The Effect of the Composition of a Concrete Mixture on Its Volume Changes.

Martin Ťažký,Lucia Ťažká,Rudolf Hela,Milan Meruňka,Lenka Bodnárová,Petr Hlaváček

doi:10.3390/ma14040828

Martin Ťažký, Lucia Ťažká + Show 4 more

Open Access

https://doi.org/10.3390/ma14040828

Copy DOI

Abstract

The presented research aims to clarify the specific effect of the individual components of concrete with Portland cement CEM I 42.5 R on the volume changes of concrete. The effect of the filler component was evaluated from the point of view of the composition and type of aggregate (crushed versus mined) and from the point of view of the mineralogical composition of the aggregate. Concrete formulas with a maximum aggregate grain size of 16 and 22 mm were assessed. The effect of the binder component on the shrinkage of the concrete was monitored on the concrete mixtures produced using the same aggregate and maintaining the same strength class of concrete, C 45/55. The effect of the addition of finely ground limestone, finely ground granulated blast furnace slag and coal high-temperature fly ash was monitored. It was found that the maximum aggregate grain and the type of grading curve do not have a significant effect on the volume changes of concrete. Concretes with mined aggregates showed lower shrinkage than concretes with crushed aggregates. The most significant is the effect of the type of aggregate on the volume changes in the first 24 h. Mineral additives have a positive effect on the elimination of the volume changes of concrete, while the addition of high-temperature fly ash proved to be the most suitable.

Highlights

The widespread usage of concrete around the world is mainly due to its excellent formability in the fresh state and its good mechanical parameters and durability in its hardened state
It can be said that the good mechanical resistance and the resulting durability of the concrete composite depends on its hydration processes and the volume changes that have taken place during this hydration [1].The resulting micro-cracks due to excessive volume changes become a place for the penetration of aggressive media from the surrounding environment into the micro-structure of concrete, which has a negative impact on the durability of the composite [2]
The results presented in this experiment demonstrate that most of the volume changes take place in the fresh state, which is in conflict with some standardization methods, which consider the beginning of measurement to measurement after gaining handling strength from 1 day of age

Summary

Introduction

The widespread usage of concrete around the world is mainly due to its excellent formability in the fresh state and its good mechanical parameters and durability in its hardened state. The resulting mechanical parameters and durability of the concrete composite are affected by its microstructure without signs of micro-defects. It can be said that the good mechanical resistance and the resulting durability of the concrete composite depends on its hydration processes and the volume changes that have taken place during this hydration [1].The resulting micro-cracks due to excessive volume changes become a place for the penetration of aggressive media from the surrounding environment into the micro-structure of concrete, which has a negative impact on the durability of the composite [2]. A significant negative impact of micro-cracks is the reduction of the resistance of concrete to mechanical abrasion and to abrasion caused by flowing liquids, while in micro-cracks, the further development of discontinuities occurs due to contact with abrasive particles and flowing media. One of the important requirements for concretes for the construction of dams, drainage

Methods

Results

Conclusion