Hydration Heat Of Concrete Research Articles

Study of Semi-Adiabatic Temperature Rise Test of Mineral Admixture Concrete

The concrete used in the main structures of subway stations has a high degree of constraint. Consequently, temperature changes and shrinkage during construction frequently lead to significant constraint stress, which can result in structural cracking. Therefore, cement with low hydration heat is commonly used in engineering to reduce the temperature of concrete during its age. Aiming at the problem of hydration and heat release caused by concrete construction, based on the principles of concrete hydration heat release and a numerical analysis method, an optimized semi-adiabatic temperature rise test method has been introduced to investigate concrete temperature rise characteristics with different mineral admixtures. The following conclusions were obtained: The effect of reducing the heat of hydration is related to the content and material properties of different mineral admixtures, but not the type of mineral admixture to be incorporated. The temperature rise performance of four common mineral admixtures is as follows: ① total cooling capacity: limestone powder > slag, fly ash > metakaolin; ② early heat generation rate: metakaolin > slag > fly ash > limestone powder; ③ heat reduction rate in the middle and late periods: metakaolin > limestone powder > fly ash > slag.

Numerical Analysis of Concrete Hydration Heat Impact on Frozen Soil Temperature around Cast-in-Place Piles.

The hydration heat generated during the concreting of cast-in-place piles causes thermal disturbance to the surrounding permafrost, leading to its thawing. This further affects the stability of the pile foundation and degrades the construction progress. To explore the influence mechanisms of the concrete hydration heat on the permafrost temperature field around the pile, as well as that of different construction seasons on the pile-side boundary conditions and permafrost temperature field, monitoring results of on-site tests and numerical simulation were used to analyze the distribution law of the pile soil temperature field in space and time, and the pile-side boundary conditions and permafrost temperature field during construction seasons. The results show that the temperature trend of the pile foundation can be divided into three stages: a rapid rise phase (0∼2 d), a rapid decline phase (2∼10 d), and a slow decline and stabilization phase (10∼90 d). As the radial distance from the pile center decreases, there occur a corresponding acceleration in temperature increase and an elevated maximum temperature rise (MTR). The influence range of the molding temperature and the hydration heat is about 1∼2 times the pile diameter and less than 1.5 m in the depth direction. Compared to the atmospheric temperature, there is a lag in the change in the permafrost temperature caused by accumulation of ground temperature, and the significant difference between the two leads to an increased rate of heat exchange at the boundary condition. Conducting drilling operation and cast-in-place pile construction in the cold seasons is conducive to reducing the thermal disturbance to the permafrost around the pile in permafrost areas.

Experimental Study and Neural Network Predictions of Early-Age Behavior of Microexpansion Concrete in Large-Diameter Steel Tube Columns

The improved mechanical performance of concrete-filled steel tube (CFST) components has led to their widespread application in megastructures. Therein, CFST hybrid arch bridge has become an optimal selection of large span bridges. Nonetheless, for massive concrete poured in CFST members with large diameter, the thermal cracking and sustained rising temperature caused by early hydration heat of core concrete are urgently required to be studied. The two large-diameter CFST columns in this work, each having a diameter of 2.1 m, had their temperature and strain fields recorded in-situ. An existing CFST arch bridge served as the model for the two CFST columns’ design. Additionally, early-age characteristics of several scaled CFST columns with varying diameters were documented. A multi-field finite element (FE) model that combines linked chemical (hydration), heat, and mechanical fields is suggested in order to properly characterize the evolutions of temperature and strain fields. The model is validated by comparing the in-situ measurements with the numerical results. Finally, to investigate the affect factors on the hydration temperature of core concrete in CFST columns, early-age hydration behaviors of CFST columns was simulated using the validated FE models input parameters as water to cement ratio (w/c), cement dosage, heat release of cement and diameter of CFST columns. Based on the numerical results under the input parameters mentioned, the LSTM neural network was constructed, and the hydration temperature variances computed by FE models were selected as the input dataset. Afterwards, the temperature variance of core concrete of CFST columns was predicted using the established LSTM network. It is discovered that the LSTM neural network that was previously constructed was able to predict the peak temperature of CFST columns as well as the hydration temperature of CFST specimens with respect to time.

A Theoretical Study on the Spatiotemporal Variation in the Temperature Field in Linings of High-Water-Temperature Tunnels.

On the basis of the theory of unsteady heat conduction, discrete equations for the unsteady temperature field in the secondary linings of high-water-temperature tunnels when considering the hydration heat of lining concrete were derived and established. Spatiotemporal variation in the temperature field of tunnel linings was revealed through the analysis of numerical examples. Research demonstrates that the temperature of the secondary lining within a thickness range of approximately 15 cm near the tunnel clearance decreases sharply under the condition that the lining thickness is 35 cm. The higher the temperature on the lining's outer surface, the more drastically the lining temperature decreases. When considering the hydration heat of lining concrete, the lining temperature increases to a certain extent after a sudden drop, reaching stability after approximately 20 h, and the lining temperature is approximately 1-2 °C higher than that without taking concrete hydration heat into account. The temperature difference between the tunnel lining's core and its inner and outer surfaces is positively and negatively correlated with the temperature of the secondary lining's outer surface, respectively. When the temperature of the secondary lining's outer surface is not higher than 65 °C, the temperature difference between the tunnel lining's core and its inner and outer surfaces is less than 20 °C. Conversely, it partially or completely exceeds 20 °C, in which case an insulation method is recommended to utilize to prevent thermal cracks in secondary linings triggered via a high temperature difference.

Superplasticizing admixtures to control the heat of hydration of conventional concrete in urban buildings

A systematic review was carried out on the influence of superplasticizing admixtures for the control of the hydration heat of conventional concrete, focused on decision making in construction processes of urban buildings during the period 2012-2022, through the identification of research papers published in high impact indexed journals such as Scopus, ScienceDirect, Tylor & Francis, Ebsco and Proquest. The study was carried out by applying certain search parameters that allowed the analysis of a total of 10 026 publications, which were organized according to their distribution by year of publication, country of origin, area of knowledge and type of publication. In this way, a bibliometric analysis was carried out, obtaining that, with 615 publications, China is the Asian country with the highest number of records during the period indicated, with the year 2021 being the period with the highest number of publications, 236 articles published. The area of knowledge with the highest number of bibliographic contributions was Engineering, with 44 % of the contributions. Once the information was organized through the necessary figures and tables, a bibliographic analysis was carried out taking into account some examples as contributions in the bibliography of some authors in each of the aspects studied, with the purpose of knowing their position on the proposed topic, concluding that: Through the use of superplasticizing admixtures it is possible to control the hydration heat of the concrete mix, reduce the amount of cement per m3, as well as, speed up the construction process on site.

Experimental Investigation on a Novel Temperature-Controlled Phase Change Aggregate Concrete: Thermo-Mechanical Properties and Hydration Heat Control.

To reduce the structural deterioration of mass concrete structures from temperature cracks, and lower energy consumption caused by the traditional mass concrete hydration heat cooling process, this paper reports the preparation of concrete temperature-controlled phase change aggregate (PCA) by a vacuum compaction method using light and high-strength black ceramite and No. 58 fully refined paraffin wax as phase change material (PCM), and the encapsulation technology of the aggregate by using superfine cement and epoxy resin. Further, through laboratory tests, the cylinder compressive strength, thermal stability and mixing breakage rate of the encapsulated PCA were tested, and the differences in mechanical properties such as compressive strength, flexural strength and splitting tensile strength between phase change aggregate concrete (PCAC) and ordinary concrete were studied. A test method was designed to test the heat storage effect of PCA, and the temperature control effect of PCAC was analyzed based on the law of conservation of energy. The research conclusions are as follows: (1) Both superfine cement and epoxy resin shells increase the strength of the aggregate, with the epoxy resin increasing it more than the superfine cement. The thermal stabilization of the PCA is good after encapsulation of superfine cement and epoxy resin. However, PCA encapsulated in superfine cement is more easily crushed than that encapsulated in epoxy resin. (2) Under the condition of water bath heating and semi-insulation, when the water bath temperature reaches 85 °C, the temperature difference between the PCA and the common stone aggregate can be up to 6 °C. Based on the law of energy conservation, the test results will be converted to mass concrete with the same volume of aggregate mixture;, the difference of PCAC and ordinary concrete temperature can be up to 10 °C, so the temperature control effect is significant. (3) The mechanical properties of PCAC with 100% aggregate replacement rate compared to ordinary concrete are reduced to varying degrees, and the performance decline of the epoxy-encapsulated PCA is smaller than that encapsulated with superfine cement; in an actual project, it is possible to improve the concrete grade to make up for this defect.

Study on sustained-release polycarboxylate superplasticizer prepared by EPEG macromonomer

Ethylene glycol monomer polyoxyethylene ether (EPEG) is a new macromonomer that has been introduced in recent years. Its special molecular structure enables it to form copolymers with acrylic acid (AA) that are closer to the ideal copolymerization structure. However, the current production capacity is relatively small, so there are not many related studies. Therefore, this paper uses EPEG as the main raw material to prepare a slow-release polycarboxylate superplasticizer SP-YH. By studying the effects of different reaction conditions on the properties of SP-YH, the optimum synthesis conditions were determined. The structure of the polymer was characterized by gel permeation chromatography (GPC) and infrared spectroscopy (FTIR). In addition, the concrete test and hydration heat test results show that it has better slump protection performance and compression resistance than the commercial slump protection polycarboxylic acid water reducer.

Towards low-temperature shrinkable synthetic fibers for internally self-prestressing concrete

Matrix cracking caused by temperature stress during the hydration heating/cooling phase of cement is one of the main causes of cracking of bulk concrete. In this study, low-cost, low-temperature shrinkable (LTS) fibers were developed, which can be stimulated to shrink by cement hydration heat in bulk concrete. The contraction stress of LTS fibers then transfers to the cement matrix through interfacial bonding, therefore, a uniform, three-dimensional self-prestressing executes on the bulk concrete matrix, to improve its cracking resistance. The modified polyester (MPET) with a low melting point was used to prepare LTS fibers with an activating temperature of about 60 °C, and their shrinkage behaviour can be activated in the temperature range caused by hydration heat in bulk concrete. The results confirmed that prestressing the cement matrix by activating LTS fibers’ axial shrinkage is an efficient approach for improving the mechanical properties of the cement matrix. This kind of fibers have demonstrated great potential in self-prestressing bulk concrete to improve its cracking resistance in engineering structures.

Early hydration heat temperature field of precast concrete T-beam under steam curing：Experiment and simulation

Precast concrete T-beam steam curing can improve production efficiency, realize large-scale production of T-beams, and achieve better economic benefits. We performed tests and numerical simulations on a 30-meter-long full-size precast concrete T-beam to study the economical and reasonable steam curing scheme. The study found that in the early stages of steam curing, the temperature at the mid-span section increases faster than that at the end-span section. The highest temperatures of the tested beams were found in end-span section., and the core-surface temperature difference increased and then decreased, with the maximum temperature difference occurring at the junction of the top and web slabs of the concrete T-beam. To meet initial prestress tensioning requirements, the steam curing of increasing the temperature for 2 h to 50 ℃, keeping the temperature constant for 7 h, and cooling the temperature for 1 h is the most economical scheme, as seen from the comparison and analysis of the development law of concrete hydration heat temperature and the results of concrete test blocks under the same curing. Under this steaming scheme, the end-span section of the concrete T-beam reached a peak temperature of 68.5 °C at 14 h, and the core-surface temperature difference reached a maximum of 8.6 °C at 4.5 h; the peak temperature of the mid-span section was 60.2 °C, with a maximum temperature difference of 8.3 °C. In order to accurately predict the law of T-beam concrete temperature development under steam curing, two subprograms, HETVAL and UMATHT, were compiled on the ABAQUS secondary development platform. When calculating by natural age t, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 30.0% and 27.7%, respectively. After considering the equivalent age te of concrete, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 8.2% and 1.9%, respectively. Therefore, the UMATHT subprogram, considering equivalent age and hydration degree, can accurately predict the development of the concrete hydration heat temperature field under the steam curing process.

Temperature Control for Mass Concrete of Bridge Cap in Summer Construction

In order to realize the accurate calculation of the temperature field of concrete hydration heat, the paper takes the concrete hydration heat temperature field of the pile cap of Liexi Bridge as a case for simulation analysis. Firstly, a three-dimensional finite element model of concrete hydration heat temperature field is established; Then, the temperature field of the hydration heat of the concrete cushion cap of the Liexi Bridge is simulated. The experimental results show that the maximum actual measured temperature of the core point of concrete hydration heat temperature is 63.1 °C, and the corresponding calculated temperature is 62.2 °C. The maximum actual measured temperature of the surface point is 54.8 °C, and the corresponding calculated temperature is 53.8 °C. The maximum temperature difference between inside and outside is 18.9 °C, and the corresponding calculated temperature is 13.4 °C. The research results show that the calculation model has high accuracy

Recycling of date kernel powder (DKP) in mass concrete for mitigating heat generation and risk of cracking at an early age

Mass concrete in many structural and non-structural applications is prone to early age cracking and chemo-damage from the exothermic hydration reactions of the cement binder. Date kernels are a waste product generated in large quantities in the date processing industry in the Middle East, North Africa and other countries worldwide. The use of calcined date kernel powder (DKP) as a mineral admixture in concrete to reduce the heat of hydration and temperature rise in mass concrete is a novel idea for which no prior research has been condcuted. A combined experimental and numerical investigation was conducted to assess the performance of DKP as a heat-reducing material in mass concrete. Concrete mixes with 10%, 20% and 30% DKP replacing cement and similar mixes with fly ash (FA) were investigated for evolution of mechanical and thermal properties and the adiabatic heat of hydration. 3D finite element models of mass concrete blocks 2mx2mx2m in size were validated using the data obtained from similar blocks in field instrumented with thermocouples. The 3D FE model was subsequently used to predict the heat of hydration, temperature rise and cracking index of a mass concrete block with 30% DKP powder. Experimental results showed a significant reduction in the heat of hydration in DKP concrete, with levels comparable to the FA concrete without a significant impact of strength properties. The DKP waste material has a strong potential for reducing heat of hydration in mass concrete structures, thereby promoting waste utilization, recycling and sustainability.

Experimental and finite element investigations on hydration heat and early cracks in massive concrete piers

The concrete hydration heat and different construction methods directly affects the early crack resistance of massive concrete structures and may lead to concrete cracks. In this work, the hydration heat test and finite element simulation were conducted to investigate the early cracking resistance and the main influencing factors of the massive concrete bridge pier. The size of the bridge pier was 8 m (length) × 4 m (width) × 22.5 m (height), and the pier was poured in two layers (8.5 m/14 m) with an interval of 37 h. The internal temperature of the pier was tested 16 days after the concrete pouring using pre-buried temperature sensors, and the crack expansion on the surface of the pier was continuously observed during the test period. The test obtained a maximum concrete temperature of 64.25 °C after 100 h after the concrete pouring, and 3 cracks were found on the surface of the pier. The pier simulation model is established according to the actual situation in the test, The maximum temperature inside the bridge pier obtained from the simulation is 61.73 ℃, and the temperature field development pattern and the crack expansion on the pier surface were basically consistent with the test, which confirmed the reliability of the simulation method. Besides, the simulation process found that the maximum main tensile stress on the surface of the bridge pier was 2.77 MPa, which was mainly distributed near the interface of the 2 layers, indicating that the layered pouring scheme adopted in the test was improper. The effect of layered casting schemes on the early cracking resistance of massive concrete has rarely been discussed, and further simulations revealed that: the maximum main tensile stress can be reduced by gradually improving the number of layers, layer height and interval between each layer. By changing the original layered pouring scheme to 3 layers with an interval of 3 days between each layer, the maximum principal tensile stress is reduced to 1.50 MPa, and early cracking of the bridge pier can be avoided. This work provides a general numerical analysis method with high accuracy, parameterization and quantification for early crack control of massive concrete structures in a multi-factor complex environment.

Effect of recycled ceramic aggregate on hydration heat and permeability of high performance concrete

The application of recycled ceramic aggregate (RCA) in concrete construction has attracted increasing attention recently. In this study, the effect of RCA on the exothermic reaction in HPC is investigated, which reveals the mechanism underlying the role RCA plays in regulating hydration heat output and permeability of HPC for the first time. The porosities and the pore distributions of three types of RCA are investigated through microscopic test, and the internal structures of HPC with different types of RCA are also analysed. Hydration heat test is then carried out to measure the maximum temperature obtained during exothermic process and the time at peak temperature. Finally, chloride ion penetration experiment is conducted to further investigate the effect of RCA on the permeability of HPC. It is found that RCA can lower the temperature during exothermic reaction and prolong the cement hydration process, while the permeability of HPC is increased.

Study on Thermal Disturbance of Frozen Soil Around Piles by Concrete Hydration Heat

In order to study the influence of the heat of hydration of concrete on the thermal disturbance of the frozen soil around the pile during the construction of cast-in-place piles in permafrost regions, a two-dimensional temperature field numerical model was established with non-steady state based on the heat conduction control equation and the freezing-thawing phase transition process. This model has been used to analyze and discuss the refreezing process of the concrete pile foundation, the heat flow transfer process between the pile foundation and the frozen soil, and the positive temperature curing process of the pile body. The research results have shown that the refreezing process of the pile foundation is a slow process. It took 28 days after the completion of the pile foundation construction that the negative temperature arose at the bottom of the pile. And 196 days after construction the temperature at the center of the pile dropped to negative. The heat brought by the cast-in-place pile is mainly released to the surrounding soil through the horizontal heat flow, and the thermal conductivity of the soil has a greater influence on this process.

Control of Early-Age Cracking in Super-Long Mass Concrete Structures

The early-age cracking problem in concrete has long been recognised by civil engineers and scientists because it can jeopardise the intended serviceability of concrete structures. However, the effects of various crack control methods are different. This paper carried out field monitoring on a super-long wall with different crack control measures and compared the temperature and strain development process of the wall. In the middle of the super-long wall, the pipe cooling method reduced the hydration heat of concrete by 13 °C via a vertical pipe arrangement, but the wall could reach the maximum tensile strain earlier than with the other methods. By embedding an I-shaped steel plate in the induced joint method, a structurally stiff mutation zone was generated, and the maximum strain was generated at the induced seam web. By calculating and setting a reasonable construction length, the alternative bay construction method reduced the internal tensile strain of the structure. The early-age cracking of super-long mass concrete structures is affected more by restrained shrinkage than by temperature, so it is difficult to control early-age cracking by addressing only one factor.

Impact of particle size of fly ash on the early compressive strength of concrete: Experimental investigation and modelling

Fly ash (FA) was commonly used for admixture in concrete to change the durability and workability of concrete due to its dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect. The efficient utilization of FA based on particle size has now become a hot research topic at present. In this work, FA particles with gap-graded sizes were prepared by sieving method and then prepared for concrete mixing. The hydration heat, compressive strength and pore structure of concrete were studied using isothermal calorimetry, mercury intrusion porosimetry (MIP) analysis. Hydration degrees of the concrete with gap-graded FA particles were calculated, and a primary mathematical model was tentatively established and verified according to the particle sizes of FA and early compressive strength (7 days) of concrete based on Neville's theory, where the hydration degree was used as an intermediate variable. However, the mathematical model can just roughly reflect the relationship between FA particle sizes and the early compressive strength of concrete due to the lack of consideration of porosity in Neville's theory. Therefore, to improve the accuracy of the model, calculation error of the model with pore characteristic parameters were used as correction coefficients. The calculation error was significantly reduced from 30 ~70% to 3~17%. The modified model was proved to be effective to predict the early compressive strength of concrete prepared with gap-graded sizes of FA. It is of great significance to the prediction of concrete strength and the efficient utilization of FA.

Analysis of Early-Age Hydration Behavior and Micro-Mechanism of Coral Sand Cement Mortar.

Coral sand cement (CSC) mortar is increasingly used in reef projects, which is prepared by mixing coral sand with cement and water in certain proportions. Considering that early-age hydration behavior is closely related to the strength and durability of the mortar, the early-age hydration process and micro-morphology of CSC mortars with various water–cement ratios (W/C) and sand–cement ratios (S/C) were studied. A monitoring system based on FBG is proposed in this paper, which uses the high sensitivity and conformability of optical fiber to measure the hydration temperature and internal shrinkage strain simultaneously and continuously. The standard sand cement (SSC) mortar with the same sand gradation and mix proportion is also prepared for comparison. The micro-morphology is observed by a scanning electron microscope (SEM) for measurement results’ explanation. The results show that the variation of the hydration temperature and shrinkage strain with hydration time of both CSC mortars and SSC mortars follow a unimodal function. Differently, the peak hydration temperature for CSC is obviously lower than that of SSC. The peak temperature of CSC mortar decreases linearly with the increase in S/C, and the decrease rate of the peak temperature is higher for CSC with small W/C than that with higher W/C. For mortars with lower W/C, the peak shrinkage strain of CSC is larger than that of SSC. Meanwhile, for mortars with higher W/C, the peak shrinkage strain of CSC changes to be lower than that of SSC, which is attributed to the significant water absorption characteristic of CSC. Therefore, as an eco-friendly lightweight aggregate, CS is more suitable than SS for the design of high W/C and alleviating the hydration heat of mass concrete under the meeting of strength.

Experimental and numerical assessment of thermal properties of self-compacting mass concrete at early ages

Although many attempts have done to evaluate the effect of hydration heat in normal concrete, no valuable assessment has yet been proposed for thermal behavior of SCC structures. In this paper, a different approach was used to comprehensively evaluate how the temperature rise affects the thermal and mechanical properties of the SCC, as compared with that for the normal one. Twelve mixtures in three w/c ratios of 0.3, 0.37, and 0.44 were prepared. The compressive, tensile, and flexural strength and also elastic modulus of the concretes were determined. The Hydration heat evolution and induced thermal strain between core and surface layer of simulated mass concretes were measured using a temperature matched curing cabinet (TMCC). Numerical analysis of the induced thermal stresses and strains of massive fresh concrete columns was done. The result showed that the SCC specimens experienced lower thermal strains compared with that for the normal concrete. The results of numerical thermal analysis also revealed that the risk of thermal cracking of the SCC specimens was 36% lower than that for the normal concrete.

Case study on ventilation and cooling control technology of multi heat source coupling in long distance subsea tunnel construction

To solve the high-temperature environmental hazards caused by concrete hydration heat release in tunnel construction, this paper studies the heat generation mechanism of heat source in the tunnel using theoretical analysis and numerical simulation, and analyzes the temperature control in the tunnel under different ventilation wind speed (1 m/s, 2 m/s, 3 m/s, 4 m/s, 5 m/s) and ventilation temperature (298 K, 293 K, 288 K, 283 K, 278 K). The results show that: increasing the ventilation speed can effectively reduce the environmental temperature in the tunnel, and the ventilation cooling effect is the best when the air duct outlet speed is 3 m/s. Reducing the ventilation temperature can further reduce the tunnel temperature based on increasing the ventilation speed. When the ventilation temperature is set at 293 K, it can meet the needs of ventilation and cooling at the tunnel face. The simulation results show that when the tunnel ventilation speed is 3 m/s and the ventilation temperature is 293 k, the maximum cooling value of the working face can reach 6.66 k, and the maximum cooling rate is 2.18%. Within 5 m from the tunnel working face, the cooling effect of the enclosure structure is the most obvious, which can effectively ensure the comfort of the working environment.

Hydration Heat Analysis and Temperature Control on Steel Shell Concrete Immersed Tube during Precasting

In order to support the high-precision and high-quality prefabrication of steel shell concrete immersed tube for Shenzhen-Zhongshan Bridge, this paper analyzes the influence of temperature field produced by concrete hydration heat on the deformation and local stress of steel shell concrete immersed tube considering the influence of strength time-varying, autogenous shrinkage and creep of concrete and casting technology. Then, this paper puts forward the temperature control index of concrete molding based on the control requirements deformation and local stress of immersed tube. The results show that: the hydration heat of concrete is beneficial to the deformation control of steel shell concrete immersed tube, and it has little influence on the final deformation, the molding temperature of concrete should be controlled below 3°C of the ambient temperature to prevent the cracking of steel concrete interface of immersed tube. The research results of this paper have been applied to the control of concrete casting process of steel shell concrete immersed tube for Shenzhen-Zhongshan Bridge, which can make up for the domestic research blank and provide technical reference for similar projects.