Abstract The incorporation of recycled waste glass into lightweight self-compacting concrete (LWSCC) has developed as a sustainable technique to reducing natural aggregate consumption and environmental impacts. In this study, the effect of combining waste glass in two particle size kinds that is coarse glass (greater than 1.18 mm) and fine glass (less than 1.18 mm) as a partial replacement for fine aggregate at percentage of replacement of 0, 10, 20, 30, and 40% on the fresh properties (slump flow, T500, v-funnel, L-box and fresh density), mechanical properties (equilibrium density, compressive strength, splitting strength, flexural strength, modulus of elasticity and impact resistance strength), and durability properties (sorptivity, water absorption and alkali – silica reaction) of LWSCC were evaluated. Two groups of mixtures, assigned as GC and GF, were prepared with various replacement percentages. Results of fresh properties showed all mixtures confirm requirements of EFNARC indicating that the presence of waste glass did not affect the self-compacting properties. A fresh and equilibrium density showed a gradual reduction with increasing glass content. GC mixtures displayed a continuous reduction in all mechanical properties, but GF mixtures exhibited considerably improvement mechanical performance up to 20%. GF mixture showed a superior performance in durability of LWSCC than GC, which reduced water absorption, sorptivity, and ASR expansion, indicating a denser and more stable microstructure. In terms of fresh properties, the best results were best replacement level at 20% for GC mixtures and 10% for GF mixtures. Among the investigated mixtures, GC10 and GF20 exhibited the most favorable overall balance of the measured fresh, mechanical, and durability properties. These results confirm that LWSCC incorporating waste glass, particularly fine glass at best levels, can be used as structural lightweight concrete.
Abstract This research examines the dual role of Carbon Fiber Reinforced Polymer (CFRP) U-shaped wrapping and spike anchors (SA), installed laterally or vertically, in enhancing stress transfer at the concrete-laminate interface and mitigating premature debonding. In addition to the RC control beam, eight beams organized into three groups were investigated. Group 1 evaluated the strength gain provided by Externally Bonded Reinforcement (EBR) alone or EBR supplemented with a single anchorage system, either a U-wrap or spike anchor, to secure the CFRP laminate. Group 2 investigated EBR with a single end U-wrap paired with either double lateral or single vertical bottom SAs. Group 3 employed double end U-wraps alone or in combination with single or double lateral SAs per sheet. The results revealed that incorporating spike anchors alone was more effective than U-wrapping. Flexural capacity increased by over 81% compared to the control beam and by 50% relative to the beam strengthened solely with EBR. On the other hand, hybrid configurations of spike anchors and U-wraps showed limited additional benefit, except for the case of double U-wraps combined with double lateral SAs, which achieved flexural strength gains of over 96% and 62% compared to the control and EBR-only beams, respectively. Anchoring also resulted in an enhanced flexural behaviour where most of the anchored specimens failed by CFRP rupture rather than CFRP debonding, indicating a better utilization of CFRP material.
Abstract This study presents a rigorous investigation into the inelastic flexural response of steel-encased composite reinforced concrete beams incorporating out-of-plane segmental configurations fabricated from normal strength concrete and high-strength concrete. A total of thirteen beam specimens were organized into two series of geometrically and mechanically identical configurations, differentiated solely by concrete compressive strength grade, thereby isolating the influence of this material variable on the observed failure mechanisms and load-deformation characteristics. Parametric results indicated that the introduction of out-of-plane segmental geometry induced a progressive and monotonic deterioration in ultimate load-carrying capacity, cracking load beam, and yielding resistance, with the magnitude of degradation correlating directly with the number of segmental joints. While failure of straight beam specimens was uniquely in pure flexure with peak midspan deflections, segmented configurations demonstrated a coupled shear-torsional failure mechanism with oblique deformation paths traversing along the interior perpendicular axes of the segmental interfaces; an indication of stress redistribution mustered by geometric discontinuities introduced at the joint locations. While HSC specimens exhibited higher initial flexural stiffness than their NSC counterparts on account of initial load-deflection relationship, this advantage did not extend to post-cracking response due to the inherent brittleness associated with HSC causing an abrupt drop in strength after cracking occurs for the non-composite behaviour configuration and ultimate load capacity alone is not sufficient for assessing structural adequacy. The presence of continuous internal steel section was the most significant parameter considering all configurations under investigation yielding simultaneous ultimate resistance increases close to 200 kN in NSC comparative beams, yet with large displacements ductility and energy dissipation capacity enhancements. More importantly, the surrounding steel element has changed the nature of structural functionality: no longer are segmental connection zones regions of stress concentration and early failure, but areas of cohesive and relatively uniform stress transfer, returning global structural continuity over multiple joints.
Abstract Many methods have been developed for strengthening and repairing damaged reinforced concrete (RC) structures as alternatives to removal or replacement. The conventional way of strengthening RC columns is to use a steel jacketing composed of four steel angles plus battens. This study offered an alternative strengthening technique that is simple to use and low-cost. They are strengthened by thin (0.5 mm thick) steel plate strips that are placed transversely and longitudinally at the middle height and 0.25 length of the column, as well as the full length of the column. This research focused on RC slender columns and experimentally studied the effect of this technique of strengthening under different eccentric loads on six RC slender columns using self-compacting concrete. The experiment’s results illustrated the impact of strengthening, as well as eccentric loads, on the behaviour of the columns. The reduction of lateral deflection increased from 3.83% to 5.10%, and column capacity increased from 4.25% to 36.55%. There was a clear rise in eccentricity as the energy absorption capacity improved by 9.65% to 72.63%. Furthermore, regarding strengthening efficiency measured per unit volume of steel was range 13.22% to 19.10%. In addition, by strengthening the columns, failure was delayed, the failure position changed, and strain was decreased. This technique gives structural engineers a dependable, safe way to strengthen RC slender columns easily and economically.
Abstract Interlayer bonding in flexible pavements has an essential influence on their structural strength and performance. In this study, the combined outcome of application rate of tack coat and the condition of geotextile coverage on the interlayer shear strength (ISS) and the rutting resistance of double-layer asphalt systems is investigated. Specimens of binder and wearing courses were prepared with CSS-1H (cationic slow-setting asphalt emulsion, low-viscosity grade, with harder asphalt residue) emulsified tack coat at amounts of 0, 0.3, 0.6, 0.9 and 1.2 L/m 2 . Three interface patterns of geotextile coverage were tested; unreinforced, 50% and 100%. The bonding between layers was assessed by direct shear bond test, and the rutting resistance was evaluated by wheel tracking test. Results revealed that the optimal amount of tack coat was highly dependent on the interface condition. Unreinforced specimens achieved the maximum ISS of approximately 1083.89 kPa at 0.3 L/m 2 , while the geotextile-reinforced mixes required higher tack coat rates to develop sufficient bonding due to emulsion absorption by the geotextile. In general, control specimens showed higher ISS values compared to specimens compromising geotextile between layers, but there is a significant enhancement in resistance to permanent deformation for specimens modified with geotextile with a sufficient amount of tack coat. The full geotextile coverage with 1.2 L/m 2 tack coat resulted in the best rutting performance, reducing the rut depth by approximately 28% when compared with the optimum unreinforced condition. At its optimum tack coat application rate of 0.9 L/m 2 , partial geotextile coverage achieved a 17.4% reduction in rut depth relative to the optimum unreinforced condition, indicating a potentially economical alternative. The results emphasize the need to optimize the application rate of tack coat and geotextile coverage to provide balanced interlayer bonding and rutting resistance of asphalt pavements.
