Effect of Water-Cement Ratio on the Compressive Strength of gravel - crushed over burnt bricks concrete.

The research was conducted to study the effect of water-cement ratio on the compressive strength of gravel-crushed over burnt bricks concrete. Trial mixes were prepared using the crushed over burnt bricks as coarse aggregates only (control), mixture of crushed over burnt bricks and river wash gravel as coarse aggregates and river washed gravel as coarse aggregates only (control) at water – cement ratios of 0.4, 0.5,0.55 and 0.6. Cubes of concrete were prepared and tested to study the compressive strength in relation to the water-cement ratio. The results indicate that the concrete having over burnt bricks as aggregates may be termed as medium light weight concrete having a density between 2000-2200 kg/m3 and that by reducing the water-cement ratio from 0.6 to 0.4 increases the compressive strength from by more than 30%. Use of broken over burnt bricks as coarse aggregate for structural concrete is recommended when natural aggregate is not easily available, high strength of concrete is not required and the bearing capacity of the soil is low. Key words: Aggregates, concrete, compressive strength, water-cement ratio, crushed over burnt brick

Comparative Analysis of the Compressive Strength of Concrete with Gravel and Crushed Over Burnt Bricks as Coarse Aggregates

The research was conducted to study the possibility of utilizing the waste over burnt bricks abundantly available in most parts of Gwer-West Local Government Area of Benue State, particularly Naka, the Local Government capital, as coarse aggregates in structural concrete. Trial mixes were prepared using the crushed over burnt bricks known also as brick bats as coarse aggregates only, mixture of crushed over burnt bricks and river wash gravel as well as using river washed gravel from River Benue. Cubes of concrete were prepared and tested to study the compressive strength. The result indicate that the concrete having brick bats as aggregates may be termed as medium light weight concrete having a density between 2000-2200 kg/m3. To produce the same workability, the brick aggregates concrete requires greater proportion of water than the normal gravel aggregate concrete. Use of broken over burnt bricks as coarse aggregate for structural concrete is recommended when natural aggregate is not easily available, high strength of concrete is not required and the bearing capacity of the soil is low.Keywords: compressive strength, concrete, crushed burnt bricks, coarse aggregate

Derivation and optimization of deflection equations for tapered cantilever beams using the finite element method

This study derived analytical solutions for the deflection of a rectangular cross sectional uniformly tapered cantilever beam with varying configurations of width and breadth acting under an end point load. The deflection equations were derived using a numerical analysis method known as the finite element method. The verification of these analytical solutions was done by deterministic optimisation of the equations using the ModelCenter reliability analysis software and the Abaqus finite element modelling and optimisation software. The results obtained show that the best element type for the finite element analysis of a tapered cantilever beam acting under an end point load is the C3D20RH (A 20-node quadratic brick, hybrid element with linear pressure and reduced integration) beam element; it predicted an end displacement of 0.05035 m for the tapered width, constant height cantilever beam which was the closest value to the analytical optimum of 0.05352 m. The little difference in the deflection value accounted for the numerical error which is inevitably present in the analyses of structural systems. It is recommended that detailed and accurate numerical analysis be adopted in the design of complex structural systems in order to ascertain the degree of uncertainty in design. Keywords: Deflection, Finite element method, deterministic optimisation, numerical error, cantilever beam

The optimum amount of waste glass aggregate that can substitute fine aggregate in concrete

The study that is reported in this paper was carried out to study the effects of glass sand on the properties of concrete and determine the optimum amount of waste glass aggregate that can effectively replace fine aggregate in cement concrete. The objectives of the study were to prepare concrete specimens containing various amounts of glass sand as partial replacement for fine aggregate and to determine the properties of fresh and hardened concrete specimens so produced. It was found that glass sand does not have significant effect on the workability of concrete. The density of concrete containing glass sand was slightly lower than the density of normal concrete by a factor of 1-2%. The presence of glass sand did not alter the established strength-time relation of concrete. The strength of concrete containing glass sand increased progressively with curing time. Glass sand had significant effect on the strength of concrete. A plot of concrete strength and glass sand content was a parabola curving downward. The peak strength, obtained at 10% glass sand content, was 1.2 times the target strength of 25 N/mm2. The study concluded that the optimum amount of glass sand that can effectively substitute river sand in grade C25 concrete is 16% of the proportion of fine aggregate in the concrete. For plain concrete, glass sand alone can be used as fine aggregate. It was recommended that supplementary cementitious materials should be incorporated in the concrete to suppress the deleterious alkali-silica reaction that may take place when glass concrete is exposed to moisture

The Optimum Amount of Waste Glass Aggregate that can Substitute Fine Aggregate in Concrete

The study that is reported in this paper was carried out to study the effects of glass sand on the properties of concrete and determine the optimum amount of waste glass aggregate that can effectively replace fine aggregate in cement concrete. The objectives of the study were to prepare concrete specimens containing various amounts of glass sand as partial replacement for fine aggregate and to determine the properties of fresh and hardened concrete specimens so produced. It was found that glass sand does not have significant effect on the workability of concrete. The density of concrete containing glass sand was slightly lower than the density of normal concrete by a factor of 1-2%. The presence of glass sand did not alter the established strength-time relation of concrete. The strength of concrete containing glass sand increased progressively with curing time. Glass sand had significant effect on the strength of concrete. A plot of concrete strength and glass sand content was a parabola curving downward. The peak strength, obtained at 10% glass sand content, was 1.2 times the target strength of 25 N/mm2. The study concluded that the optimum amount of glass sand that can effectively substitute river sand in grade C25 concrete is 16% of the proportion of fine aggregate in the concrete. For plain concrete, glass sand alone can be used as fine aggregate. It was recommended that supplementary cementitious materials should be incorporated in the concrete to suppress the deleterious alkali-silica reaction that may take place when glass concrete is exposed to moisture