5 research outputs found
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