Grouting materials, typically dense liquids, play a crucial role in reinforcing and sealing structures by effectively filling and repairing the pores in existing building systems. This paper provides a comprehensive overview of recent advancements in physical, chemical, composite, and environmentally friendly grouting materials. Emphasis is placed on the modifications of physical grouting materials, including silicate cement, sulfoaluminate cement, and ultrafine cement-based variants, which are widely used due to their robust performance. Among these, ultrafine cement-based grouts exhibit injection properties similar to those of chemical grouts, yet without the need for chemical additives, presenting significant potential for application. The paper also explores the latest advancements in the modification of chemical grouting materials, such as acrylic salts, epoxy resins, and polyurethanes, which offer diverse properties tailored to specific engineering needs, progressively replacing traditional cement-based solutions. Additionally, the paper synthesizes key grouting reinforcement theories, including permeation, fracturing, and compaction grouting, which together optimize the overall effectiveness of the grouting process. Finally, the paper identifies current challenges in the research on grouting materials and proposes promising directions for future development.
Repeated low-velocity impacts can induce barely visible damage in composite laminates, which accumulates progressively and may eventually result in catastrophic structural degradation. Predicting the transition from stable damage accumulation to rapidly accelerating damage remains challenging because impact energy, contact geometry, and damage evolution are strongly coupled. In this study, published repeated-impact damage curves were digitized and continuously fitted, and the second change point was defined as the catastrophic damage-transition threshold. This threshold serves as an early-warning precursor to macroscopic failure. The data analysis first established separate empirical relationships between the transition threshold and impactor diameter and impact energy. These relationships were then combined into a unified threshold surface that captures the coupled geometric and energetic trends within the calibrated range. To interpret the empirical model, a mechanical derivation was developed by considering diameter-insensitive resistance, global plate bending, local Hertzian indentation, and cumulative damage growth. The derivation establishes a normalized power-law structure that connects the separate empirical relationships with the unified surface while showing that the fitted exponents remain condition-dependent. Independent repeated-impact datasets were further examined to assess the transferability of the framework. The external data support an inverse power-law energy-life relationship and a positive diameter effect after dataset-specific recalibration. Although the external studies use penetration or perforation life rather than the same change-point criterion, the numerical proximity of the corresponding impact counts provides a reasonable basis for comparing the scaling trends. The proposed framework therefore provides a physically interpretable tool for interpolation, preliminary impact-tolerance assessment, and test planning.
The need for non-toxic radiation-shielding composites has increased because conventional lead-based and heavyweight shielding solutions raise environmental, handling and structural-load concerns. This study aimed to evaluate whether thermally treated colemanite, a naturally occurring boron-rich mineral, can improve photon and neutron attenuation in a cement-based matrix while clarifying the associated mechanical penalty. Portland-cement composites containing 0, 1, 5 and 10 wt.% colemanite were prepared and tested for X-ray/gamma-ray mass attenuation, neutron attenuation, 7-day compressive strength, SEM morphology and XRD phase identification. Colemanite addition modified photon attenuation in an energy-dependent manner, with the strongest average low-energy improvement observed for the 5 wt.% mixture (+5.5% relative to the control). The effective linear neutron attenuation coefficient increased from 0.248 cm -1 for the control to 0.346 cm -1 for the 5 wt.% composite, whereas the highest density-normalized neutron attenuation value was obtained at 10 wt.% colemanite. This shielding benefit was accompanied by severe strength loss: 29.3%, 93.0% and 98.0% at 1, 5 and 10 wt.% colemanite, respectively. SEM and XRD findings indicate that colemanite was incorporated as a crystalline particulate phase, but heterogeneous dispersion and hydration interference governed the shielding-mechanical trade-off. The composites are therefore more suitable for non-load-bearing radiation-protective panels, partitions and surface layers than structural concrete applications.
Continuous-reinforced thermoplastic composites are becoming increasingly important for mass production of lightweight components across various industrial sectors. This paper describes a novel process chain for the production of continuous fibre reinforced thermoplastic matrices with a rotationally symmetric cross-section, using rotational moulding technology. The process chain is based on wound and pre-consolidated preforms, which are then formed into the final geometry by rotational moulding. To support the manufacturing of smaller diameters, a composite core is used to increase the pressure during manufacture. The experimental results are examined by cross-sectional micrographs and show the approach’s feasibility.
This study investigates the mechanical properties of carbon fiber-reinforced epoxy composites reinforced with recycled textiles from the automotive industry-specifically airbag fabric (nylon 6.6) and seat-belt webbing (polyester). The objective was to assess the potential of these recycled reinforcements to enhance impact resistance, which is critical for automotive safety applications. Six composite configurations with different lay-ups were manufactured: a reference carbon composite (C), a carbon composite reinforced with a conventional aramid fabric (A), and four hybrid composites incorporating nylon 6.6 (AB), seat-belt webbing (P), an aramid/seat-belt combination (AP), and a nylon 6.6/seat-belt combination (PB). Specimens were produced by hand lay-up and subsequently subjected to mechanical testing. Tensile properties were evaluated in accordance with & Ccaron;SN EN ISO 527-4, and Charpy impact performance was measured according to ISO 179-2 (unnotched). The results showed that incorporating recycled seat-belt reinforcement (P, AP, PB) led to a pronounced increase in impact strength (most notably for AP) compared with the reference carbon composite (C). However, this improvement in toughness was accompanied by a reduction in tensile strength. The aramid-only configuration (A) achieved the highest average tensile strength. The hybrid AP and PB laminates, combining carbon plies with aramid fabric/nylon 6.6 and seat-belt reinforcement, exhibited the best impact energy absorption capability. Overall, the findings suggest that recycled seat-belt textiles represent a promising alternative reinforcement for improving the toughness of carbon composites in applications requiring high impact resistance, provided that the trade-off between toughness and static strength is carefully considered.
