DTA/TG analysis and XRD investigations were carried our on pastes of pozzolanic cement and a mixture of pozzolanic cement and Rv ash from municipal solid waste in order to examine their relative hydration processes. The presence of hv ash. from a municipal solid waste incinerator. provoked in the first curing period the slowing of hydration reactions of calcium silicates of cement and formation of gypsum and ettringite. With the progress of hydration in the pastes the calcium silicate hydrate phase developed and formation of calcium chloroaluminate was observed. The compressive strength of the hardened pastes confirmed good solidification attained by die materials. The leaching test allowed the degree of stabilization of the fi! ash in the hardened pastes to be determined.