The research aims to investigate the possibilities of crushed oyster shell (OS) not have to go through the process of burning as a substitution cement for concrete blocks. The cement was replaced with crushed oyster shell not process burning (OS) at 0% 10203040 and 50% by the weight of the binder. After that the concrete blocks were tested to determine the compressive strength and moisture absorbed of the concrete blocks cured for 7 142856 and 90 days The result showed that the compressive strength of the concrete blocks which replaced cement with OS (at the proportion of 10% by the weight of the binder) at 28 days had the compressive strength and water absorbed accordance with the TIS 58-2533 on non-load bearing concrete blocks.Moreover the concrete blocks which replaced cement with OS at the proportion of 20 % and 30 % had the compressive strength equivalent to 28 days compressive strength of TIS 58-2533 standard at 56 and 90 days respectively and decreased when the percentage in addition to OS in concrete blocks of 40 and 50 %. Tested results also showed that the water absorbed of concrete blocks increased when the percentage of replacement of OS in binder increased at 10 20 30 40 and 50%. The economical of concrete blocks it has manufactured unit cost is 2.60 baht. Whereas the concrete block containing crushed oyster shell at 10-30% it has manufactured unit cost at 2.12-2.44 baht respectively.

This research studies of crushed oyster shell (OSP) as a substitution for cement in producing the interlocking block. Research process are design the mixtures which contain 0 10 20 30 40 and 50%. Control water at optimum moisture content (OMC). Results of the tests the compressive strength at 7 14 28 60 90 days and the moisture absorbed at 28 days showed that increasing the amount of OSP decreased compressive strength and increased water absorption. By using OSP to replace cement 10% 20% passed the community product standard 602/2547 these were classified as non-load supportive type