Study on Properties and Mechanism of Liquid Alkali Free Set Accelerating Admixture for Sprayed Concrete

摘要

A high-performance liquid alkali-free setting accelerator (HSL) in sprayed concrete was prepared by dimethyl sulfoxide modified sepiolite and aluminum hydroxide as the main raw materials. The sprayed concrete rebound have been investigated by concrete penetration resistance tester. Its set accelerating mechanism is studied by pore structure analysis,XRD characterization methods. The pore structure analysis shows that the total porosity and pores larger than 3.94 in. [100 mm] of cement pastes mixed with HSL are slightly reduced after 28 days hydration and the hydration of C_3A was accelerated by the polyamine complexation of accelerator, resulting in forming a large number of acicular ettringite and reducing the amount of Ca(OH)_2 crystal, which will not affect the later hydration of cement,to improve the final compressive strength. The 1day compressive strength of the concrete mixed with HSL reaches 22.3 MPa (3234 psi), the 28 days compressive strength ratio increasing by 118.5%.