Investigation of the effect of a multicomponent additive on the structure formation and hardening of cement composites

Abstract

The development and application of multicomponent multifunctional additives for cement composites is an important research area since the use of such additives allows controlling both the rheological properties of the freshly prepared mixture and the physical and mechanical characteristics of the finished composite. This work proposes to use a multicomponent multifunctional additive with the composition of “SiO2 nanoparticle - superplasticiser - polypropylene fibre” for the modification of cement composite materials based on sand and chalky flour. We studied the peculiarities of the influence of this additive on the technological characteristics of mixtures (plasticity and form stability) and the processes of setting-up, hydration, structure formation, and strength gain of the composite materials. It was shown that the introduction of this additive allows increasing the plasticity limit and structural strength and reducing relative plastic deformations of the cement mixture at the manufacturing stage. At the same time, this additive accelerates the processes of setting-up, hydration, and strength gain of cement composites. It was proved that the increase in strength is due to the formation of a dense structure of hydrated new growths of the cement substance formed by phases of low and highly basic calcium silicate hydrates of various compositions and morphologies, as well as the absence of a portlandite phase.

Keywords

• cement hardening systems
• modification
• structure formation
• multifunctional additives
• rheological characteristics
• compressive strength