Research on Elastic Modulus of Gangue Concrete

The effect of gangue content on concrete strength and elastic modulus was studied in this paper and the mathematical model of modulus calculation was built up for gangue concrete. In the tests, concrete specimens in four strength grades of C20-C50 were prepared using equivalent replacement with substitution of 20%-100% gangue for gravel, and adjusted the concrete workability by admixture adding. The specimens were tested according to Standard GB/T50081, then the effect of gangue content on concrete strength and elastic modulus were studied. The mathematical model of strength, elastic modulus and apparent density of gangue concrete were built up. The tests results showed that specific strength of C20 concrete changed little, the strength changed in the range of +/-2MPa with the variation of gangue content. The strength of C30 concrete did not changed obviously when gangue content was lower than 40%, but the strength decreased significantly when the content was in the range of 40%-60% while the maximum strength reduced by 10.4%; The strength tended to be steady when the content was greater than 60%. The strength gradually decreased with the increase of gangue content for C40-C50 concrete and the strength decreased by 10% when the content increased to 40%. The strengths of C40 and C50 concrete decreased by 17% and 27.5% respectively when the content ran up to 60% while the specific strength decreased in the range of 10%-20%. On the whole, the concrete elastic modulus gradually decreased with the increase of the gangue content. The conclusions were: The gangue content could be unlimited for the concrete whose grade was equal to or lower than C20 because the content variation would not affect its strength and specific strength. The content would be strictly limited within 40% for C30 concrete because its strength decreased significantly if the content was greater than that. The content should be limited within 20% for C40-50 concrete because the strength decreased by 5% when the content increased to 20%. By studying the relationship between concrete strength and modulus, the mathematical model of elastic modulus calculation for gangue concrete was built up based on the test data and results, and the calculation formula was deduced: E-c = 429.1/(9.003 + 151.4/f(c)) or E-c = 6.036x10(-3)x rho xf(c)(0.2388).