Search

Silica fume is a by-product of induction arc furnaces and has long been used as a mineral admixture to produce high-strength, high-performance concrete. Owing to the pozzolanic reaction between calcium hydroxide and silica fume, compared with Portland cement, the hydration of concrete containing silica fume is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing silica fume. The heat evolution rate of silica fume concrete is determined from the contribution of the cement hydration and the pozzolanic reaction. Furthermore, the temperature rise in silica fume concrete is evaluated based on the degree of hydration of cement and silica fume. The proposed model is verified using experimental data on concrete with different water-to-cement ratios and silica fume substitution ratios. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted to examine the behaviour of high-strength reinforced concrete (RC) columns subjected to reversed cyclic and axial compressions, and to find the relationships between amounts of lateral reinforcements and axial load ratios. Twenty column specimens were tested. The test parameters of column specimens were the compressive strength of concrete (fc′ = 25, 52, 70 MPa), axial load ratios (0.3, 0.5 fc′Ag) and volumetric ratios of lateral reinforcement (ρs = 1.05, 2.1, 3.15%). Test results indicated that axial load ratios and the shape of lateral reinforcement could significantly affect and alter the behaviour of high-strength RC columns under inelastic cyclic loadings. [ABSTRACT FROM AUTHOR]

This paper evaluates the ultimate strength of high-strength concrete (HSC) columns subjected to both axial load and biaxial bending. Fifteen square section (200 × 200 mm) columns with concrete compressive strength of 34, 57 and 64 MPa, respectively, were axially loaded with bi-directional eccentricities. The loading point was at an angle of 0°, 22.5° and 45° and the distances of eccentricity were determined to induce tension, balanced and compression failures, respectively. Test results were compared with the results of nonlinear analysis on P-M interaction curves and load contours. It was observed that, as concrete strength increases from 34 to 57 MPa, the concrete strength has a minor effect on the biaxial moment strength of reinforced columns, but as concrete strength increases up to 64 MPa, the concrete strength has a significant influence on biaxial flexural strength. This observed result is complementary when compared with the load contour method of ACI, in which biaxial bending design constants of columns are limited to concrete compressive strength of 41 MPa and estimate the effect of concrete strength to be minor. [ABSTRACT FROM AUTHOR]

An experimental and analytical study was conducted to develop the confined concrete model of reinforced high-strength concrete tied columns subjected to mono tonically increasing concentric axial compression. Twenty-one large-scale columns (260 × 260 × 1200 mm) of high-strength concrete of 50 MPa and 85 MPa were fabricated to simulate full-size structural members. The effects of the main variables such as the concrete compressive strengths, tie configurations, amount of the transverse reinforcement, tie spacing and the spalling of the concrete cover were studied in this research programme. More confinement is required in columns of high-strength concrete than in columns of low-strength concrete to achieve the same degree of strength enhancement The proposed model satisfactorily predicted the experimental stress-strain behaviours for the confined high-strength concrete up to 100 MPa. [ABSTRACT FROM AUTHOR]