Although vegetable fibers demonstrate great advantages as a reinforcement element, their degradation susceptibility is currently the main concern in geotechnical works and requires further investigation to advance their durability. In recognition of these needs, this study aims to evaluate the effects of silica and polymer surface treatments on sisal fiber biodegradability and on the mechanical behavior of sand matrix reinforced with these fibers exposed to actual environmental conditions for up to eight months. Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (FRX), scanning electron microscopy (SEM), direct tensile and consolidated-drained triaxial tests were performed. Overall, the secondary cell wall of the fiber was the main structure affected by the exposure, reflecting the degradation by natural soil microflora. The strain-hardening behavior acquired by the addition of fiber to the sand at zero time was gradually reduced with natural aging. Increments in cohesive intercept of the composite over the biodegradation of fibers point to biofilm formation. Due to the inorganic base, silica treatment resulted in the most effective barrier against fiber biodegradation, contributing to composite durability along the eight months. Notwithstanding the degradation process, both natural and surface-treated sisal fibers resulted in shear strength parameters superior to those of the nonreinforced soil, encouraging their sustainable applications in engineering works, such as temporary landfills.

Recent events involving the rupture of tailings dams in Brazil have motivated the search for alternatives to incorporate the material into the production chain. At the same time, the consumption of raw materials by the civil construction sector is high, requiring the incorporation of alternative materials to achieve sustainable development. Thus, this paper proposes a new construction material based on the mechanical and microstructural behavior of polymer-stabilized and fiber-reinforced gold ore tailings composites. Unconfined Compressive Strength tests were performed on different polymer contents (6% and 9%), dry unit weights (1.7 g/cm³ and 1.8 g/cm³), and curing periods (7 and 28 days), according to 2K Experimental Design. Microstructural tests were performed using X-ray Diffraction, X-ray Fluorescence Spectrometry, Optical Microscopy, Scanning Electron Microscopy, and X-ray Micro-Computed Tomography. The results demonstrate that adding polymer increased tailings’ mechanical behaviors by forming packages with the lamellar particle, which was observed in microstructural tests. The polymeric composites’ brittle behavior was improved using fiber insertion, leading to an increase of the strain energy absorption capacity. The polymer-stabilized and fiber-reinforced gold ore tailings composites demonstrated its potential as a construction material, especially in landfill structures, tailings stockpiles, and paving base layers. The association of mechanical and microstructural analysis established a new understanding of the effect of the stabilizer and the reinforcement.

The large amounts of construction waste (CW) generated yearly and its high landfilled proportion worldwide motivate the search for sustainable solutions. Thus, the effect of sandy soil partial replacement for construction waste in cemented mixtures was assessed in the present work in terms of mechanical behavior and microstructure. Distinct cement contents, compaction efforts, and curing periods were evaluated from soil-waste proportion of S75W25, S50W50, and S25W75. Tests of unconfined compression strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity, water absorption, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were conducted. The presence and increase in the amounts of cement and construction waste increase the optimum moisture content of the mixture. In contrast, only the CW content significantly affects maximum dry density. Both S75W25 and S50W50 mixtures resulted in similar UCS and ITS values, which was proven to be statistically equal by analysis of variance (ANOVA) at a 0.05 significance level, favoring CW replacing soil up to 50%. MIP and SEM results explained the sharp mechanical behavior transition obtained in 75% of CW. Cementation reactions resulted in macropores peak reduction and/or peak area translation to the left of the horizontal axis of the PSD curve, while its translation to the right indicates the cement mainly acting as filler, which was supported by SEM tests.

Stabilized soil with cement has been a widely used solution in geotechnical projects and requires the molding of numerous specimens to investigate their properties in destructive tests, restraining the reuse for other analysis. Also, distinct sample dimension has been utilized in the research without taking this effect into account. Recognizing these needs, the height and diameter (H/D) ratio effect on cement-stabilized soil mechanical behavior was assessed in the present work. Using sandy soil, Unconfined Compression Strength (UCS), Indirect Tensile Strength (ITS) and Ultrasonic Pulse Velocity tests were performed varying the curing period (7 and 28 days), cement type (I and III) and content (6, 7, 8, 9 and 10%), based on conventional (127 x 100 mm) and reduced dimension (105 x 50 mm) specimens. All variables, individually and combined, affected the compression and tensile strengths of the mixtures, resulting in greater gains for the ones molded with type III cement in reduced dimension, at 28 days of curing. The dimension as an influential variable was statistically established using the variance analysis (ANOVA) at a significance level (α) of 0.05, in which reduced dimension showed an average superior resistance of 21.3%. Mixtures molded with H/D ≥ 2 demonstrated strong correlation (R2 = 0.93), pointing to the possibility of ITS prevision through the P-wave velocity nondestructive tests.