بحوث سكوبس — ياسر محمد جبر

Premature failure of hot mix asphalt (HMA) pavements in Iraq is typically caused by heavy loading, which requires frequent maintenance. Several approaches should be developed to prevent such failure and construct efficient and cost-effective pavements. In this study, a stone matrix asphalt (SMA) mixture is suggested as an alternative to reduce the damages in terms of rutting resistance and prolong the pavement’s service life. The SMA is a gap-graded mix of two ingredients, asphalt mortar and coarse aggregate. This study aims to design and evaluate SMA mixtures utilizing two kinds of asphalt binder (virgin and modified) and a stabilizing agent. Crumb rubber (CR) is a type of recycled rubber utilized as a binder modifier with four mixing proportions (5, 10, 15, and 20%). On the other hand, cellulose fiber pellets (CFP) are plant-based waste materials utilized as stabilizing agents with four percentages (0.2, 0.3, 0.4, and 0.5%). It is believed that incorporating these wastes into asphalt mixtures significantly impacts the environmental footprint. The generated Superpave SMA mixtures are assessed regarding their mechanical characteristics (air voids, voids filled with asphalt, and voids in mineral aggregate). Several lab tests were conducted to evaluate the performance of the produced SMA mixtures, including a drain-down test, tensile strength ratio (TSR) test, resilient modulus (MR) test, and flexural fatigue test. The findings indicated that the SMA mixtures with (0.4% CFP + 15% CR) had superior resistance to permanent deformation and moisture damage. In addition, at (0.4% CFP + 15% CR), the SMA mixtures achieved the lowest drain-down value and the highest resistance to flexural fatigue against the control mix. © The Author(s), under exclusive licence to Chinese Society of Pavement Engineering 2024.

Concrete is weak in tension, causing brittle failure without warning. Fiber is one of the simplest techniques to increase tensile strain. Several kinds of fibers (synthetic) are available such as steel fiber, glass fiber, and carbon fiber. However, these fibers are expensive and cannot be easily accessible. Researchers use agricultural fiber in concrete instead of synthetic fibers to offset this deficiency. Although, several studies have shown that agricultural fiber may be utilized to increase concrete tensile strength. However, a details review is required which combines all relevant information and the reader can evaluate the benefits of agricultural fiber. Therefore, this review focus on a comprehensive and up-to-date overview of the impact of agricultural fiber on concrete slump flow, mechanical quality, and durability. Furthermore, scanning electronic microscopy, enhancement methods, and agricultural fiber-reinforced concrete (AFRC) applications are also reviewed. Five different types of agricultural fiber including coconut, jute, banana, rice straw, and hemp fibers were selected. According to the findings, agricultural fiber increased concrete’s mechanical and durability qualities while comparably decreasing the slump. The optimum dose is essential as the higher dose adversely affects mechanical performance. The typical optimum amount varies from 1% to 2% by weight/volume of the binder. Among various types of agricultural fiber, coconut fiber is super performance. Less research is carried out on hemp, straw ash, and banana fibers than on coconut and jute fibers. © The Author(s) 2024.

One of the most popular and widely used cementitious nanoparticle materials is nanosilica (NNS). Although several researchers discuss how NNS affects the characteristics of concrete, knowledge is dispersed, making it difficult for the reader to assess the precise advantages of NNS. Therefore, a detailed review is required for the substitution of NNS in concrete. The present reviews collect the recently updated information on NNS as concrete ingredients. First, a summary of the manufacturing, physical, and chemical characteristics of NNS is provided. Second, the characteristics of fresh concrete are examined, including its effect on setting time, flowability, air content, and fresh density. Third, strength properties such as compressive, tensile, and flexure capacity are discussed. Finally, microstructure analyses such as scanning electronic microscopy and X-ray diffraction are discussed. The results show that NNS enhanced the mechanical and durability of concrete due to the pozzolanic reaction and microfilling voids but decreased the slump flow. The optimum dose is important for maximum performance. The typical optimum dose of NNS varies from 1 to 3% by weight of cement. This article also suggests future research directions to improve the performance of NNS-based concrete. © 2024 the author(s), published by De Gruyter.

Mineral filler is a mineral fine particle that passes through the No.200 sieve which plays a critical role in the performance of Hot-Mix Asphalt (HMA) mixes. A better understanding of how fillers affect the characteristics of HMA mixes is critical for good mix design and higher HMA performance. The main objective of this paper is to assess the impact of mineral filler on the mechanical characteristics of HMA using the Marshall mix design method. For this purpose, two different mineral filler types, namely, limestone and ordinary Portland cement (OPC) with three filler contents were utilized to prepare asphalt mixture samples. Optimum asphalt content was determined by the Marshall mix design method using six different asphalt contents (4.0%, 4.5%, 5.0%, 5.5%, 6.0%, and 6.5%). In this paper, the characteristics of two kinds of filler were assessed using three experimental tests: Marshall test, retained strength test, and indirect tensile strength test. This study considered three filler percentages: 4, 7, and 10% by aggregate weight. These percentages fall within the limit specified in the SCRB specification (SCRB, R/9, 2003). The results indicated that HMA containing cement filler resulted in higher stability levels, tensile strength, and index of retained strength values compared to the limestone dust. Therefore, the utilization of cement filler provides better performance for asphalt mixes. The addition of cement filler with 10 % and limestone filler with 7 % seem to be the optimum filler contents due to satisfying all SCRB specification requirements. © 2024 American Institute of Physics Inc.. All rights reserved.

This review aims to collect the positive and negative influence of volcanic ash (VA) on concrete properties. The review discussed a general background of VA, classification, preparation, chemical aspects and its impact on concrete properties. Furthermore, the performance at elevated temperatures and environmental benefits associated with the utilization of VA are also discussed. The finding reveals that the concrete flow properties and strength properties improved with VA due to micro filling and pozzolanic action. The optimum percentage of VA varies from 5 to 10% depending on the source of VA, mix design, and aggregates. Also, VA-based concrete performance is comparable with conventional concrete at elevated temperatures. Furthermore, the environmental assessment shows that the utilization of VA decreased CO2 emissions. The assessment concluded that conflict exists among different researchers as some researchers observed a positive impact while some researchers observed a negative impact on concrete performance. Therefore, the study recommends further research to identify the exact parameter that causes variation. © Springer Nature Switzerland AG 2024.

Ceramic waste (CW) has a significant negative environmental influence on the society. However, CW may benefit the environment if it is handled carefully and recycled in concrete production. Recycling CW may lessen the demand for raw materials and waste disposal, thereby preserving natural resources and lowering greenhouse gas emissions. Numerous studies discuss the possibility of CW utilization as concrete ingredients. However, data are spread, making it difficult for the reader or user to assess the benefits and drawbacks of using CW in concrete, which limits its applications. To study the benefits and drawbacks of using CW in concrete and provide the guidelines to the consumer with relevant information, a detailed review is required. Therefore, this study is carried out to collect all relevant updated information from published articles. The major topics of this article include the general history of CW, physical and chemical features, and the influence on concrete parameters including fresh, strength, elevated temperature, and cost benefits. Results indicate that CW decreased concrete flowability and strength. However, with up to 10% substitution, the results are satisfactory, and concrete can be used for a normal-strength structure. Furthermore, the review also identifies the research gaps that need to be investigated. © 2023 the author(s), published by De Gruyter.

The residential cooling and heating sectors account for approximately 45 percent of the world's total energy consumption. Utilizing phase change insulators to store energy and prevent its loss is one of the most effective methods for reducing energy consumption. In the beginning of this essay, the authors attempt to determine the most efficient way to use multiple phasing materials in the wall structure simultaneously. Taking Phuket, Thailand's climate into account, a simulation is performed to determine which Phase Change Material (PCM) is the most effective and where it should be placed within the wall. In this construction, it was determined that the PCM with a melting temperature of 25 °C and an annual energy savings of 22% performed the best. This decrease in Energy consumption was a result of Phuket's climate. During the course of the research, it was determined that it is preferable to use the Fanger thermal comfort model to zero in on PCMs and eliminate unrelated factors. According to the simulation results, the thickness of the wall has a negligible effect on the performance of these materials. The size of the window openings will be decisive in the opposite direction. © 2023

Crushed waste concrete (CWC) has been added to soil subgrades with inadequate natural stability to evaluate how it affects their behavior. The soils were mixed with various percentages of crushed waste concrete 0 %, 25 %, and 50 %, which were selected based on previous studies. Natural clay soil (Neat Soil)-crushed waste concrete CWC mixes were compacted at the optimum water content and then subjected to a variety of laboratory tests. The results revealed that soil samples stabilized with CWC improved significantly in terms of swelling pressure, maximum dry density, and California Bearing Ratio (CBR). The swelling pressure decreased by increasing CWC contents for all samples and the maximum dry density value, CBR value of Blend Soil (X1, X2) samples increased with increasing CWC contents. Therefore, the CWC is a valuable material for modifying the properties of soil in order to make it appropriate for construction. Based on the results analysis, mix designs containing 50 % CWC and 50% silty clay soils were found to be appropriate for use as sub-base material. © 2023 American Institute of Physics Inc.. All rights reserved.

A crucial factor in the efficient design of concrete sustainable buildings is the compressive strength (Cs) of eco-friendly concrete. In this work, a hybrid model of Gradient Boosting Regression Tree (GBRT) with grid search cross-validation (GridSearchCV) optimization technique was used to predict the compressive strength, which allowed us to increase the precision of the prediction models. In addition, to build the proposed models, 164 experiments on eco-friendly concrete compressive strength were gathered for previous researches. The dataset included the water/binder ratio (W/B), curing time (age), the recycled aggregate percentage from the total aggregate in the mixture (RA%), ground granulated blast-furnace slag (GGBFS) material percentage from the total binder used in the mixture (GGBFS%), and superplasticizer (kg). The root mean square error (RMSE) and coefficient of determination (R2) between the observed and forecast strengths were used to evaluate the accuracy of the predictive models. The obtained results indicated that—when compared to the default GBRT model—the GridSearchCV approach can capture more hyperparameters for the GBRT prediction model. Furthermore, the robustness and generalization of the GSC-GBRT model produced notable results, with RMSE and R2 values (for the testing phase) of 2.3214 and 0.9612, respectively. The outcomes proved that the suggested GSC-GBRT model is advantageous. Additionally, the significance and contribution of the input factors that affect the compressive strength were explained using the Shapley additive explanation (SHAP) approach. © 2022 by the authors.

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0–10% for mixtures with 20% RAP, 12.5–17.5% for mixtures with 40% RAP, and 17.5–20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5–1.0% for mixtures with 20% RAP, 1.0–1.5% for mixtures with 40% RAP, and 1.5–2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5–17.5%, and 17.5% of WEO, <10%, 12.5%, and 17.5% of DSO, and 0.5–1.0%, 1.0%, and 1.5–2.0% of the commercial rejuvenator, corresponding to the three adopted percentages of RAP. © 2022 by the authors.

Geotextile reinforcement techniques have been widely used in paving works around the world and have proven to be effective in improving pavement performance. This study has focused on using different positions and numbers of geotextile reinforcement sheets between the layers of flexible pavement for rutting reduction. Fitting depth was measured in the field at seven constructed sections of the pavement of the road model. Each section has been strengthened with different reinforcement approaches. All road sections were subjected to a maximum load repetition of 10,000 cycles. The results indicate that using three layers of geotextile beneath each course of the designed road pavement sections (surface, binder, and base) reduced rutting by 96%. Traffic benefit ratio (TBR) has been employed in this study to reveal the behavior of geotextile reinforcement in increasing the service life of the road. TBR values are the load cycling ratio between the reinforced and unreinforced section for the exact recorded rut depth, it has been found to be minimally equal to 4 for the case of using one layer of reinforcement at interface I, and that value keeps growing up for other reinforcement cases. © 2022 Abdul Hadi Meteab AL Sa'adi et al., published by De Gruyter.

Seepage from the earth dam's body reduces the amount of water in the dam's reservoir and threatens its stability. In this paper, the earth-type Sattarkhan Dam on the Aharchai River has been investigated. In this regard, the SEEP/W model from the GeoStudio 2018 software suite was used for modeling. This study examines the effects of various lengths and positions of cutoff wall and horizontal drainage on seepage, uplift pressure, and exit gradient. Increasing the length of the cutoff wall reduces seepage in both sections, with a more significant effect on Section 2; it also decreases the uplift pressure and the exit gradient. Changing the position of the cutoff wall has a significant effect on seepage fluctuations in Section 1 but has no effect on seepage in Section 2; in positions 2 to 7, the uplift pressure values are nearly identical, and the exit gradient is most significant at position 1 and least at position 2. Increasing the horizontal drainage's length increases seepage, reduces uplift pressure, and increases the exit gradient. The closer proximity of the horizontal drainage position to the dam's core increases seepage and decreases uplift pressure and exit gradient. Finally, it is concluded that the construction of a cutoff wall and horizontal drainage with appropriate lengths and positions reduces risk and improves the stability of earth dams. © 2022 Widodo Brontowiyono et al.

– Despite the numerous advantages of using modified asphalt binders, there are a number of challenges associated with their use. One of these challenges is related with specifying the temperatures at which modified asphalt binders should be mixed and compacted. The Equiviscous method aims to calculate the Mixing and Compaction Temperatures (MCTs) of the unmodified binder. Nevertheless, the implementation of this method for modified asphalt binder results in very high MCTs, which may not be appropriate during the asphalt mixes construction. This paper investigates two alternative methods for the modified binder with Crumb Rubber (CR), referred to as the High Shear Rate (HSR) viscosity and Zero Shear Viscosity (ZSV) methods. Besides, the MCTs obtained from these methods are compared to the ones obtained using the Equiviscous method. For this purpose, one type of asphalt binder modified with three percent of CR has been used. The results have shown that the application of the ZSV method has resulted in more reasonable MCTs for the rubberized binder, which have been from 30 to 50 °C lower than the ones obtained using the Equiviscous method. © 2022 Praise Worthy Prize S.r.l.-All rights reserved.

As the climate temperature decreases, the flexible pavement will be subjected to high tensile stresses which exceeding to the movement resistance of asphalt binder leading to low temperature cracking. SHRP identified a Bending Beam Rheometer (BBR) for measuring the value of flexural-creep stiffness of asphalt binder at low temperatures which consider this value a good indicator for resistance of low-temperature cracking. This study developed a method for measuring the flexural-creep stiffness of asphalt binder by modification of an apparatus instead of Bending Beam Rheometer due to its expensive cost and unavailable in most research laboratories. A (40-50) penetration grade of asphalt binder used in this study at different test temperatures (-5, 0, 5)°C. The experimental results indicate to the modified apparatus and developed test is suitable for testing an asphalt binder at different temperature and loading time. © Published under licence by IOP Publishing Ltd.