Steam Curing Research Articles

Macro Performances and Microstructures of Graphene Oxide-Modified Cement Mortar Under Steam Curing Conditions

Macro Performances and Microstructures of Graphene Oxide-Modified Cement Mortar Under Steam Curing Conditions

Effect of steam curing on strength, durability and microstructure of concretes with and without mineral admixtures

This research explores the effect of steam curing on the strength, durability and microstructure of concretes with and without mineral admixtures of fly ash (FA) and ground granulated blast-furnace slag powder (SL). Two types of C55 strength grade concretes (one was pure cement concrete, the other was a concrete made by replacing part of the cement with 12% FA and 18% SL) were prepared and their compressive strength, chloride diffusion coefficient and carbonation depth under standard and steam-curing conditions were measured and compared. The phase composition and microstructure of the concretes under the two curing conditions were tested by X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry. The results showed that, on the one hand, compared with standard curing, steam curing is beneficial to the early strength, but not conducive to the later strength development and chloride permeability resistance of both types of concretes. Furthermore, for the steam-cured concrete, the 28 days carbonation depth of the forming surface is higher than that of the bottom surface. In addition, steam curing can reduce the carbonisation resistance of pure cement concrete and improve the carbonisation resistance of concrete mixed with FA and SL. On the other hand, composite mineral admixtures of FA and SL reduce the early strength and the carbonisation resistance of concrete cured by standard curing, but improve the later strength, the carbonisation resistance and chloride permeability resistance of concrete cured by steam curing. FA and SL are thermally activated under steam curing and can react with the calcium hydroxide formed by cement hydration in the early stage, which produces a larger amount of secondary hydration products to improve the pore structure and interfacial microstructure of the concrete with FA and SL. In this way, the adverse effects of steam curing on later strength and durability of concrete are significantly restrained by composite mineral admixtures of FA and SL.

The Potential of Seawater in Geopolymer Mixtures – Effect of Alkaline Activator, Seawater, and Steam Curing on the Strength of Geopolymer Paste

The Potential of Seawater in Geopolymer Mixtures – Effect of Alkaline Activator, Seawater, and Steam Curing on the Strength of Geopolymer Paste

Mechanical and autogenous shrinkage properties of coarse aggregate ultra-high performance concrete (CA-UHPC): The effect of mineral admixtures

To reduce the shrinkage and explore the best content of mineral admixtures of coarse aggregate ultra-high performance concrete (CA-UHPC), this study conducted 12 groups of autogenous shrinkage, basic material properties (compressive strength, tensile strength, and flowability), and X-ray diffraction experiments on CA-UHPC with coarse aggregate and different amounts of mineral admixtures (slag powder, limestone powder). The effects of coarse aggregate and mineral admixtures on the autogenous shrinkage and basic material properties of CA-UHPC were analyzed, and the measured values of CA-UHPC autogenous shrinkage strain were compared with the theoretical values calculated by six commonly used concrete shrinkage prediction models. The experimental results show that under the condition of 15 % coarse aggregate content and no steam curing, a CA-UHPC with a compressive strength greater than 110 MPa, a tensile strength greater than 11 MPa, a flowability greater than 290 mm, and an autogenous shrinkage of less than 700 after 120d can be obtained. The mineral admixture has a significant impact on the fundamental properties of CA-UHPC. The compressive strength, tensile strength, and flowability of CA-UHPC with 15 % limestone powder and 15 % S95 slag powder increased by 6.6 %, 5.4 %, and 27.6 % compared to UHPC with only coarse aggregate added, and the autogenous shrinkage after 120 days decreased by 10.5 %. However, when the dosage of limestone powder and S95 slag powder exceeds 30 %, the tensile and compressive strength of CA-UHPC will rapidly decrease. This study also revised the GL 2000 shrinkage prediction model based on the CA-UHPC autogenous shrinkage test results, introduced the influence coefficient of mineral admixture content on autogenous shrinkage strain, and established a theoretical calculation model suitable for CA-UHPC autogenous shrinkage strain.

Comprehensive Utilization of Industry By-Products in Precast Concrete: A Critical Review from the Perspective of Physicochemical Characteristics of Solid Waste and Steam Curing Conditions

Solid wastes have been widely used as a cement substitute in precast concrete. On the one hand, solid waste can effectively ameliorate a series of problems caused by steam curing. On the other hand, the use of solid waste can reduce the amount of cement used in the construction industry and reduce carbon emissions. However, due to the complexity of the steam curing system, the performance of precast concrete prepared under different steam curing conditions varies greatly. Moreover, there are a wide variety of solid wastes, and the differences in the physicochemical properties of different solid wastes are significant. Therefore, it is necessary to systematically determine the mechanism of action of commonly used solid wastes. In this paper, the steam curing system is introduced in detail, and the mechanism of action of solid waste in precast concrete is systematically summarized. It was found that an appropriate increase in the temperature and duration of steam curing facilitates the strength development of precast concrete. In addition, there is a difference in the effect of the addition of solid wastes on the early and late strength of precast concrete, which usually leads to a decrease in the demolding strength of precast concrete, but increases the late strength of precast concrete. This study provides a reference for rationally regulating steam curing systems and realizing the comprehensive utilization of solid wastes in precast concrete.

A Review on the Curing of Concrete using Different Methods

The hardened properties and durability of concrete are dependent on the moisture and temperature condition of the concrete during its hydration process. This review explores various methods of curing concrete focusing on their effectiveness in improving the performance and sustainability of concrete structures. Traditional methods of curing (such as ponding, sprinkling) and the modern curing techniques (such as curing compounds, self-curing agents and steam curing) are compared. The advantages and disadvantages of these methods are highlighted and water curing is found to be the most effective method of concrete curing, for it allows for the maintenance of adequate moisture and temperature, and it does not change the macro and microscopic structure of the concrete. The research methodology includes extensive literature, experimental studies and performance evaluations. The review aimed at providing a comprehensive understanding of the best curing practices for different projects and working conditions.

Phase evolution and heavy metal solidification of cement desulphurized electrolytic manganese residue composite cementitious system under steam curing conditions based on thermodynamic simulation

The mechanical properties and microstructure of desulphurized electrolytic manganese (D-EMR) cement mortar under steam curing at 80 °C for 7 h and 7 days and standard curing for 3 days and 28 days were studied. The hydration products, microstructure and pore distribution were studied by Quantitative X-ray diffraction analysis (QXRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric-differential thermal analysis (TG-DTA) and backscattered electron (BSE). At the same time, the evolution of hydration products with age and the existence form of heavy metals under different curing conditions were simulated by GEMS thermodynamics. The results show that steam curing can promote the hydration reaction of cement and the secondary hydration of D-EMR. With the extension of steam curing time, the mechanical properties of the early stage are significantly improved. At a D-EMR content of 15 %, the compressive strength of D-EMR cement mortar after steam curing for 7 days is 1.15 times that of the control group under the same conditions, and the content of calcium hydroxide (CH) is 65.91 % of the control group. Steam curing can significantly improve the degree of C3S hydration of cement clinker and the secondary hydration of D-EMR, and increase the degree of polymerization of hydrated calcium silicate (C-S-H) gel. In addition, thermodynamic simulation showed that when the pH value was greater than 7.5, Mn2+ was mainly stable in the form of Mn(OH)2, MnOOH and Mn3O4, and there was no leaching risk. This will provide theoretical support for the use of D-EMR as a new type of supplementary cementitious material (SCM).

The Influence and Mechanism of Curing Methods and Curing Age on the Mechanical Properties of Yellow River Sand Engineered Cementitious Composites.

This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in Engineered Cementitious Composites (ECC). With an annual accumulation of approximately 400 million tons in this region, YRS presents a substantial resource. ECC specimens with 100% YRS replacement with quartz sand were subjected to various curing methods: natural, steam, standard, and sprinkler. Extensive mechanical testing including flexural, compressive, uniaxial tensile, and four-point flexural tests was conducted. Additionally, Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses investigated microscopic mechanisms influencing macroscopic mechanical properties. Finally, the mechanical properties of the YRS-ECC test block after 14 days of standard curing and the traditional sand ECC test block were compared and analyzed. The results indicate that ECC specimens with 100% YRS substitution under natural curing show an optimal ultimate tensile strain of more than 4%, providing the best resistance to the reduction in ultimate flexural load and deflection due to aging. Steam curing enhances flexural and compressive strength, achieving an ultimate flexural load of 5 kN and a maximum deflection of 4.42 mm at 90 days. SEM analysis revealed lower C-S-H gel density under natural curing and higher under steam curing, enhancing fiber pull-out in steam-cured specimens. The MIP tests demonstrated that natural curing had the highest porosity (32.86%) and average pore size (51.69 nm), whereas steam curing resulted in the smallest average pore size, with 44% of pores under 50 nm. Compared with traditional sand, it is found that the ultimate bending load and deflection of YRS-ECC are 5.7% and 9.4% higher than those of traditional sand ECC, respectively, and its ultimate tensile strength and strain are also improved. These findings highlight YRS as a sustainable alternative to natural sand in ECC, with natural curing proving the most effective for superior mechanical performance, including tensile strain, crack resistance, and durability.

Mechanical and Drying Shrinkage Performance Study of Ultra-High-Performance Concrete Prepared from Titanium Slag under Different Curing Conditions.

This research investigates the effects of various curing regimes, the incorporation of titanium slag, and the utilization of quartz sand on the strength properties and shrinkage behavior of ultra-high-performance concrete (UHPC). By using low-heat silicate cement to prepare UHPC, this study conducted standard curing and steam curing, and comprehensively analyzed the macro and micro performance of UHPC under different curing conditions. The findings indicate that the application of steam curing markedly enhances the mechanical attributes of UHPC while efficiently decreasing its drying shrinkage. In the comparative tests, we found that the compressive strength of concrete that had undergone 2 days of steam curing was 9.15% higher than that of concrete cured for 28 days under standard conditions. In addition, under the same curing conditions, titanium slag sand had higher mechanical properties than quartz sand. Under standard curing conditions, the 28-day compressive strength of UHPC using titaniferous slag aggregate was 12.64% higher than that of UHPC using standard sand. Through the data analysis of XRD, TG, and MIP, we found that the content of Ca(OH)2 in the hydration products after steam curing was reduced compared to the standard curing conditions, and the pore structure had been optimized. The UHPC prepared with titanium slag sand has greater advantages in mechanical properties and drying shrinkage, and has a smaller pore structure than the UHPC prepared with quartz sand. Moreover, the use of titanium slag sand offers ecological and economic benefits, making it a more sustainable and cost-effective option for high-performance construction applications.

Effect of steam curing system on compressive strength of recycled aggregate concrete

Abstract Steam curing prefabrication is a feasible way to promote the application of recycled aggregate in the background of building industrialization. The combined use of slag and fly ash contributes to the comprehensive improvement of both the early and later-stage performance of recycled aggregate concrete (RAC). However, the steam curing regime for RAC composed of slag and fly ash remains unclear, including appropriate curing temperatures and time. In this study, the influences of curing temperatures (20, 40, 60, and 80°C), steam curing time (6, 9, and 12 h) and mineral admixtures (slag powder and fly ash) on the demoulding strength and strength development of RAC were investigated. Based on the Arrhenius formula, the hydration reaction rate was characterized by the development of compressive strength, the apparent activation energy related to the steam curing time was calculated, and the energy-based compressive strength model was proposed to realize the early strength prediction of the steam-cured RAC.

Utilization of industrial wastes in non-sintered bricks: microstructure and environmental impacts.

Recycling industrial solid wastes as building materials in the construction field exhibits great environmental benefits. This study designed an eco-friendly non-sintered brick by combining multiple industrial solid wastes, including sewage sludge, fly ash, and phosphorus gypsum. The mechanical properties, microstructure, and environmental impacts of waste-based non-sintered bricks (WNBs) were investigated comprehensively. The results revealed that WNB exhibited excellent mechanical properties. In addition, steam curing could further promote the strength development of WNB. The compressive strength of WNB with 10 wt% of sewage sludge reached 13.5MPa. Phase assemblage results indicated that the incorporation of sewage sludge promoted the generation of ettringite. Mercury intrusion porosimetry results demonstrated that the pore structure of WNB varies with the dosage of sewage sludge. Life-cycle assessment results revealed that the energy consumption and CO2 emission of WNB were 45% and 17% lower than those of traditional clay bricks. Overall, the development of WNB in this study provided insights into the co-disposal of industrial solid wastes.

Synthetical improvement of dynamic mechanical property and toughness for precast concrete element based on optimization design of composition and curing regime

The brittleness and toughening measures of steam-cured concrete are currently less researched aspects. This study focuses on exploring the improvement in the toughness of steam-cured concrete and evaluating its influence on dynamic mechanical properties through a series of macroscopic performance tests. These tests include four-point bending tests, three-point bending fracture tests, uniaxial compression tests, and drop hammer impact tests, all conducted from the perspective of optimizing composition materials and steam curing regimes. The experimental results indicate that, under a relatively short heating time and a prolonged constant temperature curing period, the pure cement steam-cured concrete (S1 group), compared to the S2 group which used 20 % FA and 10 % GGBS to replace cement while also increasing the aggregate content with a modified steam curing regime, exhibited higher strength and elastic modulus but also showed greater brittleness. For example, the damping ratio increased to 0.6–0.7, the flexural-to-compressive strength ratio exceeded 6, and the number of specimens damaged by drop hammer impact significantly decreased, and the notch specimen exhibits lower peak load and displacement during fracture, with generally lower fracture parameter values. The fracture energy of the S2 group is 100–130 N·m-1 higher than that of the S1 group, reaching approximately 670 N·m-1, and the ductility index increased by 0.3–0.4. This research can provide technical support for the high-quality preparation of precast components using steam-cured concrete and offer a theoretical basis for reducing the brittleness of steam-cured concrete.

Effect of hydration degrees on the accelerated carbonization (3 % CO2) behavior of natural hydraulic lime

Natural Hydraulic Lime (NHL), as a low-carbon binder, possesses a significantly higher carbon sequestration potential compared to cement-based materials. This study aims to elucidate the accelerated carbonation mechanism of NHL5 by investigating the evolution of phase composition and microstructure during the accelerated carbonation process, as well as the preferential reactivity of different carbonatable components. Different hydration levels of NHL5 paste were achieved by controlling various steam curing durations (with a water-to-binder ratio of 0.5); accelerated carbonation conditions included 3±1 % CO2, 25±3°C, and 70±5 % relative humidity. The results indicate that higher hydration levels positively impact the mechanical properties of samples after carbonation. The compressive strength of the sample with carbonation curing 28 after 7 days of steam curing (S7C28) reached 45.6 MPa, and the carbon sequestration per unit mass increased. Specifically, S7C28 achieved an increase in carbon sequestration from 71.8 g/kg to 364.3 g/kg after 28 days of incomplete carbonation, while the high degree of hydration also limited the diffusion of CO2. Qualitative and quantitative analyses confirm that the carbonation reactivity in NHL5 paste follows the order: Ca(OH)2>C-S-H gel>C2S. The continuous generation of carbonation by-products, such as calcite and silica gel, fills the pores of the samples, enhancing their strength. These results suggest that higher hydration levels in NHL5 significantly promote the effectiveness of carbonation curing at a 3 % CO2 concentration, leading to improvements in mechanical performance, carbon sequestration capacity, and microstructural characteristics.

Low-carbon microwave curing of limestone calcined clay cement (LC3): Performance and mechanism

Limestone calcined clay cement (LC3) incorporates calcined clay and limestone as supplementary cementitious materials that can replace up to 50 % of conventional cement, significantly reducing the carbon emissions associated with cement production. However, challenges remain, including the inefficiencies of traditional curing methods and suboptimal early strength properties. Consequently, this study presents the low-carbon microwave curing approach for LC3 mortar. A comparative analysis of 15 different microwave curing systems was carried out. The results show that the optimum microwave curing efficiency is 300 W of heating power, 5 minutes of heating, 25 minutes of rest, and eight cycles. Three curing methods, including microwave curing, standard curing, and steam curing, were also compared. Microwave curing significantly increased the early strength of LC3 mortar, with 1-day compressive strength 1.78 times greater than standard curing and 1.26 times greater than steam curing. Microscopic studies show that the “thermal effect” of microwaving increases the internal Hc content of LC3, promotes the secondary hydration reaction of Ca(OH)2 within the LC3 material, and reduces the porosity of LC3, achieving reductions of 37.8 % and 8.9 % compared to standard and steam curing, respectively. This helps to improve the efficiency of the curing process. The results of this research will advance the use of low-carbon LC3 in building structures.

Experimental investigation on properties of gold tailings recycled brick-concrete aggregate concrete under microwave curing

Tailings are the low-value solid waste by-products, which can be expected to serve as sustainable material through activation. In this study, activated gold tailings (GT) were utilized as supplementary cementitious materials to produce GT-cement slurry and gold tailings recycled brick-concrete aggregate (GT-RBCA) concrete. By varying curing methods including microwave curing and steam curing, the effects of resting time and curing temperature on compressive strength of GT-cement slurry specimens were experimentally analyzed. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the hydration products and microstructure. Additionally, the compressive strength of GT concrete including GT-RBCA concrete under these curing methods were explored, followed by an assessment of environmental and economic benefits. The results demonstrated that a curing temperature around 40 °C with microwave method and 10%–20 % GT will benefit the strength development of GT-cement slurry specimens, reach the highest 28-day compressive strength of 42.6 MPa compared with steam curing and standard curing. This could be attributed to the “hot spot" effect of GT under microwave curing, leading to effective promotion of the pozzolanic reaction and subsequent enhancement of the hydration reaction. For GT-RBCA concrete, microwave curing exhibited the best effect on early compressive strength of GT-RBCA concrete compared with other curing methods. Particularly, whether the standard water-cement ratio condition (w/c = 0.42) or the low water-cement ratio condition (w/c = 0.35), GT-RBCA concrete under microwave curing at 40 °C and 10 % gold tailings substitution rate, achieved a maximum 12.3 % increase in 28-day compressive strength compared to steam curing and standard curing conditions. In addition, the GT-RBCA concrete under microwave curing obtained 11.7 % CO2 emissions reduction compared with steam curing.

Ion transportation properties of cement-based material under standard curing and steam curing

In coastal and saline environments, the infiltration of chloride and sulfate ions into cementitious materials can result in erosion and deterioration. This research focuses on the impact of temperature-related curing methods on the ion transport properties and microstructure of these materials. The results show the curing method does not alter the hydration products of cementitious materials. High-temperature curing reduces the content of ettringite, resulting in decreased Friedel's salt and gypsum after chloride ion corrosion. Meanwhile, high-temperature curing reduces the content of Ca(OH)2 and SiO2, decreasing the content of gypsum after sulfate ion erosion. It indicates that high-temperature curing reduces the binding capacity of both chloride ions and sulfate ions. Besides, high-temperature steam curing deteriorates the pore structure compared to standard curing. As a result, the resistance of concrete to ion corrosion is reduced under high-temperature steam curing. Besides, the surface ion concentration and binding capacity of chloride ions and sulfate ions both increase with the duration of erosion. Under the same erosion age, the binding capacity of sulfate ions is significantly higher than that of chloride ions. This research provides new insights into the transport characteristics of eroding ions under high-temperature steam curing.

Influence of Steam Curing on the Performance of High-strength Concrete Incorporating Metakaolin

This study aims to investigate the influence of steam curing on the performance of high-strength concrete incorporating metakaolin. An experimental study was conducted to investigate the compressive strength, chloride permeability, initial surface absorption, and water absorption, as well as thermal degradation under various steam curing scenarios. Four concrete mixtures were prepared in this study, each with different percentages of metakaolin, as partial substitution of cement weight of 0%, 5%, 10%, and 15%. The water–binder ratio was set to 0.32 in all mixtures. The specimens underwent steam curing for 0, 4, 8, and 16 hours at a temperature of 55 °C. Results indicate that the specimens that have been steam cured and contained metakaolin exhibit improved compressive strength during the initial stages of their strength development. Steam curing has been demonstrated to enhance the concrete’s resistance to chloride penetration and reduce initial surface absorption while increasing water absorption. The optimal replacement of cement with metakaolin to enhance strength and transport properties in high-strength concrete under steam curing regimes is between 10% and 15%. Future research could examine the effects of long-term steam curing on the durability and performance of concrete incorporating an optimal proportion of metakaolin.

Time-varying analytical model and mesoscopic numerical simulation of chloride ion diffusion in prestressed concrete cylinder pipe

In this paper, a time-varying analytical model for chloride ion diffusion in Prestressed Concrete Cylinder Pipe (PCCP) protective layer is established based on the separation of variables method and Bessel function. The model takes into account factors such as steam curing, pipe radius, curing age, and exposure time. Meanwhile, the mesoscopic numerical simulation is conducted on the chloride ion diffusion behavior in the PCCP protective layer, and the effects of aggregate content, interfacial transition zone (ITZ) volume fraction, and ITZ chloride ion diffusion coefficient on chloride ion diffusion are analyzed. Results show that the aggregate has inhibitory effect on the diffusion process of chloride ions, without considering the influence of ITZ. As the aggregate content increases, the average depth of chloride ion diffusion decreases linearly. In the event of both the influence of aggregate content and ITZ are considered, there is a competitive relationship between the two. The larger the diffusion coefficient of chloride ions in ITZ, the larger the average diffusion depth of chloride ions is. In addition, the correctness of the numerical model and analytical model is compared and verified by combining their calculation results. Compared with traditional chloride ion diffusion models, the smaller the pipe diameter, the more accurately the chloride ion diffusion law can be reflected by the analytical model.

The influence of curing methods on the performance of recycled concrete powder artificial aggregates and concrete

In order to address the issues of pollution from waste concrete powder and alleviate the shortage of natural aggregates, recycled concrete powder (RCP) was used to produce artificial aggregates (RCPA). The effects of internal and external addition alkaline activator methods, as well as natural curing (20 °C), heated curing (20/40/60/80/100 °C), and steam curing (20/40/60/80/100 °C) on the properties of RCPA were investigated. It was found that the internal addition method was more effective; the heated curing method yielded the best results, with the optimal temperature being 60 °C. The highest strength of RCPA was 10.24 MPa, with a water absorption rate of 8.68 % at this point. The microstructure of the aggregate under heated curing showed significant improvement compared to that under natural curing. Concrete was prepared using aggregates cured naturally at 20 °C (20 °C NCA) and aggregates cured at 60 °C (60 °C HCA). It was found that the mechanical properties of concrete made with 60 °C HCA were superior to those made with 20 °C NCA. The compressive strength of recycled concrete powder artificial aggregate concrete (RCPAC) at 28d reached 83.73 %-89.97 % of that of natural concrete (NC), with a density lower than NC. When subjected to compression, only mortar and interfaces in NC were damaged, whereas aggregates in RCPAC were also damaged. The resistance drying shrinkage and freeze-thaw of RCPA (ellipsoidal) concrete are better than those of natural aggregate (polyhedron) concrete. The 60 ℃ HCA concrete is optimal, enduring up to 250 freeze-thaw cycles. RCPA can replace natural aggregates in concrete production, and durability is crucial; therefore, future research should explore this area more thoroughly.

Optimization of steam curing process for Chinese Western and Northeast regions' high‐speed railway concrete prefabricated components

AbstractThis article aims to address the issues of high curing temperatures and thermal damage in the production of prefabricated concrete components for high‐speed railways in high‐altitude and high‐latitude cold regions of China. Various steam‐curing processes for concrete are designed to optimize the high‐quality preparation process of steam‐cured concrete prefabricated components in cold environments. With the goal of controlling the residual expansion deformation and considering the overall impact of curing process on the mechanics, durability, and interface transition zone of steam‐cured concrete, the main conclusions obtained in this study are as follows. Within a pre‐curing time of 3–6 h, when the curing temperature is maintained at 45–60°C, the final residual expansion deformation can be controlled below 300 με. The compressive strength, dynamic elastic modulus, peak stress, water absorption and Chloride ion resistance of steam‐cured concrete show the great improvement under above curing processes. Curing at 80°C should be actively avoided, and it is recommended to adopt a 6 h pre‐curing time with a maximum curing temperature of 45°C, especially for cold regions in China. This study can serve as a valuable reference and provide support for the preparation of prefabricated concrete components in Chinese high‐altitude and high‐latitude areas.