普通硅酸盐P·O 42.5级水泥抗裂性控制指标研究及工程实践

Research and engineering practiceon the crack resistance control index of ordinary Portland P·O 42.5 cement

以广泛使用的普通硅酸盐P·O 42.5级水泥为对象,针对部分工程监测出现的异常结果,反向收集了不同工程3年内的原材料及数据开展了室内试验研究与统计分析。结果表明,即便在控制P·O 42.5级水泥比表面积≤350 m2/kg、碱含量≤0.60%、C3A含量≤8%,且不同批次水泥的上述指标相对稳定的情况下,水泥3 d胶砂强度之差可达到12.5 MPa,相同工况条件下1.2 m厚侧墙温升值之差可达到17.1℃,水泥早期水化速率、放热量及早期胶砂强度随着C3S/C2S的增加而显著增大。因此,在控制水泥比表面积、碱含量、C3A含量的基础上,建议进一步控制水泥C3S/C2S不超过4.0,水泥3 d胶砂强度宜为25~28 MPa,不应超过30 MPa。

Due to some engineering monitoring abnormal results,the widely used ordinary Portland P·O 42.5 cement was taken as the object,the raw materials,and data of different projects within 3 years were collected in reverse to carry out laboratory experimental research and statistical analysis.Results showed that even if the specific surface area of P·O 42.5 cement was controlled to be less than 350 m2/kg,the alkali content was less than 0.60%,and the C3A content was less than 8%,and the above indexes of different batches of cement are relatively stable,the difference of cement mortar strength at 3 days can reach 12.5 MPa,and the difference of temperature rise of 1.2 m thick side wall can reach 17.1℃under the same working conditions.The early hydration rate,hydration heat and early mortar strength of cement increased significantly with the increasing of the ratio of C3S to C2S.Therefore,on the basis of controlling the specific surface area,alkali content and C3A content of cement,it is suggested that further control the ratio of C3S to C2S should not exceed 4.0,the mortar strength of cement at 3 days is appropriate within the range of 25 MPa to 28 MPa,and not more than 30 MPa.