One crucial property of concrete, particularly in construction, is its thermal conductivity, which impacts heat transfer through conduction. For example, reducing the thermal conductivity of concrete can lead to energy savings in buildings. Various techniques exist for measuring the thermal conductivity of materials, but there is limited discussion in the literature about suitable methods for concrete. In this study, the transient line source method is employed to evaluate the thermal conductivity of concrete samples with natural and synthetic fibers after 7 and 28 days of curing. The results indicate that concrete with hemp fiber generally exhibits higher thermal conductivity values, increasing by 48% after 28 days of curing, while synthetic fibers have a minimal effect. In conclusion, this research opens the door to using natural alternatives like hemp fiber to improve concrete’s thermal properties, providing alternatives for thermo-active foundations and geothermal energy piles which require high thermal conductivities.

The increasing generation of mine tailings poses significant environmental challenges, but their reuse in construction materials offers a sustainable solution by reducing the demand for natural aggregates. To advance the use of tailings in construction, the thermal conductivity of mortar samples incorporating copper mine tailings as partial replacements (10% to 50%) for coarse aggregates was investigated. The thermal conductivity was measured using the transient line source method, revealing a progressive increase from 0.32 W/m·K (control sample) to 0.52 W/m·K (50% replacement sample). The statistical analysis (ANOVA) confirmed significant differences among the sample groups, with the tailings content being a key factor. The higher thermal conductivity is attributed to the quartz-rich composition of the tailings, which enhances the heat transfer compared to conventional aggregates. The findings of this study contribute to demonstrating the feasibility of using mortar with copper tailings to modify the thermal conductivity of mortar.

The increased concern with the use of environmentally friendly products in construction has led to the search for natural fiber replacements to synthetic fibers used in concrete. This research attempts to understand the trends that result from the addition of natural (hemp and luffa sponge) and synthetic fibers to concrete and its mechanical properties at the micro level. Concrete samples were prepared with fiber volume fractions of 0.4%, 0.8%, and 1.2%, and their compressive and flexural strengths were subsequently determined. Scanning electron microscopy (SEM) and energy dispersive spectroscopy were employed for assessing the fiber pattern and characteristics of the cementitious matrix–fiber interface. It was found that all fibers improved the compressive and flexural strengths of concrete in each blend relative to the reference mix. Most importantly, it was observed that the highest compressive strength of 28.15 MPa was obtained with luffa sponge fibers at 1.2% volume fraction accompanied by an enhancement of flexural strength. This was further supported by SEM analysis, which showed the evidence of the natural fibers’ better distribution on the concrete matrix than the synthetic ones, thus improving the structure. The results of this research underscore the versatility of natural fibers, especially luffa sponge, to be used as a construction material with long-term value. This article offers specific recommendations for civil engineers and construction practitioners who wish to improve concrete performance as well as undertake environmentally conscious construction practices.