钙质砂水泥砂浆力学性能试验研究及微观结构分析

Experimental Study and Microstructure Analysis of Calcareous SandCement Mortar

为探究新型建筑材料钙质砂的工程性质,对钙质砂水泥砂浆进行了力学性能试验,研究了水灰比、养护条件、养护龄期、级配对其抗压、抗折强度的影响,采用SEM对钙质砂颗粒及水泥砂浆的微观结构进行分析,建立了钙质砂细度模数与吸水率之间的关系曲线。结果表明:钙质砂水泥砂浆早期强度比标准砂稍高,但其28 d强度低于标准砂砂浆;养护初期海水养护试样强度较高,而养护后期淡水养护试样强度明显大于海水养护试样强度。SEM结果显示,水泥水化后的细粒组(GS1)颗粒表面孔隙被C-S-H、Ca(OH)2和C-A-H水化产物胶结良好,粗粒组(GS3)颗粒间仍可以产生较好的咬合力,而中粒组(GS2)因不存在这些优势所以强度小于GS1和GS3。钙质砂吸水率比标准砂高5%~6%,吸水率越低,强度越高;钙质砂细度模数与吸水率为二次多项式关系,在考虑吸水率的情况下,对钙质砂水泥砂浆的抗压强度计算进行了修正。

In order to explore the engineering properties of calcareous sand,a new building material,the mechanical properties of calcareous sand cement mortar were tested and the influences of water-cement ratio,curing conditions,curing age and size were studied by the compressive and flexu-ral strength,the microstructure of calcareous sand particles and cement mortar were analyzed by SEM,and the relationship between the fineness modulus of calcareous sand and water absorption was established.The results show that:the early strength of calcareous sand cement mortar is slightly higher than that of standard sand,but the strength is not as good as that of standard sand mortar at 28 d;The strength of cement mortar in seawater conservation is higher in the early stage of curing but significantly weaker in the later stage of curing than that in freshwater conservation.SEM revealed that,after the process of cement hydration,surface pores of the GS1 particles are well cemented by the hydration products such as:C-S-H,Ca(OH)2 and C-A-H,and the GS3 particles can have better bite force between the particles,however,GS2 does not have these advantages so that its compressive strength is less than the cement mortar of GS1 and GS3.The water absorption of calcareous sand is about 5%—6%higher than that of standard sand,the strength increases as the water absorption rate decreases;The water absorption and the fineness modulus of calcareous sand are in quadratic polynomial relations,the compressive strength calculation of calcareous sand cement mortar was corrected in consideration of the water absorption.