Chloride diffusion in steel fibre reinforced marine concrete

The paper presents some results from a continuing research programme on the marine durability of steel fibre reinforced concrete. A mix of proportions by weight of 1 : 1.5 : 0.86 with a water/cement ratio of 0.4 was reinforced with three types of steel fibres. The cement content of the mix was 590 kg/m3. Uncracked prism specimens were cured under marine splash and tidal zone exposure in the laboratory and at Aberdeen beach. In one batch of prism specimens, flexural cracks of width ranging between 0.07 and 1.08 mm were induced prior to marine exposure. Chloride diffusion characteristics in uncracked and pre-cracked concrete were determined at up to 2000 cycles of marine exposure (1250 days). The results show that Cl− concentrations are significantly greater in laboratory cured specimens relative to those cured on the beach. Most of the Cl− penetration occurs within 150 tidal cycles of exposure at the beach. Cl− concentrations increase with increasing crack widths although the influence of small crack widths of ⩽ 0.2 mm is marginal.