건설재료시공학연구실

Building material & construction lab.

Abstract
Recently, the use of EEZ(Exclusive Economic Zone) sand for concrete aggregate has been increasing because of the exhaustion of good natural fine aggregate. However, the use of EEZ sand in concrete may give a bad effect on the fluidity and mechanical properties of concrete because the fineness modulus (F.M) of EEZ sand is very low, that is about 1.5 to 2.0.

 In this paper, we used the crushed sand with fineness modulus of 3.0 at replacement ratios of 0%, 50%, 75% and 100% to improve the properties of concrete with EEZ sand. And the effects of replacement ratios of crushed sand on the air content, unit weight, slump, bleeding, setting time, compressive strength, elastic modulus, carbonation depth and chloride ion penetration depth of concrete with EEZ sand were investigated. Test results indicated that using crushed sand at replacement ratios of 50% and 75% in concrete with EEZ sand resulted in improvement in the fresh and hardened properties of concrete. The slump of concrete using crushed sand was improved as compared to the concrete with only EEZ sand, though the slump of concrete using only EEZ sand was lower than that of the Plain concrete using normal sand. In addition, the compressive strength of the concrete using crushed sand was higher than the concrete with only EEZ sand.