Consolidation mechanism of NaCl in soil by various industrial solid wastes

With slag,fly ash,desulfurized gypsum,lime and aluminium sulphate as soil stabilizers,the compressive strength of consolidated soil first increased and then decreased with the amount of added NaCl increasing.The compressive strength of consolidated soil in every curing age reached its maximum value when the content of added NaCl was 2%.The consolidation rates of Na⁺ and Cl^- increased very fast when the curing age prolonged from 3d to 7d,then slowed down from 7d to 28d,and finally kept stable in the range of 60% to 80% after 28d.The results of nuclear magnetic resonance(NMR) of ²⁹Si and ²⁷Al showed that there were amounts of 4-coordinated and 6-coordinated Al in the C-S-H net.The NMR analysis also indicated that in the C-S-H net some of Si⁴⁺ was substituted by Al³⁺.The substitution provided a condition for Na⁺ solidification.NaCl can promote the transformation of Al coordination from 4-coordinated one to 6-coordinated one,and improve the polymerization degree of the cementitious system.