High Volume Wastes Concrete (HVWC)

Abstract

High volume waste concrete (HVWC) containing hundreds of kg of waste-derived materials in unit volume of concrete as raw materials was prepared to examine the workability, strength development, hydration of cement, composition and structure, and dissolution of harmful elements from hardened concrete to increase the amounts of waste-derived material that can be used for manufacturing concrete. The waste-derived materials tested in this experiment were incineration ash of urban refuse and sintered coal ash as the substitution for fine aggregates, and sintered sewage sludge and glass cullet as the substitution for coarse aggregates. It was determined that HVWC could keep good workability without segregation and developed higher strength than ordinary concrete even if the amounts of waste-derived aggregates in concrete exceeded 600 kg/cu m. Increase in combined water in hardened HVWC and the production of cement hydrates including C-S-H with age was normal and the influence of trace elements contained in waste-derived aggregates on the cement hydration was negligible. Decrease in the amounts of Ca(OH)2 and increase in C-S-H which was estimated from the pore volume of 3 to 6 mm in diameter was recognized in later age in the case when blast furnace slag or fly ash was used as a binder. Non-uniformity in distribution of aggregate, large pore and microgroove between aggregate and cement paste which might occur by the use of large amounts of waste-derived aggregate was not observed. There was no remarkable difference in type and quantity of elements between HVWC and ordinary concrete dissolved from them. From the results described above, it is considered that the use of HVWC is a very promising technique to safely consume large amounts of wastes.