Abstract:
A comparative study was carried on Hand Crushed and Machine Crushed Volagonj stone (major rock of Bangladesh) graded between 1 in [25 mm] to 0.5 in [12.5 mm]. Stone crushed by both hand and machine were tested for abrasion value, crushing value, flakiness index, and elongation index. These stone groups were used to prepare concrete cylinders (6 in. [150 mm] diameter and 12 in. [300 mm] height) for W/C ratio ranging from 0.45 to 0.60. Hand crushed stone was showing abrasion and crushing value more than machine crushed stone by about three and one percent respectively. Machine crushed stone is flakier and elongated than hand crushed stone by about six and two percent respectively. Cylinders made with hand crushed stone showed more compressive strength than machine crushed stone with an exception of early age (1 day) and high W/C ratio (0.60). This phenomenon suggest low strength of cement matrix-aggregate interface bond firstly due to low maturity and secondly due to low strength of cement matrix to bond with aggregate.
