The Effects of Construction Joint in Mass Concrete

摘要

The basemat of Kawasaki man-made island is made of flowable concrete, because only superplasticized concrete can meet the stringent performance requirements of this project. One of the major concerns before the construction of this basemat is the uncertain effects of construction joint in the mass flowable concrete. Due to the large volume of concrete required, various difficult logistic conditions present and limited lay-down area available at the site, it is not possible to place the whole basemat concrete in one pass. Construction joints are bound to occur. To generate relevant technical data and to assist the development of an ultimate concrete placing cycle for the basemat, a series of tests are conducted to evaluate the possible effects of construction joints in this mass concrete. The general testing procedure for these tests is designed to simulate the worst real condition that could be encountered in the field. Simulation of construction joints is achieved by creating an artificial joint in each of the concrete test samples. Since there are no readily-adaptable standards for determining the maximum allowable re-vibration time in the kind of superplasticized concrete used, compressive strength and concrete flowing capability are used as the main criteria. The key data generated and observations made during the evaluation as well as the conclusions and recommendations regarding placement of mass flowable concrete are presented in this paper.