Abstract
Siliceous fly ash (FA) is the main additive to currently produced concretes. The utilization of this industrial waste carries an evident pro-ecological factor. In addition, such actions have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as a Portland cement 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 prefabrication, where it is required to obtain high-strength composites after short periods of curing. In order to minimize these negative effects, this research was undertaken to increase the early strength of concretes with FA through the application of a specifically formulated chemical nano-admixture (NA) in the form of seeds of the C-S-H phase. The NA was used to accelerate the strength growth in concretes. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with innovative NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in five time periods, i.e., after 4, 8, 12, 24 and 72 h. The results of tests carried out with the use of NA clearly indicate the possibility of using FA in a wide range of management areas in sustainable concrete prefabrication.
Highlights
Accepted: 26 October 2021In the modern technology of concrete composites, there is great interest among scientists and practical engineers concerning the possibility of modifying the microstructure of cement-based materials by using chemically active mineral additives
Due to the fact that, in the vast majority of countries in the world, energy generated for industrial and domestic needs is still produced by burning hard coal, siliceous fly ash (FA), which is a by-product of these processes, is the main additive to currently produced concrete composites [16,17,18,19,20]
In order to gain a thorough understanding of the relationship between the microstructure and mechanical parameters of commonly used FA-modified concrete composites, which were further modified with the modern NA with CSH seeds, an extensive laboratory measurement program was developed
Summary
In the modern technology of concrete composites, there is great interest among scientists and practical engineers concerning the possibility of modifying the microstructure of cement-based materials by using chemically active mineral additives. In order to minimize these negative effects and enable the use of the waste in question in a wide range of management areas, research has been undertaken to increase the early strength of the ash-filled concretes through the application of a formulated nano-admixture (NA) At this point, it should be noted that admixtures that accelerate the setting and hardening of cement composites have great potential in the concrete industry. It was found that after the application of the nano-admixture, the terms of the possibility of using the NA in sustainable concrete composites, reCSH In structure develops on the cement grains and its hydration products but search has been conducted to date to a rather limited extent It has mainly consisted of on the added seeds [68]. An attempt was made to correlate the results of the basic mechanical parameters of the composites with the morphology of the structures forming their internal skeleton
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