Evaluating the effect of different types of dried automotive paint sludge as cement-based composite

Abstract

In this project, we aim to probe four different automotive paint sludge (APS) types­­­­; primer coat, phosphate pretreatment coat, base coat and clear coat sludge, as potential additives in cement paste. Specifically, Portland Cement paste was doped with the different APS types which only underwent drying and milling on receipt from a vehicle assembly plant. The mixture was then cured for 7 days, and the resulting concrete was subjected to consistency, setting time, flexural strength and compressive strength tests. On comparison with the control cement paste, the primer coat sludge generally increased the setting time, by as much as 40 % for the final setting time. The compressive strength is negatively affected by the addition of all the different APS. This is somewhat mitigated if clearcoat sludge is used at a 1 wt.%: the difference is less than 10 % to the control. The phosphate pre-treatment coat is the worst performer with a difference of more than 90 %, even at a low APS concentration of 3 wt.% in the cement paste. In contrast, the flexural strength increases with the addition of all but one of the four APS types: phosphate pre-treatment coat. Primer coat sludge is associated with as much as 50 % increase in flexural strength. These results tentatively, show the utility of APS as an additive in cement paste to potentially tailor its properties, thereby decreasing the detrimental environmental impact of disposing of it. APS may also find application in refractory and clay brick manufacture.