A model for predicting thermal conductivity of concrete

Abstract

This study investigates the thermal conductivity of fly ash concrete. Experiments were conducted to obtain the thermal conductivity of fly ash-cement pastes and mortars. Pastes were prepared to investigate the effect of fly ash, and mortar specimens were prepared for studying the effect of aggregates. It was found from the test that the replacement of cement by fly ash resulted in lower thermal conductivity. Thermal conductivity of mortar was higher than that of the cement paste. A simple parallel model for predicting thermal conductivity of fly ash concrete was proposed as a time-, material-and mix-proportion-dependent function. Thermal conductivity of concrete was computed based on the volumetric fractions and respective thermal conductivity values of each ingredient including the hydrated and pozzolanic products. Thermal conductivity of all ingredients in concrete are obtained from other studies except for the fly ash powder and hydrated products. In this study, thermal conductivity of hydrated product was obtained by the use of regression analysis together with the test results of cement paste, and thermal conductivity of fly ash powder was derived from the test results of cement-fly ash paste. The model was satisfactorily verified with various experimental results for pastes, mortars and concretes.

Effects of Chloride Content on Thermal Properties of Concrete

“…The results of this study, showed in Fig. 8, verified with result of Choktaweekarn [1]. For the controlled specimens of both mixture, the obtained results clearly showed that due to the low specific heat of water to binder ration w/b=0.4, its temperature increased proportionally higher than that of water to binder ration w/b=0.6.…”

“…A proposed model to predicted the specific of concrete by Choktaweekarn [1] clarified that the water to binder ratio significantly affects the specific heat of concrete. Specifically, the predicted model estimates that for concrete with water to binder ratio w/b=0.4, its specific heat is approximately 814.75 / .…”

“…Particularly, in attempt to know the ability of generating, retaining and conducting the heat inside concrete, the thermal properties are required. Since concrete is a compound of many materials, thus, its thermal properties is computed based on the volumetric fraction and the thermal properties of those compound materials respectively [1]. Table 1 shows the thermal properties of materials [2][3][4][5][6].…”

“…The fact is that sand particle is relatively larger and its specific heat is lower than silica fume. Another recent study investigated the thermal properties of fly ash concrete [1]. The results showed that fly ash replacement results in high specific heat at young age but decreases in later age due to pozzolanic reaction.…”

“…The results showed that fly ash replacement results in high specific heat at young age but decreases in later age due to pozzolanic reaction. Choktaweekarn [1] also proposed that the concrete with different mix proportion will result in different thermal properties.…”