Dynamic compression behavior of ultra-high performance concrete with hybrid polyoxymethylene fiber and steel fiber

Alkali-activated concrete (AAC) features excellent mechanical properties and sustainability. The incorporation of crumb rubber (CR), recycled concrete aggregates (RCAs), and recycled steel fibers (RSFs) can further enhance environmental sustainability. This paper mainly investigated the dynamic behaviors of a novel rubberized AAC incorporating RCAs and RSFs (RuAAC) through Split-Hopkinson Pressure Bar (SHPB) tests. The variables included three types of RSF content (1%, 2% and 3%), five types of rubber content (0%, 5%, 20%, 35% and 50%) and five impact pressures (0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa and 0.9 MPa). Dynamic stress–strain curves, dynamic strength, the dynamic increase factor (DIF), impact toughness and the synergistic effects of RSF and CR were discussed. The results show that increasing RSF and CR contents could improve the impact resistance of RuAAC under impact loading. The RuAAC exhibited significant strain rate sensitivity, and the sensitivity increased with larger contents of RSF and CR. The increase in strain rate sensitivity was more pronounced with higher CR contents, which was reflected in larger dynamic increase factor (DIF) values. Under high impact pressure, the impact toughness was obviously enhanced with higher RSF contents, while the contribution of increased CR content to impact toughness was not apparent, which may be attributed to the fact that this study only calculated the integral under the dynamic stress–strain curve before the peak stress to determine impact toughness, neglecting the potential contribution of CR particles after the peak point. The obvious strain sensitivity exhibited by the RuAAC in the SHPB tests indicated superior impact performance, making it particularly suitable for architectural structures prone to seismic or explosive impacts.

Section: Split-hopkinson Pressure Bar Testmentioning

confidence: 99%

Section: Split-hopkinson Pressure Bar Testmentioning

confidence: 99%

Section: Split-hopkinson Pressure Bar Testmentioning

confidence: 99%

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Impact Resistance of Rubberized Alkali-Activated Concrete Incorporating Recycled Aggregate and Recycled Steel Fiber

Che,

Li,

Chen

et al. 2024

“…UHPC is known for its extremely high compressive strength (≥120 MPa), durability, and high toughness [4][5][6]. However, it also has limitations, in terms of deformation and crack control [7,8].…”

Section: Introductionmentioning

confidence: 99%

Effect of Na2CO3 Replacement Quantity and Activator Modulus on Static Mechanical and Environmental Behaviours of Alkali-Activated-Strain-Hardening-Ultra-High-Performance Concrete

Zhuo,

Chen,

Luo

et al. 2024

Self Cite

The application of alkali-activated concrete (AAC) shows promise in reducing carbon emissions within the construction industry. However, the pursuit of enhanced performance of AAC has led to a notable increase in carbon emissions, with alkali activators identified as the primary contributors. In an effort to mitigate carbon emissions, this study introduces Na2CO3 as a supplementary activator, partially replacing sodium silicate. The objective is to develop a low-carbon alkali-activated-strain-hardening-ultra-high-performance concrete (ASUHPC). The experimental investigation explores the impact of varying levels of Na2CO3 replacement quantity (0, 0.75 Na2O%, and 1.5 Na2O%) and activator modulus (1.35, 1.5, and 1.65) on the fresh and hardened properties of ASUHPC. The augmentation of Na2CO3 replacement quantity and activator modulus are observed to extend the setting time of the paste, indicating an increase in the modulus of the activator and Na2CO3 replacement quantity would delay the setting time. While the use of Na2CO3 intensifies clustering in the fresh paste, it optimizes particle grading, resulting in higher compressive strength of ASUHPC. The tensile crack width of ASUHPC conforms to the Weibull distribution. ASUHPC with a Na2CO3 replacement quantity of 0.75 Na2O% exhibits superior crack control capabilities, maintaining a mean crack width during tension below 65.78 μm. The tensile properties of ASUHPC exhibit improvement with increasing Na2CO3 replacement quantity and activator modulus, achieving a tensile strength exceeding 9 MPa; otherwise, increasing the activator modulus to 1.5 improves the deformation capacity, reaching 8.58%. Moreover, it is observed that incorporating Na2CO3 as a supplementary activator reduces the carbon emissions of ASUHPC. After considering the tensile performance indicators, increasing the activator modulus can significantly improve environmental performance. The outcomes of this study establish a theoretical foundation for the design of low-carbon, high-performance-alkali-activated-strain-hardening-ultra—high-performance concrete.

“…Additionally, the utilization of aggregates in UHPC, such as natural river sand, has resulted in increased mining costs due to the diminishing availability of natural resources. Coupled with the high cost of steel fibres, this considerably escalates the production expenses of UHPC [7][8][9][10][11][12]. Consequently, the carbon footprint of UHPC is 2.52 times that of ordinary concrete, and the production cost is 8.3 times higher than that of ordinary concrete [1,13,14].…”

Section: Introductionmentioning

confidence: 99%

Ultra-High-Performance Alkali-Activated Concrete: Effect of Waste Crumb Rubber Aggregate Proportions on Tensile and Flexural Properties

Li,

Chen,

Che

et al. 2024

The declining availability of natural sand resources and the significant carbon footprint associated with the extensive use of cement are posing severe limitations on the advancement and application of ultra-high-performance concrete (UHPC). In this study, waste tyre-derived recycled crumb rubber particles (CR) were employed to replace quartz sand, and an alkali-activated cementitious material was used to produce waste tyre-alkali-activated UHPC (T-UHPAC). The influence of different CR replacement ratios (0%, 5%, 20%, 35%, 50%) on the tensile and flexural performance of T-UHPAC was investigated, and a predictive model for the stress–strain response considering the CR replacement ratio was established. An optimization method for improving the tensile and flexural performance of T-UHPAC was proposed. The results indicate that the effect of rough-surfaced CR on the interfacial properties of concrete differs from that of smooth quartz sand. A CR replacement ratio exceeding 35% led to a reduction in both the tensile and flexural strengths of UHPAC, while a replacement ratio at or below 20% resulted in a superior tensile and flexural performance of T-UHPAC. The established predictive model for tensile performance accurately forecasts the stress–strain behaviour of T-UHPAC under varying CR replacement ratios, with the accuracy improving as the CR replacement ratio increases. By utilizing CR to replace quartz sand in proportions not exceeding 20%, the production of low-carbon UHPC with exceptional comprehensive mechanical properties is achievable. Moreover, the development of T-UHPAC through the comprehensive utilization of waste tyres presents a promising and innovative approach for the low-carbon and cost-effective production of UHPC, thereby facilitating the sustainable development of natural resources. This research represents a significant step towards the widespread adoption and application of UHPC and thus holds substantial importance.