Rational Design of Concrete Mixes Using Uncrushed Aggregates

Abstract

This paper presents the study carried out on naturally deposited gravel for use in the production of concrete mixes. Physical properties of the coarse aggregates was carried out and was found to satisfy specifications requirements to produce normal grades of 20,25,and 30 concrete with continous, single size grading, natural deposit grading,gap grading (continous) and gap grading (single size). Also, maximum aggregate of 10mm, 20mm and 40mm with low slump 10-30mm and and medium slump of 30-60mm were considered. The properties of the mixes both in the plastic and hardened states have been found to vary depending on the coarse aggregate grading used. Based on these results, the starting estimate for the compressive strength and free-water cement requirements to give various levels of workability for uncrushed aggregates presented in the DOE design manual have been found to be invalid. The appropriate charts, tables and standard deviations for the revised relationship have been re-presented, which can be used directly in designing concrete mixes using the gravel as coarse aggregates