ABSTRACT
Concrete strength and behavioural aspects can be influenced by environmental conditions, higher temperatures and changes in relative humidity can remarkably affect concrete performance and durability properties. For better comprehension of different environmental conditions on concrete behaviour, the investigation is aimed at determining the effect of relative humidity on the mechanical properties of rice husk ash concrete under different humidity conditions.
Fabricated air-tight chamber laced with saturated salt solution was used to determine the fixed-point relative humidity condition with hygrometer instrument used to verify and track daily humidity and temperature readings in the surrounding and ambient environment. The humidity curing condition of 31% which corresponds to average humidity condition of regions like Kano, Katsina, Sokoto and humidity condition 51% which corresponds to average humidity condition of regions like Nassarawa, Kaduna, Kogi were selected, while that of 78% humidity condition corresponds to average southern climatic regions in Nigeria. Concrete cube size of 100 mm × 100 mm ×100 mm were prepared and cured in these conditions for 7, 14, 28, 91 days for control and RHA percentages of 5%, 10% and 15%. Laboratory test to determine the workability, compressive strength, ultra-pulse velocity, water absorption and carbonation test were carried out.
The results showed that the compressive strength for 31% and 51% relative humidity condition for all percentages replacement of RHA concrete was significant but didn’t meet grade 25 concrete target strength while that of 78% humidity condition for 0%, 5% and 10% RHA concrete met the design requirement for target strength at grade 25 concrete. Using the ultra-pulse velocity tester, excellent grade of concrete was observed mostly at 51% and 78% relative humidity condition of 5% partial replacement RHA concrete. There was an increase in water absorption as percentages replacement increase for RHA concrete in all climatic conditions. At low humidity regions 5% RHA content can be utilized for high grade concrete. Attention should be placed on early maturing stage of RHA concrete in these regions to avoid rapid loss of moisture content.
