Replacement of raw mix in cement production by municipal solid waste incineration ash

The feasibility of municipal solid waste incineration (MSWI) ash utilized as the replacement of raw mix in cement production is investigated. Result shows that sieving, self-grinding, and magnet separation processes are necessary to remove the debris, salt, and metallic contents that existed in the MSWI ash. By using the pretreated MSWI ashes, the produced cement specimens were in compliance with the unconfined compression strength (UCS) standard in Taiwan at small replacement percentage (<5%). When ash replacement percentage is large (more than 10%), the strength development of specimens would be hindered due to the deficient formation of the calcium silicate. Calculation on lime saturation factor (LSF) also shows a descending trend in consequence of the increase in replacement percentage. Thus, compositional effect should be taken into consideration for promoting the calcium silicate formation at the case of large ash replacement. In this research, adjustment of chemical composition was achieved by adding 183 g calcium oxide per kilogram of cement raw mixture with 15% ash replacement. After adjustment, the produced cement could develop seven- and fivefold increase on UCS compared with those without calcium oxide supplement at 3 and 7 days of curing, respectively. Results concluded that the MSWI ash was suitable in reuse for cement production under a well-conditioned situation.     

固化废弃软黏土的强度特性及水稳定性研究

为了提高水泥和粉煤灰固化高含水率废弃软黏土的固化效果,选取水玻璃作为外加剂,吸水性强的生石灰作为分散剂,采用无侧限抗压强度试验、X 射线衍射、扫描电镜试验研究掺量与龄期对固化软黏土水稳定性和强度特性的影响。试验结果表明,3%(质量分数)的水泥、7%(质量分数)的粉煤灰、2%(质量分数)的生石灰与2%(质量分数)的水玻璃复合时能较好提高高含水率软黏土固化后的强度和水稳定性,其强度能达到水泥粉煤灰类基底层最低强度(1 MPa)。在水泥、粉煤灰和水玻璃质量掺量相同情况下,生石灰质量掺入比由0%增加至2%,其强度增大约375 kPa,且有利于后续固化剂的均匀搅拌,说明生石灰的减水和分散效应在固化土中起主导作用。此外,扫描电镜结果显示加入复合固化剂后大集聚体消失,产生大量的片状结构,大孔隙被填充,土体的强度也随之提高。     

A dimensional description of the unconfined compressive strength of artificially cemented fine-grained soils

Abstract

This study aims at establishing a universal predictive model for the unconfined compressive strength (UCS) of artificially cemented fine-grained soils. Model development, its validation and calibration were carried out using a comprehensive database gathered from the research literature. The dimensional analysis concept was successfully extended to the soil–cement UCS problem, thereby leading to a practical dimensional model capable of simulating the UCS as a function of the blend’s index properties — that is, cement content, specific surface area, curing time, and the compaction state parameters (including water content and dry density). The predictive capability of the proposed model was examined and further validated using routine statistical tests, as well as conventional fit-measure indices which resulted in R²?>?0.95 and NRMSE < 5%. A sensitivity analysis was also carried out to quantify the relative impacts of cement content, curing time and soil plasticity on the UCS. The higher the soil plasticity, the higher the positive sensitivity to cement content, implying that soils of higher plasticity would require higher cement contents for stabilization. On the contrary, the higher the soil plasticity, the lower the positive sensitivity to curing time, indicating a more effective cement hydration in soils of lower plasticity. Finally, an explicit calibration procedure, involving a total of three UCS measurements for three recommended soil–cement mix designs, was proposed and validated, thus allowing for the proposed model to be implemented with confidence for predictive purposes, preliminary design assessments and/or soil–cement optimization studies.     

水泥/玄武岩纤维复合固化剂分别对泥炭质土静力特性的影响

为了研究单掺水泥及复合固化剂(由水泥、生玄武岩纤维、石灰和生石膏组成)对滇池地区高原湖相泥炭质土静力特性的影响,对不同掺量水平下的水泥改良土和复合固化剂改良土进行静三轴不固结不排水剪切试验,研究了两种改良土的三轴应力应变关系与抗剪强度变化规律。研究表明:随掺量的增加,两种改良土的主应力差峰值强度增大;当掺入复合固化剂的质量分数为15%时,相比5%、10%两个掺量水平,复合固化剂改良土的三轴应力应变关系由“应变硬化型”转变为“应变软化型”,且抗剪强度显著提升;当改良土的内部结构发生破坏时,水泥改良土的抗剪强度有较大损失,而复合固化剂改良土仍保持较高的抗剪强度。     

Performance of irradiated blended cement paste composites containing ceramic waste powder towards sulfates,chlorides, and seawater attack

Within the scope of this study, blended cement pastes were prepared by replacing different proportions of ordinary Portland cement with ceramic waste powder (CWP). The hardened blended cement pastes were cured under tap water for different periods of time up to 180 days. Physico‐mechanical properties of specimens were studied in terms of free lime content, chemically combined water, compressive strength, and particle size distribution. The results manifested that the optimum content of ceramic waste which gave a marked improvement in the mechanical properties was 10% as compared to the other specimens at the same curing age. Besides that, similar specimens of the hardened blended cement paste containing 10% CWP were impregnated with unsaturated polyester and exposed to different doses of gamma rays from 10 to 50 kGy. Both the impregnated specimens that irradiated at a dose of 30 kGy and the neat blended cement paste that contained 10% ceramic waste were soaked in 1, 3, and 5% magnesium sulfate, sodium chloride solutions, and in seawater for up to 180 days. The results indicated that the composite specimens became more resistant to aggressive solutions and their durability increased as compared to the neat blended cement paste prepared under the same previous conditions. J. VINYL ADDIT. TECHNOL., 26:24–34, 2020. © 2019 Society of Plastics Engineers     

Comparison of the binding properties of hydrated lime and cement in brick manufacture

The effect of replacing cement by hydrated lime in autoclaved brick specimens with binder contents of 7.5–25% has been studied on a laboratory scale and the results have been compared with non-autoclaved cement-bound specimens. It has been shown that the strength of cement-bound specimens autoclaved for 8 h was similar to that of specimens air-cured for 28 days. Lime was shown to be superior to cement in autoclaved specimens for strengths up to the maximum of 23 MN/m² obtainable with the lime binder. For a given compressive strength up to this value, half as much binder was required in the mix and, in addition, the green strength was greater and the drying shrinkage was lower when lime was used instead of cement. Maximum strengths of up to 42 MN/m² were achieved at high binder contents with blends of lime and cement.     

Effect of mechanical property of cemented soil under the different pH value

Cemented soil has been widely used in civil engineering. Groundwater affected by several environment factors, such as agriculture, industry, living and seawater, is often acid or alkaline and usually aggressive to cemented soil. In practice, unconfined compressive strength (UCS) is often used as one of the basic indicators to evaluate the mechanical property of cemented soil. This paper mainly studies the impacts of environmental contamination on the mechanical property of cemented soil, the factors such as cement content, curing age and pH value are taken into consideration. The results show that, the appearance of cemented soil is seriously eroded under acid conditions; while in alkaline conditions it is affected slightly. The UCS of cemented soil increases with cement content and curing age. However, the increase is much slower than that of regular cemented soil. In strong acid and strong alkaline environments, the strength loss can reach 30%. In addition, the electron scanner was used to observe the microstructure of test blocks, and microscopic mechanism of failure was analyzed. The results of this paper can provide reasonable basis for durability evaluation, residual life prediction and durability design of cemented soil.     

水泥窑用低水泥浇注料性能的研究

以矾土为主要原料,铝酸钙水泥和硅微粉为结合系统,研究了不同热处理温度对水泥窑用低水泥浇注料性能的影响。试样自然干燥24h脱模后,再经110℃烘干24h,分别于300℃、500℃、700℃、900℃、1100℃、1300℃和1500℃热处理3h。检测各温度热处理后试样的体积密度(B.D)、线变化率(P.L.C)、常温抗折强度(M.O.R)、常温耐压强度(C.C.S)、常温耐磨性能以及试样的热膨胀系数和抗热震性能。结果表明,随着热处理温度的提高,水泥窑用低水泥浇注料的体积密度呈现先减小后不变再增大的变化规律;线变化率呈现收缩先增大后减小再增大的变化规律;常温抗折强度和常温耐压强度呈现先增大后减小再增大的变化规律。水泥窑用低水泥浇注料经过1500℃热处理后的磨损量小于经过1300℃热处理后的磨损量。水泥窑用低水泥浇注料具有相对优良的抗热震性能。     

Residual compressive strength of fire‐damaged mortar after post‐fire‐air‐curing

The effects of cooling regimes and post‐fire‐air‐curing on compressive strength of mortar were investigated. Mortars were made with CEN reference sand, CEM I 42.5 R cement and natural spring water. The sand–cement and water–cement materials' ratios were chosen as 3.0 and 0.50 for all mixtures, respectively. At 28 days, the specimens were heated to maximum temperatures of 400, 600, 800 and 1000°C. Specimens were then allowed to cool in the air, furnace and water. After cooling, the specimens were air‐recured. Compressive strength test was carried out before air‐recuring and after 7 days of air‐recuring. The highest reduction in compressive strength was observed at 1000°C regardless of cooling regime. Gradual cooling regime in air and furnace without post curing showed almost no difference in terms of compressive strength reduction for four elevated temperatures. Shock cooling in water caused significant reduction in compressive strength compared with both gradual cooling regimes without post curing. After air and furnace cooling regimes, 7 days air‐recured specimens showed further reduction in compressive strength for four elevated temperatures. Specimens cooled in water and subjected to 7 days air‐recuring showed significant strength gain approximately 39, 100 and 130% for 400, 600 and 800°C elevated temperature, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Mineralogical and microtextural changes associated with lime stabilization of marine clays from eastern Canada

Four clayey soils displaying the range of properties of the marine clays from eastern Canada were selected for this study. They were treated with different amounts of quick, hydrated and agricultural lime, at different water contents. The mineralogical and the microtextural aspects involved in lime stabilization of these clays as well as the mechanisms responsible for gain of strength have been investigated. In soils stabilized with quick and hydrated lime at a water content near the liquid limit, (1) the clay minerals appear to be the main targets for chemical attack, (2) reaction products of CASH and CSH types are formed, affecting the pore size distribution, and (3) the gains in strength are related to the progressive formation of these new phases.     

高渗透改性环氧树脂充填砂浆材料裂隙试验研究

制作含4种裂隙倾角(0°、30°、45°、60°)的圆柱体砂浆试样,选用高渗透改性环氧树脂作为充填材料,在重力作用下无压力充填试样裂隙,并对充填前后的试样进行单轴压缩试验.试验结果表明:高渗透改性环氧树脂能依靠自身的渗透性渗进试样的裂隙,固化后能不同程度地提高不同裂隙倾角试样的抗压强度,其中45°倾角和60°倾角的试样...     

绿色节能环保型无熟料白水泥的研究

以偏高岭土、石灰和石膏为主要原料，进行了无熟料和少熟料的白水泥试验研究。试验结果表明：（1）用偏高岭土、石灰和石膏三组份原料可以制得28d强度超过32．5MPa的无熟料白水泥，其最佳质量配比为：偏高岭土：石灰：石膏=50：30：20．（2）用偏高岭土、石灰、石膏和少量白水泥熟料四组份配料可以制得28d强度超过42．5MPa的少熟料白水泥，其中白水泥熟料掺量只要20％；基础原料——偏高岭土、石灰和石膏的相对质量配比为14：3：3。文章同时对白水泥强度增长特点、养护条件、耐水性进行了分析；研究了生石灰和熟石灰、生石膏和熟石膏对无熟料白水泥的强度影响差异，确定了最优石灰和石膏类型。     

Cr2O3对矾土基喷涂料性能的影响

以铝矾土为主要原料,铝酸钙水泥、硅微粉为结合系统,分别研究了不同添加量的Cr2O3对矾土基喷涂料性能的影响。试样自然干燥24h脱模后,再经110℃烘干24h,分别于1000℃、1300℃和1500℃热处理3h。检测各温度热处理后试样的线变化率、体积密度、抗折强度、耐压强度以及试样的热膨胀系数、耐磨性能和抗热震性能。结果表明,在矾土基喷涂料中添加Cr2O3不利于提高材料的低温和中温强度,但利于提高材料的高温强度;在矾土基喷涂料中添加Cr2O3不能提高材料的耐磨性能;试样中添加Cr2O3后增大了试样的热膨胀系数。添加适量的Cr2O3可提高试样的抗热震性能;过量的添加Cr2O3会对试样的抗热震性产生负面的影响。     

The influence of initial water curing on the strength development of ordinary portland and pozzolanic cement concretes

The effect of initial water-curing period on the strength properties of concretes was investigated. Three types of cement, one ordinary Portland cement (OPC) and two natural pozzolanic cements (blended and trass cements), were used in the concrete mixtures. Six different curing regimes were applied to the specimens, the first of which was continuous water storing, and the second continuous air storing. In the remaining four regimes, the specimens were stored under varying initial water-curing periods of 3, 7, 14, and 28 days, respectively. The compressive strength tests were carried out on the cubic specimens at the ages of 7, 14, 28, 90, and 180 days. The variation of compressive strength with time was evaluated by using a semilogarithmic function and the strength-gaining rates were calculated by using this equation for different curing conditions. It was found that poor curing conditions are more adversely effective on the strength of concretes made by pozzolanic cements than that of OPC, and it is necessary to apply water curing to the former concretes at least for the initial 7 days to expose the pozzolanic activity. However, when the pozzolanic cement concretes have sufficient initial curing, they can reach the strength of OPC concretes in reasonable periods of time.     

免烧淤泥砖的设计制备优化及抗冻性能研究

系统研究了石灰掺量、水泥掺量、养护温度和时间对淤泥免烧砖力学性能的影响,优化了淤泥免烧砖的设计制备。在此基础上,探讨了淤泥免烧砖的抗冻性能。结果表明：30％～40％的石灰掺量可使淤泥-石灰免烧砖有较高的强度;而增强相水泥的掺量越高,淤泥-石灰-水泥系统免烧砖力学性能和抗冻性能越佳;综合考虑生产、经济因素,养护温度在80℃为佳。     

石灰-水泥-粉煤灰改性磷石膏对水泥物理性能的影响研究

采用石灰、水泥、粉煤灰对磷石膏进行改性处理,测定了改性磷石膏中硫酸根的溶解性能,对比了原状磷石膏与改性磷石膏对水泥物理性能的影响,并结合X射线衍射（XRD）和扫描电镜（SEM）分析了改性前后磷石膏对水泥不同龄期水化产物的影响。结果表明：随着石灰掺量的增加改性磷石膏的pH逐渐增大,当石灰掺量为4%（质量分数）时磷石膏的pH达到12.22,此时磷石膏中的可溶性磷、氟转化成难溶性的磷酸盐、氟化钙;随着水泥和粉煤灰掺量的增加,改性磷石膏的溶解性能呈现降低趋势。当石灰掺量为4%、水泥掺量为10%（质量分数）、粉煤灰掺量为10%（质量分数）时,改性磷石膏经过7 d养护在水中浸泡8 h所得滤液中硫酸根的质量浓度为0.30 g/L,比未改性磷石膏在水中浸泡8 h所得滤液中硫酸根的质量浓度降低了81.8%。与掺加未改性磷石膏的水泥浆体相比,掺加改性磷石膏的水泥浆体的水灰质量比由0.41降低到0.38、初凝时间和终凝时间分别缩短34.6%和27.2%、28 d抗压强度提高21.1%。石灰、水泥、粉煤灰改性处理磷石膏后,生成的水化硅酸钙和钙矾石等水硬性产物包裹在石膏颗粒表面,使硫酸根在水中的溶出速率降低,减少了对水泥中铝酸三钙的影响,使得硬化体内部结构变得致密、力学性能显著提高。     

粒度分布对磷石膏-石灰-粉煤灰胶结材物理性能的影响

针对磷石膏-石灰-粉煤灰体系胶结材大量利用磷石膏时,强度发展以及耐水性能的缺陷,采用机械粉磨以改善其粒度分布。探究了不同粒度分布对磷石膏-石灰-粉煤灰体系胶结材的物理性能和耐水性的影响。将磷石膏样品与生石灰以及粉煤灰按一定比例混合,陈化24h再通过粉磨不同时间,达到不同的粒度分布。将不同粒度的样品外掺5%水泥,3%AC增强剂以及0.5%聚羧酸减水剂,按照标准稠度用水量加水在160 mm×40 mm×40 mm试模中成型,在养护室中养护到规定龄期再测定试件的物理性能以及微观分析。结果表明,磷石膏掺量达到40%,通过粉磨的物理活化,该体系按照水泥砂浆砌块成型,28 d抗压强度≥27.76 MPa,软化系数达到86%的胶凝材料,并且无废水排除,杜绝二次污染。     

化学合成高纯铝酸钙水泥的特性及应用

研究了化学合成高纯铝酸钙水泥的物理特 性,包括强度发展、凝结时间、水化结合水量和水化放 热特性,并与市售的以传统烧结法生产的水泥进行了 在典型耐火浇注料中的应用比较。结果表明:(1)化 学合成高纯铝酸钙水泥胶砂的强度发展快且充分,早 期强度高;(2)化学合成高纯铝酸钙水泥的水化放热 速率在水化2h时最大,放热快且放热量集中;(3)化 学合成高纯铝酸钙水泥的水化活性较高;(4)化学合 成纯铝酸钙水泥用于耐火浇注料中,浇注料表现出较 高的烘干强度,且浇注料的烧后强度等性能指标也与 用传统烧结水泥的大体相当。     

Relations between structure and mechanical properties of autoclaved aerated concrete

Laboratory specimens of autoclaved aerated concrete were produced under varying conditions, mainly with cement and lime as binders. The type and amount of reaction products, the porosity and the pore size distribution were studied. Shrinkage and compressive strength were measured. The reaction products belonged to the tobermorite group of calcium silicate hydrates and the term crystallinity was defined as the percentage of 11.3 Å tobermorite out of the total amount of calcium silicate hydrates. The shrinkage decreased with increasing crystallinity while the compressive strength increased up to an optimum value. The strength also increased with increasing amounts of hydrates and with decreasing porosity. Other features of the reaction products were indicated by thermal behaviour and micropore size distributions and may have been of importance for the mechanical properties of the material.     

Recycling of polyurethane foam waste in the production of lightweight cement pastes and its irradiated polymer impregnated composites

This study aimed at using polyurethane foam waste in the production of lightweight white cement pastes by a partial replacement of white cement with different ratios of polyurethane foam waste (10%, 20%, 30%, and 40%) based on the weight of cement. The lightweight white cement pastes specimens in addition to conventional white cement paste were cured under tap water for 7 and 28 days. The physical, mechanical, and thermal properties were evaluated. The results showed that the specimens cured for 28 days achieved better properties as compared to the specimens cured for 7 days. Furthermore, at each curing age the specimens of lightweight white cement pastes showed relatively lower properties as compared to the conventional white cement paste and as the polyurethane waste content increased, the properties in terms of compressive strength and bulk density decreased while the total porosity percentage increased especially at higher ratios. On the other hand, the effects of styrene–butadiene rubber latex and irradiation dose on the properties of irradiated polymer impregnated lightweight white cement composites have been investigated. The results confirmed that the impregnation of the hardened lightweight white cement pastes with styrene–butadiene rubber latex and their exposure to different doses of gamma rays (50, 100, 150, and 200 kGy) showed a gradual improvement in the mechanical and physical properties up to 150 kGy and then started to decrease at 200 kGy. Characterization of some selected specimens was carried out by the studying of thermogravimetric analysis, scanning electron microscopy, and X‐ray diffraction. J. VINYL ADDIT. TECHNOL., 25:328–338, 2019. © 2019 Society of Plastics Engineers