Abstract
This study aims to investigate the relationship between the heat of hydration and the strength development of cast‐in‐situ foamed concrete. First, indoor model tests are conducted to determine the effects of the casting density and the fly ash content on the hydration heat of foamed concrete in semiadiabatic conditions. Second, compression tests are carried out to evaluate the development of the compressive strength with the curing time under standard curing conditions and temperature matched curing conditions. Third, the hydration heat development of the foamed concrete is tested in four projects. The results showed that the peak temperature, the maximum temperature change rate, and the maximum temperature difference increased with the increase in the casting density at different positions in the foamed concrete. For the same casting density of the foamed concrete, the peak temperature, the maximum temperature change rate, and the maximum temperature difference decreased with the increase in the fly ash content. For the foamed concrete without the admixture, the early strength was significantly higher under temperature matched curing conditions than under standard curing conditions, but the temperature matched curing conditions had a clear inhibitory effect on the strength of the foamed concrete. The strengths during the early stage and the later stage were both improved under temperature matched curing conditions after adding the fly ash, and the greater the fly ash content, the larger the effect. The maximum temperature increments were higher in the indoor model test than in the field tests for the same casting density. Reasonable cooling measures and the addition of fly ash decreased the maximum temperature increments and increased the corresponding casting times.
Highlights
Cast-in-situ foamed concrete is composed of cement, an admixture, and a proportion of stable tiny bubbles, and it is cast, molded, and cured at the construction site [1,2,3]. is type of concrete is a new type of geotechnical material developed in recent years and possesses the advantages of low weight, stable performance, convenient construction, and so forth. [4,5,6,7]. e applications of cast-in-situ foamed concrete have expanded considerably in civil engineering as a result of scientific and technical advances in its production
The increase and decrease of the hydration heat lead to the expansion and contraction of the foamed concrete structures, which affects the structure itself and adjacent buildings. e maximum temperature is used as an indicator of this problem
After the samples were unmolded, they were wrapped in bags cured in the constant temperature and humidity box (Figure 4). e temperatures for the different densities were collected in the same manner as for the indoor model test. e humidity value remained at 100%
Summary
Cast-in-situ foamed concrete is composed of cement, an admixture, and a proportion of stable tiny bubbles, and it is cast, molded, and cured at the construction site [1,2,3]. is type of concrete is a new type of geotechnical material developed in recent years and possesses the advantages of low weight, stable performance, convenient construction, and so forth. [4,5,6,7]. e applications of cast-in-situ foamed concrete have expanded considerably in civil engineering as a result of scientific and technical advances in its production. Is produced by the hydration of foamed concrete, which may affect the strength of the material. Because the coefficient of thermal conductivity for this material is low, high temperatures are maintained for very long periods in the structure Regarding these problems, Jones [11] stated that the heat evolution in foamed concrete is affected by a greater number of parameters than that in normal-weight concrete. The effect of hydration heat on the strength development of foamed concrete was not considered, and the experiments were carried out in the laboratory without considering external influencing factors. Fly ash is a pozzolanic material and has been widely used as an admixture in concrete to address the problem of the hydration heat. E main goal of this study is to investigate the relationship between the hydration heat and the strength development of foamed concrete. The changes in the temperatures of the foamed concrete were analyzed in four field tests
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