Coarse Aggregate In Concrete Research Articles

Investigations on mineralogical characteristics and feasibility of coal gangue as a concrete aggregate from guizhou province, China

Coal gangue (CG) is an industrial solid waste produced by coal mining and separation that is considered to have a significant effect on the soil or water environment when exposed to the air, exacerbating ecological pollution. The comprehensive utilization of CG has always been a difficult problem due to the complex mineralogical characteristics. Producing concrete aggregates with CG is an effective strategy for utilising CG resources synthetically. This work studied the mineralogical characteristics of CG discharged from a coal mine in Guizhou Province, China, and the feasibility of producing concrete coarse aggregate by using CG particles. The results indicated that some CGs were mainly composed of coal particles, whereas others were mainly composed of noncoal particles. Based on their apparent characteristics, texture, and cross-sectional characteristics, the CG samples at this sampling point could be divided into 8 categories, and the mass ratio suitable for concrete aggregate production was less than 50%. The average pore size of CG was 5.5 nm smaller than that of the industrial (IS) aggregate, but its porosity and total pore area were 2.31% and 4.5 m2/g greater than those of the IS aggregate, respectively. CG aggregate concrete achieved a compressive grade of C40 at the appropriate mix ratio, but the mechanical properties of CG aggregate concrete were lower than those of IS aggregate concrete. The compressive strength of the concrete with the addition of coarse aggregate decreased by 17.26% at 7 days (7 d) of curing and 29.16% at 28 days (28 d) of curing compared with that of the concrete with the addition of the IS coarse aggregate. In addition, roasting at 500 °C for 2 h could increase the microhardness of this CG 40.06% higher than that without roasting. The separation of raw CG was a prerequisite for the preparation of concrete aggregate with CG, and also a direction to realize the comprehensive utilization of CG resources efficiently. Moreover, the roasting modification of this CG was an effective way to improve the mechanical performance of CG particles as concrete aggregates.

Assessing recycled concrete’s sustainability with emergy theory and input–output modeling

This study is the first to integrate emergy theory, life cycle assessment (LCA), and input-output analysis (IOA) to analyze the environmental performance of conventional concrete (CC), recycled coarse aggregate concrete (RAC), recycled fine aggregate concrete (RFC), and recycled powder concrete (RPC). It comprehensively covers the entire life cycle from raw material extraction to waste disposal, employing dynamic emergy flowcharts to visually represent emergy inputs and pollutant emissions at each stage. By introducing an emergy-based input-output emission coefficient, this study standardizes environmental impact assessments across different material flows, enhancing both accuracy and comparability. The findings reveal that recycled concrete significantly reduces emergy consumption and pollutant emissions, especially in cement production, where its reduction potential is most pronounced. Additionally, the findings highlight recycled concrete’s ability to enhance resource efficiency and minimize environmental degradation. This study contributes an innovative emergy-input-output evaluation framework based on Cradle to Cradle (C2C) principles, providing valuable insights for optimizing and selecting sustainable building materials to promote a circular construction economy.

FA-GGBFS based geopolymer concrete incorporating CMRW and SS as fine and coarse aggregates

Abstract Geopolymer concrete, which utilizes aluminosilicate precursor materials such as metakaolin, volcanic ash, industrial solid waste including fly ash and ground granulated blast furnace slag as a binder, is an eco-friendly alternative to Portland cement concrete. Although geopolymer concrete does not use cement, it still has shortcomings in terms of environmental friendliness because the aggregates (fine and coarse) used to prepare geopolymer concrete are natural resources and their excessive use in concrete manufacturing leads to natural resource depletion. In view of this, several researchers have tried to replace natural aggregates with various waste materials, which not only conserves natural resources but also helps in waste management. In the present study, the potential of steel slag and coal mine rock waste as a substitute for coarse and fine aggregates in geopolymer concrete to make it truly green is experimentally evaluated. The use of steel slag and coal mine rock waste as coarse and fine aggregates in geopolymer concrete was observed to significantly improve its strength and durability properties compared to fly ash based geopolymer concrete.

Study on Mechanical Properties and Carbon Emission Analysis of Polypropylene Fiber-Reinforced Brick Aggregate Concrete.

Given the current construction waste accumulation problem, to utilize the resource of red brick solid waste, construction waste red brick was used as a concrete coarse aggregate combined with polypropylene fiber to prepare PPF (polypropylene fiber)-reinforced recycled brick aggregate concrete. Through a cube compression test, axial compression test, and four-point bending test of 15 groups of specimens, the influences of the aggregate replacement rate of recycled brick and the PPF volume on the mechanical properties of recycled brick aggregate concrete reinforced by PPF were studied, and a strength parameter calculation formula was constructed and modified based on the above. Finally, combined with a life cycle assessment (LCA), the carbon emissions of raw materials were analyzed and evaluated. It was found that the mechanical properties of recycled concrete enhanced by PPF are critical at an addition rate of 50% and then decrease slowly with an increase in the aggregate content. PPF effectively alleviates the problem of strength reductions caused by regenerated aggregate substitution through the fiber-bridging effect. Based on the experimental data, a mechanical transformation model considering fiber reinforcement and BA weakening was constructed, and the regression accuracy R2 was around 0.90. The environmental benefit obtained when only replacing the natural aggregate is low. Although the incorporation of fiber improves the carbon emissions of the material to a certain extent, the benefits are more noticeable compared with the increase in strength. The results show that garbage recovery and strength demand benefits are achieved when the amount of recycled brick aggregate is 50% of the total. The strength conversion model established in this paper has of high accuracy and was created with careful consideration of fiber reinforcement and the regenerated aggregate weakening correction, providing it with more robust adaptability and extensibility. The mechanical properties of the recycled brick aggregate concrete enhanced by PPF are excellent and sustainable when the replacement rate of BA is 50% and the PPF volume is 0.1%.

Formulation of a Mixture of Nutmeg Shell Waste with Coarse Aggregate for Optimal Compressive Strength Values in Lightweight Concrete

Nutmeg shell waste (CP) has light and hard characteristics which can be used as a replacement material for coarse aggregate for lightweight concrete. The aim of the research is to determine the influence of aggregate characteristics after being mixed with nutmeg shells as a constituent material for concrete and determine the compressive strength value of the concrete. The method used is a laboratory experimental method with CP waste percentages of 2.5%, 5% and 7.5% of the sand volume. The results of the research show the effect of using nutmeg shells in the concrete mixture, where the compressive strength value of the concrete increases along with the increase in CP waste used. The compressive strength values of nutmeg shell concrete (CP) at compositions of 2.5%, 5% and 7.5% were obtained at 234.26, 263.56 kg/cm2, kg/cm2 and 280.14, increasing at 28 days.

Concrete production using marble powder and marble coarse aggregates: an analysis of mechanical properties and sustainability

The growing demand for concrete driven by infrastructure and urbanization puts pressure on natural resources and harms the ecosystem. Using recycled materials like waste marble powder (WMP) and marble coarse aggregates (MCA) in concrete can address this demand while maintaining quality. This study explores the mechanical properties of eco-friendly concrete with varying levels of marble waste substitution, replacing cement with WMP (0%-10%) and natural aggregates with MCA (10%-90%). A combination of destructive and non-destructive tests, including the Schmidt hammer and ultrasonic velocity tests, was used to assess flexural, compressive, and split tensile strengths. Results showed a 15.78% increase in workability when marble coarse aggregates were added. Compressive strength gained up to 44.02% on day 14 with 10% marble powder and 70% marble aggregates, compared to the control mixture. Split tensile strength improved by 11.02%, 11%, and 10.33% on days 7, 14, and 28, respectively, for mixes with 70% marble aggregates. Ultrasonic pulse velocity ranged from 3.68 km/s to 4.71 km/s, indicating no negative impact on concrete quality. The Schmidt hammer results correlated well with compressive strength from destructive tests. Overall, the study highlights the potential of using marble waste as an effective substitute for natural aggregates in concrete.

Recycled coarse aggregate concrete and its application in CFRP reinforced concrete beam

This paper deals with performance of concrete by using recycled coarse aggregate (RCA) to replace 30%, 50%, and 70% of natural coarse aggregate. Three concrete types were studied: Group A using RCA with 10% of silica fume (SF) addition by weight of cement, Group B using RCA with 30% of fly ash (FA) substitution by weight of cement, and the control concrete without RCA, SF, FA. Group A demonstrated a considerable improvement in compressive strength whereas group B exhibited a noticeable reduction, in comparison to the control concrete. Secondly, three reinforced concrete beams, representing three concrete types, strengthened with carbon fiber reinforced polymer (CFRP) sheet were tested under a three-point bending fixture. All the flexural parameters of the tested beam, including load bearing capacity, deflection capacity, stiffness, ductility, and crack patterns were evaluated and discussed. Finally, an analytical model was suggested to estimate moment and shear resistance of the beams.

Flexural Behavior of Zero Coarse Aggregate Concrete Beams reinforced with Glass Fibers: An Experimental Comparative Study

In recent decades, engineers have focused on finding solutions to reduce the weight of concrete structures. Undoubtedly, the coarse aggregate weight in concrete is important. This study examined the flexural behavior of zero coarse aggregate concrete with Glass Fiber (GF) added to the steel reinforcement. Also, normal-weight fine aggregate was substituted with autoclaved aerated concrete (Thermostone) by 50% and 75% by weight. The process involved comparison of the test results of two groups. The first group comprised normal reinforcement Lightweight Aggregate Concrete (LWAC), while the second group comprised fiber-reinforced LWAC and a specimen of Lightweight (LW) mortar. Fiber addition boosts energy absorption and slows down the rapid development of crack formation. GFs by 1.5% of concrete weight were added. The results revealed a decrease in the failure load of beams reinforced with GF compared to those reinforced with steel bars. The decrease amounted to 54%, 50%, and 59% for aggregate replacement percentages of 0%, 50%, and 75%, respectively. Replacing steel reinforcement with GF reduced the ultimate load by almost half. All beams with steel reinforcement experienced flexural failure, while the beams with GF reinforcement underwent shear failure.

Flexural behavior of reinforced recycled concrete coarse aggregates rectangular beams with and without splice bars

Flexural behavior of reinforced recycled concrete coarse aggregates rectangular beams with and without splice bars

EXPERIMENTAL STUDY OF CONCRETE AS PARTIAL REPLACEMENT OF COARSE AGGREGATE BY SILICA SLAG

Aggregate is a key component of concrete, greatly impacting its volume and influencing its mechanical strength, durability, and serviceability. This study examines using silica slag, an industrial by-product waste, as a partial replacement for coarse aggregate (Recycled Brick Chips) in concrete. It assesses concrete properties with silica slag replacing recycled brick chips at 0%, 20%, 40%, and 60%. The findings show that adding silica slag with recycled brick chips enhances both compressive and tensile strengths. Concrete mixes, prepared with superplasticizer (ASTM C-494: Type A & F), achieved improved workability while maintaining the required water-cement ratio. Various mechanical properties of silica slag, such as impact resistance, specific gravity, unit weight, void ratio, and water absorption, were thoroughly tested. The study reveals that a 40% replacement of coarse aggregate with silica slag results in optimal compressive strength, around 18 MPa. This indicates that concrete incorporating recycled brick chips and silica slag can achieve moderate compressive strength and meet structural requirements effectively to achieve sustainable development.

Bond Behavior between Reinforcing Steel and Recycled Coarse Aggregate Concrete after Carbonation

Bond Behavior between Reinforcing Steel and Recycled Coarse Aggregate Concrete after Carbonation

Shear Strengthening of Recycled Lightweight Coarse Aggregate Concrete Beams Using NSM Technique

The NSM technique began to apply as a modern technique to treat defects in structural elements and to increase the shear and flexural strength of structural elements. For this technique to be effective, a series of practical experiments were conducted to characterize the behavior of the element strengthened by the NSM technique for flexure and shear. Shear strengthening with GFRP rods is the focus of this paper for concrete beams that contain 30% coarse aggregate replacement ratio of bonza (volumetric ratio) obtained from the rubble of demolished buildings. A total of 7 beams were loaded under four-point load test, the parameters examined were the angle of inclination and the distance between the GFRP bars, the presence and absence of stirrups and the bonza aggregate replacement ratio. The characterization of the tested beams includes failure mode, load-deflection curves, load-strain curves of stirrups, rebars and GFRP rods and the surface concrete strain in the shear zone of beam. The results showed that the use of GFRP rods used to strengthen concrete beams was relatively effective, especially in the presence of stirrups, where the gain in shear strength was 8.8% and 4.1% when the distance between the vertical GFRP bars was (200 and 300) mm, respectively, with the presence of stirrups. While the gain in shear strength was (5.9%) when the GFRP bars were inclined at 45o with presence of stirrups. The deflection of strengthened beams was greater than the deflection of unstrengthened beam, where the maximum deflection of strengthened beams reaches 29.6mm at 177kN, while the maximum deflection of unstrengthned beam was 18.9mm at 185kN.

A novel biomass bamboo coarse aggregate concrete: Cyclic axial compression behaviour and modelling

This study pioneers in exploring the cyclic compressive behavior of bamboo coarse aggregate (BCA) concrete (BAC). BAC columns with BCA replacement rates ranging from 0 % to 45 % were tested, using either unmodified or epoxy mortar-modified methods. The evaluation focused on their cyclic compressive stress-strain relationship, failure modes, and the effects of BCA replacement rates and modification methods on plastic strain, stiffness and stress degradation, terminal strain on the reloading curve, and hysteretic energy dissipation. Research indicates that adding BCAs reduces concrete's peak stress but enhances its other cyclic mechanical behaviors, including improved ductility, stronger hysteretic energy dissipation, and lower degrees of performance degradation. Plastic strain in BAC is generally lower than in normal aggregate concrete (NAC) at the same unloading point strain, with BCA replacement rate and modification methods having negligible effects on plastic strain. Stiffness degradation decelerates as BCA replacement rate increases, and stress degradation lacks a clear trend, though it is more pronounced in unmodified BAC. Higher BCAs replacement rates lead to a slower decline in hysteretic strain energy over cycles, with hysteretic strain energy during decline surpassing that of NAC. Finally, the study establishes comprehensive cyclic compression stress-strain equations, providing a theoretical foundation and practical guidance for future BAC research.

Effect of Aggregate Gradation on the Properties of 3D Printed Recycled Coarse Aggregate Concrete

Effect of Aggregate Gradation on the Properties of 3D Printed Recycled Coarse Aggregate Concrete

Uniaxial compressive behavior and unified damage constritutive model of various types of recycled coarse aggregate concrete under freeze-thaw action

To promote the application of recycled coarse aggregates in concrete structures in cold regions, this paper focuses on the damage evolution of natural coarse aggregate concrete (NAC), recycled concrete coarse aggregate concrete (RAC) and brick-concrete mixed recycled coarse concrete (MRC) under the freeze-thaw-load coupling action. The relative dynamic modulus of elasticity is used to assess the freeze-thaw damage degree of various types of concrete after 0, 25, 50, 75, 100, 125, and 150 freeze-thaw cycles, and a freeze-thaw damage evolution model is established. Uniaxial compression tests are conducted on concretes after different freeze-thaw cycles to study the effects of freeze-thaw cycles on the failure mode, peak stress, peak strain, static elastic modulus, and toughness of the specimens. The relationship between the freeze-thaw damage variable and stress-strain characteristic parameters is analyzed, and an unified damage constitutive model for various types of concrete under the freeze-thaw-load coupling action is further established. The results show that with the increase in the number of freeze-thaw cycles, the specimens exhibit vertical splitting failure under axial compression rather than typical shear failure. The freeze-thaw cycles reduce the ability of recycled concrete to resist deformation. The peak stress and static elastic modulus decrease with the increase of freeze-thaw cycles, while the peak strain and toughness increase with the increase of freeze-thaw cycles. NAC has the best frost resistance and axial compression bearing capacity, followed by RAC and MRC. The presence of recycled brick coarse aggregate further exacerbates the freeze-thaw damage of concrete. There is an interesting finding that the water absorption of recycled aggregates is well correlated with the shape parameters of the freeze-thaw damage model and the descending section of uniaxial compression damage constitutive in recycled concrete. When the descending branch of the stress-strain curve modified by water absorption of recycled aggregates, the proposed freeze-thaw-load coupling damage constitutive model demonstrates good predictive performance for the stress-strain behavior of recycled concrete.

Impact of geopolymer aggregate on the mechanical properties and durability characteristics of concrete

This study examined the use of geopolymer aggregate (GPA), produced from slag and an alkaline solution, as a substitute for coarse aggregate in conventional concrete. The research aimed to evaluate how different proportions of GPA (25%, 50%, 75%, and 100% replacement) affect the durability and mechanical properties of concrete. A series of tests were conducted, including slump, compressive strength, flexural strength, chloride resistance, sulfate resistance, sorptivity, and water absorption. The results demonstrated significant improvements in concrete properties with the inclusion of GPA. The compressive strength of GPA concrete ranged from 31 to 38 MPa, showing a 10%–15% increase over that of standard concrete. Flexural strength improved by 6% at 7 days and 7.5% at 28 days compared to control mixes. Water absorption was reduced by 42.58%, and sorptivity decreased by 47.9% compared to ordinary aggregate concrete. GPA concrete also excelled in acid resistance, with a weight loss of 28.6% and a lower reduction in strength compared to traditional acidic aggregates. In sulfate resistance tests, GPA concrete showed a 31% reduction in both weight and strength loss. These results highlight the advantages of using GPA as an alternative to conventional coarse aggregates. GPA not only enhances the mechanical and durability properties of concrete but also presents a more sustainable option, contributing to reduced environmental impacts associated with traditional aggregate materials.

Influence of fiber shapes on the compressive behaviors of ultra-high performance concrete containing coarse aggregate

The addition of coarse aggregate in ultra-high performance concrete (UHPC-CA) has the potential to reduce autogenous shrinkage and improve mechanical properties. However, it also affects the fiber distribution and crack propagation, thereby compressive relationship of UHPC. This study investigated the effects of different fiber shapes on the compressive behaviors of UHPC-CA. Three fiber shapes (straight fiber, hooked fiber, and hybrid fiber) and six coarse aggregate content (0–1200 kg/m3) are the main variables. The test results have indicated that the addition of coarse aggregate in UHPC rendered wider main cracks. Hybrid fiber was preferred over the hooked-end and straight fibers to optimize ductility in UHPC-CA. An increase in compressive strength of up to 17.7 % and elastic modulus of UHPC of up to 23.7 % after moderate addition of coarse aggregate contents, The fiber shape affected peak strain and ultimate strain values for UHPC-CA. Their peak and ultimate strains were improved by 12.8 %–15.3 % and 38.2%–127.4 % with the inclusion of 2 % hooked and hybrid fibers. Based on the experimental data and relevant equations, a proper rational equation from the existing literature is used to generate the complete compressive stress-strain curves of UHPC-CA with different fiber shapes. In summary, this study establishes that hybrid fiber shapes significantly enhance the compressive properties of UHPC-CA. The high elastic modulus and ductility of the UHPC-CA with hybrid fiber are particularly promising for blast and impact applications.

Assessing the Impact of Shredded Polyethylene Terephthalate (PET) Post-Consumer Plastic as a Partial Replacement for Coarse Aggregates in Unreinforced Concrete.

This study investigates the feasibility of incorporating shredded polyethylene terephthalate (PET) post-consumer plastic waste as a partial replacement for coarse aggregates in unreinforced concrete such as masonry blocks. Standard concrete blocks were produced with varying PET content (0%, 5%, 25%, 35%, 50%) and tested for workability, air content, density, compressive strength, flexural strength, and thermal conductivity. Results indicated that replacing up to 25% of traditional aggregates with PET maintains adequate compressive strength for non-load-bearing applications and enhances thermal insulation by reducing the thermal conductivity from 0.7 W/m·°K to 0.27 W/m·°K at 25% replacement level, representing a significant improvement of approximately 61%. Higher PET content (35-50%) resulted in reduced structural integrity but improved insulation, suggesting its suitability for non-structural applications. This research highlights the potential of using PET plastic waste in unreinforced concrete, promoting sustainable construction practices by reducing plastic waste and conserving natural resources.

Experimental Study on Direct Shear Behavior of New-to-Old Interface for Recycled Aggregate Concrete with Different Replacement Ratios

The large amount of construction waste produced by the construction industry brings severe natural resource consumption and environmental pollution, elevating the awareness of sustainable development. Recycled aggregate concrete, crushed from construction waste, is recognized as an eco-friendly material and the current optimal solution for the environmental problem. The interface shear failure between substrate recycled coarse aggregate concrete (RAC) and overlay natural aggregate concrete becomes vital for structural safety. In order to study the direct shear performance, a total of 19 specimens were designed to carry out the direct shear test with different replacement ratios, interface types and curing ages. The whole process and failure mode were recorded. The relationships between the shear capacity and deformation, ductility, damage evolution, and energy dissipation were evaluated and discussed. The results demonstrate that the RAC component in the interface was the weak line in the shear plane, accelerating the damage evolution. In the early curing stage, the replacement ratio had a slight influence on the shear properties. Increasing the recycled aggregate replacement ratio from 0 to 100% improved the normalized strength ratio by 8.94% and 14.62%, respectively, for curing ages of 3 days and 7 days. A regression equation was proposed to predict the shear strength, accounting for the curing ages. With the increase in the replacement ratio, the ductility and energy dissipation gradually enhanced.

Effect of coarse aggregates on contact explosion resistance of concrete—A mesoscopic investigation

The intricate relationship between the mechanical properties of concrete and its internal microstructure underscores the importance of comprehending explosion performance and damage mechanisms at a mesoscopic level to effectively enhance blast resistance. This study employed three-dimensional (3D) mesoscale models to numerically investigate the dynamic behavior of concrete mixed with coarse aggregates under contact explosion. Rigorous validation of numerical models and simulation techniques was untaken through the contact explosion tests. The study explored mesoscopic damage mechanisms in heterogeneous concrete targets with randomly distributed coarse aggregates, drawing comparisons with a homogeneous concrete target. Critical mesoscopic parameters influencing the contact explosion resistance of concrete were thoroughly examined. Structural effects of coarse aggregates emerge as pivotal, shifting the damage mode from overall failure with spalling-dominated damage in homogeneous concrete to localized failure in mesoscopic concrete. The mesoscopic concrete experienced a distinct four-stage damage evolution—cratering, crack initiation, perforation, and dynamic fragmentation—diverging from homogeneous concrete with multi-layer spalling originating from the boundaries. The exponential attenuation of shock waves observed in homogeneous concrete was locally disrupted by coarse aggregates in mesoscopic concrete, attributed to wave impedance mismatch and aggregate extrusion effects. Mortar strength primarily contributed to concrete cracking, with minimal impact on damage modes. Failure modes were predominantly influenced by the content and particle size of coarse aggregates. Higher volumetric fractions significantly reduced concrete spalling, while increased coarse aggregate size exacerbated perforation failure. This comprehensive study advances our understanding of blast-resistant concrete design at a mesoscopic level, providing valuable insights for strategies aimed at enhancing structural resilience.