Laboratory testing of unconfined compressive strength of cement stabilised soil cores

Abstract

Nowadays, reclamation has been one of the key civil engineering works in Hong Kong and deep cement mixing (DCM) technique is widely used in reclamation works especially for mega projects. Compliance tests like unconfined compression test on cement stabilised soil will be carried out to verify the quality of the works during construction. However, most international testing standards are not directly applicable to testing cement stabilised soil cores in Hong Kong. Therefore, in September of 2017, a Task Force, established under the auspices of the Geotechnical Division of The Hong Kong Institution of Engineers, prepared the Interim Guidelines on Testing of Unconfined Compressive Strength of Cement Stabilised Soil Cores in Hong Kong. This proposal is intended to provide some scientific support and technical recommendations to enhance the Interim Guidelines, eventually to develop a testing standard of mechanical properties of cement stabilised soil cores formed by wet mixing method in field or in laboratories. Two aspects are primarily concerned with. One is to determine best-fit equations of correction factors to UCS values for cement stabilised soil specimen with varying length-to-diameter (L/D) ratio. Another one is to learn about stress-strain behaviour of cement stabilised soil cores, including UCS value and elastic modulus (E). To achieve the goal, 128 laboratory cement stabilised soil specimens are prepared in general accordance with Appendix B of the Interim Guidelines, in Public Works Central Laboratory, GEO. During the specimen preparation procedure, the following variables are controlled, such as binder content, L/D ratio, and curing time. By carrying out unconfined compression test on cement stabilised soil specimens, multiple sets of test results are obtained and analysed.