Calcium carbonate [CaCO3] is a key raw material used in the clarification of sugarcane juice for syrup production. The CaCO3 sludge produced during the clarification process is waste that needs to be stored, creating a geoenvironmental problem. On the other hand, it has been found that cement-stabilized subgrade is a suitable alternative for improving the quality of a subgrade course. This study aimed to investigate the influence of calcium carbonate sludge on the quality of the subgrade. The subgrade was composed of a mixture of 10% to 30% CaCO3 sludge, 1% to 3% of original Portland cement (OPC), and 67% to 100% of unqualified crushed rocks by weight. The modified Proctor method was used to compact soil-cement admixture samples, which were then tested for mechanical properties and electrical resistivity. The Wenner electrode array was used to measure electrical resistivity and compare it to the unconfined compressive strength of 16 different types of soil-cement mixtures after 7 days. The results of experiments show that the basic properties of CaCO3 sludge, when mixed with OPC and packed down, can make the best soil-cement mixture. As a result of this study, electrical resistivity was found to be in good correlation with unconfined compressive strength, thus opening up a time-saving and cost-effective way to check the quality of a soil-cement mixture.
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