Preparation and properties of new type low-temperature early strength accelerator
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摘要: 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。Abstract: 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.
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Key words:
- early strength accelerator /
- low temperature /
- compressive strength /
- adaptability
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表 1 水泥化学组成分析
Table 1. Chemical compositions of Portland cements
质量分数/% SiO2 CaO MgO Fe2O3 Al2O3 K2O Na2O SO3 烧失量 总量 22.83 59.03 1.54 3.29 6.54 0.68 0.18 2.01 3.63 99.73 表 2 因素水平
Table 2. Factor level table
水平 因素 CB TIPA nano-SiO2 LB 1 0.50% 0.03% 0 0.10% 2 1.00% 0.50% 0.20% 0.30% 3 1.50% 1.00% 0.50% 0.50% 表 3 5 ℃养护下砂浆抗压强度
Table 3. Compressive strength of mortars cured at 5 ℃
样品编号 掺量/% 抗压强度/MPa CB TIPA nano-SiO2 LB 1 d 3 d 7 d 28 d 对比样−20 ℃ − − − − 10.7 28.8 41.8 56.8 对比样−5 ℃ − − − − 1.8 17.4 27.4 52.0 Z1 0.50 0.03 0 0.10 10.0 26.1 41.7 55.5 Z2 0.50 0.50 0.20 0.30 10.8 28.0 42.5 57.7 Z3 0.50 1.00 0.50 0.50 10.1 29.0 44.4 56.2 Z4 1.00 0.03 0.20 0.50 8.9 25.4 38.2 52.7 Z5 1.00 0.50 0.50 0.10 7.5 24.1 33.8 52.5 Z6 1.00 1.00 0 0.30 8.0 29.3 41.0 58.6 Z7 1.50 0.03 0.50 0.30 8.4 29.0 42.0 60.6 Z8 1.50 0.50 0 0.50 7.6 26.9 40.5 59.6 Z9 1.50 1.00 0.20 0.10 5.3 24.0 35.5 53.5 表 4 早强组分配比的直观分析结果
Table 4. Result of intuitive analysis
龄期/d 最佳掺合量/% CB TIPA nano-SiO2 LB 1 0.50 0.50 0.20 0.30 3 1.00 1.00 0 0.30 7 0.50 1.00 0.50 0.50 28 1.50 0.03 0.50 0.30 表 5 掺低温早强剂砂浆的抗压强度(温度适应性)
Table 5. Compressive strength of the mortars containing early strength accelerators
样品编号 温度/℃ 1 d 3 d 7 d 28 d 抗压强度/MPa 抗压强度比/% 抗压强度/MPa 抗压强度比/% 抗压强度/MPa 抗压强度比/% 抗压强度/MPa 抗压强度比/% 对比样 20 10.7 100 28.8 100 41.8 100 56.8 100 1# 24.2 226 41.5 144 49.6 119 61.8 109 2# 23.0 215 40.6 141 49.2 118 60.1 106 对比样 5 1.8 100 17.4 100 27.4 100 52.0 100 1# 8.6 476 34.3 198 44.6 172 59.7 115 2# 7.6 424 32.0 185 43.2 167 59.0 113 对比样 −5 1.2 100 3.1 100 4.3 100 1# 4.6 383 9.2 296 12.2 284 2# 3.1 258 5.7 184 9.0 209 -
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