Short-term lime solution-kaolinite interfacial chemistry and its effect on long-term pozzolanic activity

Soils stabilization with lime addition is a widespread technique in geotechnical field. Better understanding of interaction mechanism is central for optimization of the technique. In the present work, the short-term kaolinitelime solution interfacial chemistry and the effect on the dissolution and long-term reaction has been investigated. Calcium adsorption from saturated lime solution (i.e. simulated alkaline pore solution ([Ca] = 22 mmol/l and pH = 12.63)) characterized by initial fast uptake followed by slower adsorption rate curves, whereas only initial fast uptake is identified from chloride solution ([Ca] = 22 mmol/l and pH = 7). Species of calcium available for adsorption are strongly dependent on the pH conditions (i.e. Ca2+ at pH 7 and CaOH+ at pH 12.63). The adsorption increased with increasing initial concentration of calcium. On the other hand, the more the quantity of calcium adsorbed, the less the measured concentration of silicon and aluminum in the supernatant. The adsorbed calcium distribution has been mapped using mu-XRF. Regardless of the quantity of calcium adsorbed, homogeneous distribution has been identified suggesting coating of kaolinite particle by adsorbed calcium. The coating in turn prevented the kaolinite particles from alkaline attack and retards long-term pozzolanic reaction.