Efecto de las cargas cíclicas sobre la adherencia hormigón-acero en hormigones sumergidos

Effect of cyclic loading on concrete-steel bond in underwater concrete

Placing concrete underwater has been used for many years in construction, due to the impracticalities of creating a watertight basin in a marine environment or in ground which is severely waterlogged. Unfortunately the process is hindered by the action of cement washout from the concrete mass, which creates an impairment in the concrete mechanical properties, including loss of compressive strength and the bond between the set concrete and the reinforcement.The available technical literature on this subject show that the results of tests on samples of underwater concrete are significantly affected by the way in which the samples are taken, and these may not be representative of the real underwater conditions. Furthermore, there appears to have been no research conducted on the high cyclic loading on the underwater concrete to which many marine structures are often subjected.This paper concerns research undertaken into the bond strength between reinforcement and underwater concrete for concrete cylinder strength of 40 MPa. Monotonic and cyclic loading has been applied to 5 cycle samples sets (namely 1, 2000, 20,000, 200,000, and 2,000,000 cycles). The results show that, for monotonic loading, the (Tu) values in underwater samples reduce by 5% compared to samples cast in dry conditions. In addition the monotonic tests on the samples subjected to high cyclic loading show an increase in the (Tu) value compared to those samples not subjected to cyclic loading. This may be a result of the micro-compaction experienced by the concrete due to the high cyclic loading, which leads to an increase in compressive resistance.