The influence of cement fineness on the structural characteristics of normal concrete

This research presents the influence of cement fineness on the structural characteristics of normal concrete. The cement was divided into different fineness zones (150 μm – 7 5μm, 75 μm – 45 μm and 45 μm – 0 μm). Thirty (30 Nos.) cement mortar cubes, 54 Nos. of 150 x 150 x 150 mm concrete cubes and 36 Nos. of 150 x 300 mm cylinder specimens were cast, cured by immersion and tested at 3, 7, 14, 21, 28 and 45 days. A concrete mix ratio of 1:2:4 (Cement: Fine aggregate: Coarse aggregate) with water/cement ratio of 0.5 was used. The results reveal that an increase in the fineness of cement particle led to an increase in workability. The setting times (initial and final setting time) reduces progressively as the cement fineness is increased from 175mins (initial setting time) for sizes 150 μm – 75 μm to an initial setting time of 140mins for sizes 45μm - 0μm. The final setting time also reduces from 300 mins to 240 mins as the cement fineness is increased. The tensile and compressive strengths recorded an increase due to the increase in cement within the concrete matrix. It was concluded that the finer the cement particle the greater the concrete strength

A comparative study on the strength characteristics of Grade 25 and Grade 30 rice husk ash blended cement concrete

Rice husk ash (RHA) is an agricultural waste which is a pozzolanic material that can be blended with cement in producing concrete. This research presents investigation carried out on the comparative strength characteristics of concrete produced with grade 25 and grade 30 cement blended concrete using a replacement level of 10% rice husk ash as substitute. Two mix ratios (1:2:4 and 1:1.12:3.01) were used. A total of 60 cube size of 150mm were cast, tested and their mechanical properties determined. The RHA was made in the laboratory by burning the husk obtained from Ifo in Ogun State Nigeria using an Electric furnace, with the temperatures of the furnace at about 700°C. The results showed that the compressive strength at 28 days decreased as the percentage replacement of Portland Limestone cement (PLC) with RHA increased from 0% to 10% respectively with compressive strengths of 29.78 N/mm2 to 21.56 N/mm2 for grade 25 concrete and 32.12 N/mm2 to 26.82 N/mm2 for grade 30 concrete. It was concluded that RHA replacement in concrete can be used for the production of concrete for light structural works in the development of sustainable and green structures