纳米二氧化硅改性再生混凝土的单轴受压动态力学性能

Dynamic Mechanical Properties of Nano-Silica Modified Recycled Aggregate Concrete under Uniaxial Compression

摘要:

基于新提出的纳米二氧化硅水泥净浆二次改性再生骨料方法，通过混凝土单轴受压动态力学试验，获得了不同应变率（10^-5s^-1、10^-3s^-1、10^-1s^-1）、不同改性方法（纳米二氧化硅水泥净浆二次改性、纳米二氧化硅粉煤灰复合改性、纳米二氧化硅预浸泡）的再生混凝土单轴受压应力-应变曲线，分析对比了改性前后应力-应变曲线特征。结果表明，新的改性方法能够有效改善再生混凝土力学性能，准静态下峰值应力提升25.1%，弹性模量增加85.8%。改性后再生混凝土的峰值应力和弹性模量动态增长因子降低，而峰值应变动态增长因子提高。最后，提出了改性后再生混凝土动态应力-应变本构模型，对比结果显示，模型预测曲线与试验曲线吻合较好，能为工程设计和应用提供依据。

关键词:再生混凝土（RAC）;纳米二氧化硅改性;应力-应变曲线;动态增长因子;动态本构模型

Abstract:

A novel method to modify recycled aggregate concrete （RAC） by nano-silica， two steps modification of nano-silica， and cement slury， was proposed in this paper. The stress-strain curves of RACs under uniaxial compression which were modified by three different methods at different strain rates （10^-5s^-1， 10^-3s^-1， and 10^-1s^-1） were obtained by conducting dynamic uniaxial compression test to explore the distinction between the curves before and after modification （two steps modification by nano-silica and cement slury， combined modification by nano-silica and fly ash， pre-soaking modification by nano-silica）. The results show that the novel modification method proposed could effectively promote the mechanical properties of RAC. Under the quasi-static condition， the peak stress and elastic modulus were increased by 25.1% and 85.8%， respectively. The dynamic increase factors（DIF） of the peak stress and elastic modulus of the modified RAC was decreased while the DIF of peak strain was increased. Finally， the dynamic stress-strain model of modified RAC was proposed， and the comparison results indicate that the predicted curves were in good agreement with the experimental curves， which can provide references for the engineering design and applications.

Key words:recycled aggregate concrete (RAC);modification of nano-silica;stress-strain curve;dynamic increase factor(DIF);dynamic constitutive model