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

Correlating the thermomechanical indexes of concrete modified with anacardium occidentale nutshell ash using linear model polynomial analysis

This study correlated the thermal and mechanical properties of concrete produced with anacardium occidentale (cashew) nutshell ash (AONA). Cashew nutshells, agricultural waste products, was valorized to obtain AONA. AONA was replaced at 5, 10, 15, and 20 wt% of cement to produce concrete grade 25 MPa. Density, compressive strength, and thermal conductivity of the concrete samples were determined at 28 days curing, and the results were correlated using regression model analysis. The experimental findings revealed that the compressive strength increased with increasing AONA content. Moreover, both density and thermal conductivity reduced as AONA content increased. Besides, the correlation yielded a high precision with 97% “R2”. Thus, AONA has proved to exhibit higher mechanical strength with excellent thermal insulation when utilized as supplementary cementitious material (SCM) in concrete production. The developed model can also be applied to the correlation of thermomechanical properties of concrete incorporating SCMs in that time, energy, and cost in conducting laboratory works would be reduced

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

Structural Efficiency of Concrete Containing Crushed Bone Aggregates

The indiscriminate dumping of animal waste, especially cow bones in abattoir has brought about the need for adequate safe disposal and recycling of such waste. This study investigated the use of crushed bones as a partial substitute for fine aggregate and its efficiency in concrete structures. Sieve analysis test was conducted on the crushed bone and used as partial replacement of fine aggregate in concrete at 0, 25, 50, 75, and 100% by weight.  Slump test on the fresh concrete was investigated, while the density, compressive strength test and structural efficiency of the hardened concrete were also determined. The sieve analysis result revealed that the crushed bone was poorly graded, and the slump test showed that the 25% of crushed bone concrete has a low slump. The density was 2370 kg/m3, the compressive strength was 17.10N/mm2 at 28 days, while the structural efficiency was 7.22. The 50, 75 and 100% samples has compressive strength of 16 N/mm2, 6.10N/mm2 and 4 N/mm2 at 28 days respectively and these values are far below expectations. The work concluded that crushed bones could partially replace fine aggregate in lightweight concrete at not more than 25% by weight. This test is limited to a short-term test of 28 days