Abstract
Recently, high-early strength type expansive admixture was developed and commercialized. In several concrete manufacturing plants, the effect has already been recognized not only to reduce of steam curing energy, and moist curing period after demoulding, and to improve of rate of mould rotation, but also to prevent drying shrinkage crack of concrete. In this paper, the applicability for the centrifugal reinforced concrete pipe using high-early strength type expansive admixture was examined. At present, the use of expansive admixture has been popular, but prevention of the crack and improvement of the external crack strength are big problem when producing type-2 pipe with specific diameter. The confirmation of the applicability was carried out regarding to ∅ 600mm type-2 pipe, in which the external crack strength was especially severe.
The circumferential crack was easy to be generated in the pipe, and in some case, there was some the external crack strength was low, when using high-early strength type expansive admixture. Therefore, the causes of generation of the crack and of low external crack strength were estimated and examined. It is reported that the external crack strength can be improved by releasing the restraint of the circumference direction mould during the period of the pre-curing of steam curing.
