Strength Development in Cement and Fly Ash Admixed Bangkok Clay with Considering Shear Wave Velocity

Abstract

This paper aims to investigate the strength development in ordinary Portland cement (OPC) and Fly ash (FA) admixed Bangkok clay. The role of cement is to stabilize and enhance the compressive strength of Bangkok soft clay. The OPC is replaced by FA which is a sustainable method since FA is an industrial waste product from Mae Moh power plant in the northern of Thailand. Bangkok soft clay was mixed with OPC content of 20% by weight and varied FA content from 0, 10, 15, 20, 25 to 30% by weight, after curing time for 7, 14, 28 and 90 days. The initial shear modulus (G₀) was determined from the shear wave velocity (V_s) measured by a non-destructive bender element testing. For comparison and ensuring the results, the strength development of the tested clay samples was also determined by destructive unconfined compression test (UCS). From the results, it was found that the optimum of replacement fly ash is about 15-20% and showed that the strength development of this Bangkok clay admixed with OPC and FA is increased with increasing the curing time. Moreover, the research found the linear relationship between G₀ (MPa) and q_u (MPa) as G₀=27.57q_u. Last but not the less, the linear relationship between the normalized G₀/G₀₍₂₈₎ and the q_u/q₂₈ was noted as G₀/G₀₍₂₈₎ = 0.9073 q_u/q₂₈.