Experimental study on mechanical properties and pore characteristics of the modified lime mortars under freee-thaw cycles北大核心CSCD

石灰土作为路基填料代替宕渣是一种较为经济的方案，但灰土初始强度低、硬化速率慢、碳化时间长，不利于快速施工，需要进行改良研究。利用偏高岭土与石灰发生火山灰反应的原理改良灰土，通过单轴压缩试验和三轴压缩试验，分析改良灰土冻融循环条件下力学参数变化规律，利用图像处理技术提取改良灰土图像表面孔隙，建立孔隙率与强度的关系，并通过研究龄期、石灰含量和含水率变化规律，分析偏高岭土改良灰土的机制。结果表明：偏高岭土能够有效提高灰土材料反应速率，改善灰土力学特性；偏高岭土在一定程度上能够恢复冻融循环导致的灰土力学性能损失，降低冰晶体产生的孔隙；灰土强度达到最优后，其强度随着石灰的增加而降低，而经偏高岭土改良后其强度将继续增加；火山灰反应比灰土碳化过程消耗更多的水分，有效提高了灰土的抗冻性能。

Experimental study on mechanical properties and pore characteristics of the modified lime mortars under freee-thaw cycles

It is an economical solution to replace slag using lime mortars as subgrade filler. However， lime mortars has low initial strength， slow hardening rate， and long carbonization time， which is not conducive to rapid construction. In this paper， the pozzolanic reaction between metakaolin and lime is used to improve lime mortars. Through uniaxial compression testing and triaxial compression testing， the mechanical parameters of improved lime mortars under freeze-thaw cycles is analyzed. The surface porosity of improved lime mortars image is extracted by image processing technology， and the relationship between porosity and strength is established. The mechanism of improved lime mortars in metakaolin is analyzed by studying the age， lime contents and moisture contents. The results show that： metakaolin can effectively increase the reaction rate and mechanical properties of lime mortars； metakaolin can restore the loss of mechanical properties of lime mortars caused by freeze-thaw cycle to a certain extent， and reduce the pores caused by ice crystals； after reaching the optimum strength， the strength of lime mortars will decrease with the increase of lime， while it will continue to increase after being improved by metakaolin； the pozzolanic reaction consumes more water than the carbonation process of lime mortars， and effectively improves the frost resistance of lime mortars.