Author

Dr. Aref Al-Sawidani.

Published in

13TH Arab Structural Engineering Conference University of BLIDA 1 December 13-15, 2015 ALGERIA.

Abstract

It is widely accepted that any increase in the durability of reinforced concrete structures increase the sustainability of the construction industry. In order to make the concrete industry much more sustainable, it is imperative to take some effective approaches in concrete mix design. Probably, one of the most effective approaches is to substitute pozzolans for a portion of Portland cement. However, use of natural pozzolans is often associated with shortcomings such as the need to moist-curing for longer time and a reduction of strength at early ages. Syria is relatively rich in natural pozzolans (volcanic scoria). In the study, in order to investigate the influence of curing time on some durability-related properties, three curing times of 7, 28 and 90 days were studied. Corrosion resistance of reinforcement embedded in the concrete containing scoria-based cements, water permeability and chloride penetrability are particularly investigated. Concrete specimens were produced with seven cement types: one plain Portland cement (control) and six scoria-based cements with replacement levels ranging from 10 to 35%. The corrosion resistance of the embedded reinforcing steel has been investigated using an accelerated corrosion test by impressing a 12 V constant anodic potential after 7, 28 and 90 curing times. Chloride penetrability and water permeability have been also evaluated for all concrete mixes at all curing times in accordance with ASTM 1202 and EN 12390, respectively. In addition, the development of the compressive strengths of concrete cube specimens with curing time has been investigated. Test results revealed that curing time had a large influence on both compressive strengths and durability properties of scoria-based concrete. Concretes produced with scoria-based cements decelerated rebar corrosion, particularly after longer curing times and when higher cement replacement level was employed. The chloride penetrability and water permeability of scoria-based concrete mixes was also much lower than that of plain concrete, especially at high replacement levels of scoria and after longer curing times. A good correlation was observed between the rapid chloride penetrability test and the accelerated corrosion test, such that one can be estimated from knowledge of the other.

 Key words: Curing time, Chloride penetrability, Corrosion resistance, Water permeability, Blended cement, Volcanic scoria