Effect of curing conditions on the hydration and performance of CFBC ash cementitious system

Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.     

Crystallization characteristic of glass-ceramic made from electrolytic manganese residue

Electrolytic manganese residue (EMR) is a waste from electrolytic manganese industry that contains high concentration of toxic substances. Since the EMR disposal in landfill sites has a serious environmental impact, new ways of EMR utilization are being sought. Considering the melting of EMR to a glass at high temperature was a relatively less energy-intensive process, EMR was first made into a base glass and then the ground base glass was heat-treated in a certain procedure to make a glass-ceramic and the crystallization process was studied. It was determined by X-ray diffraction (XRD) that the primary crystalline phases of the EMR glass-ceramic were diopside and anorthite, which formed the surface crystallization mechanism with a crystallization activation energy of 429 kJ/mol. Scanning electron microscopy (SEM) observation showed that a layer of small spherical particles with an average size of about 0.5 μm were covered on the glass matrix surface, and among them there were some big particles. The low melting temperature and crystallization activation energy make it promising to reuse EMR for glass-ceramic production.     

Hydration of activated anhydrate phosphogypsum

Phosphogypsum(PG) calcined at 500 °C was activated by K₂SO₄ and salt lime with loose structure as seed crystal. To determine the effect of activation, hydration of the anhydrate PG activated was investigated by examination of the setting time, the proportion of hydrated anhydrate PG, the microstructure of the hardenite and the resistance to water. Results show that activated anhydrate PG hydrates much more rapidly than that in the absence of activators. The activated anhydrate PG has proper setting time and hydrated proportion. The resistance to water was greatly improved. SEM photos show that the set activated PG has hydrated products of rod-like and closely connected crystals. The different addition of activator leads to different compact structure.     

纳米SiO2对水泥基复合材料性能的影响

纳米材料具有独特的微观结构和物理、化学及机械性能,近年来得到了广泛深入的研究.介绍了纳米SiO2对水泥基复合材料流动性、水化产物、水化结构、强度和耐久性影响的研究现状,并初步探讨了纳米SiO2在水泥基复合材料应用中亟需解决的问题.     

燃煤灰渣火山灰反应活性

利用活性SiO2,Al2O3与石灰水化反应产物可溶解于稀盐酸的特性,对2种粉煤灰、2种沸腾炉渣和4种流化床固硫灰渣中具有火山灰活性的SiO2,Al2O3反应动力学进行了研究,并以此来评估不同种类燃煤灰渣的火山灰反应活性.结果表明:所采用燃煤灰渣的活性SiO2,Al2O3火山灰反应均符合一级反应动力学模型;活性Al2O3反应速率常数大于活性SiO2,而表观活化能相反;沸腾炉渣和流化床固硫灰渣火山灰活性接近,均明显高于粉煤灰;高温对粉煤灰火山灰活性的激发更为有利.     

砼Ⅰ、Ⅱ类断裂及其数值分析

本文介绍一些研究者关于砼Ⅱ类断裂的试验结果,并从能量平衡角度进一步解释了砼Ⅰ、Ⅱ类断裂现象。本文还探讨了通过数值方法来模拟砼Ⅱ类断裂,进而采用数值手段分析了随一些因素变化砼Ⅰ、Ⅱ类断裂的转化。     

粉煤灰活性的激发

总结了粉煤灰活性发研究的国内外状况。在粉煤灰活性激发试验研究的基础上，对粉煤灰活性激发机理，特别是无熟料粉煤灰水泥中粉煤灰活性激发的机理进行了分析。     

减水剂作用下粉煤灰活性激发基本系统中石灰形态因素的研究

论述粉煤灰－石灰－硫酸盐系统中石灰采用生石灰时,减水剂对粉煤灰活性激发起到了负效应;当以等ＣａＯ当量的熟石灰代替生石灰,减水剂对粉煤灰活性激发具有良好正效应,并对其原因进行了初步探讨。     

新型增密硅灰对混凝土性能影响的研究

研究了掺加新型增密硅灰混凝土性能与掺加原状硅灰混凝土性能,实验结果表明,该新型增密硅灰有效地减小了混凝土的坍落度损失率、凝结时间,泌水率。混凝土的抗压强度、劈裂强度、抗硫酸盐腐蚀、抗渗性均与原状硅灰混凝土性能相近。新型增密硅灰降低运输成本,具有良好的经济和社会效益。