Abstract:
THE MECHANISM OF ACCELERATOR AND RETARDER ACTION UPON SETTING AND HARDENING OF PORTLAND CEMENT WAS INVESTIGATED. TESTS WERE CONDUCTED ON CEMENT AND ON A SYNTHETIC SILICATE BINDER, USING ANHYDROUS CALCIUM CHLORIDE AS THE ACCELERATOR AND THE CITRIC ACID AS THE RETARDER. FINDINGS SHOWED THAT THE RATE OF HYDRATION OF THE SILICATE PHASE /I.E. RATE OF FORMATION OF TOBERMORITE GEL/ IS CHANGED BY ADDITIVES. /PREVIOUS HYPOTHESES HAD STRESSED THAT THE SILICATE PHASE REMAINED UNAFFECTED./ INSOLUBLE COMPOUNDS WITH CLINKER ALUMINATES ARE FORMED DURING THE PROCESS. THERMAL AND HEAT-ON-SETTING EXPERIMENTS ARE CONSISTENT WITH THESE CONSIDERATION. THE EFFECT OF MIXING SEQUENCE USING RETARDERS AND ACCELERATORS IS EXPLAINED.
Supplemental Notes:
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