改性高铝水泥浆的负温硬化性能及其增强机制

针对负温环境下固井水泥浆水化反应减缓甚至停滞,导致固井施工难以进行的问题,开展了改性高铝水泥浆的硬化特性优化和早期强度的增强机制研究.在0,–10和–18℃温度下,进行了改性高铝水泥浆的凝结时间、流动度及抗压强度等性能对比试验,研究了负温环境下水泥浆关键性能的变化规律及与凝结时间调节剂SCEG之间的关系;在分析水化产物...

Hardening Properties and Enhancement Mechanisms of Modified Alumina Cement at Minus Temperature

Because the hydration reaction of cement is unable to proceed below the freezing point and hinders cementing, a research on the hardening properties optimization and enhancement mechanism for early strength of modified alumina cement was conducted. Changes in setting time, fluidity and compressive strength of cement at different temperatures of 0, ?10, and ?18 °C were compared, and the relationship between these changes at different temperatures and the setting time modifier SCEG was studied. Based on the analysis of phase compositions and microstructures of hydration products, the mechanism of hardening of cement at minus temperature was studied, and gypsum was added to promote the formation of AFt so as to enhance the compressive strength of hardened cement paste. The experiment demonstrated that the cement can be hardened within 0.3–6.0 hour when SCEG about 0–3% cement mass is added to the modified alumina cement from 0 °C to ?18 °C. In that case, its compressive strength can reach 9.7–11.2 MPa within 24 hours and even rise 30% after gypsum about 10%–15% cement mass is added. X-ray diffraction (XRD) analysis indicates that the main hydrated mineral in the cement is aluminate clinker instead of silicate clinker at minus temperature, with Ca₂Al(Al,Si)₂O₇, AFm, AFt, and a few C－S－H as the main products. To be specific, a higher content of AFt can bring higher compressive strength of hardened cement paste. The results show that modified alumina cement possesses optimized hardening properties at minus temperatures, and appropriate amount of gypsum can increase the content of AFt in hydration products, improving the compressive strength of hardened cement paste.