Concrete Journal

A chemical admixture for concrete that is attracting attention recently is single-liquid viscosity agent type high-range AE water reducing agent obtained by combining viscosity agent and high-range AE water reducing agent, which allows the manufacture of viscosity agent type self-compacting concrete without having to separately add viscosity agent. Another one is shrinkage reducing type high-range AE water reducing agent obtained by combining shrinkage reducing agent and high-range AE water reducing agent, which can reduce drying shrinkage strain by about 5% to 15% compared with concrete that uses conventional high-range AE water reducing agent. This paper describes the features and advantages of these two types of chemical admixtures.

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Given the same tension load capacity, the anchorage length of post-installed bonded anchor bolts is extremely short compared with the anchorage length of cast-in-place anchor bolts. Under the Architectural Institute of Japan's “Design Recommendations for Composite Construction, Part 4: Design Recommendations for Anchor Bolts” revised in 2010, the design of the anchorage zone of anchor bolts is based on the concept that the anchorage zone is the same regardless of whether anchors are cast in place or post installed. With regard to the design method for the tension load capacity of bonded anchors, this study investigates whether evaluation based on the maximum load determined from the bond strength between the adhesive and concrete is appropriate, and proposes a tension load capacity evaluation formula. Further, it verifies that the estimates of bond strength, which declines as the result of the edge distance effect and group effect, among other things, are equivalent with the bond strengths used for cast-in-place deformed bars.

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The penetration mechanism of paint type shrinkage reducing agent was modeled and the influence of its curing effect on the hydration of cement and the hydrous properties of hardened cement was investigated. With regard to the penetration mechanism, the effect of the fluid properties on permeability, coating thickness, and drip characteristics were studied, and the feasibility of evaluating the penetration depth with the Lucas-Washburn method was confirmed. The fundamental findings that the curing effect of paint type shrinkage reducing agent inhibits the reduction in moisture content and prevents hydration delay even in dry conditions were obtained. The fact that these effects inhibit the progress of drying shrinkage and carbonation, even under dry conditions, demonstrates that paint type shrinkage reducing agent promotes sound strength development. Finally, the results of an investigation on cracks in the case of application to building structures are reported.

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