Study on Flexural Strength and Other Durability Properties of Concrete using Dredged Marine Sand

Abstract

Concrete is the most consumed product after water on earth. The development of countries is demanding infrastructures which is the reason of increasing demand of concrete. One of the most important ingredients of concrete is fine aggregates which are generally acquired from alluvial rivers and quarries. Extraction of fine aggregates from these sources has led to harmful consequences which is if continued will exhaust these sources causing more damage to the nature. To avoid these consequences some alternative needs to be thought of. Some of the options can be off shore sand, dune sand, washed soil and dredged marine sand. Dredged marine sand can be utilized to produce concrete because of its easy availability around coastline and cost effective transport. The investigation has been carried out by casting two grades of concrete M25 and M40 using Dredged Marine Sand (DMS) and Natural River Sand (RS). The present study mainly concentrates on use of DMS as an alternative of RS during casting of concrete and evaluating exural strength. Durability properties such as 5% sodium sulfate exposure and 3% sodium chloride exposure for exural strength are also evalu- ated. Further the investigation has been focused towards the comparison of corrosion resistance of concrete made of DMS and RS by casting 5 cylinders for each mix. The testing is done by embedding one stainless steel rod and one TMT rod in cylinder and connecting them to 12 volts of supply by rectifier and using half cell potentiometer for measuring corrosion rate. Also to evaluate aggregate reactivity of DMS and RS, 6 mortar bars of size 282 mm x 25 mm x 25 mm were cast for each type of sand with 1:2.75 proportion of cement to sand and were immersed in sodium sulfate solution of 5% concentration as per ASTM C 1012 and length change is measured after desig- nated period of time. The study shows that after moist curing of 1 and 3 months, the DMS concrete is having slightly more exural strength as compared to that of RS concrete. Durabil- ity property such as sulfate exposure shows that DMS concrete performs quite well than RS concrete after 1 month. At the end of 3 months of exposure DMS concrete performs exceedingly well as there is a significant amount of difference in exural strength reduction. Chloride exposure test demands further more investigations as there is a notable amount of reduction in exural strength of DMS concrete compared to RS concrete. Further the investigation about corrosion resistance demonstrates that DMS concrete consumes more time to develop crack as compared to that of RS concrete. Half cell potentiometer readings of DMS concrete are lesser on negative than RS concrete. The experiment related to length change of mortar bars shows that percentage increment in length of DMS mortar bars is less than that of RS mortar bars at the end of 13 weeks which suggests lesser reactivity of DMS mortar as compared to that of RS mortar. The study shows adequate performance of DMS concrete as compared to RS con- crete. Thus DMS can be utilized for concrete construction but for chloride exposed environment it demands further investigations to be executed.