Carbamide resins form when carbamide (urea) are polycondensed with formaldehyde.
The content of free formaldehyde in carbamide resins used for injection chemical stabilisation of soils attains 2%.
Experience has shown, that the content of free formaldehyde in air and water media in the vicinity of segments of soil stabilised with carbamide resins significantly exceeds these values.
Addition of active components to carbamide resins increase density and pH (alkalinity level) of solution, decrease viscosity and evaporation of components from solution.
The American engineer Lawton was the first to investigate the carbamide resin for its use in soil stabilisation.
Later, carbamide resin was used to stabilise soils in many different countries.
Laboratory testing of carbamide resin solutions determined to grout sandy soil
The author of this paper investigated the following properties of carbamide resin solutions: density, viscosity, pH (alkalinity level), and evaporation of components from solution.
Density of carbamide resin solution increased with increase of urea addition mass (Table 1).
Under laboratory conditions, by the experimental impregnation of a certain mass of sand with carbamide resin, and under field conditions from the average consumption of resin corresponding to 380 litres with a density of 1.10 g/[cm.sup.3] per 1 [m.sup.3] of stabilised sand is established.