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

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.

Key words:concrete strength; early strength accelerator; low temperature; mechanism; durability