The effect of graphene oxide (GO) on the mechanical strengths and durability of cement composites was researched by preparing GO-modified cement mortars. Thermogravimetric analysis (TGA) and nuclear magnetic resonance (²⁹Si MAS-NMR) were performed on the cement paste to evaluate the influence of GO on the hydration process and chain structure of calcium-silicate-hydrate (C–S–H) gels. TGA revealed that the high GO dosage increased the content of C–S–H by 5.46% compared with the control at 28 days. Similarly, ²⁹Si-NMR improved the hydration degree and main chain length (MCL) in GO-modified samples at 28 days. The GO led to increases of 2.54% and 7.01% in the hydration degree and MCL, respectively, compared with the control at 28 days. These findings underscore the multifaceted role of GO in improving the mechanical properties and durability of cement composites. Mechanical strength tests, such as compressive and flexural tests, were conducted on cement mortars. The optimal dosage of GO increased the compressive strength by 9.02% after 28 days. Furthermore, the flexural strength of cement mortars with the combination of GO and superplasticizer (SP) after 28 days increased by 21.86%, compared with reference mortar. The impact of GO proved to be more pronounced and beneficial in the durability tests, suggesting that GO can enhance the microstructure through hydration products to create a dense and interconnected microstructure.

The reinforcement of concrete by using polyolefin fibres may be considered in structural design to meet the requirements of the applicable code rules. To achieve a reliable use of such a composite material, use of full-scale real structures is needed. The conversion of lab testing data into real practice properties is challenging and significantly influenced by various aspects, among which the size effect is a key one. Given that the available literature does not report coinciding conclusions about such an effect on quasi-brittle materials reinforced with fibres, further research is justified. Therefore, this work studies the behaviour of notched beams with three proportional sizes by using self-compacting polyolefin reinforced concrete with a fibre volume fraction of 1.1%. Flexural testing was carried out according to the standard EN-14651, with the results revealing the existence of the size effect. In addition, a reduction of the residual strength identified in the larger specimens was observed in fracture surfaces with equal fibre content.

Fibre-reinforced concrete (FRC) allows reduction in, or substitution of, steel-bars to reinforce concrete and led to the commonly named structural FRC, with steel fibres being the most widespread. Macro-polymer fibres are an alternative to steel fibres, being the main benefits: chemical stability and lower weight for analogous residual strengths of polyolefin-fibre-reinforced concrete (PFRC). Furthermore, polyolefin fibres offer additional advantages such as safe-handling, low pump-wear, light weight in transport and storage, and an absence of corrosion. Other studies have also revealed environmental benefits. After 30 years of research and practice, there remains a need to review the opportunities that such a type of fibre may provide for structural FRC. This study seeks to show the advances and future challenges of use of these polyolefin fibres and summarise the main properties obtained in both fresh and hardened states of PFRC, focussing on the residual strengths obtained from flexural tensile tests.

The postcracking capacity of fiber reinforced concrete (FRC) mainly depends on the content, material, and geometry of the fibers considered. Even though the general influence of these factors on FRC behavior has been extensively addressed, the uncertainty of the FRC performance prediction along with the variability of the results still poses a challenging issue that needs to be solved to encourage the use of FRC for design and construction purposes. In this line, a database including the results of the flexural residual strength obtained from different experimental programs combined with the results of previous studies has been gathered and analyzed herein to obtain general correlations and trends providing additional information about the influence of the fibers in FRC behavior, these meant to serve for initial design stages (e.g., make decisions on the type and amount of fibers based on technical and economical requirements). The results are analyzed distinguishing between the fiber material, the fiber shape, the aspect ratio and tensile strength. The results presented herein may provide valuable information on the initial prediction of the residual strength of FRC to fully take advantage of the mechanical properties of the material.

Textile Reinforced Concrete (TRC) is a composite material where a textile fabric (typically in carbon) is embedded within a cementitious matrix. This material has emerged as a promising alternative to conventional reinforced concrete, allowing for the construction of light and durable structures with a limited impact in terms of CO ₂ ‐eq footprint. The response of TRC in tension is, however, characterized by a brittle response, limiting its potential to redistribute internal forces and penalizing the overall structural performance. To enhance the behaviour of TRC, this research explores its combination with synthetic (polyolefin) fibres. The aim is to investigate the potential benefits in terms of cracking, control of delamination (namely in overlap regions of the fabric), and enhancement of the postpeak toughness. The paper presents a comprehensive experimental programme aimed at characterizing the material response of its components, the bond between the fabrics and the matrix, as well as the composite behaviour of TRC. The experimental results are interpreted and related to various physical parameters, such as the level of undulation of the fabric or the amount of fibres used. On that basis, a simple approach for design is proposed, accounting for the potential delamination of tension ties, as well as several practical conclusions.