Civil Engineering and Architecture 8(2): 94-100, 2020 http://www.hrpub.org DOI: 10.13189/cea.2020.080207 The Temperature Field in Mass Concrete with Different Placing Temperatures Anh Kiet Bui 1 , Trong Chuc Nguyen 2,* 1 Faculty of Civil Engineering, Ho Chi Minh City Open University, Vietnam 2 Institute of Special Construction Engineering, Le Quy Don Technical University, Vietnam Received February 1, 2020; Revised March 17, 2020; Accepted March 28, 2020 Copyright©2020 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Hydration heat of concrete mix has an important role in the process of temperature increase in mass concrete at an early age. Thermal stress caused by the temperature difference between the core and the surface of mass concrete is the main reason in making thermal cracks if the stress is larger than the tensile strength of concrete. The aim of this study is to investigate the effect of placing temperature on temperature distribution and thermal stresses of mass concrete. A proportion of concrete mix of interest is used for the thermal analysis of a mass concrete sample sized 8×6×3 m. The finite element Midas Civil program is used to conduct the three-dimensional thermal simulation. Four typical scenarios of placing temperature in the range of (15-30)°C of the concrete mix, which is commonly used in actual construction condition, are presented. The analysis results of temperature distribution and thermal stress indicate that the value of 30°C of placing temperature according to the selected proportion of concrete mix may cause thermal crack in the mass concrete. The study gives a useful way for practical construction application to avoid the risk of thermal crack in mass concrete at an early age. Keywords Maximum Temperature, Temperature Difference, Mass Concrete, Placing Temperature, Thermal Crack 1. Introduction Mass concrete are normally used for hydraulic structures, bridge, foundation of high-rise buildings, and etc. One of the significant factors affecting the stress-strain state of the concrete mass during construction and operational process is temperature effect due to hydration heat of cement [1-3]. The temperature regime in mass concrete structures is affected by many factors, such as air temperature, wind speed, water temperature, intensity of solar radiation and shading effect, foundation temperature, and especially amount of hydration heat which is caused by the cement type and its content [4-6]. In addition, the temperature distribution in the mass concrete is also influenced by other factors, such as schedule of placement, aggregate size used in mass concrete, initial temperature of concrete mix, curing condition, etc. As a result, high temperature gradient occurring during the construction may cause significant tensile stresses and lead to thermal cracks [7-9]. The temperature difference between the inner zone and the outer surface of the mass concrete is the reason causing the formation of thermal stress. If the tensile stress is larger than the tensile strength of the mass concrete, thermal cracks form on the surface of the concrete structure, especially at the early age. In order to avoid the formation of thermal cracks, a general condition is that the temperature gradient ΔT should not exceed 20°C [10]. On other aspect, to minimize the temperature difference between the inner zone and the outer surface of mass concrete causing thermal cracks, past researches indicated several curing methods by using different types of insulation material together with its thickness, such as polystyrene [11], sand layers [12]. In addition, cooling pipe system is quite a perfect solution to reduce hydration heat in the core of mass concrete [13]. In the present study, effect of the placing temperatures causing different temperature gradients between inner and outer zones of mass concrete is investigated. The temperature profile versus time and its maximum value together with thermal stresses in mass concrete corresponding to different scenarios of placing temperature are simulated by using the finite element Midas Civil program. From the analysis results, it is proposed an appropriate value of placing temperature to CITE THIS PAPER [1] Anh Kiet Bui , Trong Chuc Nguyen , "The Temperature Field in Mass Concrete with Different Placing Temperatures," Civil Engineering and Architecture, Vol. 8, No. 2, pp. 94 - 100, 2020. DOI: 10.13189/cea.2020.080207.