Properties Of Coarse Aggregate Research Articles

Enhanced Imaging Analysis of Aggregates for Road and Railway Applications

The South African pavement community has shown a keen interest in the use of imaging techniques to characterize the morphological characteristics of aggregates used in road and railway construction. This interest arises from the need to overcome the limitations of the traditional methods currently employed to quantify the shapes of these materials. Recent advancements and the use of enhanced aggregate imaging techniques for quantifying the shapes of crushed stone and ferro slag materials from 10 sources across the country are presented in this paper. A wide range of railway track ballast and road aggregates were selected from various quarries and sources across different provinces for this study. As part of this research, an improved protocol was developed to standardize imaging acquisition and ensure the repeatability of shape property measurements, thereby providing meaningful results and facilitating data analysis. The imaging analysis conducted in this study, which involved close to 2000 aggregate particles, revealed valuable insights into the angularity, surface texture, and flat and elongated ratio properties of coarse aggregates. Preliminary specification limits for these shape properties have been established. This contribution represents an initial step toward supporting the South African road and railway industry in adopting advanced techniques for the selection of aggregate materials.

3D mesoscale study on the effect of ITZ and aggregate properties on the fracture behaviors of concrete based on discrete element method

The discrete element method (DEM) was utilized to study the effect of the interface transition zone (ITZ) and coarse aggregate properties on the compressive fracture behaviors of concrete at a micromechanical level, in which the ITZ was represented by the contact bond and the coarse aggregate was crushable. The linear parallel bonded model was introduced to represent the constitutive model of concrete, and the meso-scale parameters were determined by laboratory mechanical tests. And then, a series of numerical tests were conducted under compressive loading, and the research objects contain ITZ strength, and aggregate properties (i.e., strength, content, size, and shape). The simulation results show that as the ITZ strength increases, the compressive strength shows a nonlinear increase trend. Moreover, as the aggregate strength and content increase, both compressive strength and strain to damage consequently increase, the aggregate shape is independent of the compressive strength. The increase in the aggregate size can reduce the total surface area of the aggregate, leading to a small compressive strength. The compressive strength appears to increase first and then decrease in trend as aggregate surface roughness increases. In addition, the increase in aggregate strength and content induces the failure pattern changes from local microcrack propagation to global failure. Overall, this work comprehensively evaluates the effect of ITZ and coarse aggregate properties on the damage of concrete at a micromechanical level.

DEM analysis of the effect of geocell on splitting tensile behavior of asphalt mixture based on multi-phase model

Herein, an investigation was conducted upon the reinforcement of geocell on the splitting tensile process of asphalt mixture using laboratory tests and the discrete element method (DEM). Micromechanical modeling of geocell-reinforced asphalt mixture and virtual splitting tensile test was built using PFC3D based on the vital material features and mechanical properties of different ingredients (e.g., the three-dimensional irregular shapes and elastic properties of coarse aggregates and geocell, the viscoelastic properties of asphalt mastic, and the random distribution of air voids in asphalt mastic). Meanwhile, the parameters of the DE model were determined by splitting tensile test, and the effects of geocell on the splitting tensile process of contact force, displacement and stress were evaluated through the virtual splitting test. The results indicated the efficiency of the built DE model and virtual test in effectively predicting the splitting process of geocell-reinforced asphalt mixture. Besides, geocell acted mainly in the falling stage of the load-displacement curve during the splitting process, where the contact force distribution of each phase component shifted from the lower to the higher range, and the effect between coarse aggregates was the greatest, followed between coarse aggregate and asphalt mastic, with the least within asphalt mastic. Further, the maximum displacement of asphalt mixture in the X and Y directions was reduced by the geocell, significantly constraining the coarse aggregate and mastic in geocell-reinforced layer. In addition, the stress in the splitting center of asphalt mixture was greater than that at the sides, and the stress within the geocell of the reinforced layer was significantly lower compared to the unreinforced layer, especially in the falling stage. Overall, the present results forge a theoretical basis for the tensile performance of geocell-reinforced asphalt mixture from the microscopical perspective.

Uniaxial Compressive Process Simulation of Geocell-Reinforced Asphalt Mixture by Discrete Element

Based on laboratory tests and the discrete element method (DEM), this study investigated the reinforcement by geocells on the compressive process of asphalt mixture. By considering the vital material features and mechanical properties of different ingredients (the three-dimensional irregular shapes and elastic properties of coarse aggregates and geocells, the viscoelastic properties of asphalt mastic, and the random distribution of air voids within asphalt mastic), micromechanical modeling of geocell-reinforced asphalt mixture and virtual uniaxial compression test was built by using PFC3D. The effects of geocell reinforcement on the compression process of the asphalt mixture were evaluated through the virtual compression test. The results show that the built DEM and virtual test can effectively predict the compression process of geocell-reinforced asphalt mixture. The geocell reinforcement positively affected the compression process of asphalt mixture by affecting the distribution of micromechanical forces and displacements in the asphalt mixture. Moreover, the geocell reinforcement was more significant on asphalt mastic. This indicates that the geocell significantly improves the compressive performance of asphalt mixture from the microscopic perspective.

Influence of coarse aggregate morphology on the mechanical characteristics of skeleton in porous asphalt concrete

ABSTRACT The properties of coarse aggregates have a great influence on the mechanical characteristics of porous asphalt concrete (PAC). The objective of this study is to reveal the influence of coarse aggregate morphology on the skeleton mechanical characteristics of PAC-13. To achieve this goal, a microstructure analysis method based on X-ray CT was developed to acquire three-dimensional morphological characteristics of coarse aggregates, and the morphology parameters were proposed. Based on the morphology of the actual aggregate, the coarse aggregate skeleton structure and skeleton penetration test were simulated by the discrete element method (DEM) and the values of skeleton strength under different morphologies were determined. The sensitive influences of coarse aggregate morphology parameters on the skeleton strength were quantified by the GA-BP neural network and the recommended value ranges of morphology parameters were proposed. The results show that the morphology of coarse aggregates within the size range of 4.75∼9.5mm and 9.5∼13.2mm has the greatest influence on the skeleton strength of PAC-13. The composite flat-elongated index and composite texture index of aggregates in 9.5∼13.2mm and 4.75∼9.5mm, and the composite angularity index of aggregates in 4.75∼9.5mm, which are referred to as Icom(9.5∼13.2), Icom(4.75∼9.5), Tcom(9.5∼13.2), Tcom(4.75∼9.5), AIcom(4.75∼9.5), are the high-sensitive influencing factors to the skeleton strength of PAC-13.

Meso-scale analysis on the effect of coarse aggregate properties on the creep behaviors of concrete based on the 3D particle-based method

Coarse aggregate, as the main component of concrete, has a significant influence on its behaviors. In this work, a 3D particle-based method was utilized to investigate the effect of coarse aggregate properties on the creep behaviors of concrete at a meso-scale level, in which concrete was composed of mortar, coarse aggregate, and interfacial transition zone (ITZ). Firstly, cluster-based modules for aggregate were generated based on the real aggregate geometry obtained by 3D scanning, and then, the developed aggregates were randomly distributed in the model according to the specified aggregate gradation and content. Then, the Burger model, a linear viscoelastic-plastic model, was employed to define the contact mechanical characteristics of mortar and ITZ. Meanwhile, the linear parallel bond model, a linear elastic bonding interface with dimensions that can transmit forces and moments, was utilized to describe the contact bonds between balls in the aggregate. On this basis, the effects of coarse aggregate properties (i.e., surface topography, shape, gradation, content, and elastic modulus) on the concrete creep were studied quantitatively. The results show that the coarser the surface topography of aggregate, the smaller creep. Also, with the increase in the content or elastic modulus of coarse aggregate, concrete creep showed a decreasing trend. In addition, the constraint action of the aggregate can be illustrated by the displacement fields. Overall, the 3D particle-based proposed in this work can provide an effective tool to explain the creep behavior of concrete materials from the meso-scale.

Research on the calculation method of concrete compressive strength based on volume content of recycled coarse aggregate and fine aggregate

ABSTRACT In order to study the influence of physical properties and volume content of coarse aggregate on concrete strength, the effective water absorption, apparent density and crushing index of different types of coarse aggregate were tested; the contribution strength coefficient and reinforcement coefficient of coarse and fine aggregate were proposed according to the mechanics of composite materials, the optimal range of the volume content of coarse and fine aggregate was determined, the calculation equation of concrete compressive strength based on the properties of coarse aggregate and the volume content of coarse and fine aggregate was established. The results show that: the effective water absorption of recycled brick aggregate (RBA) is 8.18% and that of natural aggregate (NA) is 0.32%; the apparent density of NA is 2713 kg/m3 and that of RBA is 2100 kg/m3; the crushing index of NA is 18.07% and that of RBA is 30.59%; furthermore, the crushing value of RBA is close to that of cement mortar with water cement ratio of 0.46; NA has a greater range of strengthening the compressive strength of concrete than RBA; when sand cement ratio is between 0.3 and 2.5, both Ks’ and Ks are greater than 1; when sand cement ratio is about 0.5, Ks’ reach the maximum value; when sand cement ratio is about 0.75, Ks reach the maximum value; the calculation equation of concrete compressive strength established in this paper has a good prediction effect, which provides a new idea for the calculation method of concrete compressive strength.

Analyzing the Performance of Construction Demolition Waste Aggregates on strength for Non-structural Concrete

Construction and demolition waste (CDW) refers to the waste generated from demolished structures in the construction industry. This waste can include concrete and brick materials. In this study, the focus is on evaluating the physical and mechanical properties of coarse aggregates derived from CDW, as well as the compressive strength of non-structural concrete made by mixing CDW aggregates with natural aggregates (NA) in different proportions. The study involved preparing different mix proportions of concrete using various combinations of CDW coarse aggregates, natural coarse aggregates, and brick aggregates. The mix proportions were categorized into three groups:100% natural coarse aggregate,CDW concrete coarse aggregate mixed with natural aggregate in three proportions: (90% NA, 10% CA), (80% NA, 20% CA), and (60% NA, 40% CA) and Mixtures of natural coarse aggregate, CDW concrete aggregate, and brick aggregate in four proportions: (90% NA, 5% CA, 5% BA), (80% NA, 10% CA, 10% BA), (60% NA, 20% CA, 20% BA), and (80% NA, 30% CA, 30% BA). The physical and mechanical properties of the different mix proportions were analyzed, and it was found that all proportions, except (80% NA, 30% CA, 30% BA), met the specified limits. In terms of compressive strength, the concrete mixture with a proportion of (90% NA, 10% CA) exhibited the highest value (27.04 MPa), while the mixture with a proportion of (60% NA, 20% CA, 20% BA) had the lowest value (17.19 MPa). The mixture with a proportion of (80% NA, 30% CA, 30% BA) did not meet the targeted strength of 15 MPa. Conclusion: Based on the analysis of the test results, it can be suggested that CDW aggregates can be used as a replacement for natural aggregates up to a maximum of 40%. Additionally, a combination of CDW concrete and brick aggregates in equal proportions (20% - 20%) can be used as a replacement for natural aggregates to achieve a concrete strength of 15 MPa.

Assessment of Crushing Potential of Coarse Aggregates for Asphalt Concrete Mixtures

This paper aims to evaluate the effectiveness of a mechanical test that can assess the quality of mineral aggregates commonly used to produce asphalt concrete, in relation to crushing potential, in a more consistent and repeatable manner. Several aggregate types including limestone, dolomite, sandstone, granite, and gravel were sampled from different locations around Texas. The aggregate samples were subjected to various mechanical aggregate tests, primarily the aggregate crushing value (ACV) (BS 812-110:1990) test. A new index, the aggregate crushing potential (ACP), is proposed for the ACV test to improve its characterization potential. The main output parameters from aggregate tests such as the Los Angeles abrasion, magnesium sulfate soundness, acid-insoluble residue, and micro-deval abrasion, which are routinely performed to discriminate the properties of coarse aggregates, were collected. In addition, the dynamic friction test was conducted to measure the friction properties of several of the aggregate sources. Analyses were carried out between the ACV test results and the measured aggregate parameters. The proposed ACP index was identified as a suitable indicator of the durability of coarse aggregates. From this study, the ACV test partnered with the ACP index showed potential to delineate the quality of aggregates, in relation to crushing resistance, more practically and consistently, and eventually may supplant more tedious aggregate test methods.

An enhanced mix-design method for self-compacting concrete based on paste rheological threshold theory and equivalent mortar film thickness theories

• Coarse aggregate properties consist of shape, gradation, and content. • Coarse aggregate properties are quantified by equivalent specific surface area. • Equivalent mortar film thickness was used to modify the original model. • The modified model was verified with different coarse aggregate properties. This paper puts forward an enhanced mix design method for self-compacting concrete (SCC) based on paste rheological threshold theory and equivalent mortar film thickness theories. 18 sets of paste and SCC tests were carried out to test the initial mix design method with coarse aggregate contents of 285, 315, and 322 L/m 3 , the results show that the initial mix design method cannot accurately predict the SCC test results. The equivalent specific surface area of coarse aggregate (SSA eq ) was chosen to quantify and represent the particles’ shape, gradation, and contents on mortar film thickness, and the equivalent mortar film thickness was proposed to modify the original rheological model. In addition, 36 sets of paste and SCC tests with different coarse aggregate characteristics were prepared to verify the enhanced method. Using prediction accuracy formula to evaluate the enhanced mix design method. Both methods are used to predict the fresh SCC. Results show that the average value of relative accuracies and Intersection-over-Union (IoU) in the enhanced method are, 0.84, 0.79, respectively, whereas in the original method are, 0.60, 0.59, respectively.

Mesoscopic Fracture Model of Coarse Aggregate Interlocking Concrete

The skeleton formed by coarse aggregate has an important influence on the macroscopic mechanical properties of concrete, especially the fracture properties. Based on mesomechanics and fracture mechanics, this paper conducts theoretical simulations and experimental studies on the mechanical and fracture properties of coarse aggregate interlocking concrete through the theory of mesomechanics homogenization as well as compressive strength tests, flexural strength tests, axial compressive strength tests, elastic modulus tests, and fracture toughness tests. The results show that when the coarse aggregate is within a certain volume increase, the fracture energy and ultimate strength of concrete are significantly improved. At the same time, the proposed mesomechanics calculation model has high accuracy for calculating the fracture characteristics of concrete when the coarse aggregate increment is less than 20%.

Experimental Investigation of Flexible Pavement Using Shingles

Abstract: Huge volumes of Shingles are produced from building construction and Asbestos industries. Basically, waste Shingles Aggregates (WSA) are being produced by crushing Shingles during the process of transport and installation of roof, wall and floor. Present society are progressively moving forward to be more environment friendly. To meet up this purposes, recycling and reuse of this material can be the best alternatives than landfill disposal in respect of environment conservation and economy. To increase the usage of Shingles in pavement construction, different percentage of Shingles can be used with the natural aggregate. The technical flexibility of using waste Shingles aggregates as partial replacement of natural aggregates in bituminous mixes can be evaluated. This research work presents some of the laboratory investigation on the possible application of waste Shingles aggregates in bituminous mixes. The physical properties of coarse aggregates, fine aggregates, filler and bitumen are determined according to standard test. Marshall test specimens are prepared for testing to measure the Marshall properties. at optimum bitumen respectively are determined. According to AASHTO, Marshall stability test properties of mixes of waste shingles aggregates are satisfactory. investigated results indicate that the bituminous mixes with waste shingles aggregates give satisfactory results for construction of medium traffic road Keywords: Waste Shingles Aggregates, Marshall Mix Design, Flexible Pavement Construction

Mechanical Properties of Light Weight Concrete using Lightweight Expanded Clay Aggregate

Abstract: This research investigates the impact of partially substituting coarse aggregate with light weight coarse material (LECA). In numerous aspects, LECA mirrors the properties of coarse aggregate. Because self-weight accounts for a major amount of the total load applied to the structure, LECA is utilized in concrete to lower the need for coarse aggregate and in the design of concrete buildings. This is crucial in circumstances like poor soils and tall constructions. It also offers significant advantages in terms of lowering concrete density, which improves labour efficiency. Lightweight concrete has a lower density than standard concrete and provides better thermal insulation. The main purpose of this study is to examine the weight and strength characteristics of concrete, such as cube compressive strength, split tensile strength cylinders, and flexural strength of light weight concrete versus conventional concrete by substituting LECA for natural aggregates by 25%, 50%, 75%, and 100%, respectively. For far over two millennia, lightweight aggregate has been used successfully. Keywords: Lightweight Expanded Clay Aggregate (LECA), Light-weight concrete, Flyash, Compressive Strength, Density.

Meso-scale modelling of the effect of coarse aggregate properties on the creep of concrete

The effects of coarse aggregate properties on concrete creep were explored in the paper by meso-scale modelling approach, in which concrete was divided into coarse aggregate and matrix. Firstly, the creep constitutive model parameters of matrix were determined based on macroscopic and indentation creep tests, and then the evolution of creep and the influences of aggregate properties were discussed based on 2D meso-scale simulation. The simulation results of macroscopic creep test showed that the creep was unevenly distributed in the concrete, and the creep of matrix in vertical direction (y direction) of aggregate was greater than that in horizontal direction (x direction). Through parametric studies, it was found that: (1) the shape and gradation of course aggregate had little effect on the macroscopic creep, but the creep distribution of the matrix was changed by the aggregate shape; (2) the higher the aggregate content, the smaller the creep of concrete; (3) the larger the elastic modulus, the smaller the creep, and the matrix creep in x direction of aggregate of decreased with the increase of elastic modulus ratio of aggregate to matrix. Based on the simulation results, stress redistribution and continuous retardation time spectrum were discussed. Stress redistribution at meso-scale mainly occurred in the matrix in the x direction of aggregate. Through the retardation time spectrum, the creep process including two short-term creeps and a long-term creep and their transition retardation time were determined. The aggregate content had no effect on the transition retardation time, while transition retardation time between two short-term creep was increased by the increase of elastic modulus of aggregate.

Effect of Local Coarse Aggregates on the Compressive Strength of High Strength Concrete

This study investigates the effect of different types of local coarse aggregate, available in Saudi Arabia, on the strength of high-strength concrete. The utilized coarse aggregates are basalt and two different aggregates of limestone, denoted as limestone 1 and limestone 2. The results of 7 and 28 days compressive strength with different percentages of Micro Silica (MS) (i.e. range from 0 to 10%) show that the compressive strength of high strength concrete (HSC) is influenced by the type of coarse aggregate. Limestone 2 reaches the highest compressive strength followed by the types limestone 1 and then basalt. Properties of coarse aggregate influence the compressive strength of HSC, such as impact value (AIV), and texture. Also, the impact value variation between saturated surface dry (SSD) and dry conditions of the coarse aggregate affect significantly the compressive strength of HSC.

Effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete

Two-stage concrete (TSC) is known by various names such as colcrete, Polcrete, preplaced aggregate concrete and prepacked concrete. It is different from traditional concrete in two fundamental ways, namely method of construction and mix proportion. Two-stage concrete (TSC) is defined as firstly, coarse aggregates are placed into the formwork and grout is applied to fill in the between coarse aggregate particles voids. Secondly, the percentage of coarse aggregates in the mix proportion of TSC is higher than that in normal concrete. The typical value is about 60% as compared with 40% in traditional concrete. As coarse aggregates are preplaced first, they can occupy up to 60–70% of the total volume. As coarse aggregates are not involved in the mixing process, TSC is environmentally friendly with lesser consumption of energy. With a higher content of aggregates, TSC reduces the use of cement by 20–30% and may minimize the temperature rise. Engineering properties of TSC, including its stress–strain relationship, is mainly governed by the properties of coarse aggregates as stress is transferred from the skeleton of aggregates to hardened grout. Main advantages of TSC include a higher volume of coarse aggregates and the ability to use larger size coarse aggregates. The latter also reduces the cost of crushing. TSC has beneficial properties such as low drying shrinkage, high bonding strength, high modulus of elasticity, and excellent durability. The method of TSC has proved particularly useful in a number of applications like underwater construction, and masonry repair, where placement by conventional methods is extremely difficult. The method is also applicable in case of massive concrete where low heat of hydration is required. It is studied the feasibility of casting two stage concrete with 100% steel slag as coarse aggregate. In term of formulation, to adopt two stage concreting method we could minimize the risk of concrete bleeding and segregation due to high water absorption and quite high density of slag aggregate. The effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete has rarely been reported. Thus, the development of an eco-efficient alkali-activated grout for two-stage concrete is a new research topic that has no robust results to draw solid conclusions and it should blaze the track towards a cleaner production of building materials with outstanding sustainability.

Feasibility Studies of Engineering Properties of Coarse Aggregates from Demolition Waste and Natural Aggregates for Road Construction

Construction and Demolition (C&D) waste constitutes a major portion of total solid waste origination in the world and most of it is used in landfills. The disposal of this construction and demolition waste is becoming a major concern as it is disposed unscientifically in India. The C&D waste is usually dumped on the sides of canals, minor roads and at the entrance of the cities and towns. This causes environmental problems and affects the quality of life of people. This paper discusses the possibility of replacing natural coarse aggregate with recycled concrete from demolition waste aggregate for road construction. Aggregate strength, gradation, absorption, specific gravity, shape and texture are some of the engineering properties that are desirable for road construction. Therefore, the experimental program was focused on the evaluation of engineering properties of the recycled aggregate over a period of 6 months. The findings from the study showed that the recycled concrete aggregate can be used for construction of transportation infrastructure. However, further research is needed particularly on the long term field performance of the recycled aggregate concrete before it can be used with confidence.

Effect of crushing mechanism on the shape properties of coarse aggregates

Aggregates account for the maximum portion of the materials used in the construction of pavements (both flexible and rigid pavements) and it is estimated to reach about 95%. It is essential to know the properties of aggregates during the selection of aggregate source. The properties of aggregates get affected by various factors. Among the several factors, the process involved in the aggregate production plays a vital role. In this study, two different crushing sequences are considered to evaluate the effect of the production process on the shape properties of aggregates viz., jaw-cone and jaw-jaw crushers. Further, the aggregate particles are grouped into four groups based on the size. The aggregate samples are tested for their shape properties and classified based on the Zingg’s classification system. The results indicated that, the aggregates produced from J-C crusher showed better morphological characteristics than J-J crusher.

Relationship between Mechanical Resistance, Permeability Characteristics and Shape Properties of Coarse Aggregate of Pervious Concrete Slabs, Incorporating Steel Slag

Relationship between Mechanical Resistance, Permeability Characteristics and Shape Properties of Coarse Aggregate of Pervious Concrete Slabs, Incorporating Steel Slag

Experimental Investigation of Effect of Recycled Coarse Aggregate Properties on the Mechanical and Durability Characteristics of Geopolymer Concrete

With the increased population and industries in the global building sector, two major construction issues must be addressed: (i) Huge construction waste accumulation and (ii) Excessive use of Non-Renewable Resources. Geopolymer Recycled Coarse Aggregate Concrete emerges at a critical juncture in history to address two issues. Firstly, utilizing Geopolymers derived from the waste of industry to replace cement which reduces the use of cement and thus emissions of CO2, and secondly, Recycled Coarse Aggregate can make use of accumulated construction waste while conserving the natural resources. In the current study, Geopolymer Concrete was made with a constant ratio of fly ash and GGBS (50:50), a sodium silicate to Sodium Hydroxide ratio of 2.5, a Sodium Hydroxide concentration of 8 Molarity, an alkaline to binder ratio of 0.4, and different proportions of Recycled Coarse Aggregate that was partially and completely replaced with Natural Coarse aggregate with the percentage of (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%). The test results showed that Recycled Coarse Aggregate can be used as a Natural Coarse Aggregate in Geopolymer Concretes by replacing 70%, with a 28-day compressive strength of 60.02 MPa, which is almost same as 100% Natural Aggregate in Geopolymer Concrete. The reduction in strength after 90 days of exposure to the HCL solution was up to 1.28 percent for Geopolymer Concrete using Recycled Coarse Aggregate. The Compressive Strength of Geopolymer Concrete using Recycled Coarse Aggregate decreased by up to 1.89 percent after the same period of exposure to the Sulphate solution. In this study combination of fly ash, GGBS, 70% Recycled Coarse Aggregate, and an 8 Molarity NaOH concentration-based Gopolymer Concrete was recommended for precast construction with ambient curing.