Principle Instigator
Dr. James Marita Okwoyo

Sources of conventional concrete materials such as gravel, granite and limestone rocks are becoming scarce due to overexploitation as Kenya strives to industrialize posing great risks on their availability as well as sustainability. This research sought to assess the feasibility and suitability of tuff aggregates for the production of structural lightweight concrete. Normal-weight concrete (NWC) samples made from granite aggregates were used as control in the experiment. The main primary properties of study and comparison for the two types of concrete were the unit weights and compressive strengths. The mix design process was done according to ACI 211.2-98 Code. The workability of fresh concrete was tested according to BS EN 12350-2. The average slump value of tuff concrete mixed with water-cement ratio of 0.4 was 12 mm while that of conventional concrete was 27 mm. The unit weights of tuff and conventional concretes were determined according to ASTM C138. The results suggest average 28-day dry densities of 2038 kg/m3 and 2527 kg/m3 for tuff and conventional concretes respectively. The compressive strength tests were performed at different ages of concrete in accordance with BS 1881-part 116. In particular, the 28-day compressive strengths of 26.0MPa and 30.0MPa were obtained for tuff and conventional concretes respectively when presoaked aggregates were used with water-cement ratio of 0.4. However, an increase in the 28-day compressive strength of tuff concrete up to 25.5MPa while a decline in the compressive strength of conventional concrete up to 20.4MPa were noted at water-cement ratio of 0.6 when oven dry aggregates were used. The results of unit weights and compressive strengths from this study confirmed the concrete produced from tuff aggregates as a lightweight structural concrete as per Euro Code 2. The study further confirmed tuff aggregates to be suitable materials for the production of lightweight structural concrete which can be recommended for high-rise buildings and long-span bridges. 

Research Author
Sang G. K., Abuodha S. O., Mwero J. N.