粉煤灰对砂浆及混凝土强度影响的研究

本文研究了水胶比、掺量及龄期对掺粉煤灰的砂浆和混凝土强度的影响规律,分析了粉煤灰的作用机理,提出了粉煤灰饱和掺量的概念,探讨了充分水化条件下砂浆体系获得最佳强度时的饱和掺量。     

Effect of fly ash on drying shrinkage of thermal insulation mortar with glazed hollow beads

Drying shrinkage of thermal insulation mortar with glazed hollow beads was measured by a vertical length comparator, and the influences of fly ash with different contents (0, 18%, 36%, and 54% were used) on the long-term drying shrinkage were discussed. The mass loss was measured by the weighting method and the pore structure was characterized using three different methods, including the light microscopy, the mercury intrusion porosimetry (MIP), and the nitrogen adsorption/desorption (NAD) experiments, and the correlations among them were researched. The results show that drying shrinkage process of thermal insulation mortar includes three steps with increasing curing time: the acceleration period (before 7 d), the deceleration period (7-365 d), and the metastable period (after 365 d). Drying shrinkage in the first stage (7 d before) increases quickly owing to the fast water loss, and its development in the last two stages is attributed to the increment of the pore volume of mortar with the radius below 50 nm, especially the increment of the pore volume fraction of the pore radius within the size range between 7.3 nm and 12.3 nm. There is no change in the drying shrinkage development trend of mortar with fly ash addition, and three steps in the service life, but fly ash addition in the mortar restrains its value. There is a linear relationship between the drying shrinkage and fly ash content, which means that drying shrinkage reduces with fly ash addition.     

Effect of calcium aluminate cement variety on the hydration of portland cement in blended system

Two kinds of CACs with different monocalcium aluminate（CA） contents were used in the PC/CAC（PAC） mixtures. Effects of CA and CACs on the properties of PAC were analyzed by setting times and the compressive strength tests, and also by means of calorimetry, XRD, DTA-TG and ESEM. The experimental results show that the compressive strength of the PAC mortars decreases with increasing content of CAC while it declines sharply with a higher content of CA in CAC. Compared with neat PC paste, the content of calcium hydroxide in hydrates of PAC paste decreases significantly, and the hydration time of PC is prominently prolonged. Additionally, the higher the content of CA in CAC, the more obviously the hydration of PC is delayed, confi rming that the CA phase in CAC plays an important role in the delay of PC hydration.     

废弃电路板非金属粉末粒径对水泥砂浆性能的影响

将废弃电路板回收处理后得到的非金属粉末掺入水泥砂浆中,研究非金属粉末粒径大小对水泥砂浆性能的影响;为改善非金属粉末和水泥浆体之间的界面性能进而改善复合砂浆的性能,采用硅烷偶联剂处理非金属粉末和在砂浆中加入丁苯乳液2种改性方法.结果表明：硅烷偶联剂处理可以降低砂浆的含气量和收缩率,加入丁苯乳液改善了砂浆的抗压强度和毛细孔吸水率.偶联剂处理和加入丁苯乳液都可以提高砂浆的抗折强度和黏结抗拉强度.废弃电路板非金属粉末粒径越小,水泥砂浆的抗压强度、抗折强度和黏结抗拉强度越大,含气量、收缩率和毛细孔吸水率越小.     

煤矸石-Ca(OH)2-H2O体系反应动力学初探

通过测定不同龄期煤矸石地酸溶出量,对不同温度热激活下的煤矸石在煤矸石-Ca(OH)2-H2O体系中的反应速率进行了研究,并在此基础上建立了煤矸石火山灰反应动力学模型.该模型表明:煤矸石的反应速率(v)主要取决于煤矸石的火山灰活性(v),值大则煤矸石的火山灰活性高,反应速率常数k值大则煤矸石的火山灰反应活性高,最后采用Ca(OH)2的吸收实验来验证本模型的正确性.     

纤维素醚在水泥颗粒表面的吸附性能EI北大核心CSCD

用动态光散射测定了溶液中纤维素醚分子的尺寸、用总有机碳含量(TOC)方法测定了纤维素醚在水泥中的吸附量。结果表明:溶液中纤维素醚的粒径随浓度提高而减小,并趋于恒定值,称之为无扰直径。用无扰直径和水泥的Blaine比表面积计算其在水泥颗粒表面单层紧密堆积的量,其与TOC测定的吸附量存在良好相关性,说明纤维素醚以其无扰直径大小吸附在水泥颗粒表面,且与水泥种类无关。     

中国干混砂浆的应用研究概况

从干混砂浆的性能、组分以及聚合物干粉对其性能影响和作用机理等方面论述了干混砂浆在中国的研究进展.中国国内目前关于干混砂浆的理论研究主要集中在聚合物共混改性水泥砂浆,无机矿物外加剂和聚合物种类、成分、掺量等对水泥砂浆性能影响方面. 干混砂浆所用聚合物种类和掺量对干混砂浆的各种性能影响显著.对聚合物的作用机理研究几乎还是空白.     

硅酸盐熟料-煤矸石/粉煤灰混合水泥水化模型研究

对两种不同3CaO·SiO_2(C_3S)含量的硅酸盐水泥和分别掺有30%(质量分数,下同)煤矸石和30%粉煤灰的混合水泥中水化产物含量变化和形态进行了研究,建立了水化产物量变模型和水化产物形态模型,分析了模型的主要特征和意义。相同龄期,高C_3S硅酸盐水泥比低C_3S硅酸盐水泥生成更多的水化硅酸钙(calcium silicate hydrate,CSH)凝胶和氢氧化钙。含混合材的水泥水化时,CSH凝胶在水化早期和后期有两个增长幅度较大的阶段,并且1年后形成的CSH凝胶量与纯硅酸盐水泥的相当。水泥水化产物与混合材的二次水化反应较慢,研究掺有混合材水泥更长龄期的水化产物含量及结构变化,将有助于理解混合材对水泥性能的作用机理。     

聚合物干粉对水泥砂浆耐久性能的影响

建筑砂浆除了墙体砌筑和抹灰以及地面抹灰等普通用途外，还有防水、补强、防化学腐蚀等特殊用途的特种砂浆。特种砂浆因用途不同而对其耐久性能的要求不同。然而对于掺聚合物干粉的砂浆耐久性能，人们研究的还很少。在以前研究两种聚合物干粉——羟乙基甲基纤维素和乙烯基共聚物对水泥砂浆物理性能影响的基础上，本文主要研究这两种聚合物干粉对水泥砂浆耐久性能的影响规律，探讨其用作特殊用途的可行性。