Coarse Aggregate Ratio Research Articles

Evaluation of coarse aggregate properties in hardened concrete based on segment anything model (SAM)

The applicability of the segment anything model (SAM) algorithm, a novel technique for analyzing the characteristics of coarse aggregate from RGB images of concrete cross-sections, was evaluated. Unlike traditional deep learning method, the SAM algorithm effectively and clearly separates coarse aggregate and mortar without requiring a large database, extensive pre-training, conversion of RGB images to grayscale, or manual threshold setting. Additionally, a new technique was applied to separate the pores recognized as aggregates by using the image difference according to the change in vertical and side lighting. Consequently, the area ratio of coarse aggregate, after the separation and removal of pores from the aggregate area, exhibited an error of approximately 7.0 % when compared to the actual volume ratio of the aggregate. However, in contrast to the calculation of the area ratio of coarse aggregate, the SAM algorithm demonstrated significant errors in size analysis, leading to distortions in the sieve curve. Nevertheless, the SAM algorithm indicates potential for application in various concrete-related fields of concrete in the future.

A Study of the Main Fracture Precursor Characteristics of Polypropylene Fiber-Reinforced Recycled Concrete with Varying Coarse Aggregate Ratios

A Study of the Main Fracture Precursor Characteristics of Polypropylene Fiber-Reinforced Recycled Concrete with Varying Coarse Aggregate Ratios

Hubungan Antara Rasio Agregat dan Volumetrik dalam Menentukan Kualitas Perkerasan Jalan

Road pavement quality is a critical factor in supporting a country's mobility and economy. Around 40% of the road length in Indonesia suffers damage, including permanent deformation and early cracking. To overcome road damage, it is important to know the pavement quality parameters such as Voids in Mineral Aggregate (VMA), Voids in Mix (VIM), and Voids Filled with Bitumen (VFB), along with the factors that influence them, such as material characteristics. This study aims to determine the effect of the fine and coarse aggregate ratio on volumetric parameters in asphalt mixtures, including VIM, VMA, and VFB. The experimental method was carried out on four samples. Aggregate characteristic tests were carried out, including gradation tests. Volumetric tests were carried out on each sample with asphalt content of 4%, 4.5%, and 5%. The research results show that the smaller fine-to-coarse aggregate ratio would increase the VMA and VIM values and decrease the VFB value. Aggregate ratio significantly affects volumetric parameters, which shows the importance of selecting aggregate with the right size distribution and determining the right ratio to achieve optimal pavement performance. The results of this study can be used as a practical guide for optimizing asphalt mix design with better quality and durability.

Failure criterion and elasto-plastic constitutive model of seawater concrete incorporating coral aggregate subjected to triaxial loading

Recently, there has been a growing interest in utilizing coral reef debris as a replacement for river sands and natural coarse aggregates (NA). A novel type of seawater concrete, designated as CAC, was developed to effectively utilise raw coral debris and reduce material transportation costs. This study aimed to examine the mechanical properties of CAC under both uniaxial and triaxial loading conditions. Consequently, 18 prism uniaxial specimens and 90 triaxial cylinder specimens were prepared, considering concrete strength (C20, C40), replacement ratio of coral coarse aggregate (CA) (50 %, 75 % and 100 %), and lateral stress ratio (0, 0.1, 0.2, 0.3 and 0.5). The results indicated that the increase in peak stress and strain is associated with the triaxial stress ratio and the cylinder compressive strength of coarse aggregate. Furthermore, the compressive meridian of CAC is lower than that of conventional concrete. Based on the test results in this study, a modified William-Warnke failure criterion for CAC was established. Additionally, an elasto-plastic model considering a modified hardening and softening law was suggested for CAC under tri-axial loading. The proposed models were found to be well verified by the test results.

Study on Slump and Compressive Strength of Gangue Based on Aggregate Size Gradation

In order to solve the ecological environment pollution caused by a large amount of coal gangue accumulation and the problems of poor conveying performance and low support strength of paste filling materials. Based on the standard slump test and uniaxial compressive strength test, the slump and compressive strength (post-coagulation) of gangue paste under different aggregate size aggregations were obtained through orthogonal experiments in this study. The results show that the slump of the gangue filling paste with four types of aggregate size gradations is negatively correlated with the mass fraction, and the slump of the filling paste with a coarser aggregate content is more obviously affected by the mass fraction The increase of fine aggregate content has a significant impact on the compressive strength of the filling paste, which shows a trend of first increasing and then decreasing. When the mixing ratio of coarse aggregate and fine aggregate is 5:5, the compressive strength of the paste reaches the best. In addition, different proportions of aggregate mixing cause the filling paste to form different skeleton structures, including the skeleton void structure at 7:3 or 6:4, the skeleton dense structure at 5:5, and the skeleton suspension structure at 4:6, which are decisive for the final performance of the paste. By analyzing the experimental results of the compressive strength and slump of the gangue filling paste, it was found that the relationship between the compressive strength and slump of the gangue filling paste is a power index function. Through data fitting, it was found that the regression coefficient of the fitting function is no less than 0.97, and the fitting effect is good for evaluating the strength of the filling paste under the aggregate size grading.

Effect of Ground Granulated Blast Slag and Temperature Curing on the Strength of Fly Ash-based Geopolymer Concrete

Concrete is used most extensively after water to meet construction requirements. Since the population is increasing day by day, the demand for concrete will always increase, hence, the demand for cement will also increase. The production of cement requires a lot of energy and emits greenhouse gases into the environment. Therefore, an alternative material for cement concrete is required. Geopolymer concrete (GPC) is an alternative to cement made of aluminosilicate materials such as fly ash, Ground Granulated Blast Slag (GGBS), silica fume, metakaolin, etc. If these materials are activated with an alkaline activator, then a bond that is responsible for the strength develops. GPC made with fly ash needs temperature curing to develop its strength, which limits its use on a large scale. In this study, a mix ratio of GPC equivalent to conventional M20 concrete was obtained at ambient curing conditions. The effect of temperature curing was also studied. GPC was prepared in three different mixes. In each mix, the binder content was changed by varying the fly ash and GGBS content. Two sets of cube, beam, and cylindrical samples were prepared from each mixture. One set was cured at ambient temperatures and the other at increased temperatures. The temperature-cured specimens provided higher strength than the ambient-cured. If a strength equivalent to conventional M20 concrete is required for ambient curing, then the mix should be 70% fly ash and 30% GGBS, and the ratio of binder, fine aggregate, and coarse aggregate should be 1:1.5:3.

A Review of Chloride Corrosion Resistance of Ultra-High-Performance Concret

Extending the service life of reinforced concrete structures can effectively reduce the economic, environmental, resource and energy costs throughout their life cycle. However, a large number of reinforced concrete structures often suffer from corrosion of reinforcing bars due to chloride ion erosion in various environments, which leads to deterioration of performance, the loss of functionality and even safety accidents. As a barrier between reinforcing steel and the external environment, protective layer concrete can effectively prevent chloride ions from contacting the surface of reinforcing steel, thus delaying the corrosion of reinforcing steel and improving the durability of reinforced concrete structures. Ultra-high-performance concrete has a dense microstructure due to its low water-to-cement ratio and elimination of coarse aggregates, which can greatly impede the transport of chloride ions within it, and thus it is expected to significantly improve the service life of reinforced concrete infrastructure. Based on this, this paper firstly summarizes the basic mechanism of chloride ion transport inside cementitious materials, including the movement mode and physicochemical binding mechanism of chloride ions inside the cementitious, and analyzes the current research status and improvement methods of the chloride ion penetration and chloride ion binding capacity of ultra-high-performance concrete.

Enhancing performance of concrete with glass fiber-reinforced polymer short rebars as coarse aggregates by confinement

Cutting glass fiber-reinforced polymer (GFRP) waste into aggregate-size reinforcing bars (short rebars) as coarse aggregates in concrete shows to be an effective approach for recycling waste GFRP composites. The resulting concrete with such short rebars however exhibits a reduction in the compressive strength comparing to the corresponding normal concrete, making it unable to be directly used for structural elements. The concept of using the confining jacket is therefore employed for such concrete to improve its compressive strength and toughness and to be used in structural elements. A total of 48 cylindrical specimens were prepared and tested under axial compression with the replacement ratio of coarse aggregates by the GFRP short rebars and the stiffness of the confining jacket as the two test parameters. The test results indicate that incorporating short GFRP rebars results in a reduction in compressive performance by up to 57.2%, and the use of CFRP jacketing significantly enhances the performance of the concrete with or without GFRP short rebars. Such enhancement tends to be more significant when the stiffness of the confining jackets or the replacement ratio increases. The reduction in the compressive strength due to the incorporation of 25% recycled GFRP short rebars is from 57.2% to 30.7%, when the number of layers of the confining CFRP jacket increases from 0 to 3 piles. Comparisons were made between the test results and the predictions from two widely-used stress-strain models for confined concrete, showing that both models overestimate the ultimate axial strain and Teng et al.'s model generally produces the compressive strength slightly higher than the corresponding test results as well as the predictions from Jiang and Teng's model.

Development of high-volume fly ash concrete with improved interfacial transition zone

The interfacial transition zone (ITZ) is a vulnerable region in concrete, particularly in high-volume fly ash (HVFA) concrete where a significant portion of fly ash particles remain unreacted. In order to improve the ITZ of HVFA concrete, this work introduces a novel approach by targeted employing slag in the ITZ. Slag-modified cement paste was used to coat coarse aggregate, which was further mixed with other materials to cast HVFA concrete. Various parameters during preparing the coated coarse aggregate, such as the water-to-cementitious material ratio of the cement paste, the slag content in cementitious materials, the mass ratio of coarse aggregate to cement paste, the mixing time of coarse aggregate and cement paste, and the drying time after mixing, were investigated to uncover their influence on the porosity of the ITZ in HVFA concrete. By using the optimized values of these variables of 0.35, 3.8%, 3.2, 10 min and 1 h, respectively, it is feasible to achieve ITZ in HVFA concrete characterized by a porosity of 23.6% and refined pore structure, alongside enhanced compressive strength of the concrete.

Sulphate resistance prediction of RAC considering the coupling effect of RCA and water-binder ratio based on experimental analysis and LSSVM

ABSTRACT Waste concrete removed from old pavement can be crushed and sieved as recycled aggregate to prepare concrete, and the application of recycled aggregate concrete (RAC) can reduce the occupation of land resources by the waste concrete and save natural aggregate. In this paper, the influence of proportion of recycled coarse aggregate (RCA) replacing natural coarse aggregate (NCA) and water-binder ratio on the sulphate resistance of RAC was studied, and the compressive strength degradation rate (Df ) was introduced to evaluate the sulphate resistance of RAC. The experimental results showed that the compressive strength of RAC before and after sulphate attacks linearly decreased with the growth of the replacement rate of RCA, water-binder ratio, and the number of sulphate wet-dry cycles, respectively; while Df of RAC increased with the rise of the replacement rate of RCA, water-binder ratio, and sulphate wet-dry cycles, respectively. The results also indicated that Df of all groups of RAC was less than 25%, which can meet the engineering requirements. In addition, the Df model of RAC under a sulphate attack based on experimental data and that based on Least-Squares Support Vector Machine (LSSVM) was built and compared, and both models predict the sulphate resistance of RAC well. The prediction model based on LSSVM has higher prediction accuracy.

Prediction of Compressive Strength of Silica Fume Blended High Strength Concrete Using Response Surface Methodology Approach

Objectives: In this study, a model was developed to predict the compressive strength of High Strength Concrete (HSC) mixed with silica fume using Response Surface Methodology (RSM). This study investigated the effects of cement, water, Silica Fume (SF), Coarse Aggregate (CA), and silica fume-cement ratio (SF/C) on the 28-day compressive strength of HSC. Silica fume is added with varying amounts of SF (5% to 25%) to cement content. Methods: Response surface methodology (RSM) was performed to investigate the influence of independent variables on the compressive strength of HSC. Findings: Analysis of the response surface plot reveals a remarkably low error percentage of less than 5%. This reveals a high degree of confidence (95%) in the model's accuracy. This study yielded a coefficient of determination (R2) of 0. 9968. It is observed negligible deviation between predicted and actual 28-day compressive strength values, indicating high model accuracy. Novelty: The predicted equation is reasonably predicting the compressive strength of high strength concrete. Keywords: High strength concrete, Response surface methodology, Silica fume, Compressive strength, Prediction model

Investigating non-uniform corrosion induced concrete cover cracking with a fracture-contact coupled computational method

Corrosion of steel rebar causes cracks in concrete, significantly impacting the durability of reinforced buildings. While various computational methods aim to simulate this process, only a few successfully handle both internal corrosion pressure and surface crack width evolution. To address this limitation, the study introduces an innovative mesoscale fracture-contact coupled computational method that seamlessly integrates with ABAQUS. Unlike current methods, it creatively utilizes interface elements to model stress transfer and crack propagation under tension in concrete. Additionally, it includes an additional contact model to represent the material's response to compression and shear forces. These innovations allow for accurate simulation of plain concrete mechanical properties under both tension and compression, effectively illustrating the development and failure patterns of cracks in the reinforced concrete cover. After calibrating and validating the method, the study thoroughly analyzed the process of concrete cover cracking, considering factors such as water to cement ratio, spatial location, geometry and size of coarse aggregate, rebar diameter and cover thickness. The modeling results reveal the following findings: (i) Changes in the shape and size of coarse aggregates have minimal effects on internal pressure and crack width. (ii) Higher concrete strength correlates with increased pressure on the outer surface of the rebar in an almost linear fashion, but it has little impact on surface crack width. (iii) Increasing the bar diameter decreases rust pressure but results in more cracks and wider surface cracks. (iv) Augmenting the cover thickness intensifies rust-induced pressure while simultaneously widening surface cracks.

Optimization of mix proportion and strength prediction of magnesium phosphate cement-based composites based on machine learning

In order to optimize the mix ratio design of magnesium phosphate cementitious composites (MPCC) to obtain excellent workability and strength, this study investigated the effects of MgO-phosphate ratio, water-binder ratio, aggregate-binder ratio, the mass ratio of coarse and fine aggregates, mineral admixture content and steel fiber content on the flowability, setting time and cubic compressive strength (CCS) of MPCC using orthogonal design of experiments with a total of 32 sets of mix ratios. The experimental results were also analyzed utilizing range and variance analysis to determine the main influencing parameters and the optimal dosage of each factor, and the optimal MPCC mix ratio was obtained. In addition, the prediction of CCS for MPCC using five machine learning models was first introduced, and the predicted results were interpreted and analyzed regarding the SHAP (Shapley Additive exPlanations) features importance. The results showed that the effect of steel fiber volume content and water-binder ratio on the flowability was significant, and M/P significantly affected the setting time of MPCC. The CCS of MPCC increased with the age of curing, and MPCC exhibited high early strength, with 1-day CCS accounting for 55%～85% of the 28-day CCS. The effect of M/P on the 1-day, 3-day and 28-day CCS was highly significant, with M/P contribution rate as high as 76.3%, 80.3% and 83.6% of the CCS at 1, 3 and 28 days, respectively. Besides, the effect of steel fiber volume content on 28-day CCS was also significant. In summary, the optimal mix ratio of MPCC was A4B1C4D1E4F4G1 (M/P = 3, w/b=0.11, a/b=1.4, c/f=3, FA content =15%, MK content= 15%, steel fiber volume content= 0%). Furthermore, random forest (RF) and particle swarm optimization of back propagation artificial neural network (PSO-BP-ANN) models have a higher prediction accuracy, and the results of SHAP feature significance further confirmed the above test results.

Experimental and numerical evaluations of the shear performance of recycled aggregate RC beams strengthened using CFRP sheets

Conserving the ecosystems of the globe, protecting natural resources, and improving environmental conditions can all be achieved by considering sustainability in the construction industry. Recycling of building and demolition waste is one of the key approaches being investigated to accomplish this target. Twelve reinforced concrete (RC) beams were constructed for the current study in order to analyze the shear behavior of recycled aggregate concrete (RAC) beams externally strengthened with carbon fiber reinforced polymer (CFRP) sheets. The main goal of the experimental matrix was to investigate the effect of the recycled aggregate ratio on the shear response of RAC, where three recycled coarse aggregate ratios of 20%, 60%, and 100% were suggested. Additionally, the effects of incorporating two or four CFRP strengthening layers on the ultimate load, failure pattern, load-deflection responses, and stiffness of RAC beams were also investigated. Results revealed that, when different ratios of recycled aggregate estimated at 20%, 60%, and 100% were substituted for natural aggregates, the compressive strength decreased by 4.3%, 24.2%, and 40.0%, respectively, compared to natural aggregate concrete. Moreover, the RC beam that was cast utilizing 20% recycled aggregates and strengthened with four CFRP sheets exhibited the highest ultimate load among all the tested RAC beams of 84.8 kN, which was 22.9% higher than the un-strengthened specimen totally cast with natural aggregate. Furthermore, a three-dimensional (3D) non-linear finite element model (FEM) was constructed using the ABAQUS program in order to compare the effects of employing continuous CFRP sheets for the whole critical shear span length to intermittent strips that had been experimentally tested.

Effect of Coarse Aggregate and Multi-Wall Carbon Nanotubes on Heat Generation of Concrete

Many researchers are developing heating construction materials to remove black ice from roads, addressing the scientific challenges associated with this issue. The use of carbon-based nanomaterials in concrete is of great interest due to the excellent electrical and thermal conductivity of this material. In this study, the incorporation of multi-walled carbon nanotubes (MWCNTs) into concrete compositions results in the formation of MWCNT bridge networks. MWCNTs exhibit a low specific heat and possess the ability to promptly generate raised temperatures with minimal power input. This characteristic has the potential to induce temperature variations in concrete. The heat generation test parameters for MWCNT concrete included the mixing concentration of the MWCNTs, the mixing ratio of coarse aggregate, the water/cement (W/C) ratio, and the presence or absence of superplasticizers. The heating performance of concrete was found to improve as the mixing concentration of the MWCNTs increased, while a heating performance decrease was observed as the mixing ratio of coarse aggregate increased, owing to the reduced dispersibility of the MWCNTs. Conversely, the heating performance improved when the W/C ratio increased due to the enhanced dispersibility of the MWCNTs. Moreover, superplasticizers assist in dispersing MWCNTs, thereby improving the heating performance. Additionally, field emission scanning electron microscopy revealed that MWCNTs form a bridge network between the cement hydrates. As a result of this study, the maximum temperature variation of concrete mixed with MWCNTs was up to 73.6 °C. Therefore, by mixing MWCNT aqueous solutions with concrete and using an appropriate W/C ratio and superplasticizer, a new construction material capable of enhanced heating performance was developed.

Effects of the shape, size, and surface roughness of glass coarse aggregate on the mechanical properties of two-stage concrete

Because two-stage concrete (TSC) is obtained by placing coarse aggregate in formwork and then filling the gaps with flowable grout, the properties of the coarse aggregate can notably affect the mechanical properties of TSC. In this study, uniaxial compressive and splitting tensile tests were conducted on TSC with eleven types of glass coarse aggregate of different shapes, sizes, and surface roughness for coarse aggregate. Two types of spherical glass aggregate with diameters of 17 and 30 mm, irregular shape of crushed glass plate classified into two size groups (20–30 mm and 10–20 mm) were used. Surfaces of spherical glass aggregates were two types; those were smooth and rough. The compressive strength of grout matrices used in specimens was 44.6 N/mm2 in the normal-strength mixture and 129.8 N/mm2 in the high-strength one. The relationship between the compressive and tensile strengths and the size of the coarse aggregate changed depending on the grout matrix strength and roughness of the coarse aggregate surface. The tensile strength for crushed glass aggregate were larger than those for spherical glass aggregate. Increasing roughness of the coarse aggregate surface led to an increase in the tensile and compressive strengths. The modulus of elasticity was affected by not only the solid content aggregate but also the shape and roughness. Moreover, the mechanical properties of TSC were compared with those of conventional concrete with the same coarse aggregate and same water-cement ratio as TSC. Observations from the test program indicate the design parameters that most strongly influence the strength and stiffness of TSC specimens.

A Design Method on Durable Asphalt Pavement of Flexible Base on Anti-Rutting Performance and Its Application.

To solve the durability of flexible base asphalt pavement, especially its anti-rutting problem, a design method on durable asphalt pavement of flexible base on anti-rutting performance was put forward in the paper, based on many experiments and calculations. Firstly, a method that asphalt could be selected according to penetration and the anti-rutting factor of its base asphalt was found, which solved the problem of the asphalt selection of the flexible base asphalt mixture design. Meanwhile, a method of skeleton-density structure gradation design was proposed based on the fractal void ratio of coarse aggregate, fractal volume of fine aggregate in coarse aggregate, penetration, fractal dimension of gradation particle size, and rutting tests, which effectively solved in advance the rutting and fatigue performance of flexible base asphalt mixtures. Then, on the basis of the fatigue damage, a calculation method of fatigue life was suggested, which solved the problem that the fatigue damage of asphalt mixtures rarely considered the combined effects of creep damage and fatigue damage. In addition, a calculation method of rutting was formulated based on vehicle dynamic load and ANSYS 16.0 software. Lastly, the feasibility of the design method on durable asphalt pavement of flexible base on anti-rutting performance was verified combining with the real engineering of a supporting project and several numerical calculations and tests.

Cyclic loading tests and seismic behaviors of steel-reinforced recycled aggregate concrete filled square steel tube composite columns

To investigate the seismic performance of steel-reinforced recycled aggregate concrete (RAC) filled square steel tube composite columns, the cyclic load tests were conducted for nine columns. The effects of steel ratio of profile steel, width thickness ratio of square steel tube, the replacement rate of recycled coarse aggregate (RCA) and axial compression ratio on the seismic performance of composite columns were investigated in detail. The failure characteristics, hysteretic curves, performance indexes and stress-strain distribution of columns were analyzed in detail. The results show that an obvious plastic hinge is generated at the column base and present a compression-bending failure mode. The hysteretic curves of columns present a full shuttle shape, showing that the columns have good energy dissipation capacity and ductility. The use of RCA has little impact on the seismic performance of composite columns. In particular, the bearing capacity of columns with fully RCA is only 1.57% lower than that of ordinary concrete columns. With the increase of profile steel ratio or the decrease of width thickness ratio of square steel tube, the ductility and energy dissipation capacity of columns obviously improve. Increasing the axial compression ratio is conducive to improving the bearing capacity of columns to some extent, but not conducive to improving the energy dissipation and deformation capacity of columns. Based on the failure mechanism of composite columns, combined with AISC specification, the modified formula on the horizontal bearing capacity of steel-reinforced RAC filled square steel tube composite columns is proposed, which is well verified by the test results.

Shear strength assessment of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques

This paper presents a study to predict the shear strength of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques. The methodology involves the development of a Multi-Objective Genetic Algorithm Evolutionary Polynomial Regression (MOGA-EPR) and Gene Expression Programming (GEP) models. The input variables considered are the longitudinal reinforcement ratio, recycled coarse aggregate ratio, beam cross-section dimensions, and concrete compressive strength. Data collected from the literature were used to train and validate the models. The results showed that the MOGA-EPR and GEP models can accurately predict the shear strength of beams without stirrups. The models also performed better than equations from the codes and literature. This study provides an alternative approach to accurately predict the shear strength of reinforced recycled aggregate concrete beams without stirrups.

A novel method for measuring and analyzing the characteristics of coarse aggregates in concrete

The characteristic of coarse aggregate is an important factor affecting the building performance of concrete, so it is of great significance to measure and characterize it. In this paper, a method of measuring the characteristics of coarse aggregate in concrete buildings by using borehole camera technology is proposed. For the obtained borehole wall image, the corresponding image processing method is proposed, which can accurately recognize the coarse aggregate structure in the image. On this basis, the characteristics of coarse aggregate in the borehole wall image are calculated and analyzed. The calculation parameters include uniformity, gradation, aspect ratio, inclination angle, shape index, angularity and surface texture. The results show that the coarse aggregate in the borehole wall image used in this paper is not evenly distributed at different depths, the gradation continuity is good, and there are some coarse aggregates with large particle size. The aspect ratio of most coarse aggregates is less than 3 (AR1:97.71%; AR2:96.26%), and the content of needle flake coarse aggregate is less. The inclination angle is mostly distributed in the horizontal direction, accounting for more than 50%. The distribution of shape index and angularity has obvious correlation with the particle size range, and the shape index and angularity in the large particle size range are richer and more uniform. The distribution characteristics of surface texture of coarse aggregate in different particle size range are basically the same, and there is no obvious correlation with particle size. In this paper, a new in-situ measurement and multi characteristic parameter analysis of coarse aggregate in borehole is carried out, which provides a new idea for the evaluation of concrete building performance.