<p>The engineering application of low-alkali sulphoaluminate cement (L-SAC) is hindered due to the difficulty in adjusting the setting and hardening time. In this paper, lithium hydroxide and borax are mixed into L-SAC to regulate its setting and hardening process, so as to prepare a sulphoaluminate concrete material with high early strength and high fluidity. The effects of the ratio of lithium hydroxide to borax on the properties of L-SAC concrete were studied by hydration heat, XRD, TG-DTG, SEM and MIP. The experimental results show that the slump increases with the increase of borax content, and the early (3 h) strength increases with the increase of lithium hydroxide content. When 0.05% lithium hydroxide and 0.4% borax are added, the 0.5 h slump reaches 195 mm, and the 3 h compressive strength reaches 15.9 MPa. The increase of lithium hydroxide will promote the formation of early hydration products AFt and AH<sub>3</sub> gel and accelerate the hydration process, while borax will inhibit the dissolution and hydration of cement and delay the setting and hardening process of concrete. The combination of the two ensures that the concrete has the characteristics of high early strength and high fluidity, and the early workability and mechanical properties can be controlled by the mix ratio. For long-term mechanical properties, the special concrete does not produce AFm, which can ensure the continuous development of strength.</p>

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Effect of Lithium Hydroxide and Borax on Properties of Low Alkali Sulphoaluminate Special Concrete

  • Tingchao Chen,
  • Rongjin Liu,
  • Daiyan Jing,
  • Yingren Zhao,
  • Yixing Zhen,
  • Jiazhan Wei

摘要

The engineering application of low-alkali sulphoaluminate cement (L-SAC) is hindered due to the difficulty in adjusting the setting and hardening time. In this paper, lithium hydroxide and borax are mixed into L-SAC to regulate its setting and hardening process, so as to prepare a sulphoaluminate concrete material with high early strength and high fluidity. The effects of the ratio of lithium hydroxide to borax on the properties of L-SAC concrete were studied by hydration heat, XRD, TG-DTG, SEM and MIP. The experimental results show that the slump increases with the increase of borax content, and the early (3 h) strength increases with the increase of lithium hydroxide content. When 0.05% lithium hydroxide and 0.4% borax are added, the 0.5 h slump reaches 195 mm, and the 3 h compressive strength reaches 15.9 MPa. The increase of lithium hydroxide will promote the formation of early hydration products AFt and AH3 gel and accelerate the hydration process, while borax will inhibit the dissolution and hydration of cement and delay the setting and hardening process of concrete. The combination of the two ensures that the concrete has the characteristics of high early strength and high fluidity, and the early workability and mechanical properties can be controlled by the mix ratio. For long-term mechanical properties, the special concrete does not produce AFm, which can ensure the continuous development of strength.