Use of fluorohydride as a binder for stabilization of weak soils in road construction

In the conditions of growing attention to resource saving and environmental safety in road construction, the search for new binding materials for soil stabilisation is topical. This work is devoted to the study of the possibility of using fluoranhydride, a waste product of hydrofluoric acid production, as a binder for road base stabilisation. The object of the study is a composite material based on fluoranhydride, clay, and activator — sodium phosphate solution. The influence of fluorohydride activation on the physical and mechanical characteristics of the composite, including compressive strength, water absorption, and softening coefficient, has been studied. Fluoranhydrite is activated by 3% sodium phosphate solution, which increases the strength of the obtained material. The physical and mechanical properties of composites consisting of fluorangydrite, loam, and sodium phosphate have been investigated. X-ray phase and IR spectral analyses were carried out, as well as scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the optimum ratio of loam to fluorohydrite is 40/60 as it provides the highest economic efficiency. The compressive strength of this composition at the age of 28 days is also favourable: 8.9 MPa in the dry state and 7.3 MPa in the wet state, while the water absorption is 6.82% and the softening coefficient is 0.82. The study confirms that fluorohydrite can be used as a binder to stabilize weak soils, which helps to reduce the cost of works and reuse waste materials, reducing the environmental load.