Leaching Behavior of Construction and Demolition Waste (Concrete and Gypsum)

Recycling of Construction and Demolition Waste (CDW) aims to minimize the generation of waste and reduce the dependency on natural resources. The aims of the research are to characterize inorganic element and to determine the leaching behavior of CDW (concrete and gypsum) by means of the leaching test. The analyzed results were compared with the European unio‎n (EU) Landfill Directive to assess their acceptance criteria. Both wastes were found to have elements of Ca, Mg, Fe, Zn, Mn, Pb, Cu, Cd, As, Cr, Se, Ni, CI and SO42-. The highest concentration and variety of inorganic element found in waste gypsum (WG) were SO42->Ca>CI>Mg>Zn>Cu>Fe. X-ray diffractometric (XRD) analysis proved that the WCo was dominated by quartz, calcite, ettringite, cordierite, diopside and the WG was only dominated by gypsum. The leaching behavior of WG demonstrated pH dependent particularly for the elements of Ca, Mg, Fe, Zn, Cu and Mn but only the elements of Ca and Cr in WCo were shown to be pH dependent in the leaching test. The element of SO42- from the WG indicated a higher reading than WCo without the influence of pH. Noticeably, the concentration of SO42- within the WG strongly require regulation and control before it can be utilized as part of raw materials in the production of environmental friendly recycled building materials.