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The corrosion resistance of steel reinforcement embedded in an alkali activated cementitious material (AACM) developed by Sheffield Hallam University (SHU) is being investigated. Two main initiators of corrosion, chloride diffusion and... more
The corrosion resistance of steel reinforcement embedded in an alkali activated cementitious material (AACM) developed by Sheffield Hallam University (SHU) is being investigated. Two main initiators of corrosion, chloride diffusion and carbonation are being considered. This paper will present the results of chloride diffusion in the AACM concrete compositions under long term exposure (up to 180 days) by immersion in a 5% sodium chloride solution. Different mix compositions of the AACM concrete (four grades of mixes) suitable for structural application have been selected, representing different concentrations of the alkali activator and different binder and aggregate ratios. Parallel investigations on control samples of normal concrete of similar strength have been conducted. The chloride diffusion profiles with depth have been obtained. The results show a good correlation of chloride diffusion with Fick's second law of diffusion. A general reduction of chloride ion content within the AACM concrete matrix was observed compared to the control samples of normal concrete. Low liquid/binder ratio has a positive impact on strength, shrinkage and chloride diffusion of AACM concrete.
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Research Interests:
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An Investigation on the mineralogical and chemical characterization, pore structure, chemical shrinkage and pozzolanic activity of commercially produced rice husk ashes (RHA 1 and 2) and a control silica fume (SF) are presented in this... more
An Investigation on the mineralogical and chemical characterization, pore structure, chemical shrinkage and pozzolanic activity of commercially produced rice husk ashes (RHA 1 and 2) and a control silica fume (SF) are presented in this paper. RHA possesses high silica content like silica fume which is used as supplementary cementitious materials (SCM) in the production of concrete. There is a need for an alternative to silica fume in the production of concrete because of its high demand and relatively high cost. The mineralogical composition of RHA 1 and 2 show high silica content of 77% and 84% respectively which is close to the silica content (˃80%) of class 2 silica fume. The oxides of Ca are 3.53% and 7.68% while Al is 1.19% and 1.29% for RHA 1 and 2 respectively which suggest that RHA is a low Ca+2 content binder. The results of chemical shrinkage of RHA 1, 2 and SF are 0.42 mL/g, 0.52 mL/g and 0.11 mL/g after 500 hrs of hydration. This indicates that RHA 2 has the highest reac...
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Alkali activated cementitious materials (AACM) concrete is a sustainable alternative to Portland cement PC concrete by reducing CO2 emitted during the production of PC by 60%. Fundamental investigations on alkali activated concrete (AACM)... more
Alkali activated cementitious materials (AACM) concrete is a sustainable alternative to Portland cement PC concrete by reducing CO2 emitted during the production of PC by 60%. Fundamental investigations on alkali activated concrete (AACM) has been on their engineering properties with less emphasis on the service life and durability properties. The carbonation effect on concrete is crucial for its service life prediction. This paper investigates the suitability of phenolphthalein indicator method to determine the carbonation front in AACM. The geopolymerisation products of AACM are different from the hydration products of PC concrete and consequently, the carbonation process of these two types of concrete is expected to be different. Three mixes of AACM 1, 2, 3 and control PC concrete were produced and cured in water (20 ± 20C) for 27days and then in laboratory air (20 ± 20C, 65% R.H) for 42days. A total of twenty-four cylindrical specimens with 50mm diameter X 60mm depth were produc...
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This paper reports an investigation on the size and distribution of capillary and gel pores in an alkali activated cementitious (AACM) mortar and comparative OPC mortar. These pore properties were determined from the cumulative and... more
This paper reports an investigation on the size and distribution of capillary and gel pores in an alkali activated cementitious (AACM) mortar and comparative OPC mortar. These pore properties were determined from the cumulative and differential pore volume curves obtained by mercury intrusion porosimetry (MIP). The classification and distribution of these pores provides a useful insight to the properties of hardened concrete such as the durability, fire resistance and mechanical properties. The results show that AACM mortar mixes possess a bimodial pore size distribution while OPC concrete has unimodial pore sizes distribution. The intrudable porosity is lesser in AACM mortar than OPC mortar. The volume of the capillary pores was higher in AACM mortar compared with OPC mortar. However, the volume of the gel pores was much lower in AACM mortar than OPC mortar. The distribution of bimodal pores in AACM mortar is greatly influenced by the effects of curing type and the activator diluti...
The corrosion resistance of steel reinforcement embedded in an alkali activated cementitious material (AACM) developed by Sheffield Hallam University (SHU) is being investigated. Two main initiators of corrosion, chloride diffusion and... more
The corrosion resistance of steel reinforcement embedded in an alkali activated cementitious material (AACM) developed by Sheffield Hallam University (SHU) is being investigated. Two main initiators of corrosion, chloride diffusion and carbonation are being considered. This paper will present the results of chloride diffusion in the AACM concrete compositions under long term exposure (up to 180 days) by immersion in a 5% sodium chloride solution. Different mix compositions of the AACM concrete (four grades of mixes) suitable for structural application have been selected, representing different concentrations of the alkali activator and different binder and aggregate ratios. Parallel investigations on control samples of normal concrete of similar strength have been conducted. The chloride diffusion profiles with depth have been obtained. The results show a good correlation of chloride diffusion with Fick's second law of diffusion. A general reduction of chloride ion content withi...