A thesis submitted in partial fulfillment of the requirements for the degree of master of engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1980

Four types of coarse aggregate locally available in Thailand were tested for their physical and mechanical properties. Tests were made with different types and sizes of coarse aggregate to study the effect of aggregate properties on strength and workability of gap- graded concrete. Test results showed that the workability of fresh gap-graded concrete was considerably affected by the types and size distribution of aggregate. Among the four types of aggregate tested, sandstone produced concrete with the least workability whereas gravel gave the most workable concrete without segregation. Increasing the size of aggregate, both coarse and fine, led to a more workable concrete. gate. Test results indicated that the mechanical properties of gap-graded concrete were considerably affected by the properties of coarse aggregate used therein. Gap-graded concrete made with sandstone aggregate gave the highest strength and exhibited, in spite of the highest strength, lowest modulus of elasticity. This phenomenon is mainly caused by the absorption capacity, compressibility and bond strength between matrix and surface of coarse aggregate The modulus of elasticity of gap-graded concrete was directly related to the modulus of elasticity of gap- graded concrete. The design method suggested by LI and RAMAKRISHNAN (1) can be used to produce an optimum mix proportion for all tested crushed aggregates. However, for natural aggregates like gravel this design method has to be modified in order that an optimum proportion is attained.