EFFECTS ON PH BEHAVIOUR OF EXPANSIVE AND NON EXPANSIVE SOILS CONTAMINATED WITH ACIDS AND ALKALIS

The acidic or alkaline characteristics of a soil sample can be quantitatively expressed by hydrogen ion-activity commonly designated as pH.The hydrogen-ion concentration of soil water solution is of interest in problems involving grouting in weak rocks, soil stabilization processes using lime and resinous materials, corrosion of metals in contact with soils and reclamation of marine soils.The pH value also helps in interpreting some of the soil chemical tests.Several factors, soil-water ratio, soluble salts concentration, Carbon dioxide pressure, exchangeable cations and temperature affect the pH value of a particular soil sample.With the dilution of soil suspension, its pH increases.Increase in salt concentration, in general, decreases the pH.A definite relationship exists between Carbon dioxide pressure of soil air and pH, for example, the pH of calcareous is reduced in proportion to the logarithm of Carbon dioxide pressure of soil air.In alkaline soils, the pH is principally influenced by exchangeable cat ions.With increase in temperature, pH decreases.In the present study Attempts were made to study the pH soils treated with optimum percent of alkalis and contaminated with one normal acids.Expansive soil Black cotton soil and non expansive soils Red Earth and Shedi soil are treated individually with optimum percent of alkalis CaCO 3 and MgCO 3 and contaminated with 1N H 2 SO 4 and 1N H 3 PO 4 separately.Results of the study indicate that the evaluation factors associated with soil pH therefore are based on the full consideration of the soil constituents and not on pH value alone.