Impact of Curing Methods on the Porosity and Compressive Strength of Concrete

An experimental investigation was conducted to evaluate the impact of different curing practices on the porosity and compressive strength of concrete. The targeted compressive strength of the concrete at 28-day of curing was 20 N/mm2. Plain concrete cubes were prepared with a mix ratio 1:1.5:3 by weight and 0.6 water-cement ratio. A total of 120 concrete cubes were tested on 7th, 14th, 21st, 28th and 56th day curing periods for slump, porosity and compressive strength. The four curing methods used were immersion, jute sack, plastic sheet and sprinkling which were all carried out in the laboratory under the same average environmental conditions of 27 ± 20°C temperature and 75% relative humidity. The results from the study showed that slump values were within the range of 52mm to 58mm which is within the medium range of 25 to 100mm, hence a true slump was achieved. The porosity of all samples decreased with age (i.e. at the dried state, immersion recorded the lowest 4.35%, followed by jute sack with 5.25%, plastic sheet 5.29% and sprinkling 5.55%). Again, the pattern of increases in concrete density (immersion curing produced concrete with the highest mean densities of 2369 kg/m3, jute 2360 kg/m3 ,plastic sheet 2277 kg/m3, sprinkling 2229 kg/m3 all for 56 days) was similar to that of the compressive strength (i.e immersion curing method yielded the highest compressive strength of 25.43 N/mm2, jute method 23.90 N/mm2, plastic method 23.47 N/mm2 , sprinkling method 22.33 N/mm2 for 56 days curing ages respectively). Therefore, increases in both compressive strength and densities of concrete cube is a function of curing method. The study concludes that the immersion curing method has the greater effect on the properties of concrete since it yielded the highest strengths. The recommendation is made for further studies on the impact of curing methods on the porosity and compressive strength of concrete on the field since this study was done in the laboratory under control conditions.