水玻璃对粉煤灰矿渣地聚合物强度的影响及激发机理

Influence of Sodium Silicate on Fly Ash Slag Geopolymer Strength and Stimulating Mechanism

通过力学性能测试研究了水玻璃掺量和模数对粉煤灰矿渣地聚合物抗压强度的影响。根据水玻璃的胶团结构和地聚合物的微观形貌特征,分析了SiO2/Na2O对强度的影响规律和水玻璃胶团在地聚合物中的聚合反应过程。结果表明:当水玻璃掺量大于等于20%,水玻璃模数由0.5增加到2.0时,地聚合物的抗压强度呈先增后减的趋势;当水玻璃的模数在1.2~1.6范围内,掺量为20%时,地聚合物抗压强度达到最大。微观分析表明:粉煤灰和矿渣中的活性物质溶出使水玻璃固结,将粉煤灰和矿渣颗粒包裹其中形成冻结体,粉体颗粒与周围冻结体紧密黏结;在碱激发浆体中,粉煤灰和矿渣颗粒结构完整,而硅酸盐水泥颗粒在水化反应时则是完全解体;水玻璃既作为激发剂又作为反应物,水玻璃中的Na2O使粉煤灰和矿渣中的Si-O键和Al-O键断裂,使Si和Al等元素溶出,水玻璃中的硅质成分作为反应物与矿渣中溶出的Ca2+发生反应,生成水化硅酸钙凝胶,粉煤灰和矿渣中溶出的Al3+和Si4+深入水玻璃胶核附近,在脱水的条件下与胶核中的SiO2发生聚合反应,相邻胶核的聚合反应产物互相搭接形成整体,是地聚合物强度网状结构建立的根本原因。

The influence of content of sodium silicate and modulus on compressive strength of fly ash slag geopolymer is studied by mechanical properties test.According to the micearll structure of sodium silicate and the micro-morphological characteristics of geopolymer,the influence of SiO2/Na2O on the strength and the polymerization process of sodium silicate micelle in geopolymer are analyzed.The result shows that when the content of sodium silicate is greater than or equal to 20%and the modulus of sodium silicate increases from 0.5 to 2.0,the compressive strength of geopolymer increases at first and then decreases;(2)When the modulus of sodium silicate is in the range of 1.2-1.6 and the content of sodium silicate is 20%,the compressive strength of geopolymer reaches the maximum.The micro analysis shows that(1)The active substances in fly ash and slag are dissolved to consolidate the sodium silicate,the fly ash and slag particles are wrapped to form a frozen body,and the powder particles are tightly bonded to the surrounding frozen body.(2)In the alkali activated slurry,the particle structure of fly ash slag is complete,while the Portland cement particles are completely dissolved when hydrated.(3)Sodium silicate is both an activator and a reactant.The Na2O in sodium silicate breaks the Si-O bond and the Al-O bond in fly ash and slag,and dissolves the elements such as silicon and aluminum.As a reactant,the silica in sodium silicate reacts with the Ca2+dissolved in slag and generates hydrated calcium silicate gel.The Al3+and Si4+dissolved from fly ash and slag are deeply embedded near the sodium silicate gel core,and polymerized with SiO2 in the gel core under the condition of dehydration.The polymerization reaction products of adjacent gel cores overlap each other to form a whole,which is the basic reason for the establishment of geopolymer strength network structure.