This study investigates the hydration of Portland cement with the addition of aluminum hydroxide and aqueous wood wool extract. For this purpose the aluminum hydroxide was used as flame retardant, wood wool was obtained from coniferous trees and examinations were carried on commercial Portland-cement. Drvolit® was used as a representative of cement composites in all tests. The applied methods were the calorimetric measurements, to investigate the released heat of hydration of binding cement, burning test, to determine the heat released during the combustion of samples and X-ray diffraction on sample of hardened cement, in order to determine the impact of chemical modification on the composition of the sample. The results show that the aqueous extract of wood wool does not affect the binding of the cement paste, and the same observations were made when replaced part of the cement powder with the aluminum hydroxide. By addition of filler the only noticeable change was reducing the total heat of hydration, proportional to the amount of filler, which was expected. Also, comparing the results obtained from burning test, it is evident that cement composite, as it contains lower proportion of combustible substances, releases less heat compared to pure wood wool. The results of X-ray diffraction confirmed the conclusions of previous measurements, in which wasn`t observed the formation of new mineral phases, i.e. added aluminum hydroxide in this system is poorly reactive. The wood wool, used in this work, was of high quality and in accordance with this, its aqueous extract was devoid of components that could affect the binding of the cement paste. Another perceived advantage of the addition of aluminum hydroxide in the cement powder is its whiteness, which makes the visual aesthetics of cement composites.