Creep of lightweight concrete

Abstract

Summary Creep data covering periods of up to 18 months for concretes made with expanded-shale aggregates and having compressive strengths of 3,000 and 5,000 lb/in2 at 28 days are reported. These are compared with data for sand-gravel concretes of comparable strength. It was found that, contrary to current opinion, creep in lightweight concrete was essentially equal to or less than that in normal-weight concrete of comparable strength. The aggregates used in this investigation are typical of expanded-shale aggregates and natural sand-gravel aggregates available on the west coast of the United States, and the results may, therefore, not be directly applicable to materials available in other countries or in other parts of the United States. However, since the three expanded-shale aggregates used are typical of products that can be obtained by sintering clays and shales to incipient fusion, the results reported should be generally applicable to concretes containing such aggregates. A brief description of the hydraulic loading equipment used in the creep tests is included. The equipment, performed satisfactorily throughout this investigation with very little maintenance; it may be expected to perform similarly at any stress level normally encountered in creep studies. Some brief comments relative to the merit of current techniques for studying creep in concrete are made, and a new approach to the problem is suggested.