A recent study explores the potential of stone dust as a sustainable additive for cement gravel (CG) columns in geotechnical engineering. The research found that incorporating stone dust improved the load-bearing capacity and structural stability of CG columns used for ground improvement in foundation engineering.
Study: Using stone dust as an improvement material for cement gravel column. Image Credit: Prapat Aowsakorn/Shutterstock.com
Background
CG columns play a crucial role in stabilizing foundations and increasing load-bearing capacity while also aiding ground improvement. Their high porosity and permeability allow them to function as drainage channels, helping soft soils consolidate more effectively.
Stone dust, a by-product of stone aggregate processing, has been considered a potential concrete substitute. However, the ideal balance between stone dust content, strength, and permeability in CG columns remains unclear. While increased stone dust improves particle bonding and overall strength, it can also reduce void space and affect permeability.
Despite its promise, little research has focused on how stone dust impacts CG columns at the microstructural level—specifically in terms of strength, permeability, and failure patterns. This study aims to bridge that gap by evaluating stone dust as a sustainable enhancement material.
Methods
For this research, stone dust was sourced from waste generated at a limestone mill in Kanchanaburi Province, Thailand. It was mixed with Portland cement type I in varying proportions to create CG samples. Cement content ranged from 5 % to 20 %, while stone dust varied from 0 % to 20 %, maintaining a water-to-cement (W/C) ratio of 0.5.
The CG mixture was prepared by blending cement and aggregate with water for about ten minutes. The mixture was then poured into steel cylindrical molds (15 cm in diameter and 30 cm high) and cured at 25 °C with 90 % humidity for 24 hours. After demolding, the samples were wrapped in plastic for further curing.
A total of 60 cylindrical samples were prepared—30 for unconfined compressive strength (UCS) tests and 30 for permeability tests. UCS tests were conducted after 7 and 28 days of curing. Porosity was measured using the underwater gravity method, and permeability was assessed using a specialized testing apparatus.
Results and Discussion
The study found that adding stone dust increased compressive strength up to an optimal level of 10 %. Beyond this point, additional stone dust led to a decline in strength. CG samples with cement content between 10 % and 20 % showed compressive strengths ranging from 12 to 83 ksc, making them suitable for low- to medium-load-bearing applications.
Conversely, permeability decreased as stone dust content increased. However, CG specimens with cement and stone dust content between 5 % and 20 % still met the necessary standards for porous concrete applications.
Stone dust also influenced failure mechanisms in CG specimens. Samples without stone dust exhibited cone-shaped top failures due to weak coarse-grained bonding. As stone dust content increased, different failure patterns emerged: simple shear failures at 5 %, combined shear-compression failures at 10 %, and pure compressive failures at 15 % to 20 %. This suggests that higher stone dust concentrations enhance particle bonding and improve force distribution.
Microstructural analysis using a scanning electron microscope (SEM) reinforced these findings. CG specimens with 10 % and 20 % stone dust exhibited denser calcium silicate hydrate (CSH) gel formation and fewer voids compared to those with only 5 % stone dust. Additionally, samples with 20 % stone dust showed extensive ettringite and monosulfate formation, indicating advanced hydration that contributed to improved mechanical properties.
Conclusion and Future Prospects
All in all, this research confirms that stone dust enhances the strength and stability of CG columns while maintaining sufficient permeability. By optimizing stone dust content, CG materials can achieve both mechanical strength and hydraulic efficiency, making them a practical and sustainable option for construction.
Beyond structural benefits, incorporating stone dust supports circular economy initiatives by repurposing industrial waste. Future studies could explore different W/C ratios, stone dust particle sizes, and the impact of cyclic loading. Additionally, multi-scale modeling and AI-driven design could further refine CG column applications.
Journal Reference
Sukkarak, R. et al. (2025). Using stone dust as an improvement material for cement gravel column. Case Studies in Construction Materials, 22, e04300. DOI: 10.1016/j.cscm.2025.e04300, https://www.sciencedirect.com/science/article/pii/S2214509525000993
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