The Influence of Granite Size and Workability on the Compressive Strength of Continuous Flight Auger Pile Concrete

Abstract

Concrete achieving 30N/mm² in Continuous Flight Auger (CFA) concreting is a challenge due to coarse aggregate size and the required workability of the concrete for easy pumping. This study investigated the impact of workability and coarse aggregates on the compressive strength of Continuous Flight Auger concreting. Aggregates sizes of ¾ and ⅜ inches were used for the experiments and the slump value for the mix ratios were set in range 145 to 190mm. Three mix ratios; 1:2:4, 1:1.5:3 and 1:1:2 was adopted and mix composition was done by volume method based on what is expected on construction site. Twelve (12) cubes (150x150mm) of each type of coarse aggregate with and without superplasticizers (strength enhancement, and retarder) for the various mixes were cast for 7, 21, 28 and 58 days to determine their compressive strengths. Granite sizes ¾ and ⅜ with mix ratio 1:1:2 was found to attain the targeted strength without admixtures, whereas the ¾ inches aggregates for all the mixes with the two admixtures exceeded the targeted strength with at least 13 percent. Hence, concrete of Grade C30 is achievable for CFA pile concrete without using admixture.