Single-sized Aggregates Research Articles

Development of Aggregate – Cement Design Curves for the Production of Concrete Mixes for Different Grades of Concrete

Developing aggregate-cement design curves tailored to different concrete grades using locally sourced materials is critical for the growth of Nigeria's construction industry. Such curves provide a systematic approach for optimizing project-specific concrete mixes, enhancing cost-effectiveness, and ensuring structural reliability. This study focuses on creating these design curves by examining the engineering properties and characteristics of raw materials commonly available in Nigeria. Trial mixes were conducted with varying aggregate-cement ratios, and compressive strength tests were performed to identify the most suitable combinations. Using river sand, single-sized aggregates (10–20 mm), and limestone Portland cement, aggregate-cement curves were developed for concrete grades ranging from 20 MPa to 35 MPa. The COREN/2017/016/RC concrete mix design method was adopted to guide the research process. The study found that a mix of 35% fine aggregate, 65% coarse aggregate, and a water-cement ratio of 0.5 achieved optimal results, providing desired compressive strengths and slump values between 40 mm and 50 mm. These findings establish a framework for producing durable and efficient concrete mixes using locally available materials. This approach supports the need for sustainable construction practices in Nigeria, offering practical solutions for meeting diverse construction demands while ensuring material availability and affordability.

Study on the Basic Mechanical Properties and Discrete Element Method Simulation of Permeable Concrete

Permeable concrete pavement material has many voids and a good water permeability, which can reduce surface runoff and alleviate the problem of urban water logging. It also has the functions of acting as a supplementary source of groundwater, purifying water, bodies reducing the urban heat island effect, reducing road noise, and so on. It is an effective solution for urban infrastructures. However, at the same time, because it has a large number of pores, this also affects the strength of permeable concrete. The main factors affecting permeable concrete are particle size and the shape of the aggregate, the content of the cement paste and aggregate, the compaction degree of the mixture, and so on. In this study, the single-factor test method was used to study the effects of aggregate size, slurry-to-bone ratio and loose paving coefficient on the basic mechanical properties and permeability of permeable concrete. Here, the numerical model for permeable concrete is established by using the particle flow discrete element (Particle Flow Code (PFC)modeling method, and a numerical simulation test is carried out. It can be seen from the test results that the permeability coefficient of 50% 5–10 mm + 50% 10–15 mm mixed aggregate permeable concrete is slightly lower than that of 5–10 mm and 10–15 mm single-size aggregate, but has a higher compressive and splitting tensile strength. With the increase in paste-to-bone ratio, the permeability coefficient of permeable concrete decreases, and the compressive strength increases. The loose paving coefficient has a significant effect on the mechanics and permeability of permeable concrete with the increase in the loose paving coefficient, the water permeability decreases and the compressive strength increases. The numerical simulation results show that under the condition that the loose paving coefficient is 1.10 and the slurry-to-bone ratio is 0.5, compared with the experimental results, the error of the numerical simulation results of the compression test is less than 3%. The reliability of the simulation is verified. The discrete element modeling method in this study can be used to simulate the shape of the aggregate in permeable concrete, and the numerical model can effectively simulate the crack development and failure form of permeable concrete in compression tests.

Study on the dynamic fracturing characteristics of aggregate-mortar interface under various loading rates using DIC

Study on the dynamic fracturing characteristics of aggregate-mortar interface under various loading rates using DIC

Effect of Aggregates Packing with the Maximum Density Methodology in Pervious Concrete

The granulometric distribution of the aggregates used in pervious concrete can significantly impact its mechanical and hydraulic properties by modifying granular skeleton and pore distribution. The unit weight increases when single-sized aggregates are combined, which results in improved mechanical properties. In this study, the maximum density methodology was applied to enhance pervious concrete’s mechanical strength by using three narrow-sized basaltic aggregates and their combination. The experimental results showed that the mechanical performance of the samples created with packed aggregates improved compressive strength by up to 81.2% and the energy support impact was higher than 225 J (50% higher than the reference sample) after curing for 28 days. Although the densification of packing aggregates increased, the greatest reduction in porosity was 24.3%. The lowest infiltration rate was 0.43 cm/s, a satisfactory value according to the literature. These findings suggest that the aggregates packing methodology is effective in producing optimized and sustainable pervious concretes.

Influence of coarse aggregate granulometry on clogging in pervious concrete

The phenomenon of clogging in pervious concrete (PC) has been one of the main causes of the hydraulic useful life reduction. This phenomenon begins with the partial or total clogging of the pore network and consequently the reduction of the permeability coefficient. Considering that the porous network of the PC is directly related to the aggregate used, the present work aims to evaluate the influence of granulometry on the clogging of the PC. The results showed that the largest aggregate size (D_max=19 mm) favors the hydraulic properties of the material. However, the variation of the granulometry grading distribution (poorly graded and single-sized) does not generate a significant difference in such results. In terms of clogging, there was a marked effect on the type of the granulometry grading distribution, the use of poorly graded aggregates led to a lower permeability reduction due to clogging when compared to PCs with single-sized aggregates.

Effect of Coarse Aggregate Size and Gradation on Workability and Compressive Strength of Plain Concrete

In this study effect of coarse aggregate size and gradation on workability and compressive strength of concrete was investigated. A mix ratio of 1:2:4 with a target strength of 20/25MPa, was adopted with a water-cement ratio of 0.6. Concrete cubes were produced with uniform coarse aggregate size of 4.75, 6.7, 9.5, 13.2 and 19mm respectively, with another set of samples produced with all the coarse aggregate sizes. Slump tests were carried out for all mixes and all sets of samples were tested for compressive strength after, 7, 14 and 28 days of curing. It was observed that workability was similar for all mixes with no well-defined pattern of relationship with size of coarse aggregate used. Compressive strength was observed to increase with increase in coarse aggregate size. Authors attributed this to the less quantity of water absorbed by larger size coarse aggregate during mixing which results in lesser quantity of capillary pores after curing. Maximum compressive strength was recorded for samples with 9.5mm coarse aggregate size. These show that quality concrete can still be produced with single-sized coarse aggregate as long as the optimum size can be determined for the particular mix.

Plant-growing performance of pervious concrete containing crushed oyster shell aggregate

Global warming is the gradual increase in global temperatures owing to trapping of heat in the atmosphere by greenhouse gases. As of January 2020, 121 countries and 1 region, including Japan, pledged to achieve carbon neutrality by 2050. One of the measures for achieving this goal is the promotion of low-carbon urban development, which includes urban greening. Oysters are produced in all districts of Japan but Hiroshima Prefecture is particularly famous for its high production levels. The production of oysters generates oyster shells as a by-product, which are used commercially as livestock feed and a soil conditioner. However, the reuse of oyster shells remains limited. Pervious concrete is a special type of concrete in which single-sized aggregates are bound together with cement paste or mortar and is considered an environmentally friendly material because of its high water permeability. Therefore, we investigated whether oyster shell pervious concrete (OyPC) containing crushed oyster shell aggregate would be suitable for growing plants for potential application as a planting foundation for urban greening. Zoysia tenuifolia sod or Kentucky bluegrass ( Poa pratensis ) seeds were directly placed or sown in soil on the surfaces of OyPC and crushed stone pervious concrete specimens, which were then placed in plastic containers for either 72 days (short-term planting tests) or 802 days (long-term planting test). OyPC had a higher plant-growing performance than crushed stone pervious concrete in both the short- and long-term planting tests and also pumped the water from the container to moisten the sod and the soil covering the seeds, assisting the growth of plants. The grass on OyPC that has a small particle size could grow without water retention material which is indispensable to crushed stone pervious concrete for greening. These findings indicate that OyPC would be feasible for application as a planting foundation for urban greening.

Quality of cold-mix asphalt in bituminous pavement maintenance in Ghana: Preliminary indications

Prevalence of premature patch failures in bituminous pavement maintenance in Ghana, involving pothole and partial-depth repairs using cold-mix asphalt (CMA), has become a major concern as the failures call for repeated patching in the face of limited maintenance budget and repeated disruption to traffic. The most commonly documented failures associated with CMA patches in the country are disintegration, shoving, and dishing. All three failure modes suggest a deficiency in binder coupled with a weakness in aggregate functionality often attributable to a compromised aggregate skeletal structure lacking sufficient interlock/load-bearing ability resulting in a patch with no rigidity and stability. In this study, samples of stockpiled ready-to-use cold-mix asphalt concrete from six contractor sites and three failed patches from roads in the Ashanti, Volta, and Bono Regions in Ghana, were investigated to assess material quality. Bitumen extraction, aggregate gradation, stability, and volumetric analysis of compacted specimens were carried out on the samples. The results indicated poor CMA aggregate structure which consisted essentially of single-sized aggregates having uniformity coefficients between 4 and 6 and residual asphalt contents between 3% and 6%. All mixtures formulated using bitumen emulsion binder had values lower than those formulated with cutbacks and none satisfying specifications. Specimens compacted in the laboratory disintegrated during conditioning for stability and flow test, suggesting the absence of stickiness and cohesion within the compacted matrix. Our results suggest that pothole patching failures prevalent in the country may be blamed principally on inadequate aggregate structure and low binder content of the CMA mixes.

Toughness Behavior of SBR Acrylate Copolymer-Modified Pervious Concrete with Single-Sized Aggregates.

Pervious concrete is an eco-efficient concrete but has problems regarding its mechanical performance and permeability balance. This research investigated the feasibility of using a combination of styrene–butadiene rubber (SBR) and acrylate polymer to improve the toughness of pervious concrete while keeping its permeability. Single-sized aggregate and no sand were considered in the concrete mixture. Acrylate polymers with different solid content, PH, density, and viscosity were emulsion copolymerized with an SBR polymer. Eleven scenarios with different mix proportions and 220 specimens for compressive strength, flexural strength, flexural stiffness, impact resistance, and fracture toughness tests were selected to evaluate the effects of the copolymer on the toughness of copolymer-modified pervious concrete (CMPC). The studies showed that (1) the influence trend of the copolymers generally varied according to different mechanical indexes; (2) XG–6001 acrylate polymer mainly and comprehensively enhanced the toughness of the CMPC; (3) it was difficult to increase the enhancing property of the XG–6001 acrylate polymer with the growth of its mix proportion; (4) the zero-sand pervious concrete with 90% SBR and 10% XG–6001 acrylate emulsion copolymerization proved to have relatively high toughness. The proposed CMPC holds promising application value in sustainability traffic road construction.

Behavior of Pervious Concrete Pile based on Vertical Loading

Permeable granular piles are used to increase the time rate of consolidation, reduce liquefaction potential, improve bearing capacity, and reduce settlement. However, the behaviour of granular piles depends on the confinement provided by surrounding soil, which limits their use in very soft clays and silts, and organic and peat soils. This research effort aims to develop a new ground-improvement method using pervious concrete piles. Pervious concrete piles provide higher stiffness and strength, which are independent of surrounding soil confinement, while offering permeability comparable to granular piles. This proposed ground-improvement method can improve the performance of different structures supported on poor soils. To achieve the goal of the research project, a series of pervious concrete sample mixing has been conducted to investigate the pervious concrete material properties. Laboratory tests are carried out on a pervious concrete pile of 100 mm diameter and variation at different lengths (500mm,400mm,300mm) surrounded by sand of different density. The tests are carried out either with an entire equivalent area loaded to estimate the stiffness of improved ground or only a column loaded to estimate the limiting axial capacity. Pervious concrete is a special concrete product made primarily of a single-sized aggregate. Pervious concrete has been used in pavements to reduce storm-water-runoff quantities and perform initial water-quality treatment by allowing water to penetrate through the surface. In the United States, pervious concrete is mainly used in pavement applications, including sidewalks, parking lots, tennis courts, pervious base layers under heavy-duty pavements, and low traffic-density areas. The vertical load responses of pervious concrete are the variation of soil stresses and displacement are discussed. Nine tests are conducted on pervious concrete pile further investigate the behaviour of the pervious concrete pile and surrounding soil under vertical load condition. Therefore, Pervious Concrete Piles is particularly suitable for reinforcing subsoil that has low strength and poor permeability.

Investigation of aggregate size effects on properties of basalt and carbon fibre-reinforced pervious concrete

Pervious concrete structure consists of meso-sized pores due to partial or complete elimination of fine aggregates, resulting in decreased mechanical properties in par with conventional concrete. Meanwhile, fibres were pronounced to improve the mechanical properties of concrete without affecting its durability. The main objective of the study is to compare the properties of basalt fibre-reinforced pervious concrete (BFRPC) and carbon fibre-reinforced pervious concrete (CFRPC) with two single-sized aggregates, namely 12.5 and 20 mm. The volume of both the fibres was varied from 0 to 0.4% at intervals of 0.1%. Pervious mix with 12.5 mm sized coarse aggregates and carbon fibre content of 0.2% (12.5CFRPC0.2) was observed as an optimum mix with respect to mechanical strengths as it improved the compressive strength, split tensile strength and flexural strength by 11.59%, 32.70% and 35.32%, respectively, compared with the conventional mix.

Model Test on the Vibration Reduction Characteristics of a Composite Foundation with Gravel Cushion under Different Seismic Wave Amplitudes

Gravel cushions have been introduced as a practical and efficient seismic isolation technology to ensure the safety of nuclear power plants. This study investigated the seismic isolation effect of a gravel cushion by conducting a series of shaking table tests on a model foundation with a cushion built of three different types of graded aggregates (single-sized (2–5 mm), two-sized (2–5 mm:5–10 mm = 3 : 1), and continuously graded) under input El Centro seismic waves with three different peak accelerations (0.1 g, 0.2 g, and 0.3 g). The testing results showed that the seismic isolation effect of the gravel cushion increased with the peak seismic acceleration. The gravel cushion built with single-sized aggregates had better seismic isolation performance than gravel cushions built with two-sized or continuously graded aggregates. Under input seismic waves with 0.1 g peak acceleration, the single-sized aggregate gravel cushion still had a seismic isolation effect with a vibration reduction rate of approximately 11.81%, whereas the other two gravel cushions had no effect. Under input seismic waves with peak accelerations of 0.2 g and 0.3 g, all three gravel cushions had seismic isolation effects with vibration reduction rates of approximately 18.63% and 17.92%, respectively. An empirical model is proposed for predicting the vibration reduction rate of the cushion. Under input seismic waves with 0.3 g peak acceleration, the ultimate vibration reduction rate of the gravel cushion fell between 20.44% and 31.33%. The gravel cushion is an excellent option for nuclear power plant foundations with high requirements for seismic isolation, provided that the required bearing capacity is satisfied.

Correlation between geometric parameters of coarse aggregates and mixing rheological indices of asphalt mixture

The workability of asphalt mixtures significantly influences the construction of the asphalt pavement. In this study, a mixing rheometer was developed to characterize the workability of asphalt mixtures during mixing and further to investigate the effect of coarse aggregates. In addition, the corresponding rheological indices for evaluating the mixing rheological properties were proposed, including the b value related to the initial mixing resistance and the k value related to the steady-state mixing resistance. Moreover, the correlation between the geometric properties of the coarse aggregate and the mixing rheological indices was established. Results show that the sieving diameter/shape index of single-size aggregates (SA) and single-size aggregate mixtures (SAM) exhibits a strong linear correlation with the rheological indice k value. The fluctuation of SAM’s mixing rheological indices was reduced by about 1 time compared with SA’s. Therefore, asphalt plays a lubricating role in the mixture to reduce mixing resistance and reduce the sensitivity of aggregate geometric characteristics to mixing rheological indices. As the aggregate size increases, the mixing rheological properties of the mixture deteriorate. During the initial mixing, the b values of SA, SAM and GAM are most sensitive to the aggregate shape index, angularity and sieving diameter, respectively. During the steady-state mixing, the aggregate sieving diameter is most sensitive to the mixing rheological indice k value, followed by the shape index, while the angularity is less sensitive to the k value.

A new approach for calculating aggregate stability: Mean weight aggregate stability (MWAS)

Abstract Many different methods have been proposed to determine aggregate stability. In most of these methods, certain aggregate size is used to estimate the aggregate stability of the whole soil. Determination of aggregate stability on a certain aggregate size is insufficient to represent the aggregate stability of the whole soil and the results are strongly dependent on the size chosen. Therefore, the determination of aggregate stability should include all aggregate sizes and the quantities of the soil investigated. The Mean Weight Aggregate Stability (MWAS) is a new calculation method, which is calculated by the sum of multiplying the proportional coefficient of each aggregate size (Wi) by the aggregate stability of each aggregate size (ASi). Soil samples collected from 15 different fields are separated into 17 different aggregate sizes by dry-sieving, weighted, and then aggregate stability of each size is determined using a Yoder type wet sieving apparatus. Aggregate stability was significantly affected by the aggregate size and, in general, stability increased as the size of dry aggregates increased (r = 0.934**). While the mean lowest aggregate stability value was determined in the

Effect of mix proportion on the structural and functional properties of pervious concrete paving mixtures

Abstract In recent years, pervious concrete pavement (PCP) is emerging as a novel pavement technology that is gaining a lot of attention amongst academicians due to its storm water runoff capabilities and mitigating urban heat island. This pavement technology consists of special types of concrete which has little amount of fines or no fines and interconnected voids. The different types of aggregate gradation, water-to-cement (w/c) and cement-to-aggregate, and compaction techniques with variations in efforts plays an important role in providing an optimum balance in the mixture designing of PCP mixtures. Therefore, the present study is an attempt to explore the possibility of variation of different aggregate gradation types with different proportion of w/c ratios for the production of PCP mixtures. Also, to study the effect of these mix properties on structural, functional as well as durable properties of PCP mixtures. Five aggregate gradation types and variability in w/c ratios were adopted in the present study viz. G1, G2, G3, G4 and G5, respectively. G1 and G2 consisted of larger-sized and well graded aggregates, while, G4 and G5 consisted of natural fines in proportion of 5% and 10%. Meanwhile, G3 consisted of binary blended single-sized aggregates: 30% of 10 mm and 70% of 4.75 mm. The above considered gradations were studied for porosity, density, permeability, compressive strength, flexural strength, and resistance to sulphate attack, at varied w/c ratios 0.30, 0.35, and 0.38, respectively. From an extensive laboratory investigation, it was observed that the G3 mix showed the best-balanced relation between all the afore-stated parameters, required for PCP mixtures. Hence, it can be recommended that the utilization of binary blended single-sized aggregates at a w/c ratio of 0.35 would provide an optimal solution keeping in mind the desired parameters of pervious concrete pavement mixtures are met.

A robust time-dependent model of alkali-silica reaction at different temperatures

Abstract Alkali-Silica-Reaction (ASR) is one of the most deteriorating phenomena in concrete structures. This study uses a machine learning approach (i.e. Artificial Neural Network) to provide further insight into ASR. The approach combines chemo-mechanical and kinetics-based approaches to develop a time- and temperature-dependent model of ASR, which is eventually used in generating user-friendly charts to conveniently assess existing concrete structures. To reach a higher degree of confidence in the precision of the model, an experimental dataset was developed from the laboratory and was combined with a dataset from the literature. A comparison between the developed model and a chemo-mechanical one (Gao's model) showed higher accuracy for the developed model. This higher accuracy was more obvious regarding the specimen with fine single-size aggregate grading. This study also reveals a varying thickness of connected porosity ( t c ) for fine single-size aggregate. Based on the results, aggregate size and t c have a coupled effect on the ASR-induced expansion.

Effect of Test Geometry and Aggregate Texture on Angle of Repose of Aggregates

Abstract Properties of asphalt concrete mixtures are significantly affected by aggregate properties. Previous studies have indicated that Angle of Repose (AoR) is an indicator of aggregate properties, including texture, angularity, and shape. In this research, the effect of test geometry and aggregate texture on the AoR of aggregate is evaluated. Aggregates from two different sources were synthetically processed in a laboratory to obtain particles with different textures while retaining other characteristics. The AoR of single-sized aggregates was measured with different test geometries. The test results indicate that measured AoR was sensitive to aggregate texture and test geometry. The relation between aggregate size and AoR exhibited a positive correlation. The direct shear strength test parameters were able to capture the changes in aggregate texture and AoR. The angle of internal friction showed a positive and linear variation with AoR, irrespective of test geometry. However, exact slope was specific to aggregate type and texture level.

Strength and abrasion characteristics of pervious concrete

In this paper, the influence of the size of coarse aggregate and aggregate/cement ratio on the strength and abrasion properties of pervious concrete is reported. Pervious concrete mixes are prepared with single-sized aggregates (4.75, 10 and 12.5 mm), blends consisting of three different aggregate sizes and aggregate-to-cement ratios of 3.2, 4.5 and 5. Experimental results indicate that the strength characteristics and abrasion resistance of pervious concrete decrease with increase in the size of aggregate as well as aggregate-to-cement ratio. As voids created by higher size aggregates were filled up by lower size aggregates, mixtures with blended aggregates achieved the lowest void content. Existing equations relating splitting-tensile and flexural strengths with cube compressive strength is verified. As density increases, void content of pervious concrete mixtures decreases. A simple regression model relating abrasion resistance index, which is defined as the ratio of square root of dimensionless number of revolutions to weight loss/initial weight of specimen in Cantabro test, to cube compressive strength of concrete is proposed. The developed model had reasonable goodness of fit, which indicated high accuracy.

Laboratory Investigations and Field Implementation of Pervious Concrete Paving Mixtures

Abstract Pervious concrete (PC) is a sustainable concrete material that is being used as a strategy for reducing stormwater-related runoff and recharging ground water. As part of a smart cities initiative of the Government of India, pervious concrete pavement (PCP) mixtures were studied in the laboratory for different properties and implemented in the field to function as parking lots and walkways. A labor-based methodology was used in the construction of eighteen PC slabs encompassing six different mixtures. The construction practices followed were rational and demonstrated to the field engineers how to carry the technology further. The field-produced mixtures had higher porosity and lower density compared to laboratory mixtures. The infiltration capacities (IC) of field PC slabs were similar to those determined in the laboratory. The single-sized graded mixtures depicted lower IC compared to the mixtures with graded aggregates, which was attributed to thicker cement paste coating in single-sized aggregates, while the mixtures with lower cement-to-aggregate ratio depicted higher IC. The coring procedure resulted in a loss of aggregates that may have provided erroneous values of the in-situ properties, and hence, a methodology is deemed essential to investigate the in-situ characteristics using nondestructive techniques. In the future, the differences in the porosity between field and laboratory mixtures should be accounted for in order to avoid an overestimation of the PC properties and to achieve rational designs of PCP as most of the properties are dependent upon porosity.

Investigation of the Porosity Distribution, Permeability, and Mechanical Performance of Pervious Concretes

Pervious concrete is a kind of porous and permeable material for pavements and slope protection projects, etc. In this paper, a kind of pervious concrete was prepared with Portland cement, silica fume (SF), polycarboxylate superplasticizer (SP), and limestone aggregates. The performance of concrete, such as its porosity, pore distribution, permeability coefficients, and mechanical properties, were studied through laboratory tests. The volumetric porosity was measured by the water displacement method, and the planar porosity and pore size distribution were determined using image processing technology. A permeameter with a transparent sidewall and an exact sidewall sealing method were used to measure the permeability coefficients accurately. The results show that the segregation index and flow values of pastes increased with the increase of SP and water cement ratio (W/C). The measured porosity (volumetric porosity and planar porosity) of pervious concrete with a single-size aggregate was closer to the design porosity than that with the blended aggregate. Compared with the design porosity selected in this study, aggregate size was the main factor influencing the pore distribution of pervious concrete. The standard deviation of the permeability coefficient was less than 0.03 under different hydraulic gradients. It was found that the relationships between the permeability coefficient and volumetric porosity (or effective pore size d50) approximately obey polynomial function. Based on the test results, the optimized parameters were suggested for practical engineering: W/C of 0.26–0.30; 0.5% SP content; 5% SF content; 15–21% design porosity; and aggregate sizes of 4.75–9.5 mm and 9.5–16 mm.