新型低温早强剂的制备与性能研究

传统早强组分已不能满足绿色、高性能混凝土的要求，其长龄期力学性能和耐久性能堪忧，且现有早强剂的低温(尤其是5 ℃)早强性能有限，低温下作用机理及其对混凝土耐久性影响的研究比较缺乏。以无机盐CB，LB，三异丙醇胺和纳米SiO₂四组分制备无碱、无氯、不含SO₄2-的低温早强剂，并研究5 ℃低温下早强剂的性能、适应性。结果表明:配比为0.50% CB+1.00% TIPA+0.20% nano-SiO₂+0.30% LB的低温早强剂可靠性高，其中CB和LB为关键组分，对砂浆各龄期强度提高均起重要作用，TIPA对3 d后强度提高作用显著，而nano-SiO₂对7 d后强度提高作用明显。5 ℃下，掺低温早强剂砂浆1，3，7和28 d强度较对比样分别提高376%，98%，72%和18%，砂浆3 d后各龄期强度已超对比样20 ℃养护下强度。低温早强剂对不同种类水泥、温度的适应性良好。

Preparation and properties of new type low-temperature early strength accelerator

The traditional early strength components have not met the requirements of green and high performance concrete, especially in the long-term mechanical properties and durability. The low temperature early strength performance of the existing early strength accelerators is relatively limited, and the research on the mechanism of early strength or that on its influence on concrete durability is also insufficient. In our research, a new type of low-temperature early strength accelerator, which has no alkali, no chlorine and no sulfate ions, was prepared by using four components of inorganic salt CB, LB, triisopropanolamine and nano-SiO₂, and its early strength performance and adaptability were also analyzed. The results show that the effects of the early strength accelerator with the optimal ratio of 0.50% CB+1.00% TIPA+0.20% nano-SiO₂+0.30% LB is highly reliable. CB and LB were the key components, which played an important role in improving the strength of mortars at different ages under low temperature curing, and TIPA had a significant effect on the strength enhancement after 3 d, while nano-SiO₂ was beneficial to the strength improvement after 7 d. At 5 ℃, the 1 d, 3 d, 7 d and 28 d compressive strengths of the motars mixed with early strength accelerators could be increased by 377%, 98%, 72% and 18% respectively, and the strength development of mortars after 3 d had exceeded the strength development of the contrast samples cured at 20 ℃. Low-temperature early strength accelerator had good adaptability to different types of cement and temperature.