Coarse Aggregate Ratio Research Articles

Estimation of rapid chloride permeability of SCC using hyperparameters optimized random forest models

Discovering concrete properties takes time, money, laboratory design, material preparation, and testing with adequate equipment at the right ages. As a consequence, in the concrete sector, solutions that minimize or reduce cost, time, and other downsides are essential. So, utilizing forecasting systems to compute concrete characteristics based on historical data is quite advantageous. Employing the rapid chloride penetration test (), this study proposed novel classification models for predicting chloride penetration into self-compacting concrete (). Designs for predicting the quantity of are constructed utilizing optimized random forest () classifications, which have not yet been outlined in the literature. The fundamental objective of this research is to build innovative combined classification models that combine with optimization techniques such as particle swarm optimization (), whale optimization algorithm (), and Harris hawks optimization () for better approximation of Using and five critical model hyperparameters were fine-tuned to provide the most powerful and dependable models ever. Considered combined classifications were trained by seven variables, namely cement content, fly ash, silica fume, a ratio of coarse and fine aggregates, water to cement ratio, and temperature. The findings reveal that in the training/testing phases, all three approaches had appropriate efficiency in estimating the reflecting the allowable correlation among actual and anticipated values. outperforms the other versions in both stages, with and of 0.9854 and 28.6 for the learning phase and 0.9645 and 41.44 for the assessment phase, respectively. Although the performance evaluator indices for are lower than and models, it has acceptable results with larger than 0.9243. Overall, the findings show that the method is more capable than and at calculating the ideal value of hyperparameters.

PRODUCTION OF LOW-COST SELF-CONSOLIDATING CONCRETE (SCC) USING MANUFACTURED AGGREGATES

Limitations to the sources of aggregates and the unavailability of sand is becoming a problematic issue for concrete production. A novel technology of manufactured aggregates can produce well graded round aggregates that can substitute natural aggregates while maintaining the same characteristics needed and preserving the resources. Self-Consolidating Concrete (SCC) using manufactured aggregates is assessed in this experimental work to understand the variability of workability properties and mechanical properties with the changes in w/c ratio and percentages of Coarse Aggregates and Manufactured Sand to Natural Sand in order to choose the best mixture that satisfies an adequate overall performance. Targeting compressive strength improvement, the SCC mixes included the use of Silica Fume (SF) and Polycarboxylate Superplasticizer which exhibited a strength improvement when compared to normal SCC. After performing 6 different trial mixtures, the use of manufactured rounded aggregates of percentages 73% from total fine aggregates proportion, 2.7% of Polycarboxylate superplasticizer, and around 8% Silica Fume (SF) from total cementitious materials can succeed in reaching high strength concrete with optimum mechanical properties and a noticeable workability improvement when compared to natural aggregates.

An investigation on effect of aggregate distribution on physical and mechanical properties of recycled aggregate concrete (RAC)

The aim of the study is to optimize the aggregate gradation curve (AGC) for recycled aggregate concrete (RAC). Accordingly, TS 802 aggregate gradation curves such as A16, B16 and C16 and, also two proposed AGCs such as G1 and G2 are examined in the experiments. Hence, in total, 10 mixes are designed in consideration of A16, B16, C16, G1 and G2. The physical (density and water absorption) and the mechanical (compressive strength) properties are determined conducting the standard tests at the age of 28th days after a standard 22±2oC water curing. Also, a criterion weighting method such as Entropy Method is used in the evaluation of the properties of concretes and the weights of the properties of concretes are determined. Then, TOPSIS is used to find the best concrete in consideration of the design parameters and test results for the selection of the optimum AGC. As a result, the influence of AGC on the properties of natural aggregate concretes (NACs) and RACs are unsimilar and while A16 results in a denser NAC with higher compressive strength, C16 can be offered to decrease the open pore content of RAC in terms of water absorption leading a durable concrete with a higher compressive strength. Besides, the results of Entropy Method present interesting findings, and the coarse aggregate ratio in the mix is found as the most effective parameters among the investigated design parameters. However, the best AGCs are found as A16 for NAC and G2 for RAC according to TOPSIS results. It is concluded that further investigations are required.

Applying of No-fines concretes as a porous concrete in different construction application

Recently, the demands on the concretes with no fines aggregate has been increased as a results of the industry revolution. Many researchers are trying to recycle the concretes and rubble. In addition, the increase in noise in the surrounding environment as a result of the growing population and cars has generated an urgent need to produce concretes characterized by good sound insulation. No-fines concretes is considered as a kind of porous lightweights concretes, gained by removing the sand from the ordinary concretes mixture. The aim of this study is replace the coarse aggregate by waste ceramics in order to reduce the wastes as well as investigate strengths against compression s, density and porosity of No-fines concretes before and after substitution the coarse aggregate by waste ceramics. The methodology of this research paper has been mainly depending on strengths against compression s test and the measured ultrasonic pulse velocity as well as the density. The investigational research has been implemented by 54 samples cast by six various blending proportion consisting of (cement, coarse aggregate, water) utilizing ceramic wastes (CWs) as a substation ratio of coarse aggregates in making concretes free of fine aggregate, so that the proportions of ceramic residues are (0, 10%, 20, 30, 40, 50) as a partial substation of the coarse aggregates and examined at the ages of (7, 28 and 90) days. The mechanism of failure has been detected and categorized beside the concrete’s density and void percentage have been collected. The results show that, the increasing the substitution ratio for waste ceramic within the no-fine mixtures cause a decrease in the density with increasing the strengths against compression s for the specimens.

Shear Behavior of Reinforced Post-Filling Coarse Aggregate Concrete Beams Produced by Creative Construction Process

Different from the traditional concrete mixing procedure, the innovative post-filling coarse aggregate concrete (PFCC) reduces the cost of pumping concrete by increasing the coarse aggregate content and reducing the usage of cement. Previous studies have shown that PFCC enhances the compressive strength, elastic modulus, and flexural strength of concrete. In this paper, the shear behavior of 13 post-filling coarse aggregate concrete beams and 3 control beams was tested to determine the relationships between the shear performance of the beam and the post-filling coarse aggregate ratio, concrete strength grade, shear span ratio and stirrup reinforcement ratio. The results showed that the ultimate shear capacity of beam specimen increases first and then decreases with the increase in post-filling coarse aggregate ratio, reaching the maximum at 15% post-filling ratio. The results also indicated that the ultimate shear capacity of the beam increases with the increase in concrete strength grade and stirrup ratio. However, experimental results exhibited that the ultimate shear capacity decreases as the shear span ratio increases. This study provides a reference for the application of post-filling coarse aggregate concrete in engineering practice.

Impact of Magnetically Treated Water on Compressive and Flexural Strength of Concrete

This study was conducted to determine the effect of Magnetically Treated Water (MTW) on compressive, flexural and impact strengths of concrete. The compressive strength, flexural and impact test were determined using 100 mm cube, 100x100x500 mm, 100mm diameter and 64 mm high, respectively. MTW was produced by passing water through magnetic flux densities: 400(T1), 600(T2), 800(T3) and 997G(T4) as the treatments while Non-MTW (NMTW, T0 as control). The ratio of cement, fine aggregate and coarse aggregate was 1:2:4 and curing duration for the concretes were 7, 14, 21 and 28 days. Universal Testing Machine was used to determine the compressive and flexural strengths while drop weighing impact tester was used for determining the impact strength of the concrete. The mean forces at peak to break the concrete cured for 28 days for T0, T1, T2, T3 and T4 were 106.79, 121.25, 114.15, 107.06 and 196.68 kN, while the compressive strengths were 10.68, 12.13, 11.42, 10.71 and 19.67 Nmm-2, respectively. The maximum compressive, flexural and impact strengths of the concrete were 84.17, 22.37 and 96.93%, respectively. The effect of MTW was statistically significant on compressive, flexural and impact strengths and is recommended for use.

The study on bond-slip constitutive model of steel-fiber high-strength recycled concrete

The central pull-out tests were performed on C60 steel-fiber high-strength recycled concrete (SFHSRC) under the monotonic load. The failure mode characteristic of the specimens and the direction of the cracks were observed and described. The bond strength and slip displacement were measured. The effects of two parameters, replacement ratio of recycled coarse aggregate (RCA) and addition ratio of steel fiber, on failure mode and bond-slip mechanicals behaviors of SFHSRC were also analyzed. The experimental results showed that when the replacement ratio of RCA was kept unchanged, the slip displacement of rebar increased with the increase of addition ratio of steel fiber, but the bond strength increased first and then decreased; with the addition ratio of steel fiber was remained unchanged, the bond strength and slip displacement of rebar decreased with the increased of the replacement ratio of RCA. The bond strength and slip displacement mentioned above reached the maximum when the steel fiber addition ratio was 0.8%; that is, when the replacement ratio of RCA was 0 and the addition ratio of steel fiber was 0.8%, the bond strength reached the maximum. Based on the theoretical analysis of experimental data, a reasonable bond-slip constitutive model was established in this paper, which can help promote more extensive application of RAC and realize persistent development strategy of building, resources and environment to a certain extent.

Influence of Asphalt Concrete Internal Structure on their Packing and Mixture Properties

Hot Mix Asphalt (HMA) pavement is most used in road construction in Iraq due to its economic benefits and ease of maintenance. Several factors are affecting the performance of HMA in the field. One of the major factors is aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) specifies limits for the different types of asphalt layers and allows tolerance for the designed aggregate gradation. In the current asphalt industries, it quite difficult for contractors to achieve the required job mix due to difficulties in sieves control. This study concentrates on the effect of aggregate gradation deviations on the required specification performance. A mid gradation of the binder asphalt mixture was selected as a reference mix and more than 20 deviated mixtures were then prepared. Typical Marshall routine trials were performed on the prepared admixtures to evaluate the mixture properties. Bailey packing theory for mixture evaluation (Coarse Aggregate Ratio CA, Coarse Portion of Fine Aggregate FAc ratio) was also used to understand the impact of these deviations on the particle arrangement and mixture performance. Results showed that minor aggregate deviations do not greatly affect the mixture performance, however, a large deviation in coarse aggregate results in a drop in Marshall properties. Results showed that the Bailey method for performance evaluation is a good tool to understand the mixture performance. This paper aims to study the influence of aggregate gradation deviations on the mixture performance.

Influence of GFRP Vertical Stirrups Using NSM Technique on Shear Behavior of Reinforced Concrete Beams with Recycled Coarse Aggregate

Shear strengthening with GFRP rods is the focus of this paper on concrete beams that contain aggregate replacement ratios of thermstone and bonza (pumice materials), obtained from the rubble of demolished buildings. A total of nine beams (2400×160×300mm dimensions) were loaded under a four-point bending load test. The parameters examined in this research were the replacement ratio of lightweight coarse aggregate (20% and 30% volumetric ratio), type of lightweight aggregate replaced by (thermstone or bonza) and strengthened in shear by GFRP rods using NSM technique. The characterization of the tested beams includes ultimate load, failure mode, load-deflection curve, load strain curves of stirrups, bottom longitudinal rebars, GFRP rods at the shear zone of concrete. The results showed that the use of GFRP rods to strengthen concrete beams was effective. As the failure mode was transformed from a shear failure in the reference beam that was cast using normal concrete to a concrete compression failure in the beams which was occurred when using suitable and sufficient amount of strengthening by GFRP rods for selected used lightweight aggregate replacement ratios.

OPTIMIZING MIXTURE OF SELF-COMPACTING CONCRETE FOR CONSTRUCTING A SPILLWAY SURFACE STRUCTURE

A spillway apron is a popular hydraulic work with congested reinforcement and complex shapes. Self-compacting concrete (SCC) with excellent workability can meet the technical requirements for the work. This study focuses on determining the SCC optimal mix for efficient use of local coarse aggregates and 100% crushed sand to construct a spillway surface structure. For the purpose, research steps were carried out as follows: (1) optimize mix ratio of coarse aggregates ; (2) determine the saturatedcontent of superplasticizer, (3) design SCC preliminary mix; (4) set up an experimental plan; and (5) analyzetest data to point out the optimal SCC mix.The investigation of fresh SCC was conducted by slump flow test, slump flow time test,L-box test, and segregation resistance test. Compressive strength, watertightness, and underwater abrasion of hardened SCC were also evaluated. The abrasion tests follow the ASTM C1138-19 method and Yu-Wen Liu’s method.The results show that the optimal SCC with slump-flow of 72 cm, the H2/H1 ratio of 0.85, compressive strength at 28 days of 42.5 MPa,abrasion resistance of 0.34 g/cm2; and watertightness of B10 meets specifications of a spillway surface structure. Besides, the abrasion depth measured by Yu-Wen Liu's method of water-borne sand was about four times greater than that of ASTM C1138-19.

Characterization of Coconut Shell Ash and Eggshell Powder as Supplementary Cementitious Materials in Roller Compacted Concrete Industrial Access Pavements and Parking Facilities

Abstract The cost of cement used in concrete works is on the increase and unaffordable, yet the need for hydraulic cement concrete and other cement concrete based infrastructures keeps growing with increasing population, thus the need to find alternative binding materials that can be used solely or in partial replacement of cement. The use of waste materials with pozzolanic properties in concrete production is a becoming a worldwide practice. The assessment of the pozzolanic activity of cement replacement materials is becoming increasingly important because of the need for more sustainable cementing products. In this study, a mixture of coconut shell ash and eggshell powder is used as partial replacement of hydraulic cement in ranges of 0%, 5%, 10%, 15%, and 20%. The concrete specimens were prepared at 1: 3: 2.5 mix ratio of cementitious material, fine aggregate and coarse aggregate. The mix ratio satisfied the minimum cement content of 148.32kg/m3 (250Ib/yd3) and the minimum cementitious material content of 267 kg/m3 (450Ib/yd3) for roller compacted concrete pavement. The compressive strength, splitting tensile strength and flexural strength tests were carried out to assess the strength characteristics of ternary concrete mixture containing coconut shell ash and eggshell powder and the feasibility of using coconut shell ash and eggshell powder as partial replacement of cement in industrial plant access concrete roads and parking lots. The results indicate that a mixture of coconut shell ash and eggshell powder can be used up to 20% by weight for replacement of cement in roller compacted industrial plant access concrete roads and parking lots.

Flexural performance of reinforced concrete beams made by innovative post-filling coarse aggregate process

Concrete made by post-filling coarse aggregate process could reduce the cement content greatly compared with traditional concrete placement method. Thus, it not only lowers the production cost of concrete through lower usage of cement but also reduces the CO2 emissions to the environment. In this paper, the compressive and tensile strength of post-filling coarse aggregate concrete with different post-filling ratios (PFRs) (0%, 10%, 15%, 20%, 25%, 30%) and concrete strength grades (C30, C40, C50) were first studied. Then the flexural performance of nineteen concrete beams with different concrete strength, post-filling ratios, reinforcement ratios was investigated. The experimental results showed that the compressive strength and elastic modulus of the post-filling coarse aggregate concrete increased with the increase of the post-filling ratio of coarse aggregate, reaching the peak value at the filling ratio of 20%. It indicated that there was no obvious difference in the failure mode as well as middle-span deflections between post-filling coarse aggregate concrete (PFCC) beams and ordinary concrete (OC) beams. Ductile failure was observed for all nineteen specimens. Results demonstrated that the cracking load, yield load, and ultimate load of the post-filling coarse aggregate concrete beams all reached the peak value at the post-filling ratio of 20%. In addition, the theoretical predictions of cracking loads and ultimate load carrying capacities matched the experimental results in satisfactory agreement.

Study on strength test and hydration mechanism of phosphogypsum based cemented backfill

In view of low early strength of phosphogypsum based slag cementitious material, exploration test of filling body strength is developed to get the optimal ratio of cementitious materials. Firstly, the physicochemical analysis of the test material was carried out; secondly, the cementitious material ratio and strength of waste rock coarse aggregate filling body was tested by orthogonal test and range analysis. In the end, the hydration products and microstructure of cementitious materials were analyzed by XRD and SEM. The results show that, for the slurry with waste rock coarse aggregate, 1:4 cement sand ratio and 80% mass concentration, the optimal ratio of cementitious materials is determined as phosphogypsum 30~33%, quicklime 5.5~6.0%, NaOH 1.5~2.0%, mirabilite 2.5~3.0%. The average particle size of cementitious material is - 16μm, and the early strength agent or synergist must be added, which could meet the requirements of the Jinchuan mine.

Strength of Concrete with Recycled Manganese Slag

This paper studies the effect of replacing coarse aggregates with manganese slag on the mechanical properties of concrete. Air-cooled granulated manganese slag was used. The control sample was designed to achieve concrete strength of 30 MPa at 28 days. Tests were conducted on five different compositions of concrete having manganese slag to coarse aggregates ratios of 0, 0.2, 0.3, 0.4, and 1. The specimens were tested at 7, 14, and 28 days for their compressive and flexural strength. Test results revealed that all manganese slag concrete specimens had improved compressive and flexural strength. The maximum compressive strength achieved was 43.54 MPa, increased by 16% of the control specimen and the maximum flexural strength achieved was 4.50 MPa, increased by 22% of the control specimen. Both results were obtained in concrete with 0.4 manganese slag to coarse aggregate ratio. Besides, the study also showed that it might be possible to substitute all coarse aggregates in concrete with manganese slag without any loss in strength. However, it was observed that the concrete workability decreased when manganese slag was added. Nonetheless, this could be corrected using superplasticizer.

Research studies on composition of porous concrete on the sidewalk

In infrastructure development, technology is needed that is powerful, effective, efficient in implementation time, efficient, and environmentally friendly. Porous concrete has a cavity that can flow water directly into the ground so that it can overcome the problem of water absorption. Porous concrete can be utilized in the pavement with light traffic loads such as the sidewalk. However, because porous concrete only consists of a mixture of cement, water, and coarse aggregate, porous concrete has a low compressive strength. The research is needed on the composition of porous concrete to be used on the sidewalk. Research using the ACI-522R-10 method with a variation of the ratio of cement and coarse aggregate is 1: 3, 1: 4, 1: 5, 1: 6 and cement water factor 0,30. The test results obtained the highest average compressive strength value of 16.027 MPa with an increase of 45.30% compared with no additives, as well as being in the classification of concrete brick of C quality which is suitable for the sidewalk. The results showed that an increase in the average compressive strength value along with a reduction in the amount of coarse aggregate was obtained both under conditions and with the addition of additives.

The concept of geotechnology with a backfill is the path of integrated development of the subsoil

The article describes a modern approach to the technology of backfilling of working space, taking into account the sustainable development of mining. The aspects of economic efficiency, safety and ecology are considered. A detailed analysis of various backfilling methods that are used in modern enterprises is given. The advantages and disadvantages are given. The article describes in detail the work carried out in this area at the Mining Institute of NUST “MISiS”. One of the directions is the study of the possibility of using local natural materials or waste products as backfills. In particular, studies were carried out on the formation of backfill arrays based on sulphide-containing and halite tailings. The issues of influence on the quality of the backfill as the granulometric composition and ratio of coarse and fine aggregates, as well as their quantity per unit of volume, amount of water (water binding ratio), method of preparation, transportation and styling, conditions (temperature) and age of hardening are also considered.

Shielding Properties of Heavyweight Concrete.(Dept.C)

Heavyweight concrete can be used when particular properties, such as combined high strength and good radiation shielding, are required. Such concrete, using Ilmenite aggregates, can have a density in the range 4.2 t/m3, significantly higher than the density of concretes made with normal aggregate. The present paper deals with sand-llmenite heavy weight concrete, llmenite has been used as coarse aggregate because of high specific gravity compared with gravel. In the present work, 21 mixes were selected to achieve a slump above 5± 2 cm and strength up to 40 MPa at 56 days. The investigation used three levels of fine aggregates to total aggregates ratio (0.25, 0.4, 0.48), three cement content (350, 400, 450 kg/m3) and four levels of llmenite aggregate to total coarse aggregate (gravel + Ilmenite) ratio (0.25, 0.5, 0.75, 1) were used. The investigation provided information on compressive strength, shielding properties and indicated clear benefits from the use of lImenite as a coarse aggregate. For all type of coarse aggregate (gravel, Ilmenite), increasing the amount of fine aggregate leads to reduction in each of compressive strength and absorption co-efficient. Replacing the gravel with llmenite yields about 35% increase in absorption co-efficient.

Strength and abrasion performance of recycled aggregate based geopolymer concrete

This experimental work evaluated geopolymer concrete containing fly ash and slag by partial replacement of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) to manufacture environmental-friendly concrete. The proportion of recycled aggregates considered consists of 10%, 20%, 30%, and 40% of the total coarse aggregate amount. Also, a steel fiber ratio of 0.3% was utilized. The mechanical properties and abrasion resistance of fly ash/slag-based geopolymer concrete were then assessed. Majorly, the mechanical strength of the concrete samples decreased by the increase of RCA content. The geopolymer concrete with 40% RCA gave 28.3% lesser compressive strength and 24% lower splitting tensile strength than NCA concrete at one year. Also, the flexural strength of concrete specimens was reduced by 35% (from 5.34MPa to 3.5MPa) with the incorporation of 40% RCA. The incorporation of 30% RCA caused 23% and 22.6% reduction in compressive strength at 56 days and one year, respectively. The flexural and splitting tensile strength of the specimens was not significantly reduced (less than 10%) with the inclusion of a recycled coarse aggregate ratio of up to 30%. Furthermore, the abrasion wear thickness of every concrete sample was less than 1mm. RCA inclusion of 20% produced either insignificant reduction or better strength results compared to reference mixtures. As a result, it was considered that the combination of 0.3% steel fiber and 20% recycled coarse aggregate in fly ash/slag-based geopolymer concrete leads to an eco-friendly concrete mix with acceptable short and long-term engineering properties that would lead to sustainability in concrete production and utilization sector.

Optimization of the Fine to Coarse Aggregate Ratio for the Workability and Mechanical Properties of High Strength Steel Fiber Reinforced Concretes.

High-strength concrete is used to provide quality control for concrete structures, yet it has the drawback of brittleness. The inclusion of fibers improves the ductility of concrete but negatively affects the fresh properties of fiber-reinforced concrete. The effects of different fine to coarse aggregate ratios on the fresh and hardened properties of steel fiber reinforced concrete were investigated in this study. Mixtures were prepared with various fine to coarse aggregate (FA/CA) ratios incorporating 1% steel fiber content (by volume) at constant water to cement ratio. The workability, unit weight, and temperature of the concrete in the fresh state, and the mechanical properties of steel-fiber-reinforced concrete (SFRC) were investigated. The inclusion of fiber in concrete influenced the mobility of concrete in the fresh state by acting as a barrier to the movement of coarse aggregate. It was observed that the concrete with an FA/CA ratio above 0.8 showed better flowability in the fresh state, whilst an above 0.9 FA/CA ratio requires excessive superplasticizer to maintain the flowability of the mixtures. The compressive and flexural strength of SFRC increased with an increase in the FA/CA ratio by around 10% and 28%, respectively. Experimental values of compressive strength and flexural strength showed good agreement, however, modulus of elasticity demonstrated slightly higher values. The experimentally obtained measurements of the mechanical properties of SFRC conformed reasonably well with the available existing prediction equations, and further enabled establishing predictive isoresponse interactive equations within the scope of the investigation domain.

A new empirical model for predicting complex modulus of asphalt concrete materials

Asphalt concrete materials are often used in the construction of pavement layers. The complex modulus is one of the fundamental properties in mechanistic-empirical pavement design and analysis that can describe the mechanical response of this composite material. In the present study, a new complex modulus predictive model of asphalt concrete, called 9P50F has been established. The main objective of the paper is to develop a predictive empirical equation for the Moroccan pavement design guide based on several complex modulus tests and an existing database of asphalt concrete formulations. The proposed model equation depends on the results of classical tests that related to the most significant formulation parameters including, stiffening effect and proportion of mineral fillers, maximum aggregate size, ratio of coarse aggregates to sand, penetration point, ratio of fillers to asphalt binder, apparent density, softening point, and binder richness modulus. As a result, the developed model provides a higher correlation coefficient (R2 = 0.873). Furthermore, based on the complex modulus measurements of twenty-one asphalt concrete samples, by using a 2-point bending device, the goodness of fit measure for the E* predictions indicates a very good accuracy.