TIME-DEPENDENT BEHAVIOUR OF REACTING VISCOELASTIC CONCRETE

Abstract

CONCRETE EXHIBITS TIME-DEPENDENT BEHAVIOUR LIKE BASIC CREEP, RECOVERY AND STRESS RELAXATION. SOLIDIFICATION THEORY PROPOSED BY BAZANT AND CO-WORKERS ATTEMPTS TO SIMULATE THE AGING CREEP OF HYDRATING CONCRETE UNDER UNIAXIAL STRESS. THERE EXISTS CONSIDERABLE EMPIRICAL EVIDENCE TO THE EFFECT THAT EVEN MATURE CONCRETE EXHIBITS CREEP-LIKE PHENOMENA ON EXPOSURE TO CHEMICALLY AGGRESSIVE ENVIRONMENT. THE DISSOLUTION-PRECIPITATION MECHANISM HAS BEEN PROPOSED BY BENIPAL FOR EXPLAINING SUCH BEHAVIOUR OF REACTING ELASTIC SOLIDS. BASED ON THIS CHEMOMECHANICAL MECHANISM, A THEORY OF REACTING ISOTROPIC LINEAR ELASTIC SOLIDS HAS RECENTLY BEEN PROPOSED BY THE AUTHORS. THIS THEORY IS CAPABLE OF EXPLAINING LONG-TERM BEHAVIOUR, BUT IS INCAPABLE OF PREDICTING THE CREEP OF MATURE CONCRETE NOT INVOLVED IN ANY REACTIONS. IN THIS PAPER, A THEORY OF ISOTROPIC LINEAR VISCOELASTIC SOLIDS APPLICABLE TO BOTH REACTING AND INERT SOLIDS HAS BEEN PROPOSED. HERE, THE EARLIER MODEL DEALING WITH THE REACTING ELASTIC SOLIDS HAS BEEN NAMED REACTING RHEOLOGICAL ELEMENT. THE PRESENT THEORY OF REACTING VISCOELASTIC CONCRETE IS BASED ON THE ABOVE REACTING RHEOLOGICAL MODEL ARRANGED IN PARALLEL WITH AN AGING MAXWELL RHEOLOGICAL ELEMENT. THIS THEORY HAS BEEN SHOWN TO PREDICT SATISFACTORILY THE OBSERVED TIME-DEPENDENT BEHAVIOUR OF CONCRETE INVOLVED IN HYDRATION AND OTHER REACTIONS SIMULTANEOUSLY SUBJECTED TO MULTIAXIAL STRESS/STRAIN HISTORIES. THE THEORETICAL SIGNIFICANCE AND THE PRACTICAL RELEVANCE OF THE RESULTS OBTAINED HAVE BEEN DISCUSSED.