Mass Concrete Research Articles

Experimental and Numerical Research on Fracture Properties of Mass Concrete Under Quasi-Static and Dynamic Loading

The dynamic fracture behavior of mass concrete is crucial to the dynamic analysis and safety evaluation of concrete dams subjected to strong earthquake shocks in the framework of fracture mechanics. In the presented research, cylindrical specimens with a ring of preset cracks were cast by three-graded mass concrete, and direct tension tests were performed with two loading rates considered, i.e., 10−6/s for quasi-static loading and 10−3/s for dynamic loading. The load–crack mouth opening displacement (P-CMOD) curves were obtained, from which the fracture toughness, fracture energy, and characteristic length of the mass concrete were obtained. In this process, the influence of the eccentricity in the tests was compensated by the numerical modeling of the tests. Next, the crack propagation process of the mass concrete was modeled using the extended finite element method. From the test results, it is found that, under quasi-static loading, the crack generally propagates along the interface between the aggregates and the matrix, while, under dynamic loading, more aggregates are fractured. As compared to the case of quasi-static loading, the energy absorption capacity, fracture energy, and fracture toughness increase for dynamic loading, while the characteristic length decreases. Moreover, the numerically predicted P-CMOD curves agree reasonably well with the experimental measurements.

Investigating the Sway of Marine Brown Seaweed Gel as Natural Polymer in Properties of Concrete

In the present study, the effects of the fresh properties as slump, consistency and setting time and hardened concrete's characteristics such as compressive, split tensile and flexural strength for various ages, the brown seaweed (Sargassum wightii) gel was added to cement throughout differing proportions (1, 2, 3, 4 and 5%) by the mass of concrete. Durability and thermal tests such as water absorption, sorptivity, RCPT, acid attack and thermal conductivity also determined at various ages. Micro structural properties of seaweed gel were found out by SEM, FTIR and XRD analysis. Test results show that seaweed gel act as retarding admixture in cement up to 5% of addition. For instance, 5% alginate collections as a percentage of concrete mass showed a comparable compressive strength of about 42MPa. The use of seaweed gel improved the thermal characteristics of concrete by reducing its thermal conductivity roughly 50% for a 5% addition. The seaweed gels up to 5% addition in concrete will significantly improve the fresh-state properties of concrete without affecting its hardened properties. The future is completely dependent on eco-friendly materials; hence the use of natural organic additives to improve the strength and durability of cement concrete would be the better option for sustainability.

Inversion Analysis for Thermal Parameters of Mass Concrete Based on the Sparrow Search Algorithm Improved by Mixed Strategies

In the traditional mass concrete temperature field calculation, the accuracy of the thermal parameters is extremely important. However, the actual thermal parameters of mass concrete may have some errors with the laboratory-measured values or specification values due to the site ambient temperature, concrete surface insulation measures, cooling water flow, etc. Therefore, it can be combined with the measured temperature of the field temperature sensors using the sparrow search algorithm (SSA) for the inverse analysis of thermal parameters. Firstly, to address the problem that SSA has low convergence accuracy and easily falls into local optimum, a mixed strategy was adopted to improve the algorithm, including Logistic Chaos mapping initialization of the population, the introduction of adaptive weighting factors, and the use of the Cauchy mutation strategy. Then, the performance test was carried out to compare the performance of the algorithm with three different intelligent algorithms and reflect the superiority of the SSA that was improved by mixed strategies (SSAIMSs). Finally, the proposed method was applied to the thermal parameter inversion of a mass concrete pile cap. The inversion results demonstrated that SSAIMSs can improve the accuracy and speed of thermal parameter inversion, and the calculated results of the thermal parameters and temperatures obtained using the SSAIMSs matched well with the measured results in the field, which can meet the accuracy requirements of the actual engineering.

Incorporating concrete waste as additive in acidic fermentation–A novel approach for enhanced biohydrogen production and concrete mass reduction

Acidic fermentation (AF) of organic waste/wastewater generates valuable byproducts, including hydrogen, volatile fatty acids, and ethanol; however, its sensitivity to pH drops limits the stability and efficiency of the process. A reversal process, the acidic chemical treatment of concrete waste (CW) to recycle its aggregates, generates calcium hydroxide, which can serve as buffering agent. Meanwhile, integrating both processes can introduce a sustainable win-win approach, which is the aim of this study. To assess this approach, a series of batch AF experiments were conducted at 50 °C and pH 5.5, using glucose as the substrate. Cementitious specimen (1.5 × 1.5 × 0.8 cm) was supplemented to each 200 mL-fermenter. Unamended fermenters, with and without additional NaHCO3-buffering, were used as controls to compare with the amended ones. Introducing cementitious specimens to AF increased H2-production by 2-fold and 1.7-fold compared to controls with and without NaHCO3-addition, respectively, after three consecutive feed-cycles. The surface analysis of incorporated specimen confirmed the Ca, Al, Mg, and Si leaching. The AF efficiency and resulting cementitious mass reduction were further assessed at different organic loads and specimens’ volume, surface area, and porosity (by changing water-to-cement [W/C] ratio). Increasing the organic load from 10 to 20 g-glucose/L resulted in lower H2-production, higher specimen mass reduction (up to ∼32%), and higher Ca2+ release (up to 2 g/L); however, no significant effect was observed when using specimens with higher W/C ratio or surface area. Moreover, the presence of cementitious specimens significantly influenced the microbial composition, leading to notable developments in the abundant genera Thermoanaerobacterium and Bacillus. This study presents a novel approach to sustainably enhancing AF process using CW as both an additive and a treatable substance, with reusable aggregates as a byproduct. It provides valuable insights for optimizing the process and guiding future practical applications. This includes considering various concrete compositions, adjusting organic load conditions, and evaluating long-term stability in larger-scale systems.

Automatic Design and Monitoring of Mass Concrete Based on Information Technology

Mass concrete construction has the characteristics of large scale, complex technology, high professional requirements, and complex management. In this paper, information technology is introduced into the construction process of mass concrete, aiming to develop a system that integrates the automatic design and visual management of mass concrete construction monitoring schemes to improve its construction efficiency. In this paper, the automatic design of a mass concrete construction monitoring scheme is designed, the information of its data acquisition terminal sensor is extended, and the sensor information model is created based on the IFC framework. Finally, this paper verifies the feasibility and practicability of the automatic design and visual monitoring of the monitoring scheme through the actual case-commercial complex raft foundation. The results show that the method provides a digital and information platform for mass concrete construction, highlighting the advantages of the proposed method and the traditional method.

A Mesoscopic Approach for the Numerical Simulation of a Mass Concrete Structure Construction Using Post-Cooling Systems

This study introduces an innovative numerical approach to simulate the construction of large concrete structures incorporating post-cooling systems employing the finite element method (FEM). The proposed methodology integrates critical construction parameters, including temperature control mechanisms, while accounting for concrete hydration and environmental conditions. Compared to traditional discrete models, this approach provides similar accuracy with substantially reduced computational costs, enhancing predictive capabilities in the thermal analysis of mass concrete. The method was applied to simulate the construction of a water intake pillar at the Tocoma hydroelectric plant in Venezuela, where the simulated results closely matched in situ temperature measurements. The findings highlight the method’s efficiency and accuracy in simulating post-cooling systems, offering a practical solution for improving the safety and cost-effectiveness in large-scale concrete construction projects.

The Effect of Thermo-Mechanical Properties of Concrete on the Temperature Field in Mass Concrete

The Effect of Thermo-Mechanical Properties of Concrete on the Temperature Field in Mass Concrete

Effects of aggregates and fibers on the strength and permeability of concrete exposed to low vacuum environment

The performance and regulation of concrete in low vacuum environments are receiving increasing attention. This study investigates the effects of aggregates and fibers on the strength and permeability of concrete in a low vacuum environment, using varying gradients of sand ratios (37.5 %, 40 %, and 42 %) and aggregate-to-binder ratios (3.27, 3.92, and 4.14). Three types of non-metallic fibers are utilized: polyethylene (PE), polyvinyl alcohol (PVA), and glass fibers. Evaluations focus on concrete strength, mass loss, gas permeability, capillary water absorption, and porosity. Results indicate that higher sand and aggregate-to-binder ratios enhance both flexural and compressive strength. Fiber incorporation improves flexural and compressive toughness, with PE fibers showing the most significant toughening effect. The low vacuum environment increases the strength of the concrete but reduces its axial compression toughness ratio and increases brittleness, while fiber incorporation helps improve the compression toughness of the concrete. Higher sand and aggregate-to-binder ratios reduce mass loss and accelerate drying equilibrium, while fibers increase mass loss and prolong drying equilibrium, with PVA fibers causing greater mass loss. The pattern of concrete mass loss can be explained by the tortuosity of the moisture diffusion path. Additionally, low vacuum significantly increases the gas permeability of concrete. Enhancing the sand and aggregate-to-binder ratios reduces permeability both before and after low vacuum treatment. Although fibers increase the gas permeability, they help mitigate this increase under low vacuum condition. Capillary water absorption tests reveal that concrete under low vacuum condition has a significantly higher water absorption rate compared to air-drying condition. Increasing sand and aggregate-to-binder ratios reduces water absorption and capillary water content, whereas fibers have the opposite effect. Porosity tests show that moisture migration in a low vacuum environment is mainly related to permeable porosity, while total porosity is more closely related to compressive strength.

Thermomechanical Analysis of Cement Hydration Effects in Multi-layered Pier Head Concrete: Finite Element Approach

Mass concrete plays a crucial role in infrastructure development, yet its complex thermo-mechanical behavior poses challenges, especially in the construction of multi-layered structures like pier heads. This study investigated the thermo-mechanical behavior of a pier head during its concreting process in three stages, including the influence of temperature differences that impact the thermomechanical balance of the concrete. By utilizing the ABAQUS software, thermo-mechanical analysis was conducted to simulate temperature fluctuations during cement hydration. The model integrates thermal analysis to simulate temperature fluctuations during cement hydration and stress distribution during construction, validated through mesh convergence studies and field data comparison. The mechanical analysis considered concrete properties, temperature variations, and construction phase. Nonlinear material behavior and contact interactions between layers were incorporated to obtain a realistic simulation. The results indicated that a multi-layer system can balance temperatures, reducing thermal stress-induced cracking risks. Furthermore, specific test points within the pier head were assessed, revealing potential internal cracks by comparing thermal stresses to the concrete’s tensile strength. This research offers insight into pier head conditions during construction, highlighting critical stress zones, crack prediction, and construction sequence efficacy.

Research on Temperature Control of Mass Concrete for Multi-Tower Cable-Stayed Bridge Cap during Construction

In the construction process of mass concrete structures, the large temperature gradient due to exothermic hydration makes the mass concrete highly susceptible to cracking. This paper carried out research on temperature control methods of mass concrete for the purpose of ensuring construction quality based on the construction of Fengyi cable-stayed bridge caps. Firstly, the temperature and stress change rule in the concrete pouring process of the caps was analyzed though the finite element method (FEM). Then, targeted-oriented comprehensive temperature control schemes were formulated according to the structural characteristics and construction environment of the cap, including the optimization of the material ratio, the arrangement of crack-resistant reinforcing steel, the design of a water pipe cooling scheme and reasonable maintenance. Finally, the whole bridge cap construction process using the optimized water pipe cooling solution was monitored, and the temperature gap between inside and outside the concrete satisfied the specification requirements rigorously. In the concrete demolding session, the concrete surface was smooth and no cracks were found, which indicates the temperature control scheme is reasonable and effective. The research results have reference significance for the pouring and temperature control of mass concrete for bridge caps.

Mechanical properties and microscopic characterization of waste perlite powder as supplementary cementitious material

In this study, we conducted a comprehensive investigation on the influence of waste perlite powder (WPP) on the various properties of mortar and paste, including slurry performance, mechanical strength, hydration products, and microstructure. Additionally, we also aimed to uncover the underlying mechanism behind these effects. It was found that WPP reduced the workability and facilitated the setting process of cement-WPP pastes. WPP decreased the mechanical strength of mortar, but it exhibited significant strength enhancement during the subsequent stages. The incorporation of WPP worsened the water absorption behavior; however, this negative effect was mitigated as the curing age of the mortar was prolonged. The drying shrinkage cement-WPP binary system was significantly improved, with the prolongation of curing age. Moreover, WPP reduced the early heat release of the binary system, which may be beneficial for reducing the temperature gradient in mass concrete. It was confirmed that WPP accelerated the transformation from AFt to AFm, promoted the formation of C-A-S-H and optimized the pore structure of the system. It was confirmed that WPP was involved in the hydration reaction, which accelerated the transformation from AFt to AFm and promoted the formation of C-A-S-H. Such results suggested that the reuse of WPP in concrete production was technically feasible owing to its high pozzolanic reactivity.

Shrinkage cracking law and anti-crack inverse design in early-age concrete: A novel perspective on the development of crack resistance properties

Early-age cracking in massive concrete has long attracted research focus, essentially governed by the game between crack driving and resistance. However, cracking resistance aspect received inadequate attention. This study examines the impact of crack resistance properties development processes on shrinkage cracking law in early-age concrete, employing chemo-thermo-mechanical coupling phase-field model. Two quantitative evaluation indicators, namely the index of damage development and average growth rate of maximum damage, are introduced to characterize the process of damage and cracking. The findings demonstrate that the development processes of elastic modulus and tensile strength exert a considerable influence on shrinkage cracking process in early-age concrete, whereas the impact of fracture energy development process is insignificant. Multifactor analysis revealed substantial coupling effects among parameters. Additionally, an anti-crack reverse design method is proposed based on the global optimization analysis, which can guide the optimization design of shrinkage crack prevention and control in early-age concrete from both perspectives of crack driving and crack resistance.

Analysis on the characteristics of spatiotemporal distribution and their causes of temperature and strength in three-graded mass concrete

The use of prefabricated mass concrete blocks have gained increasing attention in construction industry. However, excessive temperature due to hydration can easily cause cracks, and the development of strength influences the lift and transportation time, thus affecting the efficiency of the precast yard. In this paper, the temperature field of three-graded mass concrete was simulated using Midas Civil, and compared to the measured results. In addition, the strength of concrete at different ages and locations was tested with different methods, and the influence of temperature inside the mass concrete on strength was explored. The results show that the finite element simulation basically agrees with the experimental temperature and can provide scientific guidance for the construction of three-graded mass concrete. The compressive strength of the specimens under the same conditions is consistent with that of the surface core samples of solid concrete blocks, and the rebound strength at different ages is lower than the compressive strength of the surface core samples. The temperature inside mass concrete has both positive and negative effects on the formation of concrete microstructure, high temperature can promote cement hydration and pozzolanic effect of fly ash to form more compact C-S-H gel. But under prolonged high temperature conditions, it can also cause morphology of CH to be coarse and loose, forming scattered needle shaped AFt. At different ages, the compressive strength of the core samples inside the concrete block is greater than that of the surface core samples. As the age increases, the concrete strength at the core location with the highest temperature may not necessarily be the highest. As the age increases, for example, at 7 days, the concrete strength at the core location with the highest temperature is 6.46% higher than that at the surface, while the concrete strength is 15.6% lower than that at locations with relatively lower temperatures.

Mesoscopic simulation of concrete drying shrinkage with hydration kinetics

Shrinkage-induced cracking significantly impacts the durability of mass concrete structures. Quantitatively evaluating drying shrinkage of concrete proves challenging due to the time-consuming experiments and overlooked microstructure changes during the hydration process. To address this concern, this study initially characterized the long-term hydration products and microstructure of low-heat Portland cement (LHPC) through microstructural experiments. Subsequently, a novel high-resolution mesoscale framework is developed to investigate the drying shrinkage with hydration kinetics. High-resolution models consist of realistic-shaped aggregates are validated by the aggregate morphology and gradation parameters of core sample from mass concrete. Concurrently, the quantitative effects of internal and external factors on LHPC drying shrinkage are explored. Results indicated that LHPC possesses a denser microstructure, lower porosity, higher carbonation resistance, and 20% lower drying shrinkage compared to moderate-heat Portland cement, suggesting promising applications. Furthermore, experimental and computational findings suggested that increasing aggregate volume, controlling aggregate morphology, and adjusting curing time and humidity could be employed to reduce and manage drying shrinkage, ensuring concrete structure durability.

Finite Element Method Simulation Study on the Temperature Field of Mass Concrete with Phase Change Material

Phase change materials can be converted between solid, liquid, and gaseous states, absorbing or releasing a large amount of heat. PCM is incorporated into concrete to adjust the temperature difference between inside and outside of concrete, which can reduce cracking. In this paper, the finite element analysis method is used to establish the model of an ordinary concrete structure, doped with phase change materials, on the basis of mechanical properties and a temperature regulation test performed by calculating the adiabatic temperature rise of concrete with different contents of composite phase change material, comparing the experimental and simulation results of the ordinary concrete structures with phase change materials, and analyzing the change in temperature field of the concrete structure with the content of self-prepared composite phase change materials. It is found that the addition of self-prepared composite phase change materials reduces the temperature peak of the concrete structure in the stage of hydration heat and delays the time taken to reach the temperature peak. Then, the temperature field of the phase change mass concrete structure is established, and the influence law of composite phase change material admixture on the temperature field of mass concrete is summarized through the time–temperature curves of different admixture amounts and positions so as to predict the possibility of cracks in mass concrete.

Experimental modeling and quantitative evaluation of mitigating cracks in early-age mass concrete by regulating heat transfer

In mass concrete structures, significant thermal gradients and deformations are generated due to the exothermic hydration reactions of cement, and these deformations are further intensified by the constraints of structural boundaries, leading to potential cracking. This study aimed to investigate the mechanisms of hydration temperature rise control in mass concrete using temperature rise inhibitors and its impact on structural cracking. Field experiments and engineering cases were combined to analyze hydration temperature rise and early-age cracking of mass concrete, employing cement hydration theory and considering inhibitors and pipe cooling temperature control. Results revealed the application of inhibitors effectively prolongs the time required for the heat release from cement hydration to reach 30 kJ/kg initially. Adiabatic temperature rise control equations for hydration inhibitor-treated concrete, based on different delayed heat release times, were formulated. The application of inhibitors was found to achieve temperature peak control effects comparable to those of pipe cooling, contributing to the control of cracking. To mitigate thermal cracks, a careful balance of temperature control and curing strategies was identified as essential, ensuring cement hydration heat in a controlled and systematic manner throughout the structure. The optimization of the hydration gradient was shown to enhance the temperature control efficiency of inhibitors and to reduce the need for cooling pipe installation. The conducted modeling and calculations allowed to determine temperature control guidelines for constructing mass concrete structures, achieving control of the hydration rate across different concrete layers, homogenizing the overall structural temperature, minimizing thermal cracks, and reducing energy consumption.

Improvements in the Characteristics of Plant Fiber Reinforced Concrete

Plant Fiber is lightweight, has a high specific strength, and the ultimate elongation is high and can improve the shortcoming of concrete. Concrete is easy to crack and break, and its tensile strength and other mechanical properties are not high. The chemical composition and mechanical properties of some plant Fibers that are often used are analyzed first. The modification of plant Fiber will also be discussed. Firstly, the chemical composition and mechanical properties of some plant Fibers are analyzed, and the modification methods of plant Fibers are also discussed; then, the mechanical properties of plant Fiber-reinforced concrete, hydration properties, heat preservation properties, durability, and other properties of plant Fiber-reinforced concrete are analyzed and summarized in detail. The conclusions are as follows. When the strength of concrete is increased by plant Fiber, the long Fiber is the best tensile strength method, the short Fiber is the most practical, and the length and content of the Fiber. The influence of factors such as water-cement ratio; plant Fiber can delay the release of the heat of hydration of cement by changing the hydration characteristics of cement, thereby improving the anti-cracking ability of mass concrete; concrete plant Fiber can improve the thermal stability and durability, and the lyotropic effect of plant Fiber on concrete Affect the flowability of paste. Plant Fibers can improve the thermal insulation and durability of concrete and reduce the thermal cracking of concrete. The plant Fiber is used as a reinforcement in the concrete of the railway foundation, which can enhance its tensile strength, impact strength, and flexural strength. The optimal loading range is 0.6-0.9%, and the long Fiber lay-flat method is the best. In the mixed method, these five physical reverse effects can be prepared in the range of 1.2-2.0%. The single tensile squeezing capacity of 30 plants using the mixed method is up to 3.69 MPa, which is the only chemical evaluation capacity of 46.5%.

Effect and mechanism of phase change lightweight aggregate on temperature control and crack resistance in high-strength mass concrete

Under temperature stress, high-strength mass concrete is brittle due to its high total heat of hydration. In this study, a control mixture of C55 high-strength mass concrete meeting the performance requirements was prepared. The effects of different functional aggregates on the thermal properties, such as setting and hardening rate, peak temperature, and temperature rise and fall rate in the early stage of cement hydration, as well as the effects of functional lightweight aggregates on the workability, mechanical properties, and deformation properties of concrete, were investigated in this paper using two types of aggregates with thermal insulation and phase change energy storage functions. The study shows that, in addition to having some early strength impacts and temperature management capabilities, thermal storage coarse lightweight aggregate (PCCLA) and thermal insulation fine lightweight aggregate (TIFLA) can both increase the workability and crack resistance of concrete. When it comes to temperature regulation, thermal storage coarse aggregate outperforms thermal insulation functional aggregate significantly. Thermal insulation fine aggregate can improve the rate of setting and hardening, while coarse thermal storage aggregate may work as in-situ self-heating curing in the early stages due to its phase change energy storage. This quickens the rate of setting and hardening and increases the resistivity of the set period, which in turn increases the rate of drying shrinkage.

Temperature Control and Crack Prevention of High RCC Dam in Cold and Drought Area

A development process is introduced for a computation program to calculate the temperature and stress field of mass concrete based on the ANSYS® platform. The temperature control scheme of a high roller compacted concrete (RCC) dam in northern Xinjiang is optimized by using the simulation program. It is suggested that the concrete pouring temperature of the dam should not exceed 16°C and that water-pipe cooling should be adopted. The dam should be permanently heat preserved by 10 cm thick extruded polystyrene (XPS) extruded panels, and the top surface of the overwintering layer should be covered with an at least 14 cm thick thermal insulation quilt. During construction, the warehouse surface should be temporarily insulated with a 2 cm thick thermal insulation quilt. The causes of cracks in a particular dam section are simulated and analysed, and it is concluded that the cracks are mainly caused by the lack of thermal insulation of the warehouse surface during cold spells.

The investigation the influence of the fiber son the evolution of mechanical properties of the concrete affected by high temperature by destructive and non-destructive test method

This paper presents an experimental examination of the effect of high temperatures on concrete prepared with different fibers types. For this study the concrete were prepared with four types of fibers (Steel, polypropylene, carbon and the combination of several types of fibers) and water/cement ratio fixed (w/c of 0.35). Specimens were heated under five different temperatures: 20 °C (ambient temperature), of 200 ºC, 300, 400 ºC and 600 ºC respectively. The following settings: compressive strength, ultrasonic pulse velocity, rebound hammer, concrete mass loss, and water porosity were examined in this Research experimental. Also A scanning electron microscopy study was used to comprehend the change in texture. The cracks were also examined using a microscope and other methods. This article is a contribution to the general understanding of the impact of fibers in high temperature concrete and highlights the significant impact of different types of fibers on the physical and mechanical properties of concrete who they were explore using destructive and nondestructive methods.