SAND WITH CRUSHED SEASHELLS AND ITS EFFECT ON THE STRENGTH OF MORTAR AND CONCRETE USED IN THE UNITED ARAB EMIRATES

The majority of UAE cities are located close to the sea and it is more economical to obtain the sand from the seashore which contains a large amount of sea shells. This study experimentally investigates the effect of crushed sea shells that exists in the sand used in the construction work in UAE on the mechanical properties of both mortar and concrete in terms of compressive and flexural strengths. Four different percentages of sea shells have been investigated by using sieve analysis of the raw sand (29%, 14%, 4%, 0%) and then used to prepare the standard mortar and concrete cubes and beams. 48 concrete cubes, 24 concrete beams, 48 mortar cubes and 48 mortar beams have been prepared for testing purposes . Results revealed that there was a slight decrement in the compressive strength of standard concrete and mortar cubes prepared using raw sand containing 29% sea shells comparing to cubes made with sand removing all exists sea shells 0%. On the other hand, the flexural strength of concrete and mortar beams was slightly higher for beams made with sand containing 29% crushed sea shells comparing to beams made using 0% sea shells in the sand. All recorded results are for samples loaded until failure after curing 3, 7, 14 and 28 days. The only exception was for the concrete beams as results are for samples loaded until failure after curing 3, 7 and 28 days. This research work recommends using the marine sand in UAE without any considerations of having the crushed sea shells; since the existence of the sea shells has no significant effect on the compressive strength of concrete and it can slightly improve the flexural strength of both mortar and concrete.