Effect of pH on Release of Metals from Conventional and Cool Cement Blocks

Pavements constructed from conventional cement blocks absorb solar radiation during the day and release it into the atmosphere at night. In contrast, cool cement blocks reflect sun’s radiation back to the sky, reducing their surface temperature and, thus, mitigating the heat island effect. Cement block pavements in contact with rain water or snow will produce leachates during their service life, which may affect soil, surface water and groundwater quality. Therefore, the objective of this work was to determine and compare the leaching behaviour of heavy metals from conventional and cool cement blocks using the tank leaching test as a function of pH, according to method CEN/TS 14429. The results showed that leaching was higher at low pH and decreased with increasing pH for all metals. The extent of leaching varied from metal to metal as a function of pH. Since some limits for inert waste landfill are exceeded, disposal of both the cool and conventional cement blocks to non-hazardous waste landfills should be permitted. Leaching of cool materials is similar with that of the conventional ones as a function of pH.