Hydration Heat Temperature Research Articles

The Study on the Temperature Effect on Steel Reinforced Concrete Girder of Transfer Story in the Construction Process

The construction of high-rise building transfer story concrete girder belongs to the mass concrete, due to the concrete hydration heat temperature is often beyond the limited temperature, so need to make temperature calculation and temperature control of transfer story concrete girder in the construction process. This paper taking a steel reinforced concrete girder of a high-rise building transfer story as an example, using finite difference method to calculate the change rule of concrete temperature field along with age, then using nonlinear analysis program ANSYS simulation the mechanical performance of transfer beam under the action of loads and temperature stress during the construction. Analysis and calculation results should provide technical support for the construction of the steel reinforced concrete girder of the transfer story. Analysis shows that, at intervals of 12 days two laminated pouring of concrete in the construction process, will meet the requirements of temperature control.

Experimental Research on Hydration Heat Temperature of Concrete Box Girder in Low-Temperature Environment

The temperature stress is one of the main reasons for early age cracking of concrete under low temperatures,it has the actual value of reference for the design and construction of concrete structures to study the regularities of hydration heat temperature of concrete box girder in low-temperature environment. Therefore, through the test of concrete box girder hydration heat temperature, this paper analyses the temp-time curves of temperature of the concrete box-bridge cross section. The results can be used for concrete temperature control and/or cracking control of box girder in similar environmental area.

Preparation of Lignin-Based Superplasticizer by Graft Sulfonation and Investigation of the Dispersive Performance and Mechanism in a Cementitious System

A practical graft sulfonation process was developed to synthesize a lignin-based superplasticizer using acid-precipitated lignin from wheat straw black liquor as raw material. The graft-sulfonated lignin, prepared in optimal reaction conditions, was named GSL. The properties of GSL in a cementitious system were investigated. The adsorption isotherms of GSL fractions separated by ultrafiltration and the thickness of their absorbed films on cement particles were measured to reveal the dispersion mechanism. Also, it was found that the molecular weight of graft-sulfonated lignin increased with the dosage of acetone and formaldehyde, but having too high a molecular weight reduced its dispersive performance. High sulfonic group content in graft-sulfonated lignin severely inhibited the increase of molecular weight, resulting in a decrease of dispersive performance. GSL has stronger compressive strength enhancement in concrete and lower hydration heat temperature than the commercial naphthalene-sulfonated formald...

Cracking Control for Diaphragm of Long-Span Prestressed Concrete Box Girder Bridge at the Early Age

This paper presents the results of a study on the early-age cracking behavior of diaphragm in long-span prestressed concrete box girder bridge with cracking control techniques. Based on the three-dimensional hydration heat temperature conduction and humidity diffusion theory, and according to the similarity of differential equation between the humidity diffusion theory and temperature conduction theory, the early-age cracking of diaphragm was simulated by a three-dimensional finite element model with consideration of concrete shrinkage, creep, cement hydration heat and variation of temperature. The numerical simulation accurately predicts the cracking region and size and stress time history of diaphragm, and provides load standard for cracking control techniques of prestressing force. The cracking control techniques of prestressing force effectively avoid the early-age cracking of diaphragm by application of practical engineering.

Research on Hydration Heat Temperature Stress of the Pier by Finite Element Method

Hydration heat, one of the most severe factors, makes great effects on the mass concrete construction, especially on bridge structures and dam structures. Based on the experiment, this paper adopted large-scale finite element method with ANSYS software to analyze the transient temperature field during concrete placement. The atmosphere temperature, construction method, thermodynamics as well as material parameters (cement hydration heat, elastic modulus) were taken into account. The results clarity the distribution characters and process of the hydration heat temperature and stress. Besides, the computational and experimental results were compared. The results indicate that the surface cracks occur due to the large stress which is induced by the extensive internal and external temperature difference. As a result, references are provided to avoid harmful temperature cracks during pier construction period.

Study of the Concrete Block Temperature Intelligent Prediction Model during the Construction

The explicit statistical model of concrete temperature variation is difficult to reasonably reflect the nonlinear relationship between the historical information and future information. This article is based on neural network intelligence tools and uses the neural network model to describe the concrete temperature variation during the construction. The relationships between the concrete temperature and initial temperature (pouring temperature), environmental temperature, the cement hydration heat temperature increase, water cooling effect and other factors are nonlinear. Establishing the neural network model of concrete temperature variation, exploring the historical temperature information could predict the future temperature information. Applying the intelligent prediction model to a construction project shows that when compared with the traditional explicit temperature statistical model, the temperature neural network prediction model established in this paper has obvious simplicity and superiority.

The Experimental Study on Controlling the Hydration Heat Temperature Field of the Zhenyuling Bridge Pile Caps

Based on the experimental study into the temperature control scheme for mass concrete pile caps of the Zhenyuling Bridge, this paper did comprehensive research on effective ways to reducing massive concrete temperature caused by hydration heat, and preventing concrete cracks caused by thermal stress. The paper analyzed the effects of cooling pipe, concrete thickness and surface insulation materials on the temperature-stress field of massive concrete. By theoretical analysis and simulation research, the temperature control scheme was developed to guide the construction of massive concrete. Temperature-controlling techniques and precaution measures of early thermal cracks are introduced, which can provide reference to construction similar structure.

Space Simulation for Pier-On Mass of Pre-Stressing Box Girder at Earlier Hydration Age

Being aimed to the earlier temperature crack phenomenon of pier-on mass for concrete box girder during construction caused by hydration. Based on the real engineering, time-dependent effect of concrete density, specific heat and heat conductivity were comprehensively considered, hydration heat attack model was proposed, element birth and dead technique and sub-model technique was adopted to analyze hydration heat temperature field of pier-on mass for pre-stressing concrete box girder. The results indicated that hydration heat attack model is practical, hydration heat temperature at the copulation location of web plate and upper plate and floor plate as well as cross plate is 75°C, gradually decreased from the inner layer to the outer layer; birth and death technology and sub-model technique of element is effective to simulate the layer-cast for pier-on mass of concrete box girder.

Numerical Simulation Analysis on Mass Concrete Thermal Stress

Cement hydration heat temperature of the concrete could result thermal stress. Which is an important reason for the concrete structure’ cracks. The cracks could reduce the structure’ durability and structural stability. A spatial finite element model analysis on a mass concrete foundation board of a project was established using large-scale finite element analysis software. Temperature stress finite element analysis was carried on model. Numerical simulation analyzed the hydration heat of mass concrete construction phase and calculated the mass concrete’ temperature and stress distribution. Results of numerical simulation of crack control had certain guiding significance to mass concrete construction.

Calorimetric determination of the effect of additives on cement hydration process

AbstractPossibilities of a multicell isoperibolic-semiadiabatic calorimeter application for the measurement of hydration heat and maximum temperature reached in mixtures of various compositions during their setting and early stages of hardening are presented. Measurements were aimed to determine the impact of selected components’ content on the course of ordinary Portland cement (OPC) hydration. The following components were selected for the determination of the hydration behaviour in mixtures: very finely ground granulated blast furnace slag (GBFS), silica fume (microsilica, SF), finely ground quartz sand (FGQ), and calcined bauxite (CB). A commercial polycarboxylate type superplasticizer was also added to the selected mixtures. All maximum temperatures measured for selected mineral components were lower than that reached for cement. The maximum temperature increased with the decreasing amount of components in the mixture for all components except for silica fume. For all components, except for CB, the values of total released heat were higher than those for pure Portland cement samples.

Study on Temperature Field and Construction Monitoring of Hydration Heat of Railway Cable-Stayed Bridge Pile Cap

The temperature control of mass concrete is regarded to be a universal problem. Because of the heavy load of railway cable-stayed bridges, the pile caps usually have large dimensions, so the thermal stress, which is caused by hydration heat, must be emphasized. In order to study the spatial distribution of temperature in mass concrete and find a functional temperature control measure during construction, the theoretical and FEM analysis of hydration heat-thermal stress field are applied, which can improve structural reliability and provide reference for design and engineering of the similar project. Based on FEM calculation, the theoretical hydration heat temperature field is obtained. In the same time, the temperature sensors as well as strain sensors are arranged in the key position of pile cap. Then the variation of hydration temperature in concrete would be measured and recorded since the concrete is pouring. According to the theoretical simulation and the monitoring results, the time-history curve of hydration heat is obtained, and the variation of inner temperature gradient along the height direction as well as the longitudinal direction with the concrete age are studied, and the feasibility of temperature control measures is also verified.

Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete (PC) box-girder bridge. The change of hydration heat temperature consists of four periods: temperature rising period, constant temperature period, rapid temperature fall period and slow temperature fall period. The peak value of hydration heat temperature increases with the increasing casting temperature of concrete; the relation between them is approximately linear. According to field tests, the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder. Furthermore, the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring. Such results show that the prevailing Chinese Code (2004) is insufficient since it does not take into account the temperature gradient of the bottom slab. Finally, some preventive measures against temperature cracks were proposed based on related studies. The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.