低强度等级自密实钢管混凝土膨胀剂的研究及其应用

Research and application of expansion agent for low strength grade self-compacting concrete filled in steel tube

利用石灰石、石膏、铝矾土、方镁石制备C_4A_3S-CaO-MgO多组分复合膨胀剂,研究C_4A_3S-Ca O体系中不同配合比、SA(硫铝比)对水泥净浆凝结时间、胶砂强度、限制膨胀率的影响;MgO体系中不同煅烧温度对水泥试样限制膨胀率的影响。借助XRD、SEM测试手段,从微观对水泥体系中的水化产物、晶体形态进行分析。结果表明,C_4A_3S-Ca O-M g O多组分复合膨胀剂早期膨胀速率快,膨胀稳定期长,能补偿后期膨胀不足,28 d仍显示为微膨胀。并利用其制备出C30自密实微膨胀钢管桩基混凝土,成功应用于武汉阳逻港深水薄壁大直径钢管桩中。

Limestone,gypsum,bauxite and periclase were used to prepare C4A3S^--CaO-MgO multicomponent composite expansion agent. The influence of different mix proportion and sulfur to aluminum ratio in C4A3S^--CaO-MgO system on setting time of cement paste,Strength of cement mortar,restrained expansion rate of cement paste were studied,the influence of different calcination temperature in MgO system on the restrained expansion rate of cement paste were also studied. Hydration products and crystal morphology in cement system were analyzed in microscopic level via testing method such as XRD and SEM. The results showthat C4A3S^--CaO-MgO multicomponent composite expansion agent has a relatively fast initial expansion rate and a relatively long expansive stability period,which can compensate the deficiency in expansion in latter period,showmicrodilatancy at an age of 28 d. Finally,C30 self-compacting microdilatancy steel pipe concrete pile foundation prepared with this expansion agent were successfully applied in deepwater port with thin wall and large diameter steel pipe pile in Yangluo of Wuhan.