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Hybrid externally-bonded reinforcements are considered a viable technique for strengthening existing concrete structures. They combine high-performance impregnated textiles with matrices containing dispersed microfibres to foster the ductility and toughness of the composite system. In this paper, the mechanical performance of textile-reinforced strain-hardening cement-based composites (TR-SHCC) is investigated in detail. A novel high-performance inorganic binder based on limestone calcined clay cement (LC3) is reinforced with both polyethylene (PE) dispersed microfibres and carbon fibre (CF) textiles as continuous biaxial reinforcement. The CF yarns are impregnated by an automated process to improve the monolithic response under uniaxial tensile loading and to ensure high production consistency. Fully inorganic suspensions, i.e., geopolymer and cement-based, are being investigated, as they can provide superior thermal stability compared to traditional polymeric impregnating agents. Interphase adhesion is investigated by single-yarn pull-out tests, microscopy and µCT at various micro scales. On the one hand, the improved adhesion promoted by cement impregnation resulted in the finest and most diffuse crack pattern. Conversely, the strength of the overall composite is mainly governed by the tensile failure of the yarns, irrespective of the bond, and dispersed fibres consistently improve the post-cracking stage and the strength of the hybrid composites.

[Display omitted] • The affinity of cement impregnation with the matrix leads to a higher bond strength. • A denser interphase zone is seen for cement-impregnated yarns in a cement-based matrix. • Hybrid composites exhibit distinctive bilinear σ-ε response due to SHCC ductility. • Mineral impregnations clearly outperform epoxy one in reducing crack width. Hybrid externally-bonded reinforcements are considered a viable technique for strengthening existing concrete structures. They combine high-performance impregnated textiles with matrices containing dispersed microfibres to foster the ductility and toughness of the composite system. In this paper, the mechanical performance of textile-reinforced strain-hardening cement-based composites (TR-SHCC) is investigated in detail. A novel high-performance inorganic binder based on limestone calcined clay cement (LC3) is reinforced with both polyethylene (PE) dispersed microfibres and carbon fibre (CF) textiles as continuous biaxial reinforcement. The CF yarns are impregnated by an automated process to improve the monolithic response under uniaxial tensile loading and to ensure high production consistency. Fully inorganic suspensions, i.e., geopolymer and cement-based, are being investigated, as they can provide superior thermal stability compared to traditional polymeric impregnating agents. Interphase adhesion is investigated by single-yarn pull-out tests, microscopy and µCT at various micro scales. On the one hand, the improved adhesion promoted by cement impregnation resulted in the finest and most diffuse crack pattern. Conversely, the strength of the overall composite is mainly governed by the tensile failure of the yarns, irrespective of the bond, and dispersed fibres consistently improve the post-cracking stage and the strength of the hybrid composites. [ABSTRACT FROM AUTHOR]

Mineral‐bonded composites for enhanced structural impact safety: material level investigations The Research Training Group GRK 2250/1 „Mineral‐bonded composites for enhanced structural impact safety" aims at the development of novel strengthening materials with various types of fiber reinforcement for enhancing the impact resistance of the critical infrastructure. Adequate testing methods and evaluation protocols are developed for a fundamental material characterization including the rate effects. The experimental results form an important basis for formulating numerical models for simulations of the composites, strengthening layers and concrete elements by linking different space and time scales. Finally, methods for evaluating the sustainability and resilience of the developed strengthening solutions and materials are developed. [ABSTRACT FROM AUTHOR]

Existing concrete or reinforced concrete structures feature, as a rule, a relatively low resistance to various types of dynamic loading, such as earthquake, impact or blast. This makes it extremely important to develop and propose effective and feasible solutions for strengthening the structures prone to such loading. The contribution will provide an overview of the Research Training Group GRK 2250 “Mineral-bonded composites for enhanced structural impact safety” established in 2017 by the German Research Society (DFG) at the TU Dresden. The goal of GRK 2250 is to bring substantial improvements in the impact resistance of existing buildings by applying thin layers of strengthening material. By using innovative, mineral-bonded composites, public safety and the reliability of vitally important infrastructure should be significantly enhanced. The scientific basis to be developed will additionally enable to build new, impact resistant structures economically and ecologically. [ABSTRACT FROM AUTHOR]

In the first part of this study, the feasibility of manufacturing resin-bonded particleboard from the recently identified Brazilian giant bamboo (Guadua magna) was evaluated. In this second part, the main goal was to study the material properties of the cement and gypsum-composites made from that bamboo species. The effect of CaCl2 addition in the physical and mechanical properties was also evaluated. Initially, the hydration test was performed to determine the inhibition index of the bamboo particles in the cement and gypsum setting. Three concentrations of CaCl2 were used to produce bamboo cement-bonded particleboards (BCBP): 0%, 2% and 4%. CaCl2 was not added into bamboo gypsum-bonded particleboards(BGBP). Mechanical and physical properties were evaluated and nondestructive testing was performed as well. The inhibition index of Guadua magna in the cement or gypsum setting was classified as "low inhibition". The addition of CaCl2 at bamboo-cement boards increased the internal bonding and reduced the water absorption. Other properties were not significantly affected. The bamboo-cement boards presented higher bending strength and lower moisture content than bamboo-gypsum boards.

In the first part of this study, the feasibility of manufacturing resin-bonded particleboard from the recently identified Brazilian giant bamboo (Guadua magna) was evaluated. In this second part, the main goal was to study the material properties of the cement and gypsum-composites made from that bamboo species. The effect of CaCl2 addition in the physical and mechanical properties was also evaluated. Initially, the hydration test was performed to determine the inhibition index of the bamboo particles in the cement and gypsum setting. Three concentrations of CaCl2 were used to produce bamboo cementbonded particleboards (BCBP): 0%, 2% and 4%. CaCl2 was not added into bamboo gypsum-bonded particle boards (BGBP). Mechanical and physical properties were evaluated and nondestructive testing was performed as well. The inhibition index of Guadua magna in the cement or gypsum setting was classified as “low inhibition”. The addition of CaCl2 at bamboo-cement boards increased the internal >bonding and reduced the water absorption. Other properties were not significantly affected. The bamboocement boards presented higher bending strength and lower moisture content than bamboo-gypsum boards.

In the first pan of this study, the feasibility of manufacturing resin-bonded particleboard from the recently identified Brazilian giant bamboo (Guadua magna) was evaluated. In this second part, the main goal was to study the material properties of the cement and gypsum-composites made from that bamboo species. The effect of CaCl2 addition in the physical and mechanical properties was also evaluated. Initially, the hydration test was performed to determine the inhibition index of the bamboo particles in the cement and gypsum setting. Three concentrations of CaCl2 were used to produce bamboo cementbonded particleboards (BGBP): 0%, 2% and 4%. CaCl2 was not added into bamboo gypsum-bonded particle boards (BGBP). Mechanical and physical properties were evaluated and nondestructive testing was performed as well. The inhibition index of Guadua magna in the cement or gypsum setting was classified as "low inhibition". The addition of CaCl2 at bamboo-cement boards increased the internal bonding and reduced the water absorption. Other properties were not significantly affected. The bamboo-cement boards presented higher bending strength and lower moisture content than bamboo-gypsum boards. [ABSTRACT FROM AUTHOR]