Development of Internally Cured Concrete for Increased Service Life

Abstract

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. Prewetted lightweight aggregate was 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 was presented. It is important the internal curing agent (lightweight aggregate (LWA) 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. Local materials were used. Before concrete could be prepared the locally produced LWA was characterized to determine absorption and desorption properties. Concrete mixtures were prepared for concrete with and without internal curing. A constant aggregate volume was maintained. Tests performed on these mixtures were designed to measure: autogenous shrinkage, drying shrinkage, plastic shrinkage cracking, drying shrinkage cracking, autogenous shrinkage cracking, water absorption, compressive strength, elastic modulus, tensile strength, thermal cracking and freeze-thaw resistance. Internally cured mixtures showed less autogenous shrinkage. In addition they were less likely to crack due to plastic, autogenous, and drying effects. Internal curing reduced the water absorption and potential for freeze-thaw damage. Further, internal curing allowed a greater temperature swing in the concrete before cracking would occur. Internally cured concrete mixtures could enable INDOT to produce more durable concrete pavements and structures that are less susceptible to cracking and have improved transport properties thereby providing great potential for more sustainable, cost-effective construction.