高钙灰矿物改性及其复合水泥化学收缩机理

研究了高钙灰矿物改性及其与钢渣和改性磷石膏等矿物复合后胶材90d的化学收缩变化,利用孔结构压汞实验分析孔最可几分布、平均孔径及孔隙率对化学收缩变化影响机理.试验结果表明:(1)50%高钙灰取代水泥,明显减小孔径,孔最可几分布为5.488E-02mm,但孔隙率为26.8360%,降低并不多,因而90天化学收缩较低;(2)50%高钙灰取代水泥并掺入改性磷石膏,孔隙率为27.2150%,降低并不多,但孔径明显减小.孔最可几分布为4.894E-02mm,因而90d化学收缩较未掺改性磷石膏试样高;(3)经过物理化学活性激发的高钙灰具有较好的水化活性,50%改性高钙灰取代水泥胶材.其24h内化学收缩率比100%水泥及50%原高钙灰取代水泥大,而90d时孔最可几分布为5.720E-02nun,孔隙率为23.1336%.化学收缩率比100%水泥小很多.     

循环流化床高硫高钙固硫灰在水泥和混凝土中的应用研究(一)

对云南省的高硫高钙褐煤CFB固硫灰的化学组成、物理性状以及掺加该种固硫灰的水泥水化机理、微观矿相和物理性能进行了试验研究。确认了经碱激发后,该固硫灰活性系数高于一般的粉煤灰和火山灰质混合材;与其他材料进行复合,用作水泥活性混合材料及水泥缓凝剂,可以代替部分水泥熟料和石膏,降低水泥生产成本和粉磨能耗。还可用于制造微膨胀水泥和混凝土膨胀剂。但使用时,必须根据该固硫灰的化学成分严格控制其掺加量。     

高钙灰-水泥颗粒群匹配与强度关系研究

本文将不同颗粒群分布的高钙灰、水泥按5:5比例混合,制成高钙灰水泥,测其3d、28d胶砂抗折、抗压强度。用激光粒度仪分别检测高钙灰、硅酸盐水泥的颗粒群分布。运用Rosin-Rammler公式对高钙灰、硅酸盐水泥及高钙灰水泥进行拟合。应用Origin软件,以宏观性能指标为z轴,水泥与高钙灰特征粒径之差为x轴,水泥与高钙灰复合胶凝粉体的特征粒径De 为y轴,进行三维区域图分析。给出强度发展趋势与水泥、高钙灰的相对位置以及复合胶凝体系总体细度的相互关系。     

高钙粉煤灰颗粒群分布与其活性关系研究

将纯硅酸盐水泥、高钙灰按不同的粉磨时间和球配处理成若干个不同颗粒群分布的试样 ,高钙灰和水泥以各种颗粒群匹配 (高钙灰掺量均为 5 0 %)制成一系列粉煤灰硅酸盐水泥 ,进行胶砂强度检验。采用灰色关联分析方法研究了粉煤灰各粒径范围颗粒与粉煤灰水泥强度的相互关系。结果表明 :( 1 )高钙灰粒径在 1 0 μm以下的颗粒体积百分数与粉煤灰水泥的强度均为正关联 ,而大于 1 0 μm的颗粒与粉煤灰水泥的强度均为负关联 ,说明小于 1 0 μm的颗粒对强度增长有积极贡献 ,而大于 1 0 μm的颗粒对强度增长不利 ;( 2 )R -R分布表明 :在粉煤灰达到一定细度的条件下 ,宽分布试样可以有较多的小于 1 0 μm颗粒 ,从而对强度增长更为有利。     

机械力活化对钢渣粒度分布和胶凝性能的影响

测试了不同粉磨时间的钢渣的粒度分布,计算了钢渣粉粒度分布的分形维数,并研究了其与比表面积、粉体活性的关系.结果表明:粉磨时间增加,钢渣粉粒度变小,小颗粒所占比逐步提升,粒度分布的分形维数也随之增大,粉磨一定时间后,其粒度分布的分形维数增长速度趋于平缓.粒度分布的分形维数与颗粒的比表面积、水化反应活性线性正相关.机械力活化能够激发钢渣的胶凝性能.钢渣胶凝材料的水化产物以钙矾石(AFt)和水化硅酸钙(C-S-H)凝胶为主.     

矿渣粉、高钙灰及其改性材料对水泥早期水化进程的影响

通过水泥化学收缩和水化热测试方法研究了矿渣粉、高钙灰和脱硫石膏、煅烧脱硫石膏、硫酸钠等改性材料对水泥浆体早期水化进程的影响,同时与不同试样的早期强度进行对比分析.50%的矿渣粉和高钙灰替代水泥后显著降低塑性阶段的化学收缩和早期强度,但对硬化后的化学收缩影响不大,矿渣粉与高钙灰按照适当比例复合对降低塑性阶段化学收缩的作用更明显,有利于降低塑性开裂;脱硫石膏和元明粉对早期化学收缩影响不大.矿渣粉、高钙灰替代50%水泥后明显降低第2放热峰并增加1个第3放热峰,纯矿渣粉的第3放热峰较高,复掺20%高钙灰后第3放热峰降低并且出现时间延后,复掺30%高钙灰使第2放热峰也降低,水化热显著减少;脱硫石膏或煅烧脱硫石膏延缓水化反应进程而对总体反应程度影响不大;水化热实验结果显示硫酸钠促进早期水化反应的作用明显.结果表明:采用20%高钙灰替代矿渣粉对早期水化程度和初始结构建立影响不大,脱硫石膏或煅烧脱硫石膏作激发材料能够分散早期的集中放热而对总体水化进程影响不大;水化热对水化过程的反映比化学收缩更清晰和更准确.     

生物质灰对水泥硬化浆体抗压强度影响的试验研究

对比研究了生物质灰与普通粉煤灰在粒度分布、颗粒形态、化学组成、活性指数等方面的不同,并开展了不同掺量生物质灰对水泥硬化浆体抗压强度的影响研究.结果表明:生物质灰颗粒形状不规则、平均粒径及粒径分布范围较大,具有特有的细长纤维状颗粒,且其活性组分Al2O3不足普通粉煤灰的三分之一;生物质灰的火山灰活性小于普通粉煤灰;相同掺量下,生物质灰-水泥复合胶砂各龄期的抗压强度均小于普通粉煤灰-水泥复合胶砂,生物质灰掺量越大,复合胶砂的强度相比纯水泥组下降程度越大;与普通粉煤灰相比,掺加生物质灰的硬化水泥浆体微观结构更为疏松多孔,特别是其特有的细长纤维状颗粒的存在.     

钢渣-固硫灰渣复合掺合料制备及其性能

钢渣安定性不良及可能含有过多的Cr组分使其作为建筑骨料和作为水泥生料配料使用存在较大的安全和质量风险,这严重限制了钢渣的资源化利用。适量钢渣作为混凝土矿物掺合料已成为钢渣利用的主要领域。本文针对钢渣粉磨能耗高、活性偏低的特点,提出引入高硫高钙的循环流化床固硫灰渣作为转炉钢渣或电炉钢渣稀释剂及改性剂,一方面减少钢渣用量、降低生产能耗;另一方面,以固硫灰渣硫钙组分激发钢渣活性。研究结果表明：钢渣-固硫灰渣复合掺合料能够充分利用钢渣粉需水量低以及固硫灰渣组分激发优势,从而克服了钢渣粉早期活性低和固硫灰渣需水量高、后期强度倒缩问题。所制备钢渣-固硫灰渣达到Ⅱ级复合矿物掺合料技术要求。该复合掺合料大掺量使用钢渣,具有较好的经济和环境效益。     

粉煤灰对脱硫石膏-矿渣-粉煤灰复合胶凝材料力学性能的影响

通过研究粉煤灰自身在硫酸盐和石灰双重激发下产生的活性、粉煤灰的碱性以及颗粒Zeta（电位）等,分析不同粉煤灰对脱硫石膏-矿渣-粉煤灰复合胶凝材料力学性能的影响。结果表明,粉煤灰的种类对复合胶凝材料的力学性能影响很大,粉煤灰本身活性的差异不是造成这种影响的主要原因,其主要原因是粉煤灰对矿渣粉的激发程度。粉煤灰的碱性对矿渣粉的激发影响很大,对于普通含钙粉煤灰,碱性越强,激发越好,复合胶凝材料力学性能越好。矿渣粉颗粒的Zeta电位为负,因此粉煤灰颗粒表面的正电荷密度过高,不利于矿渣粉活性的激发。     

分选与磨细加工对粉煤灰物化性质以及颗粒特性的影响

在半工业化分选与粉磨工艺系统中对粉煤灰进行了分选与磨细处理,并测定了不同粉煤灰样品的物化性质及颗粒特性。结果表明,分选与磨细处理对粉煤灰的化学成分影响不大,但能够明显改善粉煤灰的物理性质,如:需水量比下降、密度增加、活性指数增加。两种处理方式相比较,分选更有利于粉煤灰需水量比的降低而磨细更有利于粉煤灰活性指数的提高;分选灰的颗粒分布范围较窄而磨细灰的颗粒分布范围较宽。     

粉煤灰中玻璃体含量的化学物相分析

为快速评判粉煤灰的火山灰反应活性和分析其加工过程中技术特征,需准确测定粉煤灰中玻璃体含量.通过分析粉煤灰中各种矿物相在碱、酸溶液中溶解反应特征,提出碱-酸两段溶解来测定粉煤灰中玻璃体含量的化学物相分析法.粉煤灰中莫来石、石英、磁铁矿、赤铁矿和未燃尽碳粒,在碱、酸溶液中是稳定相;玻璃体和f-CaO在碱溶液中反应形成凝胶,凝胶在酸溶液中完全溶解,两者含量为溶解过程的质量缩减率,减去f-CaO含量即为玻璃体含量.测定操作要点,-20μm粉煤灰在90℃20%NaOH溶液溶解2.5 h,溶解1.5 h时湿磨至-12μm.碱溶解后滤渣在30℃10%的HNO3溶液溶解1.0 h.试样与试剂比例为5 g粉煤灰、500 mL NaOH溶液、200 mL HNO3溶液.     

Utilization of fly ash coming from a CFBC boiler co-firing coal and petroleum coke in Portland cement

Fly ash coming from a circulating fluidized bed combustion (CFBC) boiler co-firing coal and petroleum coke (CFBC fly ash) is very different from coal ash from traditional pulverized fuel firing due to many differences in their combustion processes, and thus they have different effects on the properties of Portland cement. The influences of CFBC fly ash on the strength, setting time, volume stability, water requirement for normal consistency, and hydration products of Portland cement were investigated. The results showed that CFBC fly ash had a little effect on the strength of the Portland cement when its content was below 20%, but the strength decreased significantly if the ash content was over 20%. The water requirement for normal consistency of cement increased from 1.8% to 3.2% (absolute increment value) with an addition of 10% CFBC fly ash; and the free lime (f-CaO) content of CFBC fly ash affected the value of increasing. The setting time decreased with an increase of CFBC fly ash content. The volume stability of the cement was qualified even when the content of SO₃ and f-CaO reached 4.48% and 3.0% in cement, respectively. The main hydration productions of cement with CFBC fly ash were C-S-H (hydrated calcium silicate), AFt (ettringite), and portlandite.     

Effects of three Turkish fly ashes on the heat of hydration of PC-FA pastes

Effects of the type and amount of fly ash substitution on the heat of hydration of portland cement-fly ash pastes were investigated. Three Turkish fly ashes were used. One of them was a high-calcium and the other two were low-calcium fly ashes. The specimens contained 0, 10, 20, and 40% fly ash by weight of portland cement. The tests were carried out as described in ASTM C 186 however one separate set of specimens were first subjected to an early external temperature of 67±2°C for six hours followed by the standard temperature until time of test. The results revealed that the low-calcium fly ashes, regardless of their type, reduce the heat evolution when used for partial cement replacement. The high-calcium fly ash, on the other hand, does not produce significant changes in the heat of hydration.     

复合碱激发剂协同处理高钙粉煤灰研制土聚水泥

采用复合碱激发剂协同处理高钙粉煤灰研制土聚水泥,试验确定了复合碱激发剂的模数和掺量、养护温度和养护时间,并研究了高钙粉煤灰基土聚水泥的抗压强度、反应产物和微观形貌。试验结果表明:复合碱激发剂适宜的模数为1.5,掺量为Na2O当量10%;适宜养护条件为75℃养护8h,然后在23℃室温养护至所需龄期,其28d抗压强度达63.4MPa;碱激发高钙粉煤灰过程中体系内同时生成土聚水泥凝胶和水化硅酸钙凝胶,并有类沸石矿物生成,反应产物与未反应的粉煤灰颗粒胶结成较为密实的高钙粉煤灰基土聚水泥硬化浆体。     

粉煤灰和矿渣粒度分布对混凝土微观结构和抗氯离子渗透性的影响

针对胶凝材料比表面积和粒度分布等物理性质存在的差异,将P·Ⅱ水泥,Ⅰ级、Ⅱ级粉煤灰和S95级、S105级矿渣进行互掺,固定水泥用量,设计了4种粉煤灰和矿渣的组合方式,通过流动度试验分析了组合方式对净浆流动性的影响,并将粒度分布曲线与Fuller分布曲线进行了比较。在净浆配合比的基础上,对不同组合方式的混凝土进行了工作性、力学性能及自由氯离子浓度测试,探讨了粉煤灰和矿渣的粒度分布对混凝土强度和抗氯离子渗透性的影响,并对硬化浆体水化产物的微观形貌和化学组成进行了分析,揭示了影响机理。研究结果表明,矿物掺合料的粒度分布是决定颗粒级配优劣的重要因素。Ⅰ级粉煤灰具有更强的滚珠效应,在提高流动性方面起了关键性作用。粉煤灰和矿渣的水化及火山灰反应程度影响着混凝土的力学性能和耐久性能,由于Ⅰ级粉煤灰有更大的比表面积,火山灰活性也较高,因此Ⅰ级粉煤灰和S95/S105级矿渣组合的净浆流动度,混凝土的工作性、抗压强度和抗氯离子渗透性均明显高于Ⅱ级粉煤灰和S95/S105级矿渣组合。其中Ⅰ级粉煤灰和S95级矿渣组合的胶凝材料粒度分布曲线与Fuller曲线最为接近,粒度分布最优,水化浆体中Ca(OH)₂含量最低,火山灰反应最为充分,对应的混凝土微观结构致密,抗氯离子渗透性最好。     

Analysis of mechanism on water-reducing effect of fine ground slag, high-calcium fly ash, and low-calcium fly ash

The addition of ultrafine powder (UFP) to concrete can improve the fluidity of concrete, showing a water-reducing effect. The aim of this article was to analyze the water-reducing mechanism of UFP both experimentally and theoretically. Three UFPs—fine ground slag, high-calcium fly ash, and low-calcium fly ash—were chosen for the study. The contrastive experiments were done to investigate the fluidity of mortars with 30%, 45%, 60%, and 75% equivalent cement replaced by fine ground slag, high-calcium fly ash, and low-calcium fly ash, respectively. The results showed the physical and chemical characteristic of the powders, such as their grain morphology, glass phase activities, densities, specific areas, and their grain cumulating conditions, can strongly affect their water-reducing effect.     

Packing effect and pozzolanic reaction of fly ash in mortar

This research is to study the effect of particle size of fly ash on packing effect and pozzolanic reaction of mortar when 20% of fly ash is used to replace Portland cement type I. Both effects can be determined by using fly ash and insoluble material which have almost the same particle size to replace Portland cement type I. Normally, the compressive strength of fly ash mortar is contributed from hydration reaction, packing effect, and pozzolanic reaction. For mortar mixed with insoluble material, the compressive strength is due to hydration reaction and packing effect. Thus, compressive strength due to pozzolanic reaction can be determined from the difference in compressive strength between fly ash mortar and insoluble material mortar. The results show that the strength activity index of fly ash mortar depends on the median particle size of fly ash and curing ages of mortar samples. At early ages, the strength activity index of fly ash mortar due to packing effect is higher than that due to pozzolanic reaction. At the ages of 3 to 90 days, the difference in strength activity index due to packing effect of fly ashes with median particle size of 2.7 and 160 μm is almost constant about 22% of the strength of standard mortar (STD). The differences in strength activity index due to pozzolanic reaction of fly ashes with median particle size of 2.7 and 160 μm are 3%, 20%, and 27%, respectively, at the ages of 3, 28, and 90 days.     

循环流化床锅炉飞灰含碳量的研究

循环流化床锅炉具有高效、低污染、煤种适应性广等优点。但我国流化床锅炉普遍存在着飞灰含碳量高,锅炉燃烧效率达不到设计值的问题。概述了影响飞灰含碳量的主要因素:如煤种、燃煤的粒径及风量等,重点探讨了燃煤的粒径对飞灰含碳量的影响,提出了维持锅炉稳定,降低飞灰含碳量,提高燃烧效率的一些措施。