Experimental study of equal biaxial-to-uniaxial compressive strength ratio of concrete at early ages

The ratio of equal biaxial to uniaxial compressive strength of concrete, denoted as beta, is an important parameter in the determination of failure criterion for concrete, which has been Widely adopted in finite element codes in simulation of fracture and failure of concrete. However, there is no experimental study on $ conducted for concretes at early ages. In this study, an experimental study on the uniaxial and equal biaxial compressive strengths of concretes at early ages up to 28 days was carried out using an in-house electro-hydraulic servo-controlled triaxial test machine. Concrete specimens with different coarse aggregate sizes (10 mm, 20 mm, 30 dim) and strength grades (C30, C40, C50) were tested at various ages (6 h, 12 h, 1 d, 3 d, 7 d, 14 d, 28 d). The results showed that beta decreases with the increase of concrete age. In comparison, there are less significant effects of concrete strength and maximum coarse aggregate size on beta. By regression analyses of experimental results, an empirical equation was proposed for beta by considering the effects of age on beta for concrete at early ages. (C) 2016 Elsevier Ltd. All rights reserved.