Influence of Particle Size on Compressive Strength of Alkali Activated Refractory Materials

Multi-Step Relaxation Characterization and Viscoelastic Modeling to Predict the Long-Term Behavior of Bitumen-Free Road Pavements Based on Polymeric Resin and Thixotropic Filler

Asphalt pavements are fundamental to modern transportation infrastructure, requiring elasticity, firmness, and longevity. However, traditional asphalt, based on bitumen, faces several limitations. To improve pavement performance, polymer resins are being used to substitute bitumen and improve requirements. Therefore, a deep understanding of the material behavior is required. This study presents the analysis of the relaxation behavior of a poly(methyl methacrylate)-based pavement and the influence of mineral fillers. An approach using a linear elastic-viscoelastic material model was selected based on evidence and validated across the linear and nonlinear deformation range. The results reveal no influence of the mineral fillers on the relaxation behavior. The presented modification of the linear elastic and viscoelastic modeling reveals accurate results to predict long-term pavement performance. This approach offers a practical method for forecasting asphalt behavior. Further research is needed to incorporate deformation behavior into the model.

Hybrid Materials Based on Fly Ash, Metakaolin, and Cement for 3D Printing

Nowadays, one very dynamic development of 3D printing technology is required in the construction industry. However, the full implementation of this technology requires the optimization of the entire process, starting from the design of printing ideas, and ending with the development and implementation of new materials. The article presents, for the first time, the development of hybrid materials based on a geopolymer or ordinary Portland cement matrix that can be used for various 3D concrete-printing methods. Raw materials used in the research were defined by particle size distribution, specific surface area, morphology by scanning electron microscopy, X-ray diffraction, thermal analysis, radioactivity tests, X-ray fluorescence, Fourier transform infrared spectroscopy and leaching. The geopolymers, concrete, and hybrid samples were described according to compressive strength, flexural strength, and abrasion resistance. The study also evaluates the influence of the liquid-to-solid ratio on the properties of geopolymers, based on fly ash (FA) and metakaolin (MK). Printing tests of the analyzed mixtures were also carried out and their suitability for various applications related to 3D printing technology was assessed. Geopolymers and hybrids based on a geopolymer matrix with the addition of 5% cement resulted in the final materials behaving similarly to a non-Newtonian fluid. Without additional treatments, this type of material can be successfully used to fill the molds. The hybrid materials based on cement with a 5% addition of geopolymer, based on both FA and MK, enabled precise detail printing.

Self-Sensing Properties of Green Alkali-Activated Binders with Carbon-Based Nanoinclusions

This paper is aimed at investigating the self-sensing properties of Portland-free alkali-activated binders doped with carbon-based nanofillers. Four different inclusions (carbon nanotubes, carbon nanofibers, carbon black and graphene nanoplatelets) were added into the matrix in the same amount. The physical and electromechanical properties were analyzed. The self-sensing capabilities of the samples were tested by applying a square wave voltage signal and measuring the variation of electrical resistance during cyclical compression tests. The results showed that the presence of nano-inclusions enhanced the sensing behavior of the materials, especially regarding the linearity and the hysteresis performances. Such results appear promising for the application of such novel and innovative nano-modified composites in the field of monitoring structures and infrastructures.