水泥砂土浆的力学性能试验研究

Experimental Study on Mechanical Behaviors of Cement Mortar Containing Excavated Soil

针对华南地区量大面广的两类渣土(花岗岩风化残积土、冲洪积土),建议用相应的处理工艺;采用处理后的可用渣土部分或全部取代天然河砂以制备水泥砂土浆,考察了基于工作性能的减水剂需求;开展了水泥砂土浆的抗压和抗折试验,揭示了相应力学性能随渣土取代率的变化规律。研究结果表明:(1)为确保水泥砂土浆的良好工作性能,减水剂用量随渣土取代率的增加逐渐增大,但其最大掺量(以固含量计)也仅为胶凝材料质量的1.1%左右;(2)采用基于冲洪积土的可用渣土部分或全部取代天然河砂时,水泥砂土浆的抗折和抗压强度以及弹性模量总体上都与无渣土时基本相当,实际工程中采用该类可用渣土完全取代天然河砂是可能的;(3)采用基于花岗岩风化残积土的可用渣土取代30%天然河砂不会对水泥砂土浆的力学性能产生明显不利影响;当该取代率提升至50%时,水泥砂土浆的28 d抗折强度、抗压强度和弹性模量相比无渣土时的最大降幅分别约为6%、15%和10%,实际工程中该类可用渣土的取代率以不超过50%为宜。

The treatment approaches for weathered residual soil of granite and alluvial-diluvial,which are the most widespread excavated soils in South China,were put forward.After the processing procedures,the usable excavated soils were utilized to partially or fully replace the river sand to prepare cement mortar,and the water-reducing admixture demand for suitable working performance of the cement mortar was investigated.The compressive and flexural tensile tests were carried out to examine the influence of the replacement ratio of excavated soil on the mechanical behavior of cement mortar containing excavated soil.The results show that:(1)on the premise of ensuring good working performance of the cement mortar,water-reducing admixture demand increases with the increase of the replacement ratio of excavated soil,but its largest dosage(calculated by solid content)accounts for only 1.1%of the binding material;(2)the compressive strength,flexural tensile strength and elastic modulus of the cement mortar prepared partially or fully with the usable content of alluvial-diluvial soil are roughly equivalent to those of the cement mortar containing no alluvial-diluvial soil,so it is practicable to fully replace the river sand with the usable content of alluvial-diluvial soil in actual practice;(3)replacing 30%of the river sand with the usable content of weathered residual soil of granite has no significant adverse effects on the mechanical behaviors of the cement mortar,but when the replacement ratio increases to 50%,the 28 d flexural tensile strength,compressive strength and elastic modulus of the cement mortar maximally drop by 6%,15%and 10%,respectively,compared with those of the cement mortar without weathered residual soil of granite.It is suggested that the replacement ratio of such soil should not exceed 50%in practice.