Eco-friendly and natural additives effect on building mixes strength at portland сement replacement

A review of studies on Portland cement (PC) replacement in concrete is conducted in order to reduce negative impact on the environment. The factors such as the additives type and characteristics, hardening conditions (time, temperature), and mixture composition (water, Solid components, alkali, and binder proportion) influence on the concretes mechanical properties and microstructural characteristics is analyzed. It was found that the geopolymer binders (GPB) usage contributes to the denser and more homogeneous with fewer voids microstructure formation, what explains the increase in strength indicators. The key oxides (SiO2, Al2O3, CaO) content optimal ranges in the raw materials composition was determined. The main conclusion is the critical importance of the mixture and technological parameters composition optimizing for high mechanical properties achievement. Insufficient knowledge of the GPB structural elements behavior is noted, what determines the need for their operation under various loads research and development of the correct models establishing the relationship between compressive strength, bending, shear and elasticity modulus.