Cement mortars and lime-pozzolan mortars have been exposed to wet/drying cycling of ‘acid rain’ solution, using realistic presentation rates, to simulate outdoor conditions. Cement type, water/cement ratio, and curing temperature were also examined. Form the pH of run-off solution, it is evident that reaction between the mortar and the ‘acid rain’ proceeds over the exposure period, with significant weight increases for the cement mortars and little influence of curing temperature for lime-pozzolan mortars. Exposure of the cement mortar gives to significant calcium loss to run-off and is also associated with retained souuble stalts; these results from the presence of free hydrated lime in the mortar. Conversely, lime-pozzolan mortars, associated with a clacium carbonate compounds, reveal comparatively reduced calcium loss,i.e by about one-tenth that of cement mortar.