UTILIZATION OF MORTAR AND COARSE AGGREGATE RECOVERED FROM LEFT-OVER CONCRETE USING A VACUUM FREEZE-DRYING METHOD

摘要

It is shown that aiming to suppress hydration during lowering of temperature and freezing of left-over concrete, when the concrete is pretreated by addition of a small amount of set-retarding agent and is vacuum freeze-dried at -10 deg C or lower at which hydration of cement becomes suspended, mortar possessing approximately the properties of the original cement and clean coarse aggregate can be readily separated and recovered. Next, it is ascertained through experiments that there is no problem of setting and hardening of mortar recovered by this method with it possible for the mortar to be preserved over a long period, that by addition of optional amounts of water and remixing at any time, it can be used together with coarse aggregate to manufacture mortars and concretes of desired flowabilities and strength, and that this is one method of effective utilization of lift-over concrete.