Flavio Stochino

Post-earthquake fire (PEF) is a secondary hazard in which seismic damage to buildings, utilities and fire protection causes uncontrolled ignition and spread. PEF in unstrengthened reinforced concrete (RC) and steel structures has been increasingly studied, whereas the behavior of structures strengthened with fiber-reinforced polymers (FRP), textile-reinforced mortars (TRM/FRCM), ultra-high-performance concrete (UHPC) or engineered cementitious composites (ECC) under consecutive earthquake and fire is largely unknown. This review combines the seismic performance of strengthened RC and masonry elements, their behavior at elevated temperatures and the coupled PEF scenario. A knowledge matrix relates the available PEF evidence to the type of study. No experimental study has subjected FRP- or TRM-strengthened elements to the complete sequence of cyclic damage at realistic drift, fire under sustained gravity load, and residual-capacity assessment. In fact, the available tests reverse the sequence or omit one stage, and no PEF data exist for UHPC or ECC. Current codes treat seismic and fire actions separately. Six research gaps are identified, from sequential experiments to codification. Moreover, this review proposes measurable damage descriptors for the post-earthquake initial state and a set of verifications that designers can perform before PEF provisions are codified.

The production of sustainable polymer-based composites from agricultural waste has gained great attention due to the growing demand for lighter and stronger materials. In this study, alkali-treated CLSF (30 wt.%) was used as reinforcement in vinyl ester composites containing 0, 5, 10 and 15 wt.% cashew nutshell biochar, fabricated by hand lay-up followed by compression molding. The effect of biochar content on the tensile strength, flexural strength, impact strength, Shore D hardness, erosion resistance and microstructure of the vinyl ester composites was systematically evaluated by mechanical testing, erosion testing, scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). Biochar inclusion remarkably enhanced the properties of the composites when compared to the unfilled composite, depending on the optimum filler content. The composite containing 10 wt.% biochar showed the best flexural strength (31.88 MPa) and Shore D hardness (83.22), coupled with minimum erosion loss (0.021%), hence high stiffness and abrasion resistance. However, 5 wt.% biochar showed the best impact resistance, indicating effective energy absorption ability. SEM study showed enhanced filler distribution and fiber–matrix interface interaction for lower levels of biochar content, but higher amounts (15 wt.%) caused agglomeration of particles with the appearance of microvoids, resulting in reduced mechanical properties. X-ray diffraction showed that biochar addition leads to better structural ordering. In general, the obtained results clearly show that using 5–10 wt.% of cashew nutshell biochar increases multifunctional properties of coconut sheath fiber/vinyl ester composites.

The use of Rubberized Geopolymer Concrete (RGC) represents a sustainable solution that can reduce reliance on Portland cement and make use of the potential uses of waste-tire rubber in construction. This review paper critically evaluates the constituent materials, design parameters, rubber pretreatment, fresh and hardened properties, durability, microstructure, and performance-enhancement measures of RGC. It is found that higher content of rubber usually lowers the workability, density, compressive strength, and elastic modulus owing to the flexible nature of the rubber and poor interface bonding between rubber and geopolymer matrix. However, a suitable content of rubber can improve the deformability, toughness, shock-absorption capacity, vibration damping, and thermo-acoustic properties. Surface treatment and matrix modifications can improve the interface transition zone and partially minimize mechanical strength loss but the efficiency of the technique varies based on rubber content, precursor mixture, activator chemistry, and curing conditions. Some of the major future research gaps are a standardization of design and testing procedures, durability and structural scale validation, and life-cycle and techno-economic analysis. In future research, it should be considered to use multi-criteria optimization for improving the strength, ductility, durability, environmental impact, cost, and constructability of RGC.

Experimental measurements of the effective Young’s modulus of an unidirectional composite obtained by embedding 3D-printed PLA–CF fibers in a cold-curing polyurethane elastomeric matrix are presented. Specimens with a controlled number of aligned fibers were tested in uniaxial compression along the direction of alignment. The force-displacement records were processed with a routine that identifies the linear loading regime, converts it to stress–strain through the specimen geometry, and returns the longitudinal modulus together with a combined uncertainty built from the repeatability of multiple tests and from the scatter of the experimental curve. The measured modulus increases monotonically, on average, with the fiber volume fraction, yet remains several orders of magnitude below the modulus of the fiber material. Finally, the data are interpreted within a mean Green-operator (mGo) based Ponte-Castañeda and Willis homogenization scheme, which provides the full anisotropic effective moduli.