In this paper it was investigated the influence of mud from the zinc plating plant "ADRIA CINK", a mixture of mud and zeolite saturated with zinc, natural zeolite from the site Donje Jesenje, lead(II) oxide, lead(II) chromate and ammonium bichromate on early hydration and physico-mechanical properties industrial cement type CEM I 42,5 R (product of CEMEX Croatia cement plant). Determination of the start and the end of setting time was performed on samples of Portland cement with different additions of mud, zeolite saturated with zinc, natural zeolite, mixture of mud and saturated zeolite, lead(II) oxide, lead(II) oxide (with 20 wt.% of zeolite in the sample), lead(II) chromate, lead(II) chromate (with 20 wt.% of zeolite in the sample), ammonium bichromate and ammonium bichromate (with 20 wt.% of zeolite in the sample). Measurements were performed by Vicat's apparatus and electrochemical method at a temperature of 20 °C and water/cement (V/C) and water/solid ratio (V/K) of 0,5. Determination of setting time was not done at normal consistency because of comparison with the conductometric and microcalorimetric results. Effect of different additions (content as well as in determining the setting time) on the development of heat (during the first 48 hours of hydration) was determined using differential microcalorimetry in isothermal conditions (T = 20 °C) and water/cement (V/C), and water/solid ratio (V/K) of 0,5. The obtained thermovoltage results are used in computer program "Hidratacija cementa" for calculation of developed heat, the heat release rate and degree of hydration. Monitoring the early hydration was performed by determining the conductivity of cement samples with different additions of mud, a mixture of mud and saturated zeolite, lead(II) oxide, lead(II) chromate and ammonium bichromate. The measurements were made using a digital conductivity meter ISKRA MA 5924 and electrode made of stainless steel. The matematical models were determined from the obtained values of setting time, heat release and conductivity which can be use for estimation of the value of setting time, maximum heat release and the time of maximum conductivity for any examined addition of mud, a mixture of mud and saturated zeolite, lead(II) oxide, lead(II) chromate and ammonium bichromate. Leaching of heavy metals (zinc, lead and chromium) from cement samples with different additions was carried out according to the modified dynamic leaching test NEN 7345. Samples were hydrated for 28 days at isothermal conditions (in the thermostat at 20°C). After 18, 72 and 168 hours leaching solution was replaced with fresh solution. Ion concentration of zinc, lead and chromium in solution after leaching was determined by EDXRF (Energy Dispersive X-ray Fluorescence) device for quantitative analysis. The concentrations were used in the diffusion leaching models for evaluation of S/S process by determining the diffusion coefficients and the leaching indices. Also, leaching mechanisms of metals from stabized materials were determined. Analysis of hydration products of cement samples with different additions of hydrated 28 days at isothermal conditions (T = 20 °C) was performed using a thermal analysis (TGDTG) and infrared spectroscopy (FTIR). Quantity of calcium hydroxide and chemically bound water was determined by thermal analysis. In mortars, where part of the cement was replaced with 2, 5 and 10 wt. % of mud and 10, 20 and 30 wt. % of saturated zeolite (with 20 wt.% of mud in the mixture), the impact of supplements on the compressive and flexural strength was determined on samples after 1, 2, 7 and 28 days of hydration and nourishing in tap water at a constant temperature of 20 ± 1 oC. S/S process can be evaluated from the leaching (average leaching index of metals) and compressive strength results and estimated the maximum acceptable amount of additions in the cement matrix.