Institute for Transportation

About the research

This study investigated the utilization of eggshell powder (ESP) as a bio-based cementitious material for soil stabilization in Iowa, a state recognized as the leading egg producer in the United States. The prominence of egg production in Iowa results in substantial eggshell waste, a byproduct that, despite its high calcium carbonate content, remains largely underutilized. Eggshells, constituted of nearly 95% calcium carbonate, present an environmentally friendly opportunity to repurpose agricultural waste into beneficial construction materials. Addressing the dual challenges of waste management and soil stabilization, this study explored the potential of ESP derived from ground eggshells to enhance the properties of subgrade soils. Through a series of treatments—no treatment, oven drying, and calcination—the study assessed the effectiveness of ESP in improving soil engineering properties. Laboratory experiments with two types of Iowa soils mixed with up to 12% ESP demonstrated that calcination significantly optimized ESP’s performance, particularly when the soil was combined with 3% additional water and cured at 40°C. The optimal addition rate for maximizing unconfined compressive strength (UCS) was identified as 6% to 8% ESP, which provided over a tenfold increase in UCS compared to soil without ESP. This enhancement was especially notable in loess soils, which exhibited marked strength improvements. Field simulations using the dynamic cone penetration (DCP) test further validated the laboratory results, indicating that the inclusion of calcined ESP substantially enhanced the tested soil’s California bearing ratio (CBR). The findings underscore ESP’s potential as an innovative and sustainable additive for soil stabilization, offering a practical solution to managing eggshell waste while contributing to the development of eco-friendly construction practices in Iowa. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that adding calcined ESP (1,830°F or 1,000°C) to soils resulted in a denser and more solid soil structure due to the formation of hydration products. This research not only addresses environmental concerns associated with eggshell waste but also highlights the broader application of agricultural byproducts in civil engineering, promoting sustainability in construction materials.