Properties of a Terpolymer-Treated Soil: A ¹³C NMR Study

The Young’s modulus and the secant modulus of a terpolymer-treated soil as a function of the polymer’s characteristics are discussed in the context of a more general inelastic property known as the toughness parameter. The soil chosen was a sample of the State of Qatar subsoil. The terpolymer, designated TPAM, was characterized by a backbone structure of acrylamide, anionic carboxylate, and cationic (3-acrylamidopropyl-trimethylammonium chloride) repeat units. The backbone unit ratio was estimated from ¹³C NMR analyses. TPAM was synthesized by straightforward NaOH hydrolyses of an acrylamide/cationic copolymer. The correlations between the NaOH molarity of the hydrolysis solution, with the corresponding ratio of the anionic and cationic units, were shown to have a significant influence on the value of the toughness parameter. It is speculated that controlling the anionic and cationic ratio of a terpolymer is a general approach to optimize the toughness parameter of treated soils. Measurements of the molecular weight of TPAM were made, and comments on the importance of this feature are given. The equivalent viscosity was also recorded. It is pointed out that the work is particularly relevant to the practical problem of subsoil pavement stabilization in which the terpolymer acts as a soil binder. Suggestions on further work are given.