Page 23 - תקצירי תזות הנדסה ירוקה 2025

Studying the properties of chert rocks towards the development of its reserves for Israeli industrial needs
Mark Tzibulsky; MarkTZ@ac.sce.ac.il
Prof. Vladimir Frid
SCE - Shamoon College of Engineering, Be’er-Sheva
The Rotem Plain is one of Israel’s largest industrial zones, covering approximately 28,000 dunams and encompassing phosphate, oil shale, and sand mining operations. Sand extraction generates significant amounts of ‘waste’ in the form of chert rock clusters, accounting for about 30% of the sand profile’s volume. Due to its high strength and resistance to weathering, to-date, there is an accumulation of approximately 20 million tons of chert waste in the area of the Rotem Plain quarry.
Chert gravel waste poses a significant challenge due to its massive accumulation and the absence of cost-effective crushing technologies. The sand quarrying industry currently avoids the reuse of chert wastes, due to the high energy costs involved, leading to wasted natural resources and increased raw material extraction. This study aims to characterize the physical and mechanical properties of the chert gravel found in the Rotem Plain, to evaluate advanced crushing methods, and to develop practical solutions for the utilizization of chert wastes as an industrial resource.
Geomechanical and geophysical tests were conducted to assess the physical and mechanical properties of chert gravel, including: specific gravity, water absorption, porosity, electrical resistivity, its dielectric constant, and P-wave velocity )VP(. This study also examined the effects of pre-treatment methods, particularly microwave heating, on crushing efficiency. Controlled crushing experiments, using a hydraulic press, were performed to evaluate the impact of pre-treatment on aggregate shape and grain size distribution.
The findings reveal that chert rock has high specific gravity )~2.65 g/cm3(, very low porosity )~0.34%(, and high electrical resistivity )23 kOhm*m(, making it suitable as an electrical insulator. The microwave radiation experiments demonstrated that high-frequency microwave heating combined with water quenching creates internal structural cracks, significantly reducing the rock’s strength and, thus, improving its crushability.
Key findings include:
• Well-gradedsamples)e.g.,GWandSW(showedimprovedmixturestrengthbutreduceddrainage capacity, making them suitable for infrastructure applications. Poorly graded mixtures proved better for high-permeability requirements.
• Dry chert mixes with air cooling resulted in a GW-type mixture, while water cooling produced an SW-type mixture.
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