锂盐对硼砂在硫铝酸盐水泥中作用的影响

在硫铝酸盐水泥实际工程应用中,硼砂作为常用的缓凝剂,容易导致硫铝酸盐水泥过度缓凝,为了更好调控水泥的凝结时间,本文研究了锂盐对硼砂在硫铝酸盐水泥中作用的影响,主要从凝结时间、抗压强度、水化产物方面进行了分析。结果表明:当硼砂掺量为0.1%(质量分数,下同)时,氢氧化锂能明显缩短硫铝酸盐水泥的凝结时间,降低水泥的抗压强度;当硼砂掺量为0.5%,氢氧化锂掺量大于0.07%时,水泥的凝结时间大幅度缩短,早期抗压强度随氢氧化锂掺量增加而略微提高,后期强度略微降低;在掺加硼砂的硫铝酸盐水泥体系中,锂盐的掺入不会改变水泥水化产物的种类,当硼砂掺量为0.5%时,1 d水化产物钙矾石衍射峰强度显著降低,28 d钙矾石衍射峰强度变化不明显。

Effect of Lithium Salt on Function of Borax in Sulphoaluminate Cement

In the practical engineering application of sulphoaluminate cement, borax is commonly used as a retarder. However, borax can cause excessive retardation of sulphoaluminate cement. In order to control the setting time of sulphoaluminate cement, lithium salt was added to sulphoaluminate cement to control the effect of borax. The setting time, compressive strength and hydration products were analyzed. The results show that lithium hydroxide significantly shorten the setting time of the sulfoaluminate cement with 0.1% borax. The addition of lithium hydroxide reduces the compressive strength. In the case of 0.5% borax, the setting time of cement is greatly shortened due to the addition of more than 0.07% lithium hydroxide. The early compressive strength increases slightly with the increase of lithium hydroxide content, and the later compressive strength decreases slightly. The addition of lithium salt does not change the type of hydration products of sulphoaluminate cement with borax. In the case of 0.5% borax, the intensities of ettringite peaks decrease significantly after 1 d of hydration, while the intensities is not influenced at 28 d.