抄録
In the construction of reinforced concrete structures, the construction joint work of early-age concrete is often required. Conventional techniques for adhesion improvement in the construction joint work are wire-brushing, green-cut, retarder spraying and epoxy resin-based adhesive spraying. However, it is difficult to apply the conventional techniques to the early-age concrete within 72 hours after placing because of the poor strength development of the concrete. The author has developed an improved technique using polymer emulsion treatment for the construction joint work of the early-age concrete. The purpose of this study is to make clear the effects of polymer type, jointing time and jointing method on the adhesion of the construction joints to which the polymer emulsion treatment technique is applied.
Concrete was placed into molds, and the surfaces of early-age concrete were treated by polymer emulsion spraying with or without subsequent polymer cement paste spraying. Then, jointing concrete was mixed and placed on the treated concrete surfaces at various jointing times for preparing construction joint. The adhesion in tension of the construction joints was determined at curing periods of 28 days and 6 months for the jointing concrete. In conclusion, the treatment of the early-age concrete surfaces by polyacrylic ester emulsion spraying within 36 hours after placing provides high adhesion in tension of the construction joints, as compared to the treatments using styrene butadiene rubber latex and ethylene-vinyl acetate emulsion. Spraying of the polymer cement pastes on the construction joints treated by the polymer emulsion spraying causes an improvement of the adhesion in tension of the joints. Accordingly, it is considered that the polymer emulsion treatment is most useful for the construction joint work of the early-age concrete.
