IMPACT OF HIGH TEMPERATURES ON MULTIBLENDED CONCRETES
International Research Journal of Engineering and Technology (IRJET)
Concrete gets affected either by the service environment to which it was exposed or physical-chemical causes due to the reasons residing within. The reduction in engineering properties of concrete such as strength, elastic modulus, and durability occur due to variety of chemical and physical causes such as corrosion of reinforcements, sulphate and sea water attack, carbonation, freezing and thawing, thermal effects, abrasion, and nature of materials (e.g., type of aggregate and cement blend).
... case of accidental fire, concrete subject to high temperature which leads to severe deterioration and it undergoes a number of transformations and reactions, thereby causing progressive breakdown of cement gel structure and consequent loss in its load-bearing capacity, reduced durability, increased tendency of drying shrinkage, structural cracking, and associated aggregate colour changes. The behaviour of concrete in fire depends on its mix proportions and constituents and is determined by complex physicochemical transformations during heating. Normal-strength concretes and high-performance concretes micro structurally follow similar trends when heated. Failure of structural concrete in fire varies according to the nature of the fire; the loading system and the type of structure. Failure could occur from loss of bending or tensile strength; loss of bond strength; loss of shear or torsional strength; loss of compressive strength; and spalling of the concrete. Assessment of the condition of concrete and extent of damage after the fire is an important requirement for taking possible corrective measures for its rehabilitation. Therefore, systematic parametric studies on simulated conditions of temperatures such as that generally experienced during an accidental fire in concrete structures are of utmost importance. The present study considered the thermal effects on concrete and reported the physicochemical, mineralogical, and morphological changes in pre-and post fired concrete. The effect of a high temperature on concrete covers changes taking place in cement paste, aggregates, as well as the interaction of these two constituents, that result in changes of mechanical and physical characteristics of concrete. This paper presents the effect of a high temperature on selected physical properties of concrete such as compressive strength for quantitative assessment and ultrasonic pulse velocity testing to assess qualitative assessment; it also includes colour change and spalling effects.