Strengthening the very early-age structure of cementitious composites with coal fly ash via incorporating a novel nanoadmixture based on C-S-H phase activators

This paper presents results of tests of modified concretes both with the addition of coal fly ash (CFA) ash and with an innovative nanoadmixture (NA). The NA is used to accelerate the strength growth in cement composites. The analyses were carried out based on the results of the macroscopic and microstructural tests in 5 time periods, i.e. after: 4, 8, 12, 24 and 72 h. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites, i.e. CSH and CH in the first 12 h of composites curing was observed. The NA of CSH application affects the faster structure building of the cement matrix and intensification of a phases formation in the composite. The NA activity in building a compact cementitious matrix structure is observed by thickening its skeleton and sealing the free spaces. It can be stated that the NA in the form of the active CSH seeds is a modern and innovative form of accelerating the curing of concretes at a very early age, leading to the formation of a more homogenized and compact cement matrix structure. Therefore, the results of tests carried out with the use of NA clearly indicate the possibility of using CFA, in a wide range of management in concrete prefabrication.