温度对水泥乳化沥青砂浆早期膨胀特性的影响

Effect of Temperature on Early Expanding Character of Cement and Emulsified Asphalt Mortar

模拟现场施工条件,测定了不同温度下灌注袋中的中国铁路轨道系统Ⅰ型水泥乳化沥青(cement and emulsified asphalt,CA)砂浆膨胀率随时间变化,并测定了浆体pH值随时间的变化。研究发现CA砂浆早期膨胀可分为4个阶段:混合后0～3h,砂浆收缩;3～6h,砂浆迅速膨胀;6～10h,砂浆再收缩;10 h以后,砂浆体积较为稳定。温度越高,各阶段开始时间越早,持续时间也越短;20～35℃,浆体膨胀率随温度升高而增大,但温度为35～45℃时,砂浆膨胀率随温度升高反而减小,温度对浆体pH值随时间变化的影响也有类似规律。扫描电子显微镜和能谱仪结果表明:对于水化10d的水泥乳化沥青砂浆,20℃浆体中可看到大量与钙矾石有关的针状物,而55℃浆体中除沥青膜层外,水泥水化产物并不明显。高温下(>35℃)乳化沥青破乳,包裹铝粉与水泥颗粒,使铝粉发气反应受到抑制可能是导致膨胀率、pH值等变化异常的原因。

The changes of expanding ratio and pH value of the paste with time of cement and emulsified asphalt （CA） mortar in the perfusion bag were examined at different temperatures under the practical construction conditions. The results show that the early expanding duration of CA mortar can be divided into four periods, namely, 1） the CA mortar has a little shrinkage from 0 to 3 h after mixing; 2） and then the CA mortar expands rapidly and persists at 3 h; 3） the CA mortar has a little shrinkage again from 6 to 10h; and 4） the volume finally keeps stable after 10h. A higher temperature resulted in the shorter early period. The expanding ratio of CA mortar increased with increasing temperature from 20 ~C to 35 ~C. However, the expanding ratio decreased with increasing tempera- ture from 35 ~C to 45 ~C. The temperature also had an effect on the pH values change with time. The results by scanning electron microscope and energy dispersive spectrometer show that there exist the more needle-shaped hydrations, which may be AFt （ettringite） of CA mortar hydrated for 10 d at 20 ~C. However, there could not exist any hydrations except some asphalt films of CA mortar hy- drated for 10 d at 55 ~C. The emulsion asphalt broke in the prepared CA mortar system at high temperature, and then enveloped the cement and aluminum particles, thereafter restraining the gas forming reactions of aluminum powder and resulting in the abnormal changes of the expanding ratio and pH value with time.