Characteristics of Fly Ash Cement Paste as an Alternative Sustainable Material for Balinese Architectural Ornaments

In Bali, the demand for ornament architecture material especially natural stone is still high. The problem is the availability of material sources especially the stones is very limited. It is necessary to study alternative environmental materials that can be used as Balinese architectural ornaments. This study aims to understand the feasibility of fly ash cement paste as an alternative material based on their properties such as bulk density and compressive strength. The material composition in this research consists of cement, fly ash, fiber, superplasticizer, and water. The binder composition is a ratio of 1 cement: 2 fly ash. The water and binder ratio is fixed at 0.35. The variation in the materials was varied according to (i) fiber (0.05%, 0.025%, and 0.01%) and (ii) superplasticizer (0.1% and 0.05%). The mixture composition was determined using the absolute volume method. All samples were mixed according to ASTM C305. The mechanical strength of the material was tested according to ASTM C109 (2002) using 50 mm cube specimens. The highest compressive strength occurred when 0.1% SP and 0.025% fiber were mixed in the mixture. Based on the result, the fly ash-cement paste has a higher strength compared with other stones while having a similar bulk density. Basalt stone, a popular ornamental architectural material in Bali, has a compressive strength of 19.42 MPa, which is 44% lower than the fly ash-cement paste mixture. Andesite stone has a better compressive strength than basalt stone but a lower compressive strength by around 29% than fly ash cement paste material. Fly ash cement paste has a similar bulk density to red brick and andesite stone. Sandstone has the lowest compressive strength, about 3.87 MPa. The temple with fly ash-cement material is brownish in color. This is due to the fact that the color of fly ash dominates the proportion. When compared to other stone materials such as basalt stone, andesite stone, and red brick, fly ash cement has the highest compressive strength and the lowest price.