Erika D. Lemos-Micolta

Seismic isolation systems are an effective passive protection strategy that decouples structures from ground motion. Their performance depends heavily on the elastomeric materials used, which must retain mechanical integrity under environmental stressors. In recent years, low-cost isolators made from natural and recycled rubber have gained attention as an affordable solution for protecting low-rise buildings in seismic-prone developing regions, particularly due to their environmental benefits and ease of installation. However, their long-term performance under real environmental conditions remains insufficiently explored. This study evaluates the durability of two types of low-cost seismic isolators: those made with natural rubber matrices (UN-FREIs) and those that use recycled rubber matrices (UR-FREIs). Mechanical tests were carried out before and after exposing the specimens to accelerated aging and low-temperature conditions, simulating environmental degradation. Changes in stiffness, damping, and energy dissipation were analyzed for both the rubber matrix and the scaled isolator prototypes. The findings indicate that both materials degrade over time, with recycled rubber exhibiting greater susceptibility to stiffness loss at low temperatures. Nevertheless, both isolator types maintained functional performance after aging, supporting their applicability in regions with moderate thermal variations. These results provide evidence for the feasibility of adopting low-cost isolators in low-rise buildings exposed to variable climates, while also emphasizing the need for standardized durability protocols during the design stage.

In Colombia, low-cost unbonded fiber-reinforced elastomeric isolators made from natural rubber (UN-FREI) and recycled rubber (UR-FREI) have emerged as a solution to mitigate damage in low-rise structures during earthquakes. However, their performance under environmental degradation caused by factors such as carbon dioxide, saltwater, relative humidity, and UV radiation has not been sufficiently studied. These agents can compromise the mechanical properties of rubber, affecting its ability to dissipate energy. This study evaluates the performance of these isolators under different environmental conditions through the initial characterization of rubber, mechanical testing of small-scale prototypes exposed to controlled environments, and seismic analysis of an isolated structure. Modification factors (λ_(ae,max) and λ_(ae,min)) were determined to quantify the impact of degradation on structural behavior. The results indicate that UN-FREI specimens are more sensitive to environmental conditions than UR-FREI specimens, whereas the mechanical properties of UN-FREI small-scale prototypes remain more stable compared to those of UR-FREI. This leads to increased drift, base shear, and demand-to-capacity ratios (DCRs) in the structural analysis. The findings emphasize the need for experimental testing of isolators to establish modification factors that accurately reflect the effects of environmental conditions on structures throughout their service life.

The construction industry faces increasing pressure to reduce its environmental impact while meeting the growing demand for infrastructure. One approach to achieving this goal is the use of industrial waste as a replacement for traditional supplementary cementitious materials (SCMs). This study investigates sugarcane bagasse ash (SCBA), addressing the future scarcity and increased cost of other commonly used SCMs. Despite existing literature, the use of SCBA is hindered by several unknowns. This research evaluates SCBA’s performance in mortars, focusing on the effects of curing temperature and particle size variation. Mortar samples were prepared with SCBA replacements from 0% to 30% by mass of cement and cured at 21 °C and 45 °C for 7, 28, and 90 days. The results suggest potential for SCBA replacement up to 30%, emphasizing its sustainability and economic benefits. A cost analysis was also conducted, demonstrating the economic viability of SCBA as an alternative to traditional cement for practical applications.