Alkali-silica reactions of mortars produced by using waste glass as fine aggregate and admixtures such as fly ash and Li2CO3

Use of waste glass or glass cullet (GC) as concrete aggregate is becoming more widespread each day because of the increase in resource efficiency. Recycling of wastes is very important for sustainable development. When glass is used as aggregate in concrete or mortar, expansions and internal stresses occur due to an alkali-silica reaction (ASR). Furthermore, rapid loss in durability is generally observed due to extreme crack formation and an increase in permeability. It is necessary to use some kind of chemical or mineral admixture to reduce crack formation. In this study, mortar bars are produced by using three different colors of glass in four different quantities as fine aggregate by weight, and the effects of these glass aggregates on ASR are investigated, corresponding to ASTM C 1260. Additionally, in order to reduce the expansions of mortars, 10% and 20% fly ash (FA) as mineral admixture and 1% and 2% Li(2)CO(3) as chemical admixture are incorporated by weight in the cement and their effects on expansion are examined. It is observed that among white (WG), green (GG) and brown glass (BG) aggregates, WG aggregate causes the greatest expansion. In addition, expansion increases with an increase in amount of glass. According to the test results, it is seen that over 20% FA and 2% Li(2)CO(3) replacements are required to produce mortars which have expansion values below the 0.2% critical value when exposed to ASR. However, usages of these admixtures reduce expansions occurring because of ASR.     

Use of Pb blast furnace slag as a partial substitute for fine aggregate in cement mortar

The technical properties of cement mortars containing natural fine aggregate that is replaced by lead blast furnace slag at 25 and 35% level were assessed at fixed water-to-cement (W/C) ratio and at fixed flow table value. The leachabilities of some toxic elements from the cement mortars were also assessed to test the environmental suitability of the slag for use in preparation of cement mortar. At fixed W/C ratio, the strength of the mortar decreased with increase of the slag content. On the other hand, at fixed consistency, strength increased with increasing slag content in the mortar composition. The concentrations of some toxic elements in the leachates collected from the mortars containing slag were slightly higher than for the control mortar, but the concentrations in the leachates remained within the regulatory limits for recycling in construction applications. For most elements, leaching from a mortar containing 35% of slag was similar to that from a mortar containing 25% of slag. Therefore, 35% of natural sand can be beneficially replaced with Pb slag to produce cement mortar without affecting the mechanical and leaching properties studied in this work.     

Evaluating the strength development of mortar using clinker fine aggregate with a combination of fly ash and its inhibitory effects on alkali–silica reaction and delayed ettringite formation

The aggregate composed of cement clinker, an intermediate cement product, improves strength development and mass transfer resistance of concrete. Fly ash (FA) is a supplementary cementitious material that can be substituted by cement. This study investigated the strength development of highly FA-substituted mortar mixed with cement clinker fine aggregate (CL) and tested its inhibitory effect against the alkali–silica reaction (ASR). In addition to these, this study provides the testing results of evaluating the effects of using cement clinker fine aggregate on delayed ettringite formation (DEF), which can be problematic for precast concrete products. The study results revealed that at 91 days of age, in the case of 80% replacement ratio of fly ash to cement, using CL exhibited similar strength development as mortar with limestone fine aggregate and no FA substitution. Furthermore, mortars with 70% and 80% FA substitution did not exhibit clear ASR-induced expansion even at 182 days of age. Lastly, mortar using clinker fine aggregate could suppress DEF-induced expansion at 182 days of age, which was similar to the effect obtained using FA. These results can promote the utilization of CL resources for concrete and using clinker as fine aggregate in precast concrete products.

     

石灰石-石膏法烟气脱硫系统处理废稀硫酸

采用石灰石-石膏法脱硫装置处理废稀硫酸.研究了石灰石浆液和废稀硫酸的不同投加顺序以及不同反应晶种(石膏浆液、石膏稀浆液)对所得石膏晶粒形态和抽滤物含水率的影响.试验结果表明:与废稀硫酸加入石灰石浆液的方式相比,石灰石浆液加入废稀硫酸的方式更利于石膏结晶,晶粒更大,所得石膏抽滤物含水率更低;以石膏浆液和石膏稀浆液作为反应...     

Use of FGD gypsum in fire resistant panels

Gypsum from power plant flue gas desulphurization units (FGD gypsum) is a combustion by-product produced in high quantities. In this paper, gypsum panels composed of 100% FGD gypsum from two power plants have been subjected to different physico-chemical (density, pH, humidity), mechanical (flexural and compressive strength, surface hardness, impact resistance), fire resistance and environmental tests (leaching and radioactivity). The results obtained have been compared with the requirements established in some European standards for commercial gypsum and other standards for similar products. In addition, the panels manufactured have been compared with commercial gypsum panels in order to determine the recycling possibilities of this kind of material in this application.     

Effect of addition diatomite powder on mechanical strength,elevated temperature resistance and microstructural properties of industrial waste fly ash-based geopolymer

This study examines the use of fly ash, a thermal power plant waste, and the effect of diatomite, a fossil algae type, on waste-based geopolymers in the production of sustainable geopolymer binders. The effects of 1%, 2%, 3%, 4% and, 5% diatomite substitution on waste-based mortars were investigated. Mortars containing 10% and 12% Na⁺ by weight based on the binder material were cured at 75 °C for 48 h. The flexural and compressive strength, abrasion resistance, determination of ultrasonic pulse velocity, and resistance to high temperatures of geopolymer mortar samples were investigated. In addition, FESEM images, EDX and XRD analyses of geopolymer mortar samples were made, and their microstructures were examined. 2% diatomite substitution increased flexural and compressive strength. In parallel with this situation, it was concluded that the abrasion resistance and ultrasonic pulse velocity of the geopolymer mortar with 2% diatomite substituted increased. In addition, it has been shown in FESEM images that the microstructure has a denser morphology. All geopolymer mortars lost strength after the high temperatures of 300 °C, 600 °C and 900 °C. As a result, it was concluded that diatomite containing highly reactive silica can be used in geopolymer systems.

     

烟气脱硫石膏催化还原为硫化钙的研究

采用Fe-Ni复合催化剂,在温度650℃条件下即可将烟气脱硫石膏催化还原为硫化钙,还原率达95%以上。研究了反应温度、催化剂加入量及还原气体含量因素对还原反应的影响。     

Use of flue gas desulphurisation (FGD) waste and rejected fly ash in waste stabilization/solidification systems

Stabilization/solidification (S/S) processes have been used as the final treatment step for hazardous wastes prior to land disposal. Fly ash is a by-product of coal-fired power generation; a significant proportion of this material is low-grade, reject material (rFA) that is unsuitable as a cement replacement due to its high carbon content and large particle size (>45 microm). Flue gas desulphurization (FGD) sludge is a by-product from the air pollution control systems used in coal-fired power plants. The objective of this work was to investigate the performance of S/S waste binder systems containing these two waste materials (rFA and FGD). Strength tests show that cement-based waste forms with rFA and FGD replacement were suitable for disposal in landfills. The addition of an appropriate quantity of Ca(OH)2 and FGD reduces the deleterious effect of heavy metals on strength development. Results of TCLP testing and the progressive TCLP test show that cement-rFA-Ca(OH)2 systems with a range of FGD additions can form an effective S/S binder. The Leachability Index indicates that cement-based waste forms with rFA replacement were effective in reducing the mobility of heavy metals.     

Influence of combustion temperature on the performance of sewage sludge ash as a supplementary cementitious material

The potential for using sewage sludge ash (SSA) as a supplementary cementitious material (SCM) has been investigated. Controlled combustion of sewage sludge collected in Croatia from two wastewater treatment plants produced SSA with different characteristics. These were used to substitute for cement in mortar samples. The chemical composition and physical properties of SSA depend on wastewater composition, the sludge treatment process and the combustion temperature. These factors influence the suitability of SSA to be used as a SCM. For three different combustion temperatures (800, 900 and 1000 °C), it was concluded that properties of fresh mortar were not affected while in the hardened state, the most favorable combustion temperature is 900 °C regarding mechanical properties. Regardless of combustion temperature, for all types of SSA used in mortars as cement replacement (up to 30%), the average decrease in both compressive and flexural strength values was less than 8% for every 10% of added SSA. The results presented indicate that using up to 20% replacement of cement by SSA produces mortars that meet the specific technical requirements analyzed in this work.     

Flue gas desulfurization gypsum and coal fly ash as basic components of prefabricated building materials

The manufacture of prefabricated building materials containing binding products such as ettringite (6CaO·Al₂O₃·3SO₃·32H₂O) and calcium silicate hydrate (CSH) can give, in addition to other well-defined industrial activities, the opportunity of using wastes and by-products as raw materials, thus contributing to further saving of natural resources and protection of the environment.Two ternary mixtures, composed by 40% flue gas desulfurization (FGD) gypsum or natural gypsum (as a reference material), 35% calcium hydroxide and 25% coal fly ash, were submitted to laboratory hydrothermal treatments carried out within time and temperature ranges of 2 h–7 days and 55–85 °C, respectively. The formation of (i) ettringite, by hydration of calcium sulfate given by FGD or natural gypsum, alumina of fly ash and part of calcium hydroxide, and (ii) CSH, by hydration of silica contained in fly ash and residual lime, was observed within both the reacting systems. For the FGD gypsum-based mixture, the conversion toward ettringite and CSH was highest at 70 °C and increased with curing time. Some discrepancies in the hydration behavior between the mixtures were ascribed to differences in mineralogical composition between natural and FGD gypsum.     

湿法烟气脱硫石膏制备硫酸铵

采用湿法烟气脱硫石膏为原料,与( NH4)2CO3反应,制备(NH4)2SO4.通过X射线衍射仪表征可知:脱硫石膏的主要成分为CaSO4,反应后CaSO4中的Ca2+大部分以CaCO3形式存在于固体沉淀物中,CaCO3粉末平均粒径为80 nm;而原先CaSO4中的不溶性SO2-4则与NH+4结合生成(NH4)2SO4,...     

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.     

中国燃煤发电厂烟气脱硫技术及应用

我国的能源结构决定了燃煤火力发电在电力供应中的重要地位，其发电产生的SO2是环境污染的主要来源。烟气脱硫技术是控制燃煤工业SO2排放的重要途径，因其脱硫效率高、稳定性较好、成本较低等优点而在工业上得到了广泛的应用。概述了燃煤发电中烟气脱硫技术的最新进展，其中包括烟气脱硫技术的分类，以及几种主要的湿法、干法、半干法烟气脱硫技术的主要特点。对不同的烟气脱硫技术的优缺点也作了简单评述，并对新建电厂脱硫技术的选择进行了讨论。最后结合中国实际，烟气脱硫技术发展和应用中要注意的几个问题进行了讨论。     

耐酸胶泥用于脱硫烟囱防腐的可行性初探

结合一失败案例，探讨了耐酸胶泥内衬用于脱硫烟囱排烟筒防腐的技术可行性。从设计、施工、材料特性等方面进行了分析，得出了耐酸胶泥内衬在脱硫后湿烟囱排烟筒中应慎用的结论。     

FGD系统中吸收塔浆液起泡溢流的原因分析及解决办法

在石灰石-石膏湿法烟气脱硫（FGD）工艺系统中，吸收塔浆液溢流是较为常见的现象，它对FGD系统的稳定运行非常不利。通过分析产生吸收塔浆液溢流的各种原因，提出解决吸收塔浆液溢流的办法，保证脱硫系统的稳定运行。     

A study of disposed fly ash from landfill to replace Portland cement

The landfills of fly ash are the problem of all power plants because this disposed fly ash is not used in any work. This research studies the potential of using disposed fly ashes which have disposal time of 6-24 months from the landfill of Mae Moh power plants in Thailand to replace Portland cement type I. Median particle sizes of disposed fly ashes between 55.4 and 99.3 microm were ground to reduce the sizes to about 7.1-8.4 microm. Both original and ground disposed fly ashes were investigated on physical and chemical properties. Compressive strengths of disposed fly ash mortars were determined when Portland cement type I was replaced by disposed fly ashes at the rate of 10%, 20%, and 30% by weight of cementitious material (Portland cement type I and disposed fly ash). The results presented that most particles of original disposed fly ashes were solid and sphere with some irregular shape while those of ground disposed fly ashes were solid and irregular shape. CaO and LOI contents of disposed fly ashes with different disposal times had high variation. The compressive strengths of original disposed fly ash mortars were low but those of ground disposed fly ash mortars at the age of 7 days were higher than 75% of the standard mortar and increased to be higher than 100% after 60 days. From the results, it could be concluded that ground disposed fly ashes were excellent pozzolanic materials and could be used as a partial replacement of cement in concrete, even though they were exposed to the weather for 24 months.     

烟气脱硫副产物资源化利用现状与发展方向

简述了我国燃煤电厂湿法、半干法烟气脱硫副产物——脱硫石膏、脱硫灰渣的利用现状，针对利用过程中所遇到的问题，提出了烟气脱硫副产物资源化利用的新技术方向，并对新技术的可行性进行了论证。     

Influences of chemical activators on incinerator bottom ash

This research has applied different chemical activators to mechanically and thermally treated fine fraction (<14 mm) of incinerator bottom ash (IBA), in order to investigate the influences of chemical activators on this new pozzolanic material. IBA has been milled and thermally treated at 800 degrees C (TIBA). The TIBA produced was blended with Ca(OH)(2) and evaluated for setting time, reactivity and compressive strength after the addition of 0.0565 mole of Na(2)SO(4), K(2)SO(4), Na(2)CO(3), K(2)CO(3), NaOH, KOH and CaCl(2) into 100g of binder (TIBA+Ca(OH)(2)). The microstructures of activated IBA and hydrated samples have been characterized by X-ray diffraction (XRD) and thermogravimetry (TG) analysis. Thermal treatment is found to produce gehlenite (Ca(2)Al(2)SiO(7)), wollastonite (CaSiO(3)) and mayenite (Ca(12)Al(14)O(33)) phases. The thermally treated IBA samples are significantly more reactive than the milled IBA. The addition of Na(2)CO(3) can increase the compressive strength and calcium hydroxide consumption at 28-day curing ages. However, the addition of Na(2)SO(4), K(2)SO(4), K(2)CO(3), NaOH and KOH reduces the strength and hydration reaction. Moreover, these chemicals produce more porous samples due to increased generation of hydrogen gas. The addition of CaCl(2) has a negative effect on the hydration of TIBA samples. Calcium aluminium oxide carbonate sulphide hydrate (Ca(4)Al(2)O(6)(CO(3))(0.67)(SO(3))(0.33)(H(2)O)(11)) is the main hydration product in the samples with activated IBA, except for the sample containing CaCl(2).     

Reuse of sewage sludge ashes (SSA) in cement mixtures: the effect of SSA on the workability of cement mortars

The influence of sewage sludge ash (SSA) on workability of cement mortars has been studied. The irregular morphology of SSA particles produced a decrease of mortar workability. A nonlinear reduction of workability in mortars containing SSA was observed, but when SSA content in mortars was increased the workability reduction was less significant. A superplasticizer is used in order to compensate the decrease of workability produced by SSA. When SSA sized fractions were used, only significant differences in workability for mortars prepared with high water volumes or with the presence of superplasticizer were observed.     

Reuse of ground waste glass as aggregate for mortars

This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75mum, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100mum thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.