不同养护方式对混合砂浆抗冻性能影响研究

Effect of Different Curing Methods on the Frost Resistance of Mixed Sand Concrete

为了解决混凝土用砂资源问题和在应对冰冻环境时传统养护方式局限性的问题,将淡化海砂、机制砂、混合砂等3种砂类成型的试件,用慢冻法进行冻融循环试验,探讨了标准养护条件下的抗冻性能。实验结果表明:淡化海砂和机制砂的比例为6︰4时,成型的混合砂试件在抗冻性能表现上优于单一砂类。此外在解决传统养护方式局限性问题时,对混合砂试件采取4种不同平行养护方式,针对其抗冻性能进行对比研究,并在养护龄期到达28 d时取平行试样内部样品,通过SEM对其微观结构进行探究和分析。结果表明:采用外养护的混合砂试件抗压强度损失率较低,但冻融后孔隙率变化幅度较大,说明其在低次数的冻融循环表现较好;采用内养护的混合砂试件冻融循环后,孔隙率变化幅度小,可以有效控制孔隙发育,但其本身抗压强度略低;当同时采用这两种养护方式时,混合砂试件冻融循环后质量、抗压强度损失率、孔隙率增长均较小,在SEM微观结构的结果分析中,也观察到较少裂缝,且抗压强度可达到标准养护的水平。综上研究后发现,适当比例混合砂的使用,能够解决混凝土用砂资源问题,在成型试件时和成型试件后,同时施作内养护和外养护可提高试件抗冻融循环的能力。

In order to solve the problem of sand resources for concrete and the limitation of traditional curing methods in dealing with the freezing environment,the freeze-thaw cycle test was carried out with the slow freezing method on the specimens formed by desalinated sea sand,mechanism sand and mixed sand,and the freezing resistance performance under standard curing conditions was explored.The experimental results showed that the frost resistance performance of the formed mixed sand specimens was better than that of single sand when the ratio of desiccated sea sand and mechanism sand was 6:4.In addition,to address the limitations of the conventional curing methods,four parallel curing methods were applied to the mixed sand specimens to compare their frost resistance performance,and the internal samples of the parallel specimens were taken at the curing age of 28 d.The microstructure was investigated and analyzed by SEM.The results showed that the loss rate of compressive strength of the mixed sand specimens with external curing was low,but the change of porosity after freeze-thaw was large,which indicates that it performs better in low number of freeze-thaw cycles;the change of porosity of the mixed sand specimens with internal curing was small after freeze-thaw cycles,which can effectively control the pore development,but its own compressive strength was slightly lower;when both curing methods were used,the mass,compressive strength loss rate and porosity increase of the mixed sand specimens were smaller after freeze-thaw cycles,and the less cracks were also observed in the result analysis of SEM microstructure,and the compressive strength could reach the level of standard maintenance.