AN EXPERIMENTAL STUDY ON INTERNAL CURING OF CONCRETE USING PREWETTED LIGHT WEIGHT EXPANDED SLATE

Concrete curing is one of the most important factor in cement hydration. Applying water externally is conventional approach. Most of the water is wasted due to evaporation and runoff. Also external curing concentrates only on surface of the concrete and does not penetrate deeply. Hence the necessity for internal curing is increased. Internal curing provides a set of water filled reservoirs within the concrete that supply water on demand to the hydrating cement paste from the time of mixing. In this project pre-wetted expanded slate is used in various proportions in partial replacement of coarse aggregate. The concrete grade used here is M30. Experimental study is done for different mix proportions and they are analyzed. Higher strength, lower water to cement ratio (w/c) concrete has been advocated over the last two decades due to its increased strength and reduced permeability. The lower w/c of these concretes makes them susceptible to autogenous shrinkage. This autogenous shrinkage can be significant and can be a contributing factor to early age cracking. Internal curing was investigated as a potential method to improve the durability of concrete pavements and bridge decks. Pre wetted lightweight slate is used to supply water to the hydrating cement paste. This additional water can counteract the hindered strength development, suspended hydration, autogenous shrinkage, and early age cracking. An overview of the concepts behind internal curing is presented. It is important that the internal curing agent (pre wetted lightweight expanded slate (PLES in this case): be able to provide a sufficient volume of water, has a structure that allows the water to be released to the paste as needed, and is small enough so that they can be appropriately spaced in the matrix. Before concrete could be prepared the LWA was characterized to determine absorption and desorption properties. Compression strength, split tensile strength and flexural strength of concrete with different mixes are analyzed and the results are compared