5 ℃低温下复合早强剂性能与早强机理

Properties and Early Strength Mechanism of Compound Early Strength Accelerator at 5 ℃

摘要:

以溴化钙、溴化锂和三异丙醇胺3种组分设计新型低温早强剂，研究5 ℃下低温早强剂的早强性能及其对混凝土综合性的影响，并探讨其早强作用机理.结果表明：掺低温早强剂C50混凝土，5 ℃养护1 d、3 d、7 d、28 d龄期下抗压强度较对比样分别提高57%、32%、23%和12%，混凝土各龄期强度已接近对比样在20 ℃下的强度.低温早强剂会使混凝土干缩略有增大，56 d前混凝土电通量增大0.7%~10.1%.5 ℃低温下，掺低温早强剂水泥水化生成新的含溴CSH凝胶和水化溴氧铝酸钙产物，孔隙或凝胶产物表面有针棒状钙矾石、片状Ca(OH)2晶体生成，产物微观结构更加致密，孔径细化，总孔隙率降低.

Abstract:

A novel low-temperature early-strength accelerator was designed with three components, such as calcium bromide, lithium bromide, and triisopropanolamine. Besides, the early strength property and its influence on the comprehensive performance of concrete were studied at 5 ℃. In addition, the early strength mechanism of the early strength accelerator was discussed. The results show that the low-temperature early-strength accelerators make the 1, 3, 7, and 28 day compressive strengths of C50 concrete cured at 5 ℃ increase by 57%, 32%, 23%, and 12% compared with the contrast sample, respectively, and the strength development is close to that of the contrast sample cured at 20 ℃. Moreover, the low-temperature early-strength accelerator will increase the dry shrinkage of concrete slightly, and the electric flux of concrete before 56 d will increase by 0.7% to 10.1%. At 5 ℃, new types of hydration products such as bromine-containing C-S-H gel and calcium aluminum oxide bromide hydrate (Ca₄Al₂O₆Br₂·10H₂O) are generated through hydration reaction. There are also much needle-rod-like ettringite and flake Ca(OH)₂ crystals formed in the pores or embedded in the surface of the gel products. Therefore, the structure of the samples will become denser, due to the refinement of pore size and the reduction of total pore porosity.