Constr. Mater., Volume 4, Issue 2 (June 2024) – 5 articles

Permeable pavements are vital in sustainable urban water management, addressing critical challenges while enhancing environmental resilience. This study focuses on the innovative polyurethane-bound Porous Rubber Pavement (PRP), which possesses high permeability and elasticity due to its unique composition of stone and crumb rubber aggregates with polyurethane binders. PRP’s useful benefits, such as noise reduction, efficient snow/ice management, and others, enhance its appeal, emphasizing the necessity for a thorough investigation into its performance and characteristics, especially in North America. To address these gaps, this paper comprehensively analyzes PRP’s durability and performance, including its strength range, failure criteria, and susceptibility to moisture-induced damage. Various testing methods are utilized, such as evaluating the abrasion loss of the stone aggregate, rutting, stripping due to moisture susceptibility, resistance to degradation from impact and abrasion, and permeability tests. This study evaluates five distinct mix compositions with varied proportions of aggregates and binders. Further, it investigates the effects of different binder types on PRP performance, such as aromatic and aliphatic binders obtained from various sources. Upon the analysis of the comprehensive test results, it was found that the mix characterized by increased rubber aggregates and a high binder content demonstrated a superior performance across various tests for PRP applications. This mix exhibited an enhanced resistance to abrasion, raveling, rutting, and permanent deformation, showcasing its durability and functionality. Additionally, when combined with an aliphatic binder, it displayed an optimal performance even in challenging freeze–thaw conditions, making it a recommended choice for long-term pavement solutions. Full article

This research focuses on the utilization of recently investigated aluminosilicate industrial wastes as precursors to produce non-structural precast alkali-activated concrete pavement blocks. For this purpose, conventional blocks (200 mm × 100 mm × 80 mm) were produced using electric arc furnace slag and municipal solid waste incineration bottom ashes as the sole binders. Portland cement and fly ash blocks were produced as references. The blocks underwent a curing regimen comprising thermal, dry, and carbonation curing stages. Control uncarbonated specimens were subjected to dry curing instead of CO₂-based curing to evaluate the influence of carbonation on the blocks’ strength development. The specimens were subsequently examined following EN 1338, which is the European standard for assessing and ensuring the conformity of conventional concrete pavement blocks. The carbonated blocks revealed improved mechanical and physical properties in relation to the uncarbonated ones. All blocks met standard dimensions, showed minimal skid potential (most indicating extremely low potential for slip for reporting unpolished slip resistance values exceeding 75), and had enhanced abrasion resistance due to carbonation, showing 30% and 11% less volume loss due to abrasion for fly ash and bottom ash, respectively. Carbonated blocks performed better than non-carbonated ones, displaying lower water absorption (0.58% and 0.23% less water absorption for bottom ash and slag, respectively) and higher thermal conductivity (20%, 13%, and 8% increase in values for fly ash, slag, and bottom ash, respectively). These results confirm the effectiveness of the accelerated carbonation curing technique in improving the block’s performance. Despite the promising outcomes, further optimization of the alkaline solution and carbonation curing conditions is recommended for future research. Full article

Rolling shear in cross-laminated timber (CLT) has been identified as the governing factor influencing design value. Likewise, densification has been found to be an effective method of enhancing the rolling shear strength of lumber and in turn, CLT. In this study, utilizing knowledge of material properties, optimization of the compression ratio for densification has been presented. Three-layered CLT beams made from non-densified lumber, grade #1 loblolly pine (Pinus taeda L.), were subjected to a bending load at a span-to-depth ratio of eight and had a rolling shear failure at the mid-layer with a shear strength of 3 MPa. Assuming the same modulus of rupture (MOR) for both lumber and CLT made from the same species and grade, the MOR of lumber was used to calculate the minimum required shear strength (MRSS) of the transverse mid-layer to change the failure mode of the CLT beam from rolling shear to tensile failure. Using the relationship between the compression ratio and the increase in rolling shear strength, the optimized compression ratio for densification was calculated. This procedure resulted in a compression ratio of 16.67% for densification of the mid-layer to avoid rolling shear in the case of CLT beams with a span-to-depth ratio of eight. To verify this process, CLT beams with mid-layers densified at 16.67% were fabricated and submitted to a bending test. Rolling shear failure was mitigated and densified CLT beams failed in tension with a MOR similar to that of lumber, 47.45 MPa. Likewise, rolling shear strength was observed to increase by 48% for CLT that had a densified mid-layer at 16.67%. Full article

Reinforced concrete (RC) columns with short lap splices built in the early 1970s or before are known to have deficient seismic strength and ductility. These short lap splices are poorly confined and located right above the foundation level, where it is known that the inelastic demands are high under seismic loading. In this study, a numerical model for estimating the lateral strength and deformation of RC columns with short lap splices is introduced. The latter model is based on local bond–slip analytical models derived from isolated anchored bars through the closed-form solution of the differential equation of bond. The proposed model is correlated to experimental data from cyclic loading tests on RC columns with deficient lap splices. It can be seen that the strength of short lap splices, the failure mode, and the column’s lateral resistance and deformation are in good agreement with the experimental results both under monotonic and cyclic seismic analyses. Full article

One of the most significant global challenges for humans is environmental pollution. The technology to control this problem is the utilization of semiconductors as photocatalysts. In the current study, iron-doped titania nanotubes (Fe/TiNTs) with increased photocatalytic effect were synthesized via a modified hydrothermal method. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy (TEM), gas adsorption, electron spin resonance (ESR) and UV–Vis diffuse reflectance spectroscopy (DRS). TEM results indicated that Fe/TiNTs have a tubular and uniform structure with an average outer diameter of 23–48 nm and length of 10–15 µm. ESR and DRS revealed that Fe³⁺ ions were successfully introduced into the TiNT structure by replacing Ti⁴⁺ ions. An enhanced light absorption in the range of 400–600 nm additionally indicated successful doping. The band gap was narrowed as iron wt% was increased. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) in the presence of Fe/TiNTs and TiTNs by monitoring the degradation of MO under UV light irradiation. An acceleration on the hydration of Portland cement was observed in the presence of 2.0 wt% Fe/TiNTs. Fe/TiNTs can be used as a nanomaterial in cement-based building materials to provide self-cleaning properties to the surface of concrete even in indoor environments. Full article