纳米二氧化硅对丁苯共聚物/硫铝酸盐水泥复合砂浆物理力学性能的影响

Effect of Nano-silica on the Physical and Mechanical Properties of Styrene-butadiene Copolymer/Calcium Sulphoaluminate Cement Composite Mortar

为厘清纳米二氧化硅(NS)和丁苯共聚物乳液(SB)在硫铝酸盐(CSA)水泥中的协同作用,同时解决SB/CSA水泥复合砂浆凝结时间长、抗压强度低的问题,采用NS和SB对CSA水泥砂浆进行复合改性,研究改性复合砂浆物理力学性能随NS掺量的变化,并通过测定水化放热及水化产物分析NS在SB/CSA水泥复合砂浆中的作用机制。结果表明:NS可有效缩短SB/CSA水泥复合砂浆的凝结时间,提高其抗压强度,并与SB对CSA水泥砂浆抗折强度提升具有协同作用;NS最佳掺量为1.5%,此时与不加NS的纯SB改性砂浆相比,28 d抗压和抗折强度分别提高了28%、30%。同时,掺入NS会降低复合砂浆的流动度,提高表观体积密度,降低含气量和干燥收缩率,并略微降低毛细孔吸水率。NS可通过促进无水硫铝酸钙和硫酸钙反应,进一步加快SB/CSA水泥复合浆体的水化进程,提高钙矾石的含量,从而缩短凝结时间并提高力学强度。

Toclarify the interaction between nano-silica(NS) and styrene-butadiene copolymer emulsion(SB) in calcium sulphoaluminate(CSA) cement,and to solve the problem of prolonged setting time and reduced compressive strength of SB/CSA cement composite mortar,NS and SB were both used to modify CSA cement mortar.The change of physical and mechanical properties of modified mortar with the dosage of NS was studied,and the mechanism of NS in SB/CSA cement composite mortar was analyzed by hydration heat and hydration products analysis.The results show that NS can effectively shorten the setting time of SB/CSA cement composite mortar and increase the compressive strength,and has a synergistic effect with SB on the improvement of the flexural strength of CSA cement mortar.The optimal addition of NS is 1.5%,which can increase the 28 d compressive and flexural strength by 28% and 30% compared with pure SB modified mortar,respectively.Meanwhile,NS can also reduce the fluidity of the composite mortar,increase the density,reduce air content and the drying shrinkage,and slightly reduce the water capillary absorption.NS can further accelerate the hydration process of SB/CSA cement composite paste and increase the content of ettringite by promoting the hydration of ye'elimite and anhydrite,which can shorten the setting time and improve mechanical properties.