Assessing the performance of palm oil fuel ash and Lytag on the development of ultra-high-performance self-compacting lightweight concrete with waste tire steel fibers

Recent advances in ultra-high-performance concrete (UHPC) materials have emphasized the necessity for continuous research. This imperative is particularly pronounced given the widespread demand for materials that facilitate the design and construction of long-span bridges, high-rise towers, and architecturally complex structures. The current study strives to address this need by developing a novel ultra-high-performance self-compacting lightweight concrete (UHPSCLWC). This research introduced Palm Oil Fuel Ash (POFA) and Lytag as replacements for specific conventional components. Specifically, 5%–25% POFA was utilized at 5% intervals as a partial substitute for cement to counter the heavy cement requirement typical of UHPC. Similarly, 5%–25% Lytag was used in 5% increments as a lightweight aggregate substitute for fine aggregate. To further optimize UHPC's production cost, waste tire steel fibers (WTSF) sourced from discarded truck tires were employed as primary reinforcement. This study comprehensively evaluates the rheological, physical, functional, and extreme durability properties of the UHPSCLWC and provides microstructural analysis. Test results suggest that samples utilizing 20% POFA and Lytag demonstrate optimal improvements across assessed characteristics, notably improved thermal and acoustic performance. At 90 days, the highest enhancement in compressive strength, modulus of elasticity, and modulus of rupture was 14.09%, 33.54%, and 17.44% for samples with 20% POFA and Lytag. Due to the unique properties and porous nature of Lytag, the hardened density of UHPSCLWC was reduced from 1993 kg/m3 to 1705 kg/m3. These modified samples also displayed enhanced durability, reduced mass loss and chloride penetration, and increased residual compressive strength when subjected to extreme conditions. Furthermore, the optimal inclusion of 20% POFA and Lytag in the mixture facilitated higher peaks of hydration phases, as observed in x-ray diffraction analysis. The findings of this study suggest the practical potential of POFA and Lytag in developing an innovative UHPSCLWC modified with waste tire steel fibers. This study adds valuable insights to the growing body of knowledge in the field of UHPC material development. •With Lytag, the hardened density of UHPSCLWC was reduced.•20% Lytag was effective in reducing thermal conductivity.•WTSF proved to enhance the modulus of rupture effectively.