The Damping Properties of Plain Concrete: Effect of Composition and Relations with Elasticity and Strength

摘要

The report describes experiments to measure the vibrational damping coefficient, dynamic Young's modulus of elasticity, flexural strength and compressive strength of three categories of plain concrete and their corresponding sand-cement mortars. The concretes comprised high strength mixes (mix proportions 1:1:2.5/0.35 by weight), pavement quality mixes (1:2.1:4.1/0.5 to 1:2.1:6.0/0.5) and lean concretes (1:6:11/1.0). Each mix was repeated with three different types of coarse aggregate: Bridport gravel, Chertsey gravel and Charnwood crushed granite, of 3/4-in. maximum size in the high strength and pavement quality mixes, and of 1 1/2-in. maximum size in the lean concrete and in additional pavement quality mixes. The damping was higher in the sand-cement mortars of each type of mix than in the corresponding concretes. Damping was greater in the lean concretes than in the pavement quality or high strength mixes, and also tended to be slightly higher in concretes containing crushed granite than in the corresponding mixes containing the natural gravels. The results support the view that damping in concrete arises mainly from the presence of water voids in the cement paste and, to a lesser extent, from the boundaries between the cement paste and the fine and coarse aggregate particles. An analysis of the results suggests that there is unlikely to be a unique relation, of the type found by other workers in a more limited investigation, between damping, dynamic Young's modulus of elasticity and either compressive or flexural strength. (Author)