HIGH STRENGTH CONCRETE MANUFACTURED FROM SPECIAL AGGREGATES FOR PARTICULAR USES IN CONSTRUCTION

Abstract

slump above IOOmm and strength up to 140 MPa at 180 days with W/C 0.24 I and 3.5% superplastizer (SP6). For lightweight concrete, 14 mixes were selected to achieve the slump over IOOmm and strength up to 71 MPa at 180 3

I days and at W/C 0.34, 0.3, 0.28 for cement content 400, 500, 600 kg/m

with

2% superplastizer (SP6). The present program deals with the use silicafume and superplasticier to produce special high strength concrete. To investigate the properties of magnetite high strength concrete, three levels of silicafume (0, 10%, 20%) by weight of cement, two ratios of coarse aggregate content (0.48, 0.65) by volume and two type of fine aggregate (magnetite, sand) were used. On the other hand, three cement content (400, 500, 600) kg/m 3 two levels of silicafume (10, 20%) and two ratios of coarse aggregate content (0.48, 0.65) by volume were used to investigate lightweight high strength concrete. For both type of concretes, information on mechanical properties, stress-strain under static and cyclic load, creep, shrinkage, permeability, surface absorption, sulphate resistance and exposure to high temperature was provided. In addition shielding properties for heavyweight high strength concrete were also provided. All experimental work was conducted with the full co-operation of the technical staff and facilities in City university, London, UK

A statistical method of analysis of experimental results was used to arrive at an optimal solution. Analysis of variance (ANOVA) was used to analyse the results, particularly for mechanical properties. The results indicated that:-

Heavyweight high strength concrete (HWHSC) - Silicafume is to be a good mineral admixture, improving all mechanical properties, fatigue life, creep , shrinkage and durability. Silicafume is effective in enhancing concrete residual compressive strength after I exposure to high temperature. Silicafume has a significant effect on reduction the thickness required to shielding. There is a significant effect of coarse aggregate content on the all mechanical properties, fatigue life, water absorption, oxygen permeability. There is no effect of coarse aggregate content on creep and shrinkage, residual compressive strength after exposure to high temperature. Magnetite as a fine aggregate gave a higher compressive strength than sand as fine aggregate. For silicafume concrete, sand as a fine aggregate gave a higher fatigue life than using magnetite as a fine aggregate.