Evaluation of Suitable Gradation of Crushed Rock Geopolymer

Abstract

A study of the compressive strength development in a geopolymer suitable for roadway applications. This study finds proper mixtures of crushed rock for geopolymer which use two mixed grading of crushed rocks sizes including: (1) use the ideal mixed size is called Ideal Grading for the road work with standard compressive strength was obtained by the most appropriate grading size, and (2) use mix of crushed rock is obtained from the stone mill, which is sorted by standard sieve sizes and mixed size that is close to the Ideal grading is called Used Working Grading. The two types of mixed sizes were used to activate with the alkaline solution, namely sodium hydroxide and sodium silicate. A sodium silicate to sodium hydroxide ratio of 0.67 and a sodium hydroxide concentration of 5 molar were used. To find a maximum dry density (MDD) and optimum liquid alkaline content (OLC), a standard compaction test and a modified compaction test were performed to obtain the compaction curve. Samples were prepared by mixing of crushed rock with alkaline liquid content in both dry and wet at 100%MDD and 95% MDD on compaction curve. The group of samples were stimulated by heat at 40ºC for 24 hours in oven in comparison with another group of samples that were cured at room temperature. After curing stage, both group of sample were left in ambient temperature to reach the curing time of 7 and 28 days before performing Unconfined Compression Test. The test results showed that compressive strengths of Used Working grading at 100%MOD for 28 days curing were higher than compressive strength of Ideal grading.