Gangue Concrete Research Articles

Experimental Investigation on Piezoresistive Properties and Acoustic Emission Characteristics of Carbon Fiber–Based Gangue Concrete

Experimental Investigation on Piezoresistive Properties and Acoustic Emission Characteristics of Carbon Fiber–Based Gangue Concrete

Compression behavior of GFRP–coal gangue concrete–steel tubular columns

The coal gangue has been proposed to replace the aggregate in concrete to reduce the construction cost and environmental condition. The glass fiber-reinforced polymer (GFRP)–coal gangue concrete (GC)–steel (GGCS) tubular columns consist of concrete, which can provide a possible way to use coal gangue. To investigate the compressive behavior of GGCS columns, the experimental work is conducted. The failure behavior is analyzed through experimental results. Then, a finite element model is proposed to predict the compression capacity of GGCS columns. The influences of concrete type, hollow rate ρ, and the thickness of steel and GFRP tubes on the loading capacity of GGCS columns are investigated through experiment and numerical analysis. Parametrical analysis is performed to reveal the confinement effect of GFRP tube. The conclusions in this work indicate that GC can replace ordinary concrete without sacrificing the loading capacity. The confinement effect of GFRP tube and steel tube is systematically investigated through parametrical analysis.

Study on Mechanical Properties, Freeze-Thaw and Chlorides Penetration Resistance of Alkali Activated Granulated Blast Furnace Slag-Coal Gangue Concrete and its Mechanism

Study on Mechanical Properties, Freeze-Thaw and Chlorides Penetration Resistance of Alkali Activated Granulated Blast Furnace Slag-Coal Gangue Concrete and its Mechanism

Application of Coal Gangue as a Coarse Aggregate in Green Concrete Production: A Review

Among the techniques for converting stacked coal gangue to reusable material, one of the most effective ways is to use coal gangue as a coarse aggregate in green concrete productions. The physical and chemical properties of rock and spontaneous-combustion coal gangue are generally suitable for being used as a coarse aggregate in green concrete. Coal gangue concrete is not recommended to be used in subsurface structures, as its water absorption law would be changed under a large replacement ratio. The mechanical performance of coal gangue concrete is degraded by raising the replacement ratio. Over-low and -high concrete grades are not suggested to be used as coal gangue aggregate, unless extra admixtures or specific methods are used. The influence of coal gangue on the durability of coal gangue concrete is remarkable, resulting from the porous structure of coal gangue that provides more transmission channels for air and liquid in concrete, but is beneficial for thermal insulation. The usage of coal gangue in structural concrete members is still limited. The mechanical behavior of some structural members using coal gangue concrete has been reported. Among them, concrete filled steel tubes are a preferable configuration for using coal gangue concrete, regarding both the mechanical and durability performance.

Experimental study on the complete stress-strain curve of gangue aggregate concrete

In order to study the complete stress-strain curve of Chinese YuShenFu district’s gangue concrete. This experiment contains seven groups of gangue concrete which are all made by different water cement ratio and different gangue replacement rate, altogether 15 standard prismatic specimens. After the axial compression of concrete’s specimens, stress-strain curves of gangue concrete were obtained. In order to study the complete stress-strain curve of gangue concrete. In this paper, 15 coal gangue prism samples (150mm×150mm×300mm) were prepared for axial compression test. The main parameters are water-cement ratio and replacement rate of gangue aggregate. The result shows that there are four stages including the whole process of gangue concrete under uniaxial compression, but the descent stage exists the phenomenon of sudden break-down. Based on the data, the gangue concrete complete stress-strain curves’ constitutive equation is fitted. The parameter of ascending section fits favorably and the parameter of descending section is dispersed.

Experimental study on the influence of temperature on compressive strength of non-spontaneous combustion coal gangue aggregate concrete

In Pingxiang mining area of Jiangxi Province, a large amount of non-spontaneous combustion coal gangue is piled up into mountains, which not only occupies the land, but also seriously pollutes the ecological environment. In order to solve this problem and improve the utilization rate of coal gangue, the study of coal gangue without spontaneous combustion in Pingxiang mining area was carried out, and the differences of chemical composition, physical characteristics and thermal activation characteristics of coal gangue were analyzed. On this basis, the coal gangue was used as coarse aggregate instead of some natural stones, and the influence of different temperatures on the compressive properties of coal gangue aggregate concrete was studied. The results show that the compressive strength of gangue concrete is lower than that of ordinary concrete at room temperature. At high temperature, under the influence of secondary hydration of cement and thermal activation of gangue, the compressive strength of concrete test blocks in each group presents an upward trend before 400°C, and reaches its maximum strength at 400°C, among which the mechanical strength of concrete with 30% gangue coarse aggregate is the best. This study provides a basis for the resource utilization of coal gangue in Pingxiang.

Axial Compression of Glass Fiber Tube‐Gangue Concrete‐Steel Tubular Hollow Columns

The replacement of coal gangue for aggregate in concrete can not only reduce the construction cost but also improve the environmental condition. The GFRP‐coal gangue concrete‐steel tubular (GGCS) columns provide a way to consume the coal gangue. The target of this work is to validate the feasibility of replacing ordinary concrete with coal gangue concrete and investigate the compression behavior of GGCS columns. The nonlinear analysis program of GGCS hollow columns under axial compression was proposed, and the axial compression tests of seven GGCS hollow columns were carried out. The program was verified through experimental results. On the basis of the correctness of the program, the influences of the typical parameters, such as the thickness of the glass fiber tube, the thickness of the steel tube, and the outer radius of the steel tube, on its axial compression performance were systematically analyzed. Finally, the analytical formula for predicting the axial bearing capacity of GGCS hollow column was proposed. The comparison of results indicated that the analytical results agreed well with the experimental results. The axial compression capacity of GGCS hollow columns increased linearly with the increase of the thickness of the glass fiber tube and the steel tube, but not linearly with the decrease of the outer radius of the steel tube. With the increase of the thickness of the glass fiber tube, the constraint effect of the glass fiber tube on gangue concrete was improved. With the increase of the thickness of the steel tube, the stiffness of GGCS hollow column increased. The conclusions of the presented work can provide references for the design and calculation of the GGCS columns.

Research on Basic Mechanical Properties and Fracture Damage of Coal Gangue Concrete Subjected to Freeze‐Thaw Cycles

In order to study the freeze‐thaw damage law of the basic mechanical properties and fracture performance of coal gangue concrete, four kinds of coal gangue concrete specimens with different replacement rates of coal gangue coarse aggregate were designed, and then, the basic mechanical test and three‐point bending loading were carried out under different times of the freeze‐thaw cycle. The test results show that the compressive strength and flexural strength of concrete decrease with the increase of coal gangue aggregate content, and the higher the content of coal gangue aggregate is, the greater the freeze‐thaw damage of coal gangue concrete is. The coal gangue reduces the fracture resistance of concrete, and the higher the replacement rate of coal gangue coarse aggregate is, the lower the fracture toughness and fracture energy of concrete is. The freeze‐thaw cycle causes the obvious decrease of fracture toughness and fracture energy of concrete because the moisture content of coal gangue particles is higher; the freeze‐thaw damage of coal gangue concrete is more serious than that of ordinary concrete, and the higher the substitution rate of replacement of coal gangue coarse aggregate is, the higher the freeze‐thaw damage of fracture toughness and fracture energy is. The correlation between the freeze‐thaw times and the two parameters of fracture toughness and fracture energy damage of coal gangue concrete after freeze‐thaw cycles is good. The relationship between the two parameters and the freeze‐thaw times can be fitted by power function y = axb, and the fitted power index value of fracture toughness is higher than that of fracture energy.

Freezing‐Thawing Damage Mechanism of Coal Gangue Concrete Based on Low‐Field Nuclear Magnetic Resonance, Scanning Electron Microscopy, and N2 Adsorption

To study waterborne frost heaving failure mechanism of coal gangue ceramsite concrete (CGCC) under freeze‐thaw cycles, capillary water absorption test, nonmetallic ultrasonic testing test, low‐field nuclear magnetic resonance (LNMR) test, N2 adsorption test, and other tests were used to determine the effect of freeze‐thaw cycles on the porosity, relative dynamic elastic modulus (RDM), and capillary adsorption rate of different coal gangue ceramsite (MT) replacement rates (0, 20%, 40%, and 60%). Combining the changes of performance indexes and the changes of micropore structure under freeze‐thaw cycles, the freeze‐thaw failure mechanism of normal concrete (OC) and CGCC was analyzed. In view of the particularity of MT material, the method based on pore size is put forward to distinguish M pores from T pores, and the reasons for different properties are analyzed from the microperspective. The results show that the freeze‐thaw cycle changes the microstructure of coal gangue concrete and has an obvious influence on its properties. And when the replacement rate is 40%, degradation mitigation performance is optimal. Due to the particularity of MT shape, T pores are dominant in coal gangue concrete matrix, which is different from the microstructure of ordinary concrete and can reduce the structural deterioration caused by freeze‐thaw. The research results of this paper can provide a reference for the research and application of CGCC in freeze‐thaw environment.

Utilization of coal gangue as coarse aggregates in structural concrete

In this paper, coal gangue is utilized as a replacement of coarse aggregate in structural concrete. The effects of coal gangue on the mechanical properties of concrete material, circular reinforced concrete column and concrete-filled steel tubular column are experimentally studied and discussed in detail. The mechanical behavior of coal gangue concrete is reduced by increasing the coal gangue replacement ratio. A model is proposed for predicting the compressive strength of coal gangue concrete. Some constants are proposed based on test results to predict the splitting tensile strength and elastic modulus of coal gangue concrete. The increase of coal gangue replacement ratio decreases the axial compressive strength and elastic modulus of reinforced coal gangue concrete stubs and coal gangue concrete-filled steel tubular stubs linearly. The enhancement factor and the confinement factor both approximately increase with the increase of coal gangue replacement ratio which indicates that concrete-filled steel tube is a more preferable product than reinforced concrete for the usage of coal gangue as coarse aggregates. A modified design method for reinforced concrete and concrete-filled steel tube towards cleaner products is proposed by considering the coal gangue replacement ratio. The full-range prediction analysis for the strength degradation of coal gangue concrete-filled steel tube implies that relative higher steel strength and lower concrete strength should be used in the preparation of concrete-filled steel tube using coal gangue as coarse aggregates in structural stubs.

Damage evaluation method based on ultrasound technique for gangue concrete under freezing-thawing cycles

As a major industrial waste, gangue has significant environmental, economic, and social benefits when used in the preparation of concrete. The durability and bearing capacity of concrete structures in cold regions are affected by freeze-thaw damage. Therefore, the damage evolution behavior and degree of gangue concrete damage under a freeze–thaw environment should be accurately evaluated. In this paper, rapid freeze-thaw tests were carried out on gangue concrete with volume replacement ratios of 0%, 20%, 40%, and 60% coarse aggregate. The compressive strength and water absorption properties of gangue concrete were tested, and the changing rules of them were analyzed. In addition, the damaged layer thickness of gangue concrete was tested by ultrasonic nondestructive testing technology. The eigenvalue of the damage layer and the residual strength of the material in the damaged area were considered. The correction coefficient was introduced to modify the measured damaged layer thickness. A method for evaluating freeze–thaw damage in gangue concrete on the basis of damaged layer thickness was proposed. Results showed that the compressive strength and damage layer characteristic value of gangue concrete decreased gradually with the increase of freeze–thaw cycles, whereas the water absorption depth, damage layer thickness, and damage degree increased gradually; change rate increased with the replacement rate of gangue. With the increase of the replacement rate of gangue, the frost resistance of gangue concrete decreased obviously, whereas the damage deterioration rate increased. After introducing the damage layer correction coefficient, the accuracy of the evaluated degree of freeze–thaw damage increased significantly. Correction coefficient increased gradually with freeze–thaw time, indicating that the evolution of the residual strength of materials in the damage area decreased continuously and the actual degree of damage increased gradually.

Research on shotcrete in mine using non-activated waste coal gangue aggregate

Concrete is a building material that has been widely used in many industries, including coal mines. Because of environmental influences related to traditional aggregates in the concrete industry, a more eco-friendly method of making concrete is needed. Gangue is waste rock produced by coal mine excavation that has led to many environmental and social problems. An eco-friendly way to make concrete is proposed in this paper that replaces traditional aggregates with crushed non-activated coal gangue (NACG). This concrete offers a sustainable alternative to mitigating the environmental problems related to the extraction and depletion of concrete raw materials and the disposal of coal gangue. This experimental research is conducted to study the slump, setting time, air content, compressive strength and splitting tensile strength of different mixture proportions of coal gangue concrete (CGC). The slump, setting time and air content were measured according to the regulations provided by the China National Standard (MOHURD, 2016) using the slump flow test. Hardened properties include compressive and splitting tensile strengths. Optimal mixes design of NACG aggregates were conducted to optimize the fresh and hardened properties of coal gangue concrete. As the percentage of fine NACG aggregates replacement increased, the workability and tensile strength of the coal gangue concrete decreased. Additionally, as the maximum size of coarse NACG aggregates increased, an increase was observed in the compressive strength of coal gangue concrete.

Mechanical and Acoustic Emission Behavior of Gangue Concrete under Uniaxial Compression.

The application of gangue concrete can be an effective method to solve the massive gangue heap and shortage of raw materials of concrete by replacing the gravel and river sand with crushed gangue. An Acoustic emission (AE) is one of the non-destructive testing methods that can be used for damage detection of the gangue concrete structure. However, there are obvious mechanics differences between gangue and gravel/river sand, so the previous analysis methods of AE signal for concrete structure detection, mainly applied to ordinary concrete, are not suitable for gangue concrete. Based on this, the physical and mechanical characteristics of coal gangue were studied, and the uniaxial compressive test, along with AE monitoring of gangue concrete, was conducted in this paper. The differences in AE behavior between gangue concrete and ordinary concrete were also analyzed. The mechanical test result shows that the compressive strength of gangue concrete can reach 35–40 MPa. Comparing with ordinary concrete, gangue concrete has larger initial porosity and abrupt rupture. Additionally, the accumulative energy growth rate of gangue concrete has two peak values before the peak load, while ordinary concrete only has one. This difference can be used to forecast damage of gangue concrete structure by AE technology. This paper shows the possibility of making concrete by coal gangue, and the possibility of identifying its damage degree with the use of acoustic emission technology.

Stress–strain behaviour and acoustic emission characteristic of gangue concrete under axial compression in frost environment

Coal gangue concrete can effectively utilise coal gangue, minimise natural stone and has substantial environmental and economic benefits. At high-latitude and high-altitude regions, the durability and bearing capacity of gangue concrete structures are critically threatened by freeze–thaw cycles. Here, the freeze–thaw cycles experiment was performed using the accelerated freeze–thaw method. Various characteristic parameters, such as stress–strain curve and acoustic emission under axial compression, were measured for the frost-damaged coal gangue concrete. The volume replacement rates of coarse aggregate mixtures (C1, C1M2, C1M4 and C1M6) were 0%, 20%, 40% and 60%, respectively. After freeze–thaw cycles, water absorption and square root of time were nonlinearly related, showing a relatively rapid growth in the early stage, a gradual increase in the middle stage and stability and balance in the late stage. Water absorption rate was positively correlated with the gangue content in concrete. The physical and mechanical properties of gangue concrete decreased with prolonged freeze–thaw cycles, and the degradation rate increased with the gangue amount. The damaged layer thickness and peak strain increased, whereas the initial elastic modulus, peak stress and toughness decreased. The parameter alterations increased with the gangue content in concrete. The damage evolution rule of gangue concrete under axial compression was accurately described by acoustic emission.

Experimental Study on Chloride Ion Penetration Resistance of Coal Gangue Concrete under Multi-Factor Comprehensive Action

In order to investigate the chloride ion penetration resistance of coal gangue concrete under multi-factor comprehensive action, the non-steady-state accelerated chloride ion migration test was used to test the chloride diffusion law of coal gangue concrete specimens by crack width, curing temperature and water-cement ratio. Three groups of crack width (0 mm, 0.05 - 0.12 mm, 0.12 - 0.2 mm), three curing temperatures (high temperature 45, medium temperature 25, low temperature 10), three water cement ratios (0.3, 0.4, 0.5) were set in the experiment. The results show that when the curing temperature and water cement ratio are constant, the crack width less than 0.12 mm has little effect on the chloride content and chloride diffusion coefficient. When the crack width is larger than 0.12 mm, the chloride penetration depth increases with the crack width. The resistance to chloride ion penetration of gangue concrete is greatly influenced by the water cement ratio. The influ-ence degree of three factors on chloride ion migration coefficient of gangue concrete is as follows: water cement ratio > crack width > curing temperature.

An Experimental Investigation on the Mechanical Properties of Gangue Concrete as a Roadside Support Body Material for Backfilling Gob‐Side Entry Retaining

Development of a safe and economical roadside support body (RSB) material is the key to successful backfilling gob‐side entry retaining (GER). By means of laboratory tests, this paper studied the effects of the water‐cement ratio, aggregate content, and age on the contractibility and resistance increasing speed, compressive strength, and postpeak carrying capacity of the concrete with gangues as an aggregate. It also discussed the rationality and adaptability of gangue concrete as a RSB material for backfilling GER. The experimental results show that the compressive strength of gangue concrete increases with age, and that the strength of gangue concrete demonstrates a nonlinear decreasing trend with the increase of the cementing material’s water‐cement ratio. The water‐cement ratio in the range of 0.46–0.60 has the most significant regulation effect on the strength of gangue concrete. Mixing with a certain amount of coal gangue enhances the postpeak carrying capacity of concrete, preventing the sample from impact failure. The field experimental results report that as a RSB material, gangue concrete can meet the design and application requirements of GER with gangue backfilling mining. A RSB material featuring high safety, high waste utilization rate, fast construction speed, and low costs is provided.

Study on Flexural Properties of Reinforced Spontaneous Combustion Gangue Concrete Beams

In this paper, the flexural properties of three kinds of reinforced spontaneous combustion gangue concrete (RSCG) beams and one group of reinforced normal concrete (RNC) beam are investigated experimentally by comparison. Three kinds of RSCG beams are constructed with 100% spontaneous combustion gangue fine aggregate, coarse aggregate or both of them and one group conventional concrete beam is constructed with natural aggregates. Effects of different combinations of aggregates on flexural properties of reinforced concrete structural elements are studied under the same conditions, including longitudinal reinforcement ratio, concrete strength grade and section size of member. The experimental cracking moment, ultimate moment and deflection under normal service state of the beams are analyzed according to theories and methods of the present code to evaluate the applicability of present code for RSCG beams. In addition, through ANSYS finite element simulation, flexural properties of the RSCG beams are analyzed. And comparing experimental results with calculated and simulated results, respectively. The results show that flexural features of RSCG beams are similar with RNC beams, and flexural property formulas for conventional concrete beams are also suitable for RSCG beams. Furthermore, simulating results also agree well with test results. It is feasible to use spontaneous combustion gangue aggregate in reinforced concrete structures under the proper design as well as within the proper limit of application.

Capillary Water Absorption Properties of Steel Fiber Reinforced Coal Gangue Concrete under Freeze-Thaw Cycles

The service life of coal gangue concrete(CGC) strongly depends on the capillary water absorption, this water absorption is susceptible to freeze-thaw cycles. In this paper, the cumulative water absorption and sorptivity were obtained to study the effects of 0, 0.5, 1.0, and 1.5 % steel fiber volume fraction added on the water absorption of CGC. Sorptivity and freeze-thaw tests were conducted, and the capillary water absorption was evaluated by the rate of water absorption(sorptivity). Three prediction models for the initial sorptivity of steel fiber reinforced coal gangue concrete(SFRCGC) under freeze-thaw cycles were established to evaluate the capillary water absorption of SFRCGC. Results showed that, without freeze-thaw cycles, the water absorption of CGC decreased when steel fiber at 1.0 % volume fraction was added, however, the water absorption increased with the addition of 0.5 or 1.5% steel fibers. Once the SFRCGC specimens were exposed to freeze-thaw cycles, the water absorption of SFRCGC significantly increased, and 1.0 % steel fiber in volume fraction added to CGC caused the lowest water absorption, except for the case of the sample without steel fibers added. The CGC with steel fiber at 1.0 % volume fraction performed better. The SFRCGC has a strong response to freeze-thaw cycles. Results also showed that the linear function prediction model is practical in the field of engineering because of its simple form and a relatively high precision. Although the polynomial prediction model presents the highest computation precision among the three models, the complicated form and too many coefficients make it impractical for engineering applications.

Properties of steel fiber reinforced coal gangue coarse aggregate concrete

In this paper, workability, strength and durability of coal gangue coarse aggregate concrete with different steel fiber content levels have been studied. The results indicate that the concrete compressive strength, flexural strength and tensile splitting strength at the age of 28 days increase with the steel fiber content increasing, while cost and impermeability reduce with steel fiber content increasing. Based on the data of the workability of fresh concrete, mechanical properties and durability of hardened concrete, the concrete cost index system are established to evaluate and optimize the steel fiber content in coal gangue concrete by Efficacy Coefficient Method. The optimization result reveals that the maximum value of the system efficacy coefficient is up to 0.87, the coal gangue concrete with steel fiber 1.5% (V:V) performs better.

Finite Analysis on Performance of Joint between Gangue Concrete Filled Steel Tubular Column with through Rebar and Gangue Concrete Beam under the Monotonic Loading

In order to study the performance of the joint between gangue concrete filled steel tubular column with through rebar and gangue concrete beam under the monotonic loading, element analysis model, which is taken into consideration the material nonlinearity, the geometrical nonlinearity and the contact nonlinearity, is established by finite element analysis software ABAQUS. The results show the force transferring mechanism, the stress distribution, the failure model and the load-displacement curve of the joint under the monotonic loading. It indicates in this paper that the joint between gangue concrete filled steel tubular column with through rebar and gangue concrete beam has such numerous advantages as high bearing capacity, large stiffness and good performance. Meanwhile, the paper provides the calculation evidences to analyze the composite construction of gangue concrete filled steel tubular column and the results can be used to make the analysis on the practical structures.