Coarse Aggregate Type Research Articles

Comparison of fracture behavior of set concretes based on natural and crushed aggregates

Abstract The studies were carried out to diagnose the effects of coarse aggregate type on the mechanical behavior of plain concretes under incremental loading. During the studies mechanical parameters including compressive strength (fcm) and splitting tensile strength (fctm), as well as fracture parameters involving critical stress intensity factor (K_Ic^S) and critical crack tip opening displacement (CTODc) were evaluated. Crushed aggregates covered: basalt (BA), granite (GT) and limestone (LM) and natural peeble gravel aggregate (GL) were used in the concrete mixtures. The composite made on pebble aggregate acted as a reference concrete, as it were, in the analysis of the test results. For better understanding of the crack initiation and propagation in concretes with different coarse aggregates, a macroscopic failure surfaces examination of the tested beams is also presented. Both of the analyzed fracture mechanics parameters, i.e. 〖 K〗_Ic^S and CTODc increased significantly in the case of concretes which were manufactured based on crushed aggregates. They amounted in comparison to concrete based on gravel aggregate at levels ranging from 20% for concrete with limestone aggregate, to over 30% for concrete with a granite aggregate, and to as much as over 70% for concrete with basalt aggregate. Moreover, a clear correlation in the changes in the obtained results between the main strength parameters and fracture mechanics parameters was observed. The fracture process in each series of concrete was: quasi-plastic in the case of gravel concrete, semi-brittle in the case of limestone concrete, and clearly brittle in the case of the concretes based on granite and basalt aggregate. The results obtained help to explain how the coarse aggregate type affects the strength parameters and fracture toughness at bending.

Mechanical Characteristics of Hardened Concrete with Different Types of Cement and Aggregate Available in Bangladesh

This paper presents the results of an investigation on the influence of aggregate and binding material type on the mechanical properties of hardened concrete. To perform this investigation, four different types of coarse aggregate (Brick Aggregate, Recycled Brick Aggregate, Black Stone and Shingles) and eight types of binding material [Ordinary Portland Cement (OPC), CEM Type II B-M, CEM Type II B-M-SL, 40% OPC – 60% Slag CEM IIIA, 80% OPC – 20% Slag(CEM II/A-S), 70% OPC – 30% Slag(CEM II/B-S), 30% OPC –70% Slag(CEM-IIIB), 15% OPC –85% Slag(CEM-IIIC)] have been used. Aggregates were collected and prepared according to grading requirements of ASTM C33-03. Several tests as specific gravity, absorption capacity, unit weight and abrasion resistance were performed for coarse aggregate. Cylindrical concrete specimens of diameter 100 mm and length 200 mm were made with different W/C ratio (0.45 and 0.5) and cement content (340 kg/m3 and 400 kg/m3). A total of 42 different cases were considered for testing. The specimens were tested for compressive strength, stress-strain curve and Young’s modulus at the age of 28 days. Non-destructive test as Ultrasonic Pulse Velocity (UPV) were also performed. To conduct UPV test Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT) were used. The major objective of this study was to investigate the mechanical characteristics of concrete for different types of aggregate and binding materials. The significance of those results is discussed here.

Effect of Coarse Aggregate Type on the Fracture Toughness of Ordinary Concrete

This research work aims to compare the strength and fracture mechanics properties of plain concretes, obtained from different coarse aggregates. During the study, mechanical parameters including compressive strength (fcm) and splitting tensile strength (fctm), as well as fracture parameters involving critical stress intensity factor (KIcS) and critical crack tip opening displacement (CTODc) were evaluated. The effect of the aggregates used on the brittleness of the concretes was also analyzed. For better understanding of the crack initiation and propagation in concretes with different coarse aggregates, a macroscopic failure surfaces examination of the tested beams is also presented. Crushed aggregates covered were basalt (BA), granite (GT), and limestone (LM), and natural peeble gravel aggregate (GL) were used in the concrete mixtures. Fracture toughness tests were performed on an MTS 810 testing machine. Due to the high strength of the rock material, the rough surface of the aggregate grains, and good bonding in the ITZ area between the aggregate and the paste, the concretes with crushed aggregates exhibited high fracture toughness. Both of the analyzed fracture mechanics parameters, i.e., KIcS and CTODc, increased significantly in the case of concretes which were manufactured with crushed aggregates. They amounted, in comparison to concrete based on gravel aggregate, to levels ranging from 20% for concrete with limestone aggregate to over 30% for concrete with a granite aggregate, and to as much as over 70% for concrete with basalt aggregate. On the other hand, the concrete with gravel aggregate showed the lowest fracture toughness because of the smooth surface of the aggregate grains and poor bonding between the aggregate and the cement paste. However, the fracture process in each series of concrete was quasi-plastic in the case of gravel concrete, semi-brittle in the case of limestone concrete, and clearly brittle in the case of the concretes based on granite and basalt aggregates. The results obtained help to explain how the coarse aggregate type affects the strength parameters and fracture toughness at bending.

Axial compression behaviour of square steel tubes encased by and filled with high-strength recycled aggregate concrete

The axial compression behaviour of square steel tube (SST) columns encased with recycled aggregate concrete (RAC) and filled with RAC (RAC-encased RACFSST) columns was investigated. Using high-strength concrete, five specimens were tested under axial compression until failure. The experimental parameters included the coarse aggregate type, stirrup spacing, wall thickness of the SST and the existence of cross-tie bars in the SST. The failure mode, load–displacement curves, load–strain curves and ductility of the composite columns were obtained. The impacts of the various parameters on the mechanical performance of the RAC-encased RACFSST columns were evaluated. The failure modes of the composite columns were comparable. The inclusion of RAC enhanced the load-bearing capacity (LBC) of the column, but negatively affects its ductility and deformation capacity. Increasing the wall thickness of the SST and reducing the stirrup spacing significantly improved the axial compressive performance of the columns, as mainly reflected in the axial compressive capacity and ductility, respectively. Cross-tie bars inside the SST improved the LBC and deformation capacity. The axial bearing capacities of the columns and those in other studies were determined using existing codes. The computed results were very consistent with the experimental data.

Tension stiffening and cracking behaviors in glass fiber reinforced polymer bar enhanced precast recycled aggregate concrete specimen

Glass fiber reinforced polymer (GFRP) bar-enhanced precast recycled aggregate concrete (PRAC) elements combine PRAC’s environmental benefits with GFRP’s corrosion resistance, making them ideal for coastal urban infrastructure. However, in-depth research on the tensile stiffness and cracking behaviors of this composite is lacking. The significant mechanical differences between GFRP bars (low modulus, high strength) and PRAC, as compared to traditional materials, raise safety concerns for widespread use. This study investigates the short-term load capacity, deformation and cracking characteristics of GFRP bar-reinforced PRAC tensile specimens through tests and analyses. The tests examine how variables like water-to-binder ratio, coarse aggregate type, recycled aggregate (RA) content and mixing methods affect the specimens' mechanical responses. Theoretical analyses, using existing equations and a partial interaction model, clarify stress-strain relationships and crack propagation under applied loads, revealing: (a) As RA content increases, PRAC shows a moderate decrease in workability and mechanical performance. The strength variability in PRAC generally falls between that of natural aggregate concrete (NAC) and conventional recycled aggregate concrete (CRAC) using RAs from construction and demolition waste, being closer to NAC. Additionally, the strength conversion relation seen in NAC applies similarly to PRAC. (b) During tension at both ends of the specimen, PRAC's resistance decreases by 24.3 % compared to NAC but is still 20.3 % higher than CRAC. (c) The number of cracks in the PRAC specimen decreases with higher RA content and basalt fibers, while the ratio of stabilized load to cracking load increases. (d) The CEB-FIP standard offers more accurate predictions of the specimen’s composite stress-strain relation, while the Chinese code excels in predicting crack width. The partial interaction model effectively predicts the specimen’s load, deformation and crack characteristics by accounting for the behaviors and bonding of both PRAC and GFRP bars.

Investigating the influence of coarse aggregate characteristics and fiber dispersion on the flexural performance of ultra-high performance concrete (UHPC)

The flexural properties of ultra-high performance concrete containing coarse aggregate (UHPC-CA) strongly depend on the characteristics of coarse aggregates and the dispersion of fibers. However, the impact of the interaction between coarse aggregate and steel fibers on the bending performance of UHPC-CA is not well-understood. This study investigated the four-point bending properties of UHPC-CA to clarify the influence of coarse aggregates. Mechanical tests, laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), and image analysis were performed to investigate the impact of coarse aggregate on flexural properties, considering coarse aggregate properties, and steel fiber dispersion. The results indicate that coarse aggregates affect both bending strength and toughness. The type of coarse aggregate primarily influences bending strength, while the quantity of coarse aggregate determines toughness. The peak strength is closely related to the strength of the parent rock, whereas toughness is significantly affected by fiber dispersion. Coarse aggregate can adversely impact toughness by their inherent brittleness and worsening the fiber dispersion within the matrix. Additionally, this paper provides parameters for selecting suitable coarse aggregate for UHPC. It is recommended that coarse aggregate added to UHPC possess a strength approximately 1.5 times that of the matrix, with a particle size not exceeding 10 mm and a content below 30 %.

Toward Optimizing Coarse Aggregate Types and Sizes in High-strength Concrete

Toward Optimizing Coarse Aggregate Types and Sizes in High-strength Concrete

Mechanical properties and fracture behavior of seawater-mixed sea sand recycled aggregate concrete

Despite their undeniable potential for promoting sustainability in construction materials, the characteristics of recycled aggregates (RCA), seawater, and sea sand may vary significantly, thereby affecting their use in structural concrete. This study exploits these materials to investigate their performance in producing sustainable concrete and establishing its mechanical and fracture behavior. The so produced material, referred to as seawater sea sand recycled aggregate concrete (SSRAC) could lend a hand in widening the usage of RCA and sea sand in a variety of applications where the use of ever-depleting natural materials as concrete constituents becomes an issue. Consequently, the variables of the study include the type of water (fresh versus seawater), type of coarse aggregate (RCA versus natural coarse aggregate, NCA), and the type of fine aggregate (dune sand versus sea sand). For each water type, three concrete mixtures are produced using NCA-dune sand, RCA-dune sand, and RCA-sea sand combinations. Analyses of the mechanical characteristics of the concrete, including compressive strength, flexural strength, modulus of elasticity, and fracture toughness, were conducted based on experimental tests. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were also conducted on the designed specimens to investigate their microstructure. In terms of fracture characteristics, the use of seawater resulted in improvement in the fracture toughness. The use of recycled aggregate along with seawater resulted in improved compressive strength. However, natural aggregate concrete (NAC) showed higher flexural strengths than recycled aggregate concrete (RAC). The results also revealed that the addition of sea sand had a detrimental impact on all mechanical characteristics. Thus, optimizing the concrete composition in which the investigated materials partially replace the conventional concrete constituents is required in order to consider alternative constituents to generate sustainable concrete for practical applications.

The Effect of Volcanic Stone and Metakaolin on the Compressive Properties of Ultrahigh-Performance Concrete Cubes

Over the past few decades, ultrahigh-performance concrete (UHPC) has been widely studied and applied because of its outstanding mechanical properties, such as its high strength and notable durability. However, because of its high cost and easy shrinkage cracking during early pouring in mass concrete construction, to reduce the cost of UHPC and reduce the cracks caused by early pouring, volcanic stone was used as a new type of UHPC coarse aggregate, while metakaolin (MK) was added to the system at the same time, and then two parameters, namely the volcanic rock particle size group and the MK dispersion ratio, were set. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric (TG) microanalysis methods were used to reveal the influence of changes in the material microstructure, phase composition, material composition and crystallinity of the mineral composition on the compressive properties of the UHPC cubes. The results show that the mechanical “lock-in effect” of the structure formed by the volcanic rock holes and mortar can effectively improve the shear resistance of the UHPC–volcanic rock interface, and the compressive strength of the UHPC cubes increases with the volcanic stone’s particle size. When the MK dispersion ratio is less than 4%, the cube compressive strength of the UHPC and the contents of CaCO3 crystals, C-S-H gel and travertine in the UHPC increase with an increasing MK dispersion ratio. At an age of 28 days, compared with the addition of 1% MK, the addition of 4% MK increases the production of C-S-H gel and travertine in the UHPC matrix by 24.82%. When the MK dispersion ratio is 4%, the crystallinity values of the C-S-H gel, travertine and limestone in the UHPC are greater. Adding MK at a 4% dispersion ratio can promote the crystallization of limestone into a large amount of calcite, which can increase the strength of UHPC. On the one hand, the addition of volcanic coarse aggregate results in the retention of more free water and bound water; on the other hand, it also makes it difficult to crystallize CaCO3. The combined action of MK at a 4% dispersion ratio and volcanic rock significantly inhibits CaCO3 crystallization.

Properties of concrete using water from the Padma River and the Shitalakshya River, Bangladesh

Assessing the impact of river water on concrete properties is an important aspect of the construction industry, especially in regions with significant exposure to riverine environments, like Bangladesh. This study investigated the applicability of river water in concrete manufacturing regarding its compressive strength and density. Water samples were collected from two major rivers (the Padma and the Shitalakshya) in Bangladesh and analyzed for thirty water quality parameters. 168-cylinder specimens were cast and tested for compressive strength after curing for 7, 14, and 28 days. The investigation was also carried out with two different coarse aggregates (brick and stone chips) in the mix design. Curing was performed with fresh and river water separately. Therefore, ten different experimental conditions were explored. The compressive strength of concrete using river water compared to freshwater decreased from 0 to 24%, except for three cases, where strength increased by 4.2%, 7.3%, and 8%. The variation in water quality between the two rivers significantly influenced the reduction in compressive strength. Higher values of pH, total suspended solids, total solids, ammonia, total hardness, alkalinity, and conductivity in the Padma River water led to a greater reduction in compressive strength than using the Shitalakshya River water. The type of coarse aggregate used also had an impact on strength. Both rivers’ water met the concrete production standards; nevertheless, a pre-treatment process is recommended. Successfully using river water in concrete production could reduce the demand for freshwater resources, contributing to the construction industry’s sustainability.

Influence of Elevated Temperatures on the Compressive Strength of Concrete Made with Different Types of Aggregate

Concrete, the backbone of modern infrastructure, exhibits varying mechanical behaviour that depends on its components, with aggregates playing a crucial role in its strength and durability. This study aimed to investigate the influence of elevated temperatures on the compressive strength of concrete made with different types of aggregate. A comprehensive evaluation of concrete mixes was conducted using quartz, crushed clay bricks, crushed andesite, expanded clay and expanded glass coarse aggregates. For each coarse aggregate type, concrete mixtures were made with the same amount of Portland cement, water-cement ratio, natural sand, and superplasticizer. The effective water-cement ratio and cement content were kept constant in each concrete mixture. The grading and maximum particle size were the same in all concrete mixtures. The results revealed that the type of aggregate has a significant impact on the compressive strength and thermal resistance of concrete, with andesite-containing concrete exhibiting the highest residual strength after heating up to 800 °C and clay brick-concrete displaying the highest strength under elevated temperatures up to 1000 °C. The study also found that the age of concrete affects its strength at elevated temperatures, as concrete in the early stages of hydration is more susceptible to thermal cracking than concrete that has had more time to cure. Generally, the compressive strength of normal-weight aggregates depends on the strength of the parent rock. But in the case of fire (elevated temperature), the cement paste matrix loses its strength, and the aggregates effects become more significant.

Utilizing wave propagation techniques to determine the influences of the type and size of coarse aggregates on the elastic properties of concrete

The results in the literature are not conclusive regarding the relationships between the strength of concrete and the particle size and type of coarse aggregates used in concrete production. Furthermore, few studies have used wave propagation to analyse these relationships. Therefore, this research used ultrasonic and static compression tests to evaluate the influences of these factors on the elastic parameters of 81 concrete test specimens produced with two maximum sizes of conventional coarse aggregates (9.5 mm and 12.5 mm) and lightweight aggregates (expanded clay). The ultrasonic testing results showed that the elastic parameters (longitudinal elastic modulus (E) and transverse elastic modulus (G)) were influenced by the type and size of the coarse aggregates; these influences were not detected in the static compression testing results. The results of the ultrasonic and static compression tests showed that the Poisson ratio was not influenced by the type or size of the coarse aggregates.

Preparation method and applicability evaluation of 3D printing alumina ceramic artificial coarse aggregate

Abstract The particle size and morphology of crushed stones impact their macroscopic mechanical and physical properties, which has become a hot topic in the study of road and geotechnical engineering. However, some reported studies fail to control the particle morphology as the only independent variable. This paper presented a new method to print artificial aggregates based on 3D printing technology of particles. The applicability of the new method was verified with uniaxial compression and dynamic modulus tests of asphalt mixtures formed by the printing aggregates. Results showed that the printing aggregates earned similar physical properties to real coarse when sintered at 1400℃ with alumina ceramic powder and CuO: TiO2 a 1:2 additive in mass. Besides, the gross volume density, compressive strength, and shrinkage of the printing aggregates show a similar trend of increasing and then decreasing with the increase of additives. The optimal mass percentage of additives was obtained to be 5%. Mechanical tests indicated that the mechanical indexes of the asphalt mixtures formed with the two types of coarse aggregates were similar, while the results of the specimens formed with artificial coarse aggregates showed less dispersion. The stability of test results was significantly improved for different asphalt mixture specimens prepared with 3D printed coarse aggregate. This provides a basic method for further research on the multi-scale properties of particle material.

The Influence of Granite Size and Workability on the Compressive Strength of Continuous Flight Auger Pile Concrete

Concrete achieving 30N/mm² in Continuous Flight Auger (CFA) concreting is a challenge due to coarse aggregate size and the required workability of the concrete for easy pumping. This study investigated the impact of workability and coarse aggregates on the compressive strength of Continuous Flight Auger concreting. Aggregates sizes of ¾ and ⅜ inches were used for the experiments and the slump value for the mix ratios were set in range 145 to 190mm. Three mix ratios; 1:2:4, 1:1.5:3 and 1:1:2 was adopted and mix composition was done by volume method based on what is expected on construction site. Twelve (12) cubes (150x150mm) of each type of coarse aggregate with and without superplasticizers (strength enhancement, and retarder) for the various mixes were cast for 7, 21, 28 and 58 days to determine their compressive strengths. Granite sizes ¾ and ⅜ with mix ratio 1:1:2 was found to attain the targeted strength without admixtures, whereas the ¾ inches aggregates for all the mixes with the two admixtures exceeded the targeted strength with at least 13 percent. Hence, concrete of Grade C30 is achievable for CFA pile concrete without using admixture.

Durability life evaluation of marine infrastructures built by using carbonated recycled coarse aggregate concrete due to the chloride corrosive environment

Due to the harsh marine environment of chloride ion invasion and corrosion, the issues of long-term chloride transport and durability life evaluation for marine infrastructures constructed/maintained by recycled aggregate concrete (RAC) after enhancement remain poorly understood. For our studies, an accelerated carbonation modification method for recycled coarse aggregate (RCA) was adopted to prepare carbonated recycled coarse aggregate (CRCA) samples, and the macroproperties, i.e., apparent density and water absorption, of CRCA were enhanced by approximately 1.40-3.97% and 16.3-21.8%, respectively, compared with those of RCA. An in-door experiment for chloride transport into concrete specimens subjected to a simulated marine environment of alternating drying-wetting cycles was conducted. The chloride profiles and transport characteristics of carbonated recycled coarse aggregate concrete (CRCAC), recycled coarse aggregate concrete (RCAC), and natural coarse aggregate concrete (NCAC) were analysed and compared. The results indicated that the chloride penetration depths and concentrations of CRCAC were approximately 52.6-96.2% of those of RCAC, which highlighted the better chloride resistance of CRCAC. A chloride transport model for marine concrete structures with various coarse aggregate types in a corrosive marine environment was established. Taking a certain harbour wharf as an example, the durability life of this case considering the application of the CRCAC was evaluated based on the chloride transport model, and the durability life of the CRCAC structure was improved by approximately 28.10% compared with that of the RCAC. The CRCAC developed in this paper has improved mechanical performance and durability than those of RCAC, and it has the potential to replace the NCAC and further support the construction and maintenance of marine infrastructures.

Machine learning unveils the complex nonlinearity of concrete materials’ uniaxial compressive strength

Uniaxial compressive strength (CS), a mechanical property that depends on the type of fine and coarse aggregates, the water-cement (w/c) ratio, age, the volume of admixtures, etc., is difficult to estimate for concrete materials. Hence, an investigation on the application of machine learning (ML) techniques to predict the UCS of concrete precisely and affordably is described here. Different machine learning algorithms, including ensemble models like Classification and regression trees (CART), XGBoost (XGB), Bagging (Bagg), AdaBoost (AdaBo) and Random Forest Regression (RF), and non-ensemble models like Ridge regression (RR), Partial least square (PLS), K-Nearest Neighbors algorithm (KNN) were used. A total of 1206 experimental results datasets were collected. The key input parameters for the soft computing method, which produces the CS of concrete as the output, are composed of nine different elements. The quantity of cement, fine and coarse aggregate, amount of water, plasticizer, slump, and days of curing are some of the major input components. By comparing the ML-derived results with the experimental findings using various performance indices, the study demonstrates that the XGBoost model effectively approximates the CS of concrete materials with reliability and robustness. Furthermore, the research includes sensitivity analysis based on the developed optimal XGBoost model, revealing the influence of different concrete mix parameters on CS and highlighting the strongly nonlinear nature of concrete materials.

Study on stress–strain relationship and constitutive model of recycled aggregate concrete under axial cyclic compression

AbstractThe effects of dry or saturated state, water–cement ratio, coarse aggregate type and steel fiber on the stress–strain relationship of RAC under cyclic loading were studied. What is more, the characteristics of stress–strain curve, plastic strain, stress degradation and stiffness degradation of RAC under cyclic loading were analyzed. The microstructure of RAC was analyzed. Based on the principle of surface energy, the reason for the decrease in compressive strength of wet concrete was analyzed. In addition, the envelope equation of stress–strain curve under cyclic loading, unloading and reloading curve was established. The test results showed that the peak stress of the envelope line of RAC under cyclic loading was affected by dry or saturated state, water–cement ratio and coarse aggregate type, but the addition of steel fiber could reduce the degradation rate of stress and stiffness of RAC after peak strain. The plastic strain accumulation of RAC before and after the peak stress was quite different, but dry or saturated state, water–cement ratio, coarse aggregate type and steel fiber have no obvious influence on the plastic strain accumulation of RAC. The pores and cracks of RAC provide space and channels for the moisture absorption and water absorption. The Weibull–Lognormal statistical distribution envelope model, unloading curve model and reloading curve model established were in good agreement with the experimental curves. The research results provided a reference for the study of the full curve constitutive model of RAC under cyclic loading.

Aggregate Type and Concrete Age Effects on Anchor Breakout Performance: Large Database and Insights

This contribution summarizes the largest available literature data collection on tensile and shear loaded anchor tests, obtained in two independent studies and performed by two different research groups. It was the objective of the two studies to investigate a possible effect that petrographically different coarse aggregate types may have on the tensile and shear load capacity for concrete breakout failure modes. In total, seven normal-strength and four high-strength concretes were tested at two different ages. Structural tests were performed on cast-in (tensile and shear tests) and post-installed adhesive anchors (shear tests). Parallel to the structural tests, each concrete was characterized in terms of compressive and tensile strength. Finally, the combined experimental data offer novel insights into the predictive quality of available design models for concrete cone capacity in tension and edge breakout in shear with respect to a potential aggregate effect. Systematic analyses indicate only minor aggregate effects after normalization by compressive strength (less than 7% difference between normalized values). However, the study reveals potential curing and concrete age effects where a 9% increase in predicted values is shown when concrete cures longer. The predictive equations remain conservative in comparison to all the investigated properties and their validity is shown in this study.

Effect of sand fineness modulus on SCC and SCLC properties

Due to the advantageous characteristics of self-compacting concrete (SCC) and self-compacting lightweight concrete (SCLC), the advancement of the SCC is considered a remarkable engineering feat. Fine aggregate is one of the main parameters of SCC; however, its effect on SCC and SCLC properties is somewhat restricted due to the limited extent of in-depth research conducted in this field. To investigate the effect of changes in sand fineness modulus (FM) on the fresh and hardened properties of SCC and SCLC, an experimental investigation with twelve mixtures was designed. Two series of mixtures were used, each with two coarse aggregate types: Light Expanded Clay Aggregate (LECA) and natural gravel. Each series included different sand FM (2.3, 2.7, and 3.1), with the incorporation of 7% micro-silica (MS) as a cement substitute in some designs. The fresh properties of the concrete were evaluated through tests such as Slump Flow, V-Funnel, U-box, L-Box, and J-Ring, in addition to the Static Segregation Column test. For evaluating the hardened properties, 192 specimens were tested, including compressive, tensile, and flexural specimens. Moreover, fracture energy was also investigated. As the sand FM increased, it was expected that the fresh properties of concrete might decrease due to coarser aggregate volume, and the hardened properties would improve under these conditions. However, the results showed that increasing the sand FM improved the fresh and hardened properties of SCC and SCLC. By increasing the sand FM, the flowability, filling ability, and passing ability of both concrete improved, but on the other hand, elevating the sand FM reduced the segregation resistance of the mixes. In contrast, the hardened properties exhibited contrasting outcomes with increasing the sand FM. Increasing the sand FM improved the compressive strength by about 20% in both concrete types.

Resistance of Concrete with Various Types of Coarse Aggregate to Coupled Effects of Thermal Shocks and Chemicals.

Rigid pavements at military airfields experience surface deterioration within 6-18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form of disintegration of aggregates and cement paste into small pieces that pose severe risks of physical injury to maintenance crews or damage to an aircraft engine. Since coarse aggregates typically occupy 60-80% of the concrete volume, aggregates' thermal properties and microstructure should play a crucial role in the degrading mechanism. At high temperatures, concrete with lightweight aggregates is reported to have better performance compared to concrete with normal-weight aggregate. Thus, the present study carried out a detailed investigation of the mechanical and thermal performance of lightweight aggregate concrete exposed to the combined effects of high temperatures and hydrocarbon oils simultaneously. To replicate harsh airfield operating conditions, standard-sized concrete cylinders were exposed to elevated temperatures using an electric oven. Additionally, a mixture of equal parts of aircraft engine oil, hydraulic oil, and kerosene was applied before each exposure to high temperatures. To identify the resistance of different concrete with various lightweight coarse aggregates, pumice, perlite, lytag (sintered fly ash), and crushed brick were used as lightweight coarse aggregates in concrete. Also, basalt aggregate concrete was used as a reference. After curing, cylinders were tested for the ultimate strength. Later, after every 20 cyclic exposures, three cylinders from each aggregate type were tested for residual comprehensive strength, thermal, chemical, and microstructural (SEM) properties. Overall, concrete with crushed brick aggregate and lytag used in this study showed superior resistance to the simulated airfield conditions. The findings of this study will provide valuable insights to select an appropriate coarse aggregate type for military airfield pavement construction, aiming to effectively minimize surface spalling.