The Influence of Packing Density on Bond Behaviour of Reinforcing Bars on Low Binder Concrete (LBC)

Abstract

The awareness of environmental problems, caused by CO2 emissions, have led the scientific community to seek more sustainable solutions, from both environmental and economical perspectives. Regarding concrete, this goal can be reached through the use of low binder concrete (LBC), consisting of partially replacing Portland cement by additions and increasing the packing density. This paper presents a research conducted to analyse the viability of using LBC in reinforced concrete (RC) structures, namely by studying the bond behaviour between LBC and reinforcing bars (rebars). With this aim, an experimental program including monotonic pull-out tests to assess the influence of concrete’s packing density {0,82; 0,84; 0,86} and the influence of aggregates’ optimization distribution (Alfred and Faury curves) was planned. In addition, concrete’s compressive and tensile strength tests and rebars’ rib measurement and rebars’ tensile strength tests were carried out to characterize the materials’ properties. The following main conclusions were drawn: (1) LBC’s packing density has a positive effect on the bond behaviour at both service and ultimate limit states, (2) the aggregates should be smaller than the rebars’ ribs spacing, (3) the design expression of fib Model Code 2010 for bond stress between rebars and concrete does not give accurate values when LBC is adopted, and (4) the compressive strength of LBC is mainly due to the high packing density of the mixture, corroborating previous studies.