Control of mechanical properties of cement composites using modifier additives

The article discusses the effectiveness of additives of redispersible polymer powder, cellulose ether, calcium formate for controlling the mechanical properties of cement composites. The initial strength of modified cement composite samples at the age of 30 – 90 minutes was determined, their hardening kinetics was studied using isothermal calorimetry. For the most promising samples, the rheological characteristics of the fresh mixture, strength characteristics at late stages of hardening (up to 28 days) were determined, the structure of the samples was analyzed using computed X-ray tomography. Additions of redispersible polymer powder and calcium formate in a dosage of 2 % of the cement mass contribute to improving the compressive strength of cement composites. Both additives increase the strength of samples by 42 – 64 % at the age of 1 day and by 21 – 47 % at the age of 3 days. At the age of 7 days, the addition of 2% calcium formate increases the strength of samples by 32 %, at the age of 28 days — by 15 %. The studied additives increase the viscosity and density of the mixture, while with the addition of 2 % redispersible polymer powder, the start and end times of setting are reduced by 15 minutes. The obtained results allow us to consider the studied additives as effective modifiers of cement composites suitable for construction using additive technologies.