Pengaruh Pengurangan Air dan Penambahan Superplasticizer terhadap Kuat Tarik, Lentur, dan Geser Beton dengan Mutu 25 dan 30 MPa

Abstract

To produce high strength and low permeability concrete can be achieved by lowering the water-cement (w/c) ratio. Reducing the water content is the one of several way to lowering the w/c ratio. Low w/c value make the mixture’s workability becoming low too, there fore the chemical additive named superplasticizer (SP) can be added to solve this problem. Superplasticizer can make the fresh concrete become more flowing in the mixture with low water content. By addition of SP from the weight of the cement content in this research is expected can increase the concrete performance and can make possible the reduction of water content from the mixture for increase the concrete strength. In this research the reduction of water content with interval 0 untill 30% from the normal compotition is done by maintaining the slump value between 150-180mm without bleeding and segregation. Compressive strength concrete planned at 25 and 30 MPa which is tested in age 28 days. Result of study shows that reduction of water andaddition of SP can reach the planned slump value 150-180 mm without bleeding and segregation. The maximum value of tensile strength, flexure strength, shear strength, and also compressive strength obtained on combination of reduction the water content 30% and addition of SP 3,29% from cement weight for planned compressive strength at 25 MPa and 2,20%) from cement weight for planned compressive weight 30 MPa. Maximum tensile strength reached at 4,7647 MPa for planned compressive strength at 25 MPa and 4,6475 MPa for planned compressive strength at 30 MPa. For maximum flexure strength reached at 5,6057 MPa for planned compressive strength at 25 MPa and 6,1116 MPa for planned compressive strength at 30 MPa. For maximum shear strength reachedat 6,7630 Mpa for planned compressive strength at 25 MPa and 8,7244 MPa for planned compressive strength at 30 MPa. This study also result the concrete permeability that more lowerfollow the reduction of water content and addition of SP that more bigger. The value of concrete permeability showed from water speed penetration inside the concrete. The biggest water speed penetration for the planned compressive strength at 25 MPa reached at 0,0064 mm/dtk (for 0% water reduction and addition of SP 0,3% from the cement weight) and the smallest reached at 0,0029 mm/dtk (for 10% water reduction and addition of SP 1,35% from the cement weight), while the biggest water speedpenetrationfor the planned compressive strength at 30 MPa reached at 0,0066 mm/dtk (for 0% water reduction and addition of SP 0% from the cement weight) and the smallest reached at 0,0029 mm/dtk (for 15% water reduction andaddition of SP 1,26% from the cement weight). Key word: water content, superplasticizer, mix compotition, planned compressive strength, workability, tensile strength, flexure strength, shear strength, permeability.