Abstract
Concrete structures often fail to perform their original functions due to problems such as deterioration and damage over time. Therefore, various repair materials have been studied to maintain deteriorated concrete structures. This study experimentally investigated the mechanical properties of high-early-strength cement-based repair materials for spraying. For spraying, the cement-based materials should have adoptable fluidity and strength: 200 ± 100 mm for flow; 20 MPa at 24 h and 40 MPa at 28 days for compressive strength, and 8 MPa at 28 days for flexural strength. Wollastonite mineral fibers (3-5 wt.%) and styrene-butadiene (SB) latex (5-7 wt.%) were studied to enhance this requirement. Fluidity was evaluated by flow test and measuring the heat of hydration; mechanical properties were evaluated in terms of compressive and flexural strength. The cement-to-silica sand ratio (C:S ratio) was also applied differently to adjust the pot life of polymer cement-based material (1:1 and 1:1.5) as a binder. Because wollastonite mineral fibers and SB latex affect workability, the water-to-binder ratio was regulated to reach the target flow according to the amount of wollastonite mineral fibers and SB latex. Regardless of the C:S ratio, all studied mixtures met the target 28 day compressive strength at 24 h, decreasing in strength with increasing amounts of wollastonite mineral fibers and latex. Flexural strength also fulfilled the target value, and it increased with increasing amounts of wollastonite mineral fibers and latex, unlike compressive strength. The optimal mix proportion of high-early-strength cement-based repair materials constituted 3 wt.% wollastonite mineral fibers and 5 wt.% SB latex as the binder in a C:S ratio of 1:1.5.