煅烧纳米凹凸棒土对再生混凝土抗冻性能影响研究

Effect of calcined nano⁃attapulgite on frost resistance of recycled concrete

为利用固体废弃物,以再生粗骨料的取代率为30%替代天然粗骨料并将煅烧纳米凹凸棒土取代水泥(0%、2%、4%、6%、8%)制成纳米再生混凝土,进行冻融循环试验,探究NAT对NRC抗冻性能的影响。利用扫描电镜及氮吸附法研究NRC微观结构的变化规律。结果表明,随着冻融循环次数增加,NRC质量损失率呈现先负增长后正增长的变化规律;在相同的冻融循环次数下,NRC的相对动弹性模量均在NAT掺量为6%时为最大值。适配掺量下NAT掺入后通过二次水化反应生成C-S-H凝胶,提高了砂浆内部及砂浆与骨料之间的密实度,填充了NRC内部部分中孔、大孔孔隙,提升界面过渡区强度,优化内部孔隙结构,进而提升再生混凝土的抗冻性能。

In order to comprehensively utilize solid wastes,NA is replaced by RA with a replacement rate of 30%,and cement(0%,2%,4%,6%,8%)is replaced by calcined NAT to make NRC.Freeze⁃thaw cycle tests are carried out to explore the influence of NAT on the freezing resistance of NRC.Scanning electron microscopy and nitrogen adsorption are used to study the microstructure of NRC.The results show that with the increase of freeze⁃thaw cycles,the mass loss rate of NRC present a negative growth first and then a positive growth.Under the same number of freeze⁃thaw cycles,the relative dynamic elastic modulus of NRC is the maximum when the NAT content is 6%.The C⁃S⁃H gel is generated by secondary hydration reaction after NAT incorporation under adaptive dosage,which improves the compactness inside the mortar and between the mortar and aggregate,fills the pores in the inner part of NRC,improves the strength of interfacial transition zone,optimizes the internal pore structure,and improves the frost resistance of RC.