Estabilidad de aditivos superplastificantes y reductores de la retracción en medios fuertemente básicos

Abstract

The present study explores the stability of different superplasticizer (polycarboxylate, vinyl copolymers, melamine and naphthalene derivatives) and shrinkage-reducing (polyproplyene glycol derivatives) admixtures in water and several alkaline media: NaOH (pH= 11. 7 and 13.6), Ca(OH)2 (pH=12.4) and waterglass (pH=13.0) solutions. The pH of the solutions was measured at different times and the structural changes taking place in the admixtures were studied using FTIR, FT-Raman and UV-VIS techniques. All the admixtures, except the naphthalene and polypropylenglycol derivatives in the NaOH pH=13.6 solution and the naphthalene derivative in waterglass (Na2O·nSiO 2, ·mH2O + NaOH), are unstable at pH < 13.0. The other admixtures all undergo structural changes in highly basic media that explain the loss of their fluidifying properties under these conditions.