Constr. Mater., Volume 5, Issue 1 (March 2025) – 17 articles

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures has increased due to its economic and environmental benefits. However, RAP integration can negatively impact the durability and performance of asphalt binders, particularly at low temperatures. This study evaluates the effects of RAP modification on the $\Delta T_C$ parameter, a key indicator of binder brittleness and resistance to non-load-related cracking, focusing on PG XX-34 and PG XX-28 grades commonly used in Kansas. Laboratory testing was conducted on virgin and RAP binders subjected to Rolling Thin-Film Oven (RTFO) and Pressure Aging Vessel (PAV) aging. Blended binders were prepared with RAP replacement levels of 15%, 25%, and 40%. The critical temperatures $T_{C,m}$, $T_{C,S}$, and $\Delta T_C$ values were calculated using data from Bending Beam Rheometer (BBR) testing. The results showed that increasing RAP content generally led to more negative $\Delta T_C$ values, indicating reduced relaxation capacity and higher susceptibility to thermal cracking. RAP source variability also affected performance, with some sources causing more severe deterioration than others. These findings highlight the limitations of conventional linear blending assumptions and underscore the need for improved RAP characterization in binder selection. The study recommends limiting RAP replacement to 25% unless the RAP source demonstrates favorable properties, incorporating $\Delta T_C$ thresholds (−2.5 °C and −5.0 °C) into binder specifications, and further investigating RAP–virgin binder interactions to enhance long-term pavement performance. The findings support the potential adoption of $\Delta T_C$ as a specification criterion for binder evaluation, helping agencies like the Kansas Department of Transportation (KDOT) balance binder durability and RAP use. Full article

The usage of geopolymer-based materials (GPBMs) in concrete structures has been broadly promoted by the current construction sector. GPBMs have an outstanding influence on enhancing concrete mechanical properties. Geopolymers (GPs) also have a potential impact on reducing the carbon dioxide emissions emitted by the current cement production procedure. Therefore, this paper aims to evaluate the impact of some variables that affect green and mechanical properties of fly ash-based geopolymer concretes (FA–GPCs), i.e., different silica fume (SF) contents, alkaline activator solution (AAS) percentages, sodium silicate-to-sodium hydroxide (SS/SH) ratios, sodium hydroxide (NaOH) molarity, and additional water. A slump test was used to evaluate the concrete workability to assess the green properties of the designed fly ash-geopolymer concrete mixes (FA–GPCMs). The 14- and 28-day compressive strengths were used to evaluate the concrete’s mechanical properties. Results indicate that the workability of prepared FA–GPCMs reduced with improving SF content (5% to 30%), SS/SH ratio (1% to 3%), and NaOH molarity (10 M to 16 M), while reducing alkaline activator percentages to 35% resulted in a decrease in the FA–GPCMs’ workability. Also, increasing SF replacement percentages from 5% to 15% in FA–GPCMs resulted in significant 14- and 28-day FA–GP compressive strength enhancements compared to FA–GPCM produced with 0% SF, while SF contents of 20%, 25%, and 30% led to a decline in the 14- and 28-day FA–GPC compressive strength compared to that of G1–SF15%. Full article

Foamed concrete, a lightweight material with excellent thermal insulation and low density, is increasingly popular in construction. This study uses the discrete element method (DEM) to simulate the compressive behavior of foamed concrete, analyzing the effects of particle radius, porosity, and void distribution. The results highlight the important role of geometric and material parameters. Smaller particle radii improve packing density and strength, while a uniform void distribution maximizes compressive strength by minimizing stress concentration. This information provides a basis for optimizing the design of foamed concrete for better mechanical performance and wider applications in sustainable construction. Full article

Plastic Concrete is a low-strength ($f_{cm,28\mathrm{d}}$ ≤ 1.0 MPa), low-stiffness impervious concrete used for cut-off walls in earthen dams worldwide. These properties are achieved through a very high w/c ratio (w/c ≥ 3.0) and water-binding additions (e.g., bentonite). To date, the effect of mix design, especially w/c ratio, as well as bentonite content and type, on the long-term time development of the microstructural properties and corresponding compressive strength of Plastic Concrete has yet to be systematically studied. Furthermore, in the literature, mercury intrusion porosimetry (MIP) and X-ray diffractometry (XRD) have yet to be applied systematically to Plastic Concrete for this purpose. The present study closes this gap. Ten Plastic Concrete mixes with two bentonite–cement ratios, three types of sodium bentonite and two swelling times were produced. MIP and XRD measurements and compressive strength tests were performed at sample ages of 7 d, 28 d, 56 d, 91 d and four years. The results show that both MIP and XRD can be successfully used; however, meticulous sample preparation and data analysis must be considered. The porosimetry results show a bi-modal pore size distribution, with two age-dependent peaks at approximately 10,000–20,000 nm and 100–700 nm. The results also exhibit a clear pore refinement over time, with coarse porosity dropping from 26% to 15% over four years. In addition, the fine porosity peak is significantly refined over time and positively correlates with the significant increase in compressive strength. The XRD results show no unexpected crystalline phases over the same period. Overall, this study links MIP and corresponding compressive strength data specifically for Plastic Concrete for the first time, confirming the key role that the mix design of Plastic Concrete plays in defining its long-term microstructural and mechanical properties and ensuring more realistic cut-off wall design in the future. In addition, the experimental boundaries for MIP testing on Plastic Concrete are set out for the first time, enabling future research in this field. Full article

This study investigates the influence of ballast and sub-ballast thicknesses on the structural behavior of a heavy-haul railway platform by using finite element modeling with SysTrain software (v. 1.84) A parametric analysis was conducted to assess how variations in layer thickness affect key performance parameters, including total deflection, bending moments in the rails, and vertical stresses within the railway track. The results indicate that reducing ballast thickness increases deflection and vertical stresses, while excessive thickness elevates system stiffness, reducing its ability to dissipate stresses. This condition can intensify the transmission of dynamic loads to track components, accelerating rail and sleeper wear and requiring more frequent corrective interventions, thereby increasing maintenance costs. Deflections remained within the 6.35 mm limit established by AREMA, except for one case (6.85 mm), where an excessive ballast thickness (160 cm) combined with low material stiffness resulted in non-compliance. Vertical stresses in the substructure ranged from 106.9 kPa to 155.9 kPa, staying within admissible limits. Additionally, the study highlights the significant role of material properties, particularly the resilient modulus, in the overall track performance. The findings enhance the understanding of how ballast and sub-ballast geometry affect railway structural behavior, demonstrating how numerical modeling with SysTrain can support decision-making in track design and maintenance strategies. Full article

Cement is widely used as an efficient binding agent in concrete; however, the production of cement is the second-largest source of carbon emissions. Therefore, there is an urgent need to explore alternative materials with similar properties. CoRncrete, a corn-based material, shows potential as an eco-friendly substitute. Our previous study showed that oven-dried CoRncrete achieved a maximum compressive strength of 18.9 MPa, which is 37% lower than traditional concrete. Nonetheless, in light of this limitation, CoRncrete still stands as a feasible choice for internal structural applications. This study aims to enhance CoRncrete’s strength by modifying drying conditions and incorporating lightweight thermoplastic polymers as admixtures. Air-drying for 7, 14, 21, and 28 days was tested, with durations of 21 days and greater showing improved internal curing, reduced porosity, and enhanced strength (23.9 MPa). Various high-strength, low-density polymers, including carboxy methyl cellulose (CMC), chitosan (CS), polyvinyl alcohol (PVA), and polyvinylpyrrolidone (PVP), were utilized. PVA demonstrated favorable interactions with cornstarch, also showing improved performance in water durability properties. Air-dried CoRncrete with PVA admixture had maximal water durability properties (up to 20 days) compared to the other samples. Micro-structural analysis revealed reduced porosity in air-dried and polymer-bound samples. Future investigations should extend to an in-depth study on air-drying duration for polymer-bound CoRn-crete and explore novel admixtures to further improve strength and water durability. Full article

Biomass offers a renewable pathway for sustainable infrastructure, particularly in bio-oil production from biomass through processes such as fast pyrolysis to be used as an alternative to asphalt binders. This review explores biomass sources, production techniques, and the role of bio-oil in addressing the demand for eco-friendly materials in the pavement construction industry. The review also examines the upgrading processes of bio-oil, its physical and chemical properties, and its application in producing bio-modified asphalt binder (BMA). The use of bio-oils in asphalt binders not only reduces the carbon footprint but also promotes the utilization of renewable resources, contributing to a more sustainable pavement industry. Additionally, bio-oil incorporation enhances asphalt binder performance by improving rutting resistance at high temperatures and stiffness at low temperatures, while reducing susceptibility to low-temperature cracking. Challenges include variability in high-temperature performance and moisture sensitivity. Based on the findings of this comprehensive review, future research directions should focus on optimizing production processes, broadening biomass feedstocks, and mitigating moisture issues to align bio-oil properties with asphalt binder specifications. Full article

The management of construction and demolition waste is a critical concern for sustainable urban development and environmental conservation. In this review, the authors provides an overview of the involvement of machine learning techniques like the support vector machine (SVM), artificial neural networks (ANNs), Random Forest (RF), K-nearest neighbor (KNN), deep convolutional neural networks (DCNNs), etc. in the estimation, classification, and prediction of construction and demolition waste, contributing to the advancement of sustainable waste management practices. The authors observed that the DCNN achieved an outstanding accuracy of 94% in the estimation and classification of construction waste. Based on the authors’ observations, the machine learning models are well suited for the prediction or classification of construction waste and are good for sustainable waste management in the future. This paper provides insights into the promising future of machine learning in revolutionizing waste management practices and future research. Full article

This paper examines the improvement in the performance characteristics and the rheological properties of modified bitumen through the addition of the thermoplastic polymer polyvinyl acetate (PVA). PVA is a synthetic polymer derived from the polymerization of the vinyl acetate. The effect of PVA on bitumen and bituminous mixtures was investigated through the conventional (penetration, softening point, force-ductility, elastic recovery, Marshall and Nicholson stripping tests) and Superpave (rotational viscosity (RV), rolling thin film oven (RTFOT), pressure aging vessel (PAV), dynamic shear rheometer (DSR) and beam bending rheometer (BBR)) tests. PVA was added to bitumen at rates of 2%, 4%, 6% and 8% by mass. Based on the bitumen test results, a PVA rate of 6% was selected for the mixture tests. The modification process was carried out at relatively low temperature (150 °C) and mixing time (20 min) based on various trials, considering the short-term aging of the bitumen. With PVA modification, the penetration value of the bitumen decreased while the softening point increased. As a result, the calculated penetration index (PI) increased and the thermal sensitivity of the bitumen decreased. Significant improvements were detected in elastic recovery and force-ductility tests. Additionally, PVA improved the resistance of asphalt to settling and cracking. Similar results were observed in the DSR and BBR tests. Furthermore, the stripping resistance increased and the stability value improved significantly in the mixture tests. Full article

This research study aims to enhance the understanding of corrosion behaviour in lapped spliced joints within reinforced concrete structures. Specifically, the effect of corrosion on bond degradation and crack formation is investigated. Accelerated corrosion tests were conducted on two sets of semi-cylindrical samples and half-beam blocks. By applying a constant voltage, the current-time relationship during the corrosion process was obtained. Subsequently, the samples were subjected to pull-out testing to assess their bond strength. Three primary modes of bond failure were observed: pull-out, splitting, or a combination of both. Notably, the results demonstrate that the reduction in bond strength is directly related to the corrosion level, considering factors such as mass loss, section loss, and diameter reduction. Furthermore, a strong correlation exists between corrosion-induced cracks and the weakening of bond strength. These findings align with existing research and enrich the experimental data in the current corrosion database for lap splice joints in reinforced concrete structures. Full article

In this study, we present a novel methodology for reducing uncertainties in detecting high-permeability regions in bricks by integrating brick imagery, color theory, unsupervised learning, and petrophysical concepts. Leveraging smartphone technology, our methodology identifies and analyzes moisture regions in red bricks, demonstrating its potential as a cost-effective tool for moisture characterization. This approach complements specialized moisture detection devices, highlighting the versatility of existing technology. Applied within the context of traditional red brick manufacturing in San Agustín Yatareni, Oaxaca, México, our results show that this methodology effectively identifies moisture-related anomalies, with water absorption values verified according to the NMX-C-404-ONNCCE-2012 and NMX-C-037-ONNCCE-2013 Mexican standards. We observed a significant inverse correlation between luminosity and moisture content, and a direct correlation between hue and moisture content. These findings suggest a reliable, non-invasive indicator of moisture levels, potentially improving the longevity of construction materials. The broader applicability of this approach in construction material analysis, particularly for bricks incorporating organic fibers, underscores its value as a tool for quality control. Furthermore, the integration of smartphone technology and interdisciplinary techniques contributes to advancing sustainable construction practices and improving material durability. Full article

Rigid road pavements and industrial floors are not only subjected to moving traffic loads, but can also be exposed to environmental influences such as acid attack. The strength and corrosion resistance of fiber-reinforced concrete with steel fibers (15–25 kg/m³) and polypropylene fibers (2–3 kg/m³) in an acidic environment were compared. The influence of the amount and type of dispersed reinforcement on water absorption and the volume of permeable voids, which in turn characterizes the durability of fiber-reinforced concrete under the action of acids, was determined. The change in the compressive strength of the studied fiber-reinforced concrete after 12 months of exposure in an acidic environment was studied. At low dosages of fibers (15 kg/m³ for steel and 2 kg/m³ for polypropylene fibers), dispersed reinforcement has little effect on the corrosion resistance of concrete. In turn, the decrease in the compressive strength of concrete without fibers after 12 months of aging in acid medium led to a reduction in the design class of the concrete from C25/30 to C20/25. At a higher consumption of dispersed reinforcement (25–30 kg/m³ of steel fiber and 2.5–3.0 kg/m³ of polypropylene fiber), fiber-reinforced concrete had a higher corrosion resistance while maintaining the design compressive strength class C25/30. Structural changes in fiber-reinforced concrete after aging in an acidic environment were determined by X-ray diffraction analysis and compared with samples aged in water. It has been experimentally confirmed that the efficiency of polypropylene fibers in an acidic environment is not lower than that of steel fibers. However, the use of polypropylene fibers is economically advantageous. Full article

Alkali-activated materials are promising alternatives to cement. This study investigated the effects of the silica content, particle size, and replacement ratio of rice husk ash (RHA) on the compressive strength and the optimization of these parameters. Seventeen mixtures with different materials were tested to evaluate their compressive strengths. Three levels of particle size, silica content, and RHA replacement ratio were used. The effects of RHA characteristics on the compressive strength were investigated based on Archimedes porosity, pH, ignition loss, and X-ray diffraction. The experimental results reveal that the replacement ratio of RHA was p-values < 0.002, which affected the compressive strength compared with the particle size (p-values < 0.450) and silica content of the RHA (p-values < 0.017). It was confirmed that the optimum values of particle size, silica content, and replacement ratio of RHA were 50 µm, 90%, and 15 wt.%, respectively. After re-testing, the compressive strength of mortar made with the optimum values was 49.8 MPa. This increase in compressive strength was also found to be closely related to the porosity, pH, and ignition loss of the paste. It was confirmed that the replacement ratio of RHA increased with decreasing porosity and pH and increasing ignition loss, which was related to the formation of calcite and C-S-H. Full article

Thermal insulation is a reliable strategy for achieving optimal thermal comfort in built environments and is among the most effective energy-saving measures. Currently, environmentally friendly insulation materials produced from plant and animal fibers constitute a significant component of the building industry, largely due to their minimal embodied energy and concerns about certain synthetic insulation materials’ potential adverse health effects. The main objective of the present study is to encourage and facilitate the utilization of environmentally friendly thermal insulation materials derived from biological sources, including vegetal and animal fibers, to improve thermal comfort and consequently reduce energy consumption in buildings. The study attempts to simulate the indoor air temperature profiles of a single building constructed using locally sourced materials and insulated in a series of stages with the aforementioned insulation materials. Firstly, insulation is applied exclusively to the roof. Secondly, the insulation is applied to the remaining wall surfaces. Alternatively, the insulation is applied to both the roof and the wall surfaces simultaneously. The objective is to ascertain the optimal combination of bio- and geo-insulating materials to achieve thermal comfort in buildings constructed with local materials in tropical climates. The Gauss-Seidel iterative method was employed to solve the energy equations that had been written on the walls and roof of the building. The equations were then discretized using the nodal method. To ascertain the thermal comfort of the simulated buildings, a comparison was made of the indoor air temperatures. The results of the simulations demonstrated that the utilization of wood fiber, reed panels, and straw bales as insulation materials led to a notable enhancement in comfort levels across all five building types, with an average increase of 17.5%. Among these materials, wood fiber emerged as the most effective insulation option, reducing temperatures by up to 19%. Its integration into the sheet metal-clad Banco building would be particularly advantageous. The findings demonstrate that the simultaneous insulation of walls and roofs with natural fiber thermal insulation materials markedly reduces indoor air and wall temperatures in buildings by up to 19% in comparison to uninsulated walls and roofs. Full article

Rapid repair materials (RRMs) have been used in concrete overlay systems to rehabilitate infrastructure for many years. The bond performance between RRMs and a concrete substrate is crucial for maintaining the desired performance and can deteriorate due to freeze–thaw action. In the case of partial depth repairs (PDRs), the mechanical and durability properties at the interface between the substrate and repair materials have not been thoroughly studied resulting in frequent failures. There is limited research on the freeze–thaw durability of RRM overlay–substrate interface, and no standardized test methods exist for evaluating the performance under freeze–thaw cycling. The proposed experimental procedure combines freeze–thaw cycling of an overlay–substrate specimen with pull-off testing of the overlay. Three RRM overlay systems were used consisting of calcium sulfoaluminate cement and ordinary Portland cement (PC), and a ternary blend of PC, calcium aluminate cement, and calcium sulfate cement. A correlation between tensile bond strength and fundamental transverse frequency in composite specimens was observed, and the results demonstrated that RRMs can maintain robust adhesion following 300 cycles of freeze–thaw exposure. Furthermore, the employed testing methodology elicited bond-only failures, underscoring the necessity for continued investigation into optimal conditioning intervals and substrate integrity to enhance the durability of repair systems. Full article

A new scheme for forming partially regular microreliefs by rotational rolling is proposed. A new transcendental curve-shaped, partially regular microrelief (of a trochoid type) is discussed; the shape and geometric parameters of its grooves are substantiated. Grooves discussed below proved to be technologically advanced, providing for a high performance of all types of equipment. Once combined, they act together to provide for the best in-service properties of planar, partially regular microreliefs formed by rotation, which are unparalleled among those of their kind. Analytical dependences are presented that describe the groove’s shape. A relationship is established between the main technological parameters, that is, feed rate and rotation frequency of the deforming element that produces microrelief grooves of different shapes and sizes. Possible location variants for microrelief grooves are given and classified. Technological layouts and movement cyclograms are substantiated for the tool that forms regular microrelief grooves by means of rotation. A comparative analysis of the profile lengths of the grooves of rotational and sinusoidal microreliefs modeled in the MathCAD environment was conducted. Full article

The inadequate resistance of traditional asphalt binders to aging, temperature fluctuations, and fatigue cracking underlines the necessity for innovative modifications to boost pavement durability. This study aims to state the inadequate exploration of the direct application of composite nanomaterials in asphalt binders by assessing their direct effects on physiochemical and durability properties without the inclusion of additional additives. The composite nanomaterials, combined with different amounts of Nano-Silica, Nano-Alumina, and Nano-Copper oxide, were incorporated into the binder at 2%, 4%, and 6% by weight. A series of conventional and rheological tests were conducted, including penetration, temperature susceptibility, Dynamic Shear Rheometer (DSR), Rolling Thin Film Oven Test (RTFOT), and Bending Beam Rheometer (BBR). The results demonstrated that the addition of 2% nanomaterials improved penetration by 34% and 41% for unaged and aged samples, respectively, while a 4% addition reduced temperature susceptibility by 64% for aged binders in a mix containing equal amounts of combined nanomaterials. DSR analysis indicated enhanced stiffness and viscoelastic properties, with increased complex shear modulus (G*) and reduced phase angle (δ). Aging resistance was enhanced as established by RTFOT, and acceptable low-temperature performance was attained per BBR results. These results found composite nanomaterials as a capable key for advancing asphalt binder performance. Full article