Many state dots require contractors to provide thermal control plans for bridge elements and other mass concrete. Concrete cast in massive sections requires special consideration due to the increased heat of hydration and temperature rise after placement. Introduction experiment of one construction techniques of major works. Guide to mass concrete reported by aci committee 207 aci 207. Mass concrete should be properly designed, placed and cured to obtain a durable structured with more economy, in mass concrete work, the major problem is temperature shrinkage. As a result of the mathematical studies and the owyhee teds, the pipe cooling method was adopted for the temperature control of hoover dam. Mass concrete is defined as concrete placement with a least dimension greater than 4. Temperature management of mass concrete structures. Drilled shafts and mass concrete institute for transportation. Development of concrete mixtures with a low adiabatic temperature rise. Often, wellestablished temperature control measures are sufficient to meet project specifications. Many dots and other entities explicitly exclude drilled shafts as mass concrete no temperature monitoring unknown issues def, thermal cracking cannot inspect surface for thermal cracking drilled shaft buried or in casing control methods more difficult and limited in drilled shafts, but can be done. Methods of controlling temperature in mass concrete 2 3.
Controlling temperature in mass concrete sometime makes drastic changes in placed concrete so we have to consider at least following parameters before ordering concrete for site pouring. The definition of mass concrete per the american concrete institute aci is any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to minimize cracking aci 116r and aci 301. Starting with a cool initial temp is key, and 4feet thick shouldnt be too much. To ensure that the results of mass concrete work properly, control of the concrete temperature must be performed. In mass concrete placements, for example, protective blankets are often used to cover the concrete and distribute the heat generated from the concrete itself. Jul 10, 2017 this requires a concrete temperature sensor to be placed near the center of the element. As the main method to reduce temperature stress under adverse environmental and climatic conditions and with concrete materials, the differences in the foundation temperatures, upper and lowerlayer temperatures, and internal and external temperatures of the gravity dam should be controlled. Starting with a cool initial temp is key, and 4feet thick shouldnt be too much of a problem with too much heat as long as the initial mix design is prepared with mass concrete in mind. How to control mass concrete temperature during construction. Temperature control and crack prevention scheme optimization.
As the main method to reduce temperature stress under adverse environmental and climatic conditions and with concrete materials. The temperature monitoring procedure that a contractor intends to follow usually must be described in a thermal control plan. Temperature control measures and temperature stress of. Other mass concrete plans cease monitoring after the core temperature is decreasing and within 60f of the average daily temperature. Oct 03, 2019 in mass concrete placements, for example, protective blankets are often used to cover the concrete and distribute the heat generated from the concrete itself. The four elements of an effective temperature control program, any or all of which may be used for a particular mass concrete project, are. The aci committee 207 provides several reports for guidance in the use of mass concrete. Every mass concrete project requires the contractor to monitor the temperature for several days after placement, sometimes even up to three weeks or longer. Development of alternative specification limits for mass concrete. This system consists of steel pipes arranged to form pipelines. Postcooling use insulation to control the maximum temperature difference between the center and the surface of the mass concrete. Hoh basics mass concrete definition mass concrete is defined by. How to plan and manage curing for mass concrete pours for. Mass concrete plays an important role in modern construction.
Impact of thermal cracking on concrete strength development. Maintaining appropriate temperatures and temperature ranges within mass concrete is a key to maintaining its durability and longevity. If the temperature differs too much within the structure. After placement, mass concrete temperature readings may be acquired. Heat is produced during concrete curing, leading to a temperature rise. Mass concrete is any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change to minimize cracking. Why mass concrete temperature monitoring is important. Prevent thermal cracking by monitoring the temperature of mass. The reader will learn how to minimize the likelihood of cracking and improve the durability of mass. Temperatures will eventually return to normal but, in massive concrete, substantial. Iowa mass concrete specifications special provision for mass concrete control of heat of hydration mix design cement. To avoid concrete damage, specifications limit the maximum internal concrete temperature and the maximum allowable temperature difference between the center and surface of a. Mass concrete is defined in aci 116r as any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and. Mass concrete temperature monitoring is the action of recording and reading the temperature of freshly poured mass concrete elements.
Temperature control measures and temperature stress of mass. Mass concrete is any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change. Concrete temperature monitoring in mass concrete giatec. Early studies are based on existing data and on a possible construction schedule. Mass placement temperature monitoring ensures you stay within specifications and reduces the risk of concrete developing severe cracking that. Many mass concrete projects specify a 35 f maximum temperature differential, and some limit the maximum internal temperature usually 160f. Aci 30116 mass concrete temperature must be controlled if limits are exceeded during construction, immediate actions have to be taken do not place additional concrete until cause of problem is identified and corrected temperature control measures must be maintained until. Prevention of thermal shock timing of formwork removal 6. Hi mass concrete is one of challenges with rate of pour as well as temperature control of concrete. Thermal effects of mass concrete pour concrete engineering.
Nov 17, 2016 fdot for example allows all monitoring and temperature control to stop when concrete is within 50 f of the average daily temperature. Mass concrete is defined in aci 116r as any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to minimize cracking. Thermal stresses and temperature control of mass concrete. Typically, the contractor must meet all of the specification requirements, but without a good understanding of mass concrete, keeping concrete temperatures within limits can be a difficult task. Mass concrete for dams what is mass concrete problems. Ds09047 new developmental specifications for mass concrete. As part of thermal control plans, supplementary cementitious materials not only help to control heat, but also mitigate the effects of elevatedtemperature curing. The design of mass concrete structures is generally based on durability, economy, and thermal. Temperature control of mass concrete for dams guideline by bureau of indian standards. Zhu bofang, in thermal stresses and temperature control of mass concrete, 2014. How is temperature controlled in mass concrete for preventing. This requires a concrete temperature sensor to be placed near the center of the element. Design and control of concrete mixtures, 15th edition, eb001. As interior temperature of mass concrete rises due to the process of cement hydration, the outer concrete may be cooling and contracting.
This system was first attempted at hoover dam development in america and is widely used today townsend,1981. Khaldoon slaiai concrete research manager saudi readymix concrete company 2. Aci 30116 mass concrete temperature must be controlled if limits are exceeded during construction, immediate actions have to be taken do not place additional concrete. Either way it should probably be blanketed or at least covered in some manor for curing and temperature control. Clearly, a more unified approach to engineering mass concrete to prevent. For mass concrete placements with a least dimension of greater than 6. Jul 29, 2014 to avoid concrete damage, specifications limit the maximum internal concrete temperature and the maximum allowable temperature difference between the center and surface of a mass concrete element. Mass concrete for buildings concrete construction magazine. Mass concrete, was organized in1930 for the purpose of gathering information about the significant properties of mass concrete in dams and factors which influence these properties aci,1996 1. As an example, to reduce the maximum concrete temperature by approximately 10 f 6 c, the concrete temperature at the time of placement should generally be reduced by 10 f 6 c. This decreases the temperature gradient difference between the surface and core of the pour, reducing the chance of thermal cracks occurring. Many dots and other entities explicitly exclude drilled shafts as mass concrete no temperature monitoring unknown issues def, thermal cracking cannot inspect surface for thermal cracking.
Mass concrete thermal control plans temperature control plans. Pdf evaluation of temperature prediction methods for mass. Thermal control plans help control cracking of mass concrete. To control both the concrete temperature and temperature difference, consider using preinstalled cooling pipes. The risk of temperature related concrete damage increases if the temperature of concrete gets too high or the temperature differential between the hottest interior point and the surface andor edge gets too large.
How to plan and manage curing for mass concrete pours. Obviously, both economy and low rise in temperature would be achieved by. Nov 28, 2018 as part of thermal control plans, supplementary cementitious materials not only help to control heat, but also mitigate the effects of elevated temperature curing. Sep, 2018 installed sensors should continue to monitor concrete temperature for the amount of time specified in the thermal control plan. Mj2 consulting is capable the following services related to mass concrete. Evaluation of temperature prediction methods for mass. Aug 27, 2018 maintaining appropriate temperatures and temperature ranges within mass concrete is a key to maintaining its durability and longevity. How is temperature controlled in mass concrete for. Mass concrete the main factor that defines a mass concrete member is its minimum dimension.
Temperature control of mass concrete for dams guideline number of amendments. In mass concrete placements, high thermal differentials between the concrete surface and the interior can result in large temperature induced stresses, which increase the risk of earlyage. Presentation on temperature control in mass concrete major works by satish aware m. Other mass concrete plans cease monitoring after the. Owing to the hydration heat of cement, the surface temperature of mass concrete is higher than the air temperature before removing forms. Installed sensors should continue to monitor concrete temperature for the amount of time specified in the thermal control plan. Temperature management of mass concrete structures concrete. Uncontrolled temperature rise can result in unacceptable surface cracks or internal damage to the concrete. Because portland cement generates the most heat in the first hours after placement, minimizing the cement content is essential.
The reader will learn how to minimize the likelihood of cracking and improve the durability of mass concrete by optimizing the mix design, as well as predicting, monitoring, and controlling concrete temperatures. Slowing the rate of heat dissipation from the surface reduces. Mass concrete is defined by the american concrete institute as. Thermal analysis of mass concrete elements alone will not directly control cracking risk. Actual exposure conditions, water temperatures, and construction progress may vary widely from the conditions as. Mass concrete plays an important role in modern construction, especially in hydraulic and hydroelectric construction. In order to ensure the quality and durability of larger projects, it is important to monitor and control concrete mix temperature, ambient temperature, and differential temperature in mass concrete. For this purpose, low heat portland cement would always be preferred for massive structures such as dams. Contractors and engineers on these projects are increasingly called upon to develop a temperature control plan to meet these specifications. Every mass concrete placement project requires the contractor to monitor concrete temperature during curing. Typically, the contractor must meet all of the specification requirements, but without a good understanding of mass concrete, keeping concrete.
Many specifications will require the development of a thermal control plan, or will specify how and where to measure temperatures. Mass concrete for buildings and bridges, eb547 this document provides practical guidance on understanding mass concrete, how to manage concrete temperatures, and prevent or minimize temperature related cracking. After removing forms, the surfaces of mass concrete come in contact with cold air. May 24, 2017 as interior temperature of mass concrete rises due to the process of cement hydration, the outer concrete may be cooling and contracting.
692 767 1502 1118 1020 638 643 1179 152 1324 1380 359 495 1038 1445 408 453 280 1525 576 319 1044 185 1365 1097 405 932 121 868 425 1479 23 301 111 300 1455 808 299 1440 626 633 207 687 1090 18 548 726 532