed circuit boards: Ultrafine milling and porous media loaded debromination agent

Resin is the main harmful substance in waste printed circuit boards (WPCBs) due to the presence of harmful bromine. In this study, the methods of ultrafine milling of resin and loading debromination agent on porous gasification slag were proposed to improve the debromination effect. The morphology, composition and phase of the gasification slag and resin were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results show that the residual carbon in the gasification slag has porous structure, which contributes to the loading of debromination agent. The specific surface area and porosity of gasification slag before and after acid treatment were analyzed by BET. Using the porous properties of gasification slag, different debromination agents were attached to prepare efficient debromination agents, which were adopted for thermal debromination of resin in WPCBs. Subsequently, ICP-MS was used to determine the content of bromine in pyrolysis residue. The results show that when FeCl₂/FeCl₃ was used as the debromination agent, the debromination efficiency was only 67.19% and 58.29%, while using gasification slag-FeCl₂/FeCl₃ composite, the debromination efficiency can be increased to 81.63% and 76.25%. Therefore, the cooperative treatment can realize the resource utilization of the two wastes.     

A novel fabrication method for TiC–Al2O3–Fe functional material under centrifugal acceleration

Compacted powders of titanium (Ti) and carbon (C) in form of pellets were exposed to a massive amount of heat generated from the thermite reaction of Fe₂O₃ and Al in a graphite–steel tube mounted in a developed centrifugal accelerator machine. The centrifugal force facilitated the formation of multi-component products during the process. Titanium carbide (TiC) product is joined to an Al₂O₃–Fe layer, which are the products of the thermite reaction. The existence of centrifugal acceleration had a significant effect on both metallurgical alloying and mechanical interlocking between different layers of the sample to form a functional material. A mathematical model developed for this experiment to describe the speed rate of iron infiltration inside the TiC product as well as viscosity rate variation was presented. The composition, microstructure and mechanical properties confirmed the model.     

Experimental assessment of flue gas desulfurization residues and basic oxygen furnace slag on fatigue and moisture resistance of HMA

Basic oxygen furnace (BOF) slag and flue gas desulfurization (FGD) residues both are industrial wastes. Research on using BOF slag as a novel aggregate and FGD residues as a filler in road construction has benefits both in environment and economics. The main objective of this research was to evaluate the effect of FGD residues and BOF slag on the fatigue performance and moisture resistance of asphalt mixtures. The fatigue performance of asphalt mixture was conducted by means of indirect tensile fatigue test. Stress loading control mode, with four stress levels (300, 400, 500 and 600 kPa), was used in this research. Statistic t‐test was adopted, and it had approved the positive effect of BOF slag and FGD residues on the fatigue lives of asphalt mixture. Moisture resistance of asphalt mixture was investigated by retained Marshall stability test and tensile strength ratio test. Research results indicate that BOF slag and FGD residues can improve the fatigue and moisture resistance, when the BOF slag and FGD residues based asphalt mixture was designed properly.     

Effect of PCs superplasticizers on the rheological properties and hydration process of slag-blended cement pastes

The effect of polycarboxylate (PC) superplasticizers with different structure on the rheological properties and hydration process of slag-blended cement pastes with a slag content between 0 and 75% has been studied. Fluidizing properties of PCs admixtures are significantly higher in slag-blended cement with respect to non-blended Portland cement. Also, it has been observed that the rise of the fluidity induced by the PCs on the cement pastes increases with the slag content. This effect is mainly attributed to a decrease in the amount of C₃A available to adsorb and consume admixture to form an organo-mineral phase. Consequently, the PC admixtures are absorbed onto the silicate phases of the clinker and onto the slag particles, inducing a repulsion and the concomitant reduction in yield stress despite a reduction in the zeta potential. The rheological results allow us to conclude that the highest increase of the fluidity is caused by the admixtures with highest molecular weight due to the higher steric repulsion induced. As a consequence of the adsorption of the PCs, a delay of the hydration process of the pastes has been observed.     

纤维/混杂纤维-矿渣地质聚合物复合材料的弯曲强度与弯曲韧性

碱激发矿渣地质聚合物存在脆性大、韧性差、易开裂等缺陷。利用纤维/混杂纤维对矿渣地质聚合物进行改性,以纤维-矿渣地质聚合物复合材料的弯曲强度与弯曲韧性作为考察指标,分析了3种单一纤维及2种混杂纤维对矿渣地质聚合物的增强与增韧效果。研究结果表明,碳纤维增强效果优于钢纤维、玄武岩纤维,钢纤维增韧效果优于碳纤维、玄武岩纤维,而玄武岩纤维增强及增韧效果相对较差;碳纤维与钢纤维混杂,可充分发挥碳纤维的增强效应和钢纤维的增韧效应,适当掺量下混杂纤维较单一纤维具有更好的增强与增韧效果;纤维与浆料的容重差对矿渣地质聚合物硬化体的均质性具有重要影响,碳纤维与钢纤维混杂可显著降低不同加载方向下矿渣地质聚合物弯曲强度与弯曲韧性的离散性。