低活性矿渣内养护水泥砂浆自收缩与孔结构分析

Analysis of autogenous shrinkage and pore structure of cement mortar with low-activity slag as internal curing material

采用预吸水饱和状态的低活性矿渣作为内养护材料部分替代砂,研究不同低活性矿渣掺量内养护砂浆的力学性能与自收缩变化规律,并通过MIP、SEM和XRD测试结果探讨了低活性矿渣内养护砂浆的微观机理。结果表明:不同低活性矿渣掺量砂浆试样在标准养护与密封养护条件下抗压强度发展规律相似,即随着低活性矿渣掺量的增加,砂浆早期强度下降幅度较大,但随着龄期的延长,砂浆后期强度降低幅度小于早期降低幅度;并且低活性矿渣能有效抑制浆体各阶段的自收缩,尤其在快速收缩阶段和短暂膨胀阶段作用最为明显;低活性矿渣内养护作用下,虽增加了浆体的孔隙率,但有效降低了平均孔径,改善了各类型孔的分布比例,细化孔隙结构;内养护作用使浆体水化产物C-S-H凝胶增多,Ca(OH)_(2)被消耗,界面过渡区薄弱结构得到显著改善。

The pre-saturated low-activity slag was used as a partial replacement of sand for internal curing materials.The mechanical properties and autogenous shrinkage of internal curing mortar with different low-activity slag contents were studied.The microscopic mechanism of low-activity slag internal curing mortar was discussed based on MIP,SEM and XRD test results.The results show that the compressive strength development law of mortar specimens with different low-activity slag contents under standard curing and sealing curing conditions is similar,that is,with the increase of low-active slag content,the early strength of mortar decreases greatly,but with the extension of age,the late strength reduction of mortar is less than early strength reduction.Moreover,low-activity slag can effectively inhibit the autogenous shrinkage of the slurry at various stages,especially in the rapid shrinkage stage and the transient expansion stage.Under the internal curing effect of low-activity slag,although the porosity of the slurry is increased,the average pore diameter is effectively reduced,the distribution ratio of various types of pores is improved,and the pore structure is refined.The hydration product C-S-H gel increases,Ca(OH)_(2) is consumed,and the weak structure of the interface transition zone is significantly improved.