Northwood, Derek O
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Publication Effect of plastering on the carbonation of a 19-year-old reinforced concrete building(1996-06) Roy, S.K.; Northwood, D.O.; Poh, K.B.; SCHOOL OF BUILDING & REAL ESTATEAn extensive carbonation survey was conducted of a 19-year-old commercial building that was situated in a tropical environment. A significant reduction in carbonation was found for those structural components that were plastered (sand-cement render) compared to those with no surface finishing. There was no carbonation of the concrete when the plaster (render) thickness exceeded 30 mm. The carbonation data on non-plastered structural components showed that the depth of carbonation decreased with increasing core strength. The measured carbonation rate constant (K= 5.05 mm yr-0.5) is consistent with previous measurements in a similar climate but is higher than reported for structures in temperate climates (K = 1 to 3 mm yr-0.5). Copyright © 1996 Elsevier Science Ltd.Publication Chloride ingress in concrete as measured by field exposure tests in the atmospheric, tidal and submerged zones of a tropical marine environment(1993) Roy, S.K.; Liam Kok Chye; Northwood, D.O.; SCHOOL OF BUILDING & REAL ESTATE; MECHANICAL & PRODUCTION ENGINEERINGFive grades of concrete were exposed in the atmosphere, tidal and submerged zones of a tropical marine environment for times up to 80 weeks and the chloride ion ingress profiles determined. The measured chloride profiles were compared with profiles calculated on the basis of diffusion theory and the agreement was found to be reasonably good for all 3 zones. Diffusion coefficients, D, for the chloride ion calculated from the measured ingress profiles agreed well with previous data from laboratory tests and from surveys of marine structures. D was found to be mainly dependent on the water/cement (W/C) ratio and changed little with the addition of superplasticizers. The use of data for the diffusion coefficient, D, and equilibrium surface chloride level, Ce, obtained from the chloride ingress profiles, to the calculation of the time-to-initiation for corrosion of the steel reinforcement is briefly discussed. © 1993.Publication The evaluation of paint performance for exterior applications in Singapore's tropical environment(1996) Roy, S.R.; Thye, L.B.; Northwood, D.O.; SCHOOL OF BUILDING & REAL ESTATETwo water-base paints, a regular non-algae and an algae resistant emulsion for decorative purposes, were exposed to artificial, i.e. accelerated, and natural weathering tests and the deterioration compared to that for similar paint applied to exterior walls on multi-unit buildings in Singapore. The artificial weathering test was found not to provide a good representation of actual performance since it only monitors the deterioration due to chemical weathering and not that due to mechanical or biological weathering. The rate of deterioration of paint exposed in natural weathering tests in an industrial region in Singapore was faster than that for paint exposed in-service on multi-unit housing situated in industrial, central or coastal regions in Singapore. Copyright © 1996 Elsevier Science Ltd.