Addition of superplasticizer on geopolymer concrete

It is already known that the Portland Cement process manufacturing produces CO₂ as emission that interfere in environment. Therefore it is necessary to find an alternative materials as a substitute for PC or alternative concrete. Today one of the alternative solution is geopolymer concrete, it is based on fly-ash or other material pozzolanic. By adding some alkali activator in fly-ash would make geopolymer concrete. The addition of high-range water-reducing admixture up to approximately 2% of fly-ash mass have improved the workability of fresh geopolymer concrete. In this study the mixtures of geopolymer binder were made with the ratio of fly-ash and alkali activator were 74%: 26%, molarity of sodium hydroxide was 12 M. Ratio of sodium silicate to sodium hydroxide were varies from 1.5 to 3, the percentage of naphthalene-based superplasticizer (SP) were varies from 1.5 to 3 of fly-ash mass. Tests performed were compressive strength, tensile strength and density. The results showed that the highest compressive strength achieved for the proportion of Na₂SiO₃/NaOH = 2 and for the percentage of SP 1.5, the highest tensile strength achieved for the proportion Na₂SiO₃/NaOH = 2,5 and for the percentage of SP 1.5. The average density of geopolymer was 2400 kg / m³.