https://jcr.guilan.ac.ir/ Concrete Research en daily 1 Tue, 23 Sep 2025 00:00:00 +0330 Tue, 23 Sep 2025 00:00:00 +0330 https://jcr.guilan.ac.ir/article_9339.html In this research, the effect of high temperature on the behavior of heavyweight geopolymer concrete plates containing Electric Arc Furnace (EAF) aggregates and reinforced with hybrid aramid and steel fibers under impact loading has been investigated. The volumetric percentage of steel fibers varied between 0.25% and 1%, while aramid fibers were used at 0.25% and 0.5%. Eight mix designs were prepared, using EAF slag as heavy aggregates and a combination of blast furnace slag and microsilica as the base material for geopolymer concrete. The compressive strength of the samples was measured at 28 days of age. Additionally, impact tests (drop-weight test) were conducted on concrete plates with dimensions of 400 × 400 × 40 mm, and parameters such as impulse for compression (Pc), impulse for restitution (Pr), total impulse (Pf), effective impact force, and impact energy were calculated. The results showed that the addition of both steel and aramid fibers to heavyweight geopolymer concrete reduces the reduction in compressive strength due to heat. However, steel fibers had a more significant effect in mitigating this loss. Under the effect of 600°C, samples containing 1% steel fibers exhibited the least loss of compressive strength. In the impact test, steel fibers significantly increased the compressive impulse and rebound impulse, with the highest values of these parameters obtained from the mix design containing 1% steel fibers. Furthermore, steel fibers had a greater impact on increasing the effective impact force compared to aramid fibers. https://jcr.guilan.ac.ir/article_9340.html The simulation of the behavior of reinforced concrete (RC) slabs using numerical software is a cost-effective method for their analysis and design. In the present study, by focusing on an ordinary RC slab element subjected to blast loading and conducting multiple simulations, a comparison of the models was performed. The software LS-DYNA, version R 4.2, and the capable, widely used, and available concrete material models: Concrete Damage R3, HJC, CSCM, and Winfrith, were used for the simulation. Based on existing tests and the information provided within them, the blast load was applied to the slab using the pressure-time history method, and the results for the maximum slab deflection obtained from the simulation using the mentioned material models were compared. The Concrete Damage R3 model provided more accurate results than the other models. In this research, the accuracy of the models was evaluated quantitatively based on the Percent Relative Error (PRE) between the simulation results and the actual laboratory data. The HJC model required the least computation time but its accuracy was second to the Concrete Damage R3 model; however, it was necessary for the user to introduce all parameters, including the equation of state, to the model. The CSCM model had lower accuracy than the HJC model but required the fewest input parameters for introduction to the software; paradoxically, this model required the longest computation time. The Winfrith model had the lowest accuracy. https://jcr.guilan.ac.ir/article_9341.html Destructive (direct) testing methods are among the most common approaches for determining the strength parameters of concrete. In addition to causing damage to the concrete, these methods are associated with relatively high costs. Under such circumstances, the application of non-destructive (indirect) testing methods can provide a more efficient and economical alternative. In the present study, destructive tests including uniaxial compressive strength, Brazilian tensile strength, and point load index, as well as non-destructive tests including the Schmidt hammer test and ultrasonic pulse velocity (UPV), were performed on three different concrete mix designs. The only difference among these mix designs was the aggregate gradation. The obtained results were then comparatively analyzed, and correlation relationships between the results of destructive and non-destructive methods were developed. The results indicated that variations in aggregate gradation have a significant effect on the mechanical strength parameters of concrete. Specifically, excessive use of coarse aggregates and the resulting very coarse gradation in the concrete mix design negatively affects the strength characteristics of concrete. https://jcr.guilan.ac.ir/article_9342.html The high potential of ultra-high-performance concrete (UHPC) due to its early-age strength makes it suitable for applications such as rapid repairs of concrete pavements and the production of precast elements. The use of local industrial pozzolans, such as slag and zeolite, can reduce cement consumption while improving the long-term performance and durability of these concretes. In this study, to evaluate the behavior of UHPC under conditions suitable for rapid repairs in cold regions, ten mix designs were tested after optimizing the amount of accelerator, with 5%, 10%, and 15% replacement of silica fume by slag and zeolite, applied individually and in combination. Fresh-state tests included internal temperature variations and setting time, while hardened-state tests included compressive strength, electrical resistivity, and water absorption at different ages. The results showed that both pozzolans improved the fresh-state behavior by controlling setting rate and reducing hydration heat. At 28 days, mixes containing 5% replacement of slag and zeolite increased compressive strength by 6–9% and electrical resistivity by over 10% compared to the reference mix. Increasing the replacement to 15% resulted in an 8–12% reduction in strength and durability. Moreover, significant correlations were observed between mechanical properties and durability tests across different ages. https://jcr.guilan.ac.ir/article_9343.html carbonation, improving the mechanical performance of concrete is of great importance. This study investigates the effect of the chemical composition of three types of aggregates (silica–alumina, calcium oxide, and calcite) on the mechanical behavior of zeolite-containing concretes subjected to high temperature and accelerated carbonation. Concretes were produced with a water-to-binder ratio of 0.45 and varying zeolite contents (0, 5, 10, 15, and 20%). After mixing and standard curing, the specimens were heated to 800 °C and subsequently exposed to a CO₂-saturated environment for 3, 56, and 90 days. The carbonation depth was determined using a phenolphthalein solution, and microstructural analyses were performed through SEM and XRD techniques to clarify the underlying mechanisms. The results showed that concrete produced with silica–alumina aggregates and 10% zeolite exhibited the highest compressive strength, as the coexistence of silica and alumina contributed to enhanced structural densification. In contrast, concretes with calcitic aggregates were more vulnerable to carbonation, leading to greater strength reduction. The influence of zeolite on tensile strength was limited across all mixes. Microstructural observations confirmed that elevated temperatures caused decomposition of C–S–H gel, increased porosity, and reduced alkalinity, which were consistent with the mechanical test results. Overall, the combination of silica–alumina aggregates with 10% zeolite is recommended as an effective option for producing concretes resistant to the deteriorative conditions of urban tunnels. https://jcr.guilan.ac.ir/article_9344.html In recent years, self-cleaning concretes have gained significant importance due to their high capacity for reducing environmental pollution and maintenance costs. These concretes, employing photocatalytic coatings with titanium dioxide (TiO₂), facilitate the removal of pollutants and help maintain the beauty and cleanliness of urban facades. However, the durability and sustainability of self-cleaning concretes against chloride ion penetration, particularly in corrosive environments, remain ambiguous concerning their widespread application. This study aims to investigate the effect of TiO₂ on enhancing concrete durability against chloride ion penetration and its self-cleaning properties. For this purpose, five concrete mix designs with titanium dioxide at varying percentages of 0, 5, 10, 15, and 20% by cement weight were prepared and evaluated using the RCMT method in accordance with Section 9 of the National Building Regulations. The results demonstrated that adding up to 20% TiO₂ resulted in an 80% reduction in chloride ion penetration compared to the control sample. Furthermore, the self-cleaning properties were significantly improved in samples with 15% and 20% additive. This research indicates that utilizing titanium dioxide in concrete not only enhances durability in corrosive environments but also enables the production of self-cleaning concretes suitable for use in urban pavements and structures. https://jcr.guilan.ac.ir/article_9345.html For many years, the construction of asphalt roads has been common in Iran, and today a significant volume of asphalt waste resulting from the aging and destruction of these roads is accumulating. These wastes are often transported to the outskirts of cities, and there is no specific mechanism in the industry for their recycling. Continuation of this trend, in addition to increasing construction costs, leads to the depletion of natural resources and quarries. In line with this goal, in the present study, various volumetric percentages of recycled asphalt aggregate (including 10, 20, 30, 40, and 50%) were used as a replacement for natural coarse aggregate in the production of RCCP. Other construction requirements were also applied according to National Standard No. 14830. Additionally, in order to enhance the compaction and quality of the concrete, microsilica equal to 10% by the cement weight was incorporated. The experiments conducted in this study included measurements of specific gravity, slump, abrasion resistance, and durability evaluation against chloride ion penetration using the RCMT method. The results indicated that as the replacement percentage of recycled asphalt increased, the abrasion resistance of RCCP decreased. However, RCCP containing 10% recycled asphalt still remained within the acceptable range of the code for light-duty and low-traffic pavements. Furthermore, the chloride ion penetration rate (by the RCMT method) in samples containing 10% and 20% recycled asphalt aggregate was within the permissible limits for XCD2,3 environmental conditions. https://jcr.guilan.ac.ir/article_9360.html Non-destructive evaluation of concrete properties at early ages is critical to ensure adequate strength development for the continuation of construction activities. The maturity method is widely recognized as an effective tool for estimating compressive strength based on the temperature history of concrete hydration; however, its reliance on measuring in-situ concrete temperature using embedded instrumentation poses practical challenges on construction sites. This study aims to propose a simplified and more practical site-oriented approach by investigating the feasibility of substituting ambient temperature history for in-concrete temperature data in the maturity model. To this end, strength predictions obtained from the conventional maturity method were compared with those derived from the proposed ambient-temperature-based approach. Evaluations were conducted on concrete specimens at ages less than 28 days under two distinct environmental conditions, corresponding to hot and cold seasons. Quantitative results indicate that the maximum relative error in strength estimation using the proposed method was limited to 5% during the hot season and 10% during the cold season. Considering these relatively small deviations, it can be concluded that employing ambient temperature as the input parameter transforms the maturity method into a practical and cost-effective solution for estimating early-age concrete strength on site, while significantly reducing dependence on complex instrumentation. https://jcr.guilan.ac.ir/article_9467.html The development of multifunctional concrete with structural health monitoring capabilities requires understanding the complex interactions between various additives. This study investigates the simultaneous effects of ground granulated blast furnace slag (GGBFS), halloysite nanotubes (HNTs), silica fume (SF), and water-to-binder ratio (W/B) on the mechanical and electrical properties of cementitious composites. The Taguchi experimental design method with an L₈ orthogonal array was employed. Four factors at two levels were examined: GGBFS (10 and 20%), HNTs (5 and 10%), SF (0 and 7%), and W/B (0.35 and 0.40). Compressive strength was measured at 7, 28, 90, 180, and 360 days, while electrical resistivity was measured at 28, 90, 180, and 360 days. Results indicated that SF, with a 42% contribution, was the most influential factor in increasing electrical resistivity, whereas GGBFS exhibited an inverse effect. Regarding mechanical properties, HNTs dominated at early ages (38% contribution at 7 days), while GGBFS prevailed at later ages (35% contribution at 180 days). The optimal mixture comprising 10% GGBFS, 5% HNT, 7% SF, and W/B=0.35 was identified as the balance point between mechanical and electrical properties. https://jcr.guilan.ac.ir/article_9468.html One of the most significant limitations of concrete is its low tensile strength and brittle behavior under tensile and flexural loads. To enhance the mechanical performance of concrete, the use of reinforcing fibers and recycled materials has emerged as an effective and sustainable approach. The present study aims to investigate the combined effect of Corte macro synthetic fibers and crumb rubber on the mechanical properties of concrete, including compressive strength, flexural strength, maximum load capacity of concrete slabs, and ductility, through experimental testing. For this purpose, 24 specimens with three different mix designs containing 1% Corte fibers and 5% and 10% crumb rubber were prepared and tested. The results indicated that the mix design containing 5% crumb rubber and 1% Corte fibers (CG5F1) led to increases of 12.7% in compressive strength, 5.8% in flexural strength, and 21.6% in the maximum load capacity of concrete slabs compared to the control mix. These findings suggest that the addition of Corte fibers can mitigate the potential adverse effects of crumb rubber and improve the mechanical properties of concrete. Consequently, the targeted and controlled use of these additives can contribute to producing concrete with optimized performance aligned with sustainable development principles. In conclusion, the results of this study demonstrate that the use of Corte macro synthetic fibers as reinforcement is suitable and effective for structural applications, whereas the application of crumb rubber is not recommended in structural concrete due to its detrimental impact on certain strength parameters and should be avoided https://jcr.guilan.ac.ir/article_9469.html The use of in situ synthesized carbon nanotubes, using chemical vapor deposition in the cement production process, to improve the durability of concrete has attracted the attention of many researchers. In this study, the appropriate range of use of these nanotubes under freeze-thaw cycle conditions and tensile strength was investigated. After adding cement containing in-situ synthesized carbon nanotubes at different percentages (0, 4, 6, 8, 10, and 12) to concrete samples, the weight loss of the samples under freeze-thaw cycle conditions was measured as a factor to determine the effect of this cement. The weight loss in the control sample (without nanotubes) was 5.82%, and for the cement samples containing 4, 6, 8, 10, and 12% nanotubes, the weight loss was 1.74, 1.75, 1.38, 1.02, and 1.68%, respectively, after 300 freeze-thaw cycles. Adding 10% of cement containing in-situ synthesized carbon nanotubes to concrete samples resulted in the lowest weight loss. The indirect tensile strength of the samples, as an important parameter in the design of concrete structures, was also measured using indirect tensile testing. Samples containing 8% of this cement had the highest tensile strength, which is approximately 24% higher than the control sample. In order to better understand the desired cement and also the microstructure of the samples, Field Emission Scanning Electron Microscopy (FESEM) observations were also performed. The FESEM results indicated that the nanotubes were properly dispersed and did not aggregate in the cement matrix. https://jcr.guilan.ac.ir/article_9470.html Due to the weaker properties of recycled aggregates compared to natural aggregates, concretes containing these materials generally exhibit lower mechanical performance and durability. The aim of the present study is to investigate the effect of replacing natural aggregates with recycled aggregates on the mechanical and electrochemical properties of cement mortar. For this purpose, mortars containing 0, 50, 75, and 100 percent recycled aggregates were prepared and subjected to compressive strength, half-cell potential, linear polarization resistance, and potentiodynamic polarization tests. After 28 days of curing, the specimens were exposed to chloride conditions through eight two-week cycles (one week wet, one week dry). The results indicated that complete replacement of natural aggregates with recycled aggregates led to a 23–32% reduction in compressive strength and earlier initiation of reinforcement corrosion (third cycle versus sixth cycle). In contrast, 50% replacement resulted in only a slight reduction in compressive strength (about 7% at 90 days and negligible at 28 days), with corrosion initiation observed in the fifth cycle. Moreover, increasing the proportion of recycled aggregates reduced the quality of the passive layer and caused approximately an 80% decrease in linear polarization resistance. Overall, the findings demonstrated that the use of recycled aggregates up to a 50% replacement level has no significant effect on compressive strength and only a minor influence on electrochemical properties compared to the mix containing 100% natural aggregates. https://jcr.guilan.ac.ir/article_9471.html The durability of concrete structures is a decisive factor in their service life, especially when exposed to aggressive environments. This study aims to investigate the effects of silica oxide nanoparticles (SiO₂) on improving the durability and reducing the permeability of concrete. In this research, SiO₂ nanoparticles were used as partial replacements for cement in various mix designs, and the prepared samples were tested for permeability, porosity, and resistance to sulfate attack. The results revealed that the incorporation of well-dispersed nanoparticles enhances the homogeneity and cohesion of concrete, significantly reduces permeability and pore volume, and improves the viscosity and bonding properties of the cement paste. The pozzolanic reaction between nanoparticles and calcium hydroxide leads to the formation of more durable gels, which block the pathways of harmful agents. Furthermore, concretes containing silica nanoparticles exhibited higher resistance to sulfate attack and improved long-term durability. Overall, the incorporation of silica oxide nanoparticles can be considered an effective approach to enhance concrete durability and stability in harsh environmental conditions. https://jcr.guilan.ac.ir/article_9472.html Dowel action of longitudinal reinforcement constitutes a key shear transfer mechanism in reinforced concrete beams without transverse reinforcement. This study aims to quantitatively evaluate the contribution of dowel action to the shear strength of concrete beams reinforced with Fiber-Reinforced Polymer (FRP) bars and to validate existing design models. To this end, a comprehensive database comprising experimental results of 510 FRP-reinforced concrete beams was compiled from technical literature and compared with predictions from ACI 440, CSA S806 codes, and analytical models. The results indicate that the contribution of dowel action varies between 10% and 40% of the total shear strength, depending on the bar diameter and concrete cover. Model evaluation demonstrates that the CSA S806 code, by accounting for the axial stiffness of the reinforcement, offers the most accurate prediction with an appropriate safety margin. In contrast, the ACI 440.1R-15 code estimates shear capacity conservatively (20% to 30% lower than actual values). Furthermore, models based on evolutionary methods (such as the Kara model) exhibit estimation errors at high shear strengths (exceeding 400 kN). This research concludes that for optimal design, models that incorporate axial stiffness parameters and concrete cover interaction can be more accurate. https://jcr.guilan.ac.ir/article_9473.html Over the past few decades, the construction of buildings and infrastructure has required higher durability and performance in materials such as concrete. Concrete structures have high compressive strength and, with the presence of steel, are also flexible. The main weakness of concrete is its susceptibility to cracks caused by tensile, thermal, and environmental stresses. Although cracks in concrete may initially appear minor, they allow water, corrosive ions, and other environmental factors to penetrate, ultimately leading to reduced durability, which increases the cost of maintaining structures. A modern solution to this problem is the development of self-healing concrete. Self-healing concrete is a type of smart concrete that is capable of repairing cracks on its own without any human intervention. This concrete uses approaches such as the incorporation of bacteria, capsules containing a healing agent, or special cements to detect and repair the cracks that have formed. The advantages of this technology are contributing to sustainable development, greater durability, and reduced maintenance costs. This technology leads to increased environmental sustainability because reducing the need for maintenance and replacement of materials helps reduce the consumption of raw materials and the production of construction waste. In this study, using the science direct database and the keyword self-healing concrete, 60 articles published in the field of self-healing concrete up to 2025 were extracted and reviewed. In this section, the principles and mechanisms of self-healing concrete will first be examined. Then, the advantages, limitations and applications of this technology will be discussed. https://jcr.guilan.ac.ir/article_9474.html The objective of this study was to investigate the feasibility of producing uniform black concrete using different weight percentages of carbon black and to evaluate its effects on the mechanical properties and durability of concrete, particularly water absorption and water penetration, with a focus on architectural façade and landscaping applications. In this research, concrete mixtures containing 5, 10, 15, and 20 wt.% carbon black relative to cement were produced. To assess concrete performance, tests including slump of fresh concrete, compressive strength at 7 and 28 days, initial water absorption (30 minutes), final water absorption (72 hours), and water penetration in hardened concrete were conducted in accordance with relevant standard specifications. The mix design of the control concrete was based on the ACI 211 weight-based method. The results indicated that the incorporation of carbon black up to 10 wt.% of cement increased the compressive strength of concrete at different curing ages, which was attributed to enhanced concrete densification. At higher contents (15 and 20 wt.%), a relative reduction in compressive strength was observed, mainly due to agglomeration of carbon black particles. Furthermore, increasing the carbon black content led to an increase in both initial and final water absorption. The final water absorption of the specimens ranged from approximately 2.4% to 2.9%, which remains within the acceptable limits for concretes suitable for civil engineering applications. Overall, carbon black not only provided a deep and uniform black coloration but also demonstrated acceptable performance in terms of mechanical properties and durability of concrete.