碱激发硅钙基与硅铝基材料反应机理对混凝土性质与耐久性的研究

Hydration mechanism of alkali-activated silicate-calcium-based and aluminosilicate-based binder on properties and durability of concrete

材料的碱激发是一种化学程序,通常材料能够被强碱激发产生具有胶结性的能力,主要是因为材料中含有硅与钙或是材料中含有硅与铝。硅钙基与硅铝基胶结材料碱激发的组合条件很类似,但是他们的反应产物却大不相同,其硬化机制可分为两种模式:第一型为碱-矿渣水泥的水化反应,碱激发矿渣为典型代表,主要产物为C-S-H胶体,硅和钙为主要成分;第二型为地工聚合物的土壤聚合反应机制,碱激发粉煤灰为典型代表,主要产物为硅铝基胶体,硅和铝为主要成分。本研究旨在探讨不同液胶比与不同比例的矿渣/粉煤灰作为胶结材料,对混凝土试件的新拌性质、物理及力学性质、耐久性与微观特性进行分析。结果显示在各种液胶比下,粉煤灰/矿渣粉的比例会影响碱激发混凝土的抗压强度、劈裂强度等力学性质和吸水率、吸水速率等物理性质以及快速氯离子渗透、健度试验、电阻值等耐久性质,但对于坍落度的影响则不明显。由微观试验发现,当增加粉煤灰比例时,使内部结构存在比较多孔隙,会降低碱激发混凝土的力学性质与耐久性。其中当液胶比为0.5,粉煤灰/为矿渣50/50碱激发混凝土具有最好的力学性质与耐久性。

The hardened mechanism of cementitious materials obtained by alkaline activation of slag/fly ash is absolutely different from that of ordinary Portland cement.The synthesis conditions for alkali-activated ground granulated blast furnace slag(GGBFS)and fly ash(FA)are quite similar,but their reaction products are quite different.Alkali activation of slag is a model of(Si+Ca)system,having C-S-H as the main reaction products,and geopolymer is a kind of(Si+Al)cement with fly ash as the main material,and the reaction products are zeolite like polymer.This study investigated the effect of liquid-to-binder ratio and slag-to-fly ash ratio on the properties,durability and microstructure of alkali-activated slag/fly ash(AASF)concrete.Test results show that the slag-to-fly ash ratio is a key factor affecting the hardened properties and durability of AASF concrete.The properties and durability of AASF concrete decreases with an increase of fly ash.The AASF concrete with 0.5 of liquid-to-binder ratio and 50/50 of slag-to-fly ash ratio has the superior performance.