Concrete high temperature effects

High temperatures during hot-weather concreting result in an increase of the amount of mixing water required to produce a given slump [91, 94]. This effect of temperature is attributable to its accelerating effect on the hydration rate of the cement. At temperatures in excess of 25 °C, the mix... 

High Temperature. The effect of temperature on compressive strength for several concrete-polymer systems is shown in Figure 2 (6). 

For concrete at high temperature the most important is the effect of cracking and dehydration process on the material properties, e.g. porosity n=f(Thydr)> intrinsic permeability k=/(T/,(/,/r. /7. T), and its deformations. Irreversible part of strains and so called thermal creep are expressed as functions of thermochemical damage parameter V, [8],... 

Interpretation. The results of concrete resistivity measurements can be used for a quantitative or qualitative interpretation. Resistivity data measured on a structure and corrected for the temperature effect can be compared to reference data of similar concrete types (Table 2.4). Usually additional information is necessary. If, for example, a wet structure made with OPC has a mean resistivity value of 50 fl m, it means that the water-to-cement ratio and the porosity must be quite high. Consequently, the corrosion rate after depassivation will be high. 

L.T. Phan, N.J. Carino Effects of Test Conditions and Mixture Proportions on Behavior of High-Strength Concrete Exposed to High Temperature, ACI Materials Journal, (2002), pp. 54-66... 

In the case of FRP laid up externally on masonry or concrete members, the exposure to high temperatures leads to a rapid decrease of the bonding capacity between the FRP and the support, and a consequent debonding of the composite with loss of effectiveness of the reinforcement. 

Section V on Testing in Environments (H. Hack, Section Editor) includes chapters on outdoor and indoor atmospheres, seawater, fresh water, soils, concrete, industrial waters, industrial chemical, petroleum, high-temperature gases, organic liquids, molten salts, liquid metals, corrosion inhibitors, in-vivo, and microbiological effects. Each chapter provides a descriptive overview of the environment and factors and variables affecting corrosion rates and mechanisms. 

Lau, A., Anson, M. (2006) Effect of high temperatures on high performance steel fibre reinforced concrete, Cement and Concrete Research, 36 1698-707. 

Losses in shielding efficiency may occur as a result of environmental conditions. Effects that should be taken into account are those due to the interactions of neutron and gamma rays with the shielding (e.g. the burnup of radionuclides that have a high neutron absorption cross-section, radiolysis and embrittlement), those due to reactions with other materials (e.g. erosion and corrosion by the coolant), and temperature effects (e.g. the removal of hydrogen and/or water from concrete). 

Schneider, in 1986, explored the effect of high temperatures in elements of concrete and examined its influence on the behavior of the set of the concrete. He confirmed that compression stress. Youngs modulus, thermal deformation, and shrinkage that were suffering the materials were depending on the type of aggregate and produced curves to show the degradation suffered by the properties of the material with respect to temperature and load. 

C. Castillo. Effect of transient high temperatures on high strength concrete. Thesis Doctoral, Rice University, Houston (Texas), 1987. 

Set retarders are used to offset the effects of high temperatures, which decrease the set time. They are also applicable when unnecessary delays occur between mixing and placement. In mass concrete, retarders prolong the plasticity of fresh concrete, and that has advantages. Elimination of cold joints is possible with the use of retarders. With retarders, the minimum initial set time should be 1 hour later, with a maximum of 3 A hours. The compressive strength should be a minimum of 90% of the control at 3, 7, and 28 days. 

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