AN EXPANSIVE CEMENT FOR CREATING SELF-STRESS IN REINFORCED CONCRETE WITHOUT THERMAL TREATMENT /IN RUSSIAN/

THE INSTITUTE OF SCIENTIFIC RESEARCH INTO REINFORCED CONCRETE HAS DEVELOPED AN EXPANSIVE CEMENT WHICH CAN BE USED TO STRESS CONCRETE REINFORCEMENT AND OBTAIN SELF-STRESS IN STRUCTURES. CEMENT EXPANSION IS LINKED TO THE FORMATION OF HIGHLY BASIC CALCIUM HYDROSULPHOALUMINATE; THE CEMENT IS OBTAINED BY THE SIMULTANEOUS CRUSHING OF GYPSUM, ALUMINA CEMENT, AND PORTLAND CEMENT. ACCORDING TO PROVISIONAL TECHNICAL REGULATIONS, EXPANSIVE CEMENT MEMBERS MUST BE SUBJECTED TO THERMAL TREATMENT OTHERWISE THEY WOULD BE DESTROYED BY INDEFINITE EXPANSION IN THE PRESENCE OF WATER. IN FACT, CEMENTS HAVE NOW BEEN DEVELOPED WHICH DO NOT REQUIRE HEAT TREATMENT BUT THE CONCRETE MUST BE PROTECTED BY A WATERPROOFING COATING DURING SETTING. PRESTRESS VALUES OBTAINED BY THIS TECHNIQUE ARE FAR LESS DISPERSED THAN THOSE OBTAINED BY FREE EXPANSION. A STUDY WAS MADE OF THE INFLUENCE OF THE CHEMICAL COMPOSITION AND FINENESS OF THE CEMENT, AND NATURE AND PROPORTION OF AGGREGATES. SETTING TIME, NORMALLY VERY SHORT, CAN BE LENGTHENED BY USING PREHYDRATION. /LCPC/RRL/