Theories COMPRESSIVE STRENGTH AND MODULUS OF ELASTICITY OF GEOPOLYMER CONCRETE WITH MANAJEMEN RISIKO KONTRAK ANTARA KONTRAKTOR DENGAN SUBKONTRAKTOR.

10 According to the research of Lisantono and Hatmoko 2009, in their research about Geopolymer Concrete Made with Bagasse Ash and Metakaolin, the compressive strength values of the three types of Geopolymer Concrete are generally very low. At 14 days, the compressive strength values as follows: bagasse ash = 0.325 MPa, metkaolin = 0.560 MPa, bagasse ash and metakaolin = 0.380 MPa while the compressive strength values at 28 days as follows: bagasse ash = 0.344 MPa, metkaolin = 0.721 MPa, bagasse ash and metakaolin = 0.852 MPa. However, geopolymer concrete based on the mixture of bagasse-ash with metakaolin gives the highest compressive strength compared to other and can be developed for future research. 11 CHAPTER III BASIC THEORY

3.1. Geopolymer Concrete

Geopolymer concrete is concrete which uses different materials and are environmental friendly during the production process. There are several advantages of the materials; such as anti-fire, used as a cover material for the exterior of mechanical equipment, durable and environment friendly. Geopolymer concrete was established by Joseph Davidovits in 1970. At that time, Davidovits investigated the materials which were in the pyramid. He found that the cement used in the pyramid consist of several different materials. At that time it was called geopolymer, which was obtained from fly ash as a result of geo-polymerization reaction mix with NaOH, KOH and so on. In the process of geopolymer, there is a chemical reaction between alumina-silicate oxide Si 2 O 5 , Al 2 O 2 with alkali poly-silicates which produces Si-O-Al bonds. Poly-silicate is generally in the form of sodium or potassium silicate obtained from the chemical industry or fine silica powder as a byproduct of the process ferro-silicon metallurgy. From the reactions that mix together in the geopolymer, there will be H 2 O or water that has been released.