| 摘要: |
| 传统早强组分已不能满足绿色、高性能混凝土的要求，尤其是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、适应性及对混凝土综合性能的影响。结果表明：配比为0.5% CB+1% TIPA+0.2% nano-SiO2+0.3% LB的低温早强剂作用效果可靠性高，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℃低温下，掺低温早强剂砂浆1 d、3 d、7 d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，其对混凝土工作性影响较小，但可明显提高C50、C40、C30不同强度等级混凝土各龄期下抗压强度，低温早强效果显著，且28 d至120 d强度保留率均超过100%。低温早强剂会使混凝土干缩略有增大，120 d干缩率较对比样增大3.6%~4.4%；56d前混凝土电通量增大0.7%~13.9%，但可减小混凝土90 d后电通量。 |
| 关键词: 低温 早强剂 强度 耐久性 适应性 |
| DOI： |
| 分类号:TV42 |
| 基金项目:国家重点研发计划项(2016YFC0401609)；国家自然科学(51739008)；云南省交通运输厅行业科技攻关项目(云交科教[2016]56号)。 |
|
| Preparation and properties of new type low-temperature early strength accelerator |
|
zhangfeng, baiyin, caiyuebo
|
|
Nanjing Hydraulic Research Institute
|
| Abstract: |
| The traditional early strength components had can not meet the requirements of green and high performance concrete, especially in the long-term mechanical properties and durability. By the way, low temperature early strength performance of the existing early strength accelerators was relatively limited, and the research on mechanism of early strength or its influence on concrete durability was also insufficient. In this paper, a new type of low-temperature early strength accelerator, which had 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, adaptability and influence on the comprehensive performance of concrete were also discussed. The results showed that the effects of the early strength accelerator with the optimal ratio of 0.5% CB+1% TIPA+0.2% nano-SiO2+0.3% LB is high 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 3d, while nano-SiO2 was beneficial to the strength improvement after 7d. At 5oC, the 1d, 3d, 7d and 28d compressive strengths of the motars mixed with early strength accelerators could increased by 377%, 98%, 72% and 18% respectively, and the strength development of mortars after 3d had exceeded the strength development of the contrast samples cured at 20oC. Low-temperature early strength accelerator had good adaptability to different types of cement and temperature, and had little influence on concrete workability. However, it could significantly improve the compressive strength at different ages of C50, C40 or C30 concrete, and the effect of low temperature early strength agent was significant, and the strength retention rates from 28d to 120d all exceeded 100%. The dry shrinkage of concrete would increased by 3.6%~4.4% compared with that of contrast sample at 120d, and the electric flux of concrete increased by 0.7%~13.9% before 56d, but decreased after 90d. |
| Key words: low temperature early strength accelerator compressive strength durability adaptability |
