International Research Journal of Engineering and Technology (IRJET) Volume: 09 Issue: 06 | Jun 2022
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e-ISSN: 2395-0056 p-ISSN: 2395-0072
Shrinkage Characterization of Cement Concrete with Various Supplementary Cementitious Materials and Fibers-A Review Ancia Cherian1, Jerison Scariah James2, Dr. Elson John3 1 Ancia
Cherian, M.Tech Student, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam 2Jerison Scariah James, Research Scholar, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam 3Dr. Elson John, Professor, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam ---------------------------------------------------------------------***--------------------------------------------------------------------2.SHRINKAGE IN CONCRETE Abstract–Volumetric shrinkage occurs frequently in cement-based materials, which may cause tensile strains and cracking. The volume changes brought on by water evaporation are known as shrinkage. Volume variations in concrete can happen early in the material's life or later on. Plastic shrinkage occurs at the plastic stage of concrete. The change in volume after the setting has occurred is known as drying shrinkage. Autogenous shrinkage is the shrinking that occurs in a conservative system, or one in which moisture cannot migrate into or out of the paste. This study tries to examine the impact of various SCMs such as fly ash, GGBFS, silica fume, etc. and fibers such as steel fiber, polypropylene fiber, glass fiber, etc. in the shrinkage characteristics of concrete.
Shrinkage is the change in volume due to expulsion of water. In concrete, volume changes occur in two stages- in early ages or in long term. There are different types of shrinkage, namely, plastic shrinkage, drying shrinkage, autogenous shrinkage, thermal shrinkage and carbonation shrinkage. Plastic shrinkage occurs at the plastic stage of concrete, due to the effects of the gravity in the bleeding state and the pore water evaporation in the drying state, from casting to the final set. Since structural concrete is always restrained, e.g., by reinforcement, incompatibility of deformations occurs, which leads to the buildup of restraint stresses. During the above-mentioned period, concrete is plastic and has only insignificant strength, which makes it highly susceptible to cracking when the stresses increase beyond the limit. Accordingly, it is said that plastic shrinkage is the source of about 80% of the early-age cracking of RC structures. The cracks that appear on the surface may grow to widths larger than 1 mm and lengths of 50 to 1000 mm, and may be spaced in an irregular pattern. In shallow elements, e.g. concrete slabs, they can even grow throughout the whole depth. The cracks furthermore accelerate the ingress of harmful substances and leads to the reduction of serviceability. Therefore, they need to be eliminated or at least their width needs to be reduced with effective methods[1]. The shrinkage of hardened concrete consists of drying shrinkage, autogenous shrinkage, and carbonation shrinkage. The contribution of the autogenous shrinkage to long-term behavior should be negligible in normal strength concretes. The carbonation shrinkage can be considered a special case of drying shrinkage as the chemical process of carbonation occurs with concomitant loss of water. Drying shrinkage is the change in volume after the setting takes place[9]. Autogenous shrinkage is the shrinkage in a conservative system, i.e., where there is no moisture movement to and from the paste permitted. Three mechanisms, namely, capillary tension, disjoining pressure and surface free energy, are proposed in the literatures for the drying shrinkage of the cement based composites[2]. Strategies developed to mitigate shrinkage include incorporation of supplementary cementitious materials,
Key Words: Shrinkage, Materials, Mechanical Properties, Plastic Shrinkage, Drying Shrinkage.
1.INTRODUCTION Concrete is the second most widely used material globally, only after water. Concrete is the most extensively used construction materials. The flowability of the plastic mix and compressive strength of the resulting material allows it to be shaped to specification, making it a prime choice for building material. Several types of concrete are used in large quantities yearly all over the world. Owing to the extensive use of concrete, numerous researchers are studying its engineering properties and durability performance. Industrialization and development of construction have made a high challenge for innovative kinds of sustainable materials, which are necessary to possess enhanced properties such as strength, deformation, and durability. Cement based materials normally undergo various types of volumetric shrinkage, which could induce tensile stresses and may in turn lead to cracking. In concrete, the development of cracks causes significant problems related to the strength and durability performance. The formation of cracks may reduce the lifespan of concrete structures by allowing the entry of harmful particles through it. Therefore, it is important to prevent crack formation and improve the durability of concrete structures. Shrinkage cracks impair the durability and serviceability of concrete structures[2].
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