Effect of Moisture Content on the Behavior of High Strength Concrete at High Temperatures

Abstract

In this paper, an experimental program was carried out to investigate the residual mechanical properties of high strength concrete and normal strength concrete, and how moisture content and temperature affect the spalling process. Three mixtures with water-cementitious material ratios, from 0.25 to 0.50, and with different saturation levels were heated in an electric furnace to elevated temperatures, from 200°C to 600°C. After heating, the specimens were cooled down to room temperature and then tested for compression and tensile strength. The results showed that high moisture content induces the spalling process and reduces considerably the mechanical properties of high strength concrete, mainly at temperatures above 400°C.

Nonlinear Deformation Model for Analysis of Temperature Effects on Reinforced Concrete Beam Elements

“…The resulting physical relations can be obtained by extracting the stresses σ b,ji and σ s,k from Equations ( 26) and ( 27), replacing the deformations ε b,ji and ε s,k by Equation (30), and substituting them into Equation (31). The system of equations can be represented in a more compact matrix form after grouping the terms containing the longitudinal relative deformations of the element, ε 0,z , at the level of the median axis and the curvatures χ x and χ y with respect to the X and Y axes: (32) where the coefficients of the stiffness matrix, A 1 , . .…”

“…Under the long-term effects of (i) temperature, (ii) a longitudinal force, and (iii) bending moments, the rheological problem is solved using the theory of concrete characteristic deteriorations over time, developed in [2,[30][31][32][33] for conditions of elevated temperatures. The principle of superposition of incremental creep deformations at a preset temperature is assumed to be applicable.…”

“…Under the preset boundary conditions, static equilibrium equations are satisfied, and the values are found for each type of problems from the solution to the system of Equation (32).…”

“…The SSS characteristics of reinforced concrete beams, calculated according to the proposed method, are compared with the results of experimental studies ([3] on Figures 2-5; [6] on Figures 6 and 7) using the values of thermal bending moments in statically indeterminate structures, as well as the values of cracking forces and deformations of the longitudinal axis of elements. Under the preset boundary conditions, static equilibrium equations are satisfied, and the values are found for each type of problems from the solution to the system of Equation (32).…”

Comportamiento Térmico y Estructural del Concreto Expuesto a Altas Temperaturas: Una Revisión de la Literatura

“…En concretos de alta resistencia, en un rango de 400°C-600°C, debido a cambios químicos y físicos en su microestructura junto con el proceso de desconchado es afectado por el nivel de saturación (Degliuomini et al, 2020).…”