The hydration of an aluminous cement with added polyvinyl alcohol-acetate

We have studied the hydration of Secar 71 high alumina cement with added poly(vinyl alcohol-acetate). These materials are used in production of macro-defect-free cements. The polymer has considerable effects on the cement chemistry; the heat output profile measured by conduction calorimetry is significantly altered and few crystalline hydrates are produced. Where hydrate crystals do occur, the calcium-rich compounds are preferred. There are some differences in behaviour between pure polyvinyl alcohol and polymers containing acetate groups. Evidence is presented for polymer complexes in which metal ions from the cement crosslink the polymer chains. Such complexes are formed most readily by aluminium ions, so the cement grains are left with a relative surplus of calcium on their hydrating surfaces.