Investigation on the Static Modulus of Elasticity of Concrete in Compression Made Using Locally Available Coarse Aggregates
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2017-03
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Addis Ababa University
Abstract
The primary objective of this study was to determine the static moduli of elasticity of concrete mixes made of three different coarse aggregate types found locally and to compare the results of the study with the recommended values by Euro code which we are adopting. To see the effect of static compression modulus of elasticity on the stability of a structure a case study was also conducted.
The coarse aggregate types considered in this study were basaltic, limestone based and scoria based coarse aggregates. The standard method stated in BS EN 12390-13:2013 is the methodology followed to determine the static moduli of the concrete mixes. Mixes were prepared for three water-to-cement ratios (0.59, 0.56 and 0.51) for each aggregate type. Mix design was done considering the physical properties of basaltic coarse aggregate type whereas the mixes prepared for limestone and scoria based coarse aggregate types have the same amount of water, cement and fine aggregate except for the coarse aggregate portion where volume based replacement is made to see the effect of coarse aggregate type. The specimens used were cylindrical molds with diameter of 10cm and height of 20 cm. The specimens were kept in a curing chamber until one day before the test. The specimens with strain measuring transducers attached were subjected to loading according to the loading and unloading sequence stated in BS EN 12390-13:2013. For the case study 40/60 saving house having 22 stories was modeled using ETABS 15.2.2, and a response spectrum analysis was done on the model.
Four Specimens for 7th day and five specimens for 28th day were tested for compressive strength and static compression moduli of elasticity. Based on the 28th day test result, the recommended correction factor by Euro code for basaltic coarse aggregate type, which is commonly used in Addis Ababa, resulted in an approximate value for water to cement ratios of 0.56 and 0.51 whereas it resulted in a higher value for water to cement ratio of 0.59 when compared to the actual Computed value. The recommended correction factor for limestone based coarse aggregate resulted in a much lower value than the actual computed values for the limestone based coarse aggregate type considered in this study. The recommended correction factor for light weight aggregate concrete overestimates the actual value of static compression moduli of light weight aggregate concrete made of scoria based coarse aggregate considered in this study. The recommended correction factor by the code for light weight aggregate
INVESTIGATION ON THE STATIC MODULUS OF ELASTICITY OF CONCRETE IN COMPRESSION MADE
USING LOCALLY AVAILABLE COARSE AGGREGATES
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concrete in general are 0.84, 0.88 and 0.89 for 0.59, 0.56 and 0.51 water-to cement ratios respectively. However, the result of this study shows the correction factors to be 0.64, 0.64 and 0.68.
Based on the result of the case study, a 20% increase in static compression modulus of elasticity resulted in a 16% reduction on the stability index. Based on the result of the current study it is recommended to check not only the compressive strength but also the static compression modulus of elasticity of concrete mixes.
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