The Properties of Cement Pastes and Mortars Processed with Some Heavy Metal Nitrates Containing Solutions

The effect of some heavy metal nitrates on the course of early hydration process and the properties of hardened cement mortars was investigated. Heavy metal compounds were introduced to the hydrating cement composites in soluble form of nitrates. The results of tests allow to make a comprehensive assessment of the impact of lead, cadmium and nickel nitrate added in amounts of 1% to 5% by weight of cement. The calorimetric measurements together with conductometric, shrinkage, compressive strength measurements and microscopic observations were carried out. These salts modify the rate of cement hydration at early age. The hydration process is particularly strongly retarded in the presence of Pb compounds. As a consequence, the compressive strength at early age is very low. In case of nitrates there is no additional products formed. However, one can observe that the properties of pastes admixtured with nitrates decline from those found in case of reference The calcium silicate phase becomes less fibrous but more compact, with very small individual particles, as the nucleation from the liquid phase is disturbed. There are the accompanying cations incorporated in this product.