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Waste tyres accumulate very quickly in a landfill as a result of the fast development of the transport industry, and mainly automobiles. The polymeric waste has limited usage and is rarely employed in a highly economic and viable product. A rigid pavement material needs to have high mechanical properties and durability when exposed to aggressive environments. In this research, a combination of waste tyre with rice husk ash and Portland Cement Composite (PCC) as a primary binder was designed to produce concrete that meets the requirements of flexural strength value of the rigid pavement based on the Indonesian Standard from Bina Marga 2018. Eight mixes with a variety of water/cement ratio (0.30-0.40), crumb rubber (2.5-7.5%), and rice husk ash (7.5-10%) were designed in this research. The control mix was PCC concrete. The crumb rubber substituted the fine aggregate content, while the rice husk ash replaced the cement content in concrete. The specimens were cast and subsequently cured in water pond up to 28 days. The mechanical properties of concrete, namely compressive strength and flexural strength were determined for all variations. Based on the results, Mix 1 with w/c ratio of 0.30, crumb rubber of 5%, and rice husk ash of 10%, performed both the highest compressive strength and flexural strength values of 36.38 MPa and 4.53 MPa, respectively, after 28 days. Both values fulfilled the requirements of the Indonesian Standard Bina Marga 2018. It can be concluded that an appropriate combination of crumb rubber and rice husk ash improves the mechanical properties of the concrete and has potential as a rigid pavement material.

Peat is superficial deposit or soil with high organic content. The soil is highly compressible and acidic. The organic acidic water in swampy peat soil consists humic acid that is potentially corrosive to concrete and metal structures. Geopolymer is a material using waste from agro-industry such as fly ash (FA) and palm oil fuel ash (POFA) that is activated with alkaline solution. In this research, the acid resistance of geopolymer mortars from fly ash and palm oil fuel ash was measured by change in compressive strength and porosity. The samples were subjected to distilled water and acidic peat water. The OPC mortars showed a considerable decrease in compressive strength after subjected in peat water for up to 180 days. There was a fluctuated trend of geopolymer FA and a high decrease in compressive strength of geopolymer POFA after subjected to the peat water. The porosity of the geopolymer specimens was higher than the control mortars. However, it was observed that the geopolymer FA is more resistant to the acidic peat water than the geopolymer POFA due to stable aluminosilicate bonding.

Geopolymer is an inorganic polymer from activation of source materials that rich of silica and alumina with alkaline activator. Previous studies reveal that the geopolymer has engineering properties and durability, which is equivalent or higher than the Ordinary Portland Cement (OPC) concrete. This paper presents properties of geopolymer concrete prepared with local Palm Oil Fuel Ash (POFA) and Fly Ash (FA) from agro-industrial waste in Riau Province, Indonesia. The POFA and FA were activated by a combination of sodium hydroxide and sodium silicate. The specimens were cured at room temperature for 24 hours before steam cured for another 24 hours at 60OC. Hardened properties namely compressive strength, tensile strength, flexural strength and modulus of elasticity, and water penetration of both POFA and FA geopolymer concrete were determined at 7, 14 and 28 days. Results showed that local POFA and FA as geopolymer source materials could produce mix with strength 19-22.5 MPa at 28 days. The compressive strength, tensile strength, flexural strength and modulus of elasticity of both geopolymer tended to increase slightly with time. In general, the results suggest that the local POFA and FA are potential as source material to produce geopolymer concrete.

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