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Structural Engineering and Mechanics
  Volume 82, Number 4, May25 2022 , pages 543-556
DOI: https://doi.org/10.12989/sem.2022.82.4.543
 


Strength and microstructure of composites with cement matrixes modified by fly ash and active seeds of C-S-H phase
Grzegorz Ludwik Golewski and Bartosz Szostak

 
Abstract
    Fly ash (FA) is the main additive to concretes currently produced. This substitute of ordinary Portland cement (OPC) have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as the OPC replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in the prefabrication, where it is required to obtain high strength composites after short periods of their curing. In order to minimize these negative effects, research has been undertaken to increase the early strength of the concretes with FA through the application of a specially dedicated chemical nanoadmixture (NA) in the form of seeds of the C-S-H phase. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with NA. 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 hours. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites in the first 12 hours of composites curing was observed.
 
Key Words
    C-S-H phase (CSH); concrete; fly ash (FA); microstructure; nanoadmixture (NA); strength parameters
 
Address
Grzegorz Ludwik Golewski and Bartosz Szostak: Faculty of Civil Engineering and Architecture, Lublin University of Technology, Nadbystrzycka 40 Street, 20-618, Lublin, Poland
 

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