PUMICE STONE ENGINEERING AND RICE HUSK ASH LIGHT AGGREGATE MATERIAL TO INCREASE THE COMPRESSIVE STRENGTH OF COMPOSITE LIGHTWEIGHT CONCRETE

Research has been carried out on the manufacture of lightweight concrete (LWC) using lightweight aggregate (LWA) material of pumice and rice husk ash. The lightweight concrete sample made is with a variety of different slump values, while the portland cement composite (PCC), sand, pumice and rice husk ash (RHA) materials are kept constant. There are two main parameters that determine the mechanical properties of lightweight concrete, each of which is the sample density and water / cement ratio. Observation of photomicro SEM pumice shows that there are many pores with a shape extending to the inside of the surface of the concrete sample. Pores come with relatively large pore density and varying sizes. This fact explains why pumice is light because it has a low mass density. As seen in Photomicro SEM lightweight concrete, the Calcium Silicate Hydrate (CSH) compound starts to grow at the beginning of the hydration process and continues to grow until lightweight concrete reaches 28 days of hydration which is characterized by solid physical properties and increased compressive strength of lightweight concrete. It can be ascertained that the Calcium Silicate Hydrate compound has an important role in regulating mechanical properties such as compressive strength. In the mixture with the variation of the largest slump value (13 cm) produces the lowest density and compressive strength of 1755.7 kg / m3 and 20.0 MPa, respectively. X-ray diffraction patterns of lightweight concrete samples show the dominance of the crystalline phase identified as quartz (SiO2) phase. However, it can be ascertained that lightweight concrete samples consist of a mixed phase between crystalline phases and a little amorph phase. This study concludes that pumice and rice husk ash are silica amorph based materials that have lower density, especially compared to other concrete forming materials such as cement. Both the density and compressive strength of lightweight concrete samples are determined by the ratio between pumice and rice husk ash. The smallest ratio of pumice stone compared to rice husk ash was 8.1 with 9 cm slump value resulting in optimum density and compressive strength values, respectively at 28 days of lightweight concrete with 1794.7 kg / m3 and 23.7 MPa. The best lightweight concrete composition obtained from the results of this study is that with a 9 cm slump value is indicated by the ratio between the compressive strength and the highest density of 1321.