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S. Grzeszczyk and K. Jurowski
clear improvement of the resistance to washout is observed in concrete mixes, where
the cement with addition of the slag (F) with higher specific surface area was applied.
This slag contains almost twice as many particles with diameter below 5 µm and
almost three times more particles below 10 µm than the slag (C). In this case the
washout of the concrete mix with the slag content of 50% by mass is only 0.9%.
Therefore, it may be concluded that the increase of fine particles in the concrete
mix, due to introduction of the slag to cement, causes higher resistance to washout,
the larger quantity of fine particles is (below 20 µm)—Fig. 2. Comparison of washout
of concrete mixes MF50 and MC50, that contain the same amount of the slag (50%
by mass), shows that the washout of the mix containing finer slag particles, and thus
a higher content of fine particles, is lower by 1.0% point.
Reduction of underwater concrete washout together with the increase of fine
particle content in CEM I, caused by addition of the slag and with introduction of
nanoparticles, can be explained if we take into account the chemical structure of AWA
used, determined in the previous study [21]. This phenomenon is closely related to the
chemical structure and mechanism of action of the AWA applied, in the liquid phase
environment of the concrete mix. Nanoparticles and fine particles of the blast furnace
slag, due to their size, have possibility to get located in the formed dense lattice of
developing ether chains of ethylene polyoxide and methyl cellulose chains, due to
hydration of ether groups occurring in both chains. It hinders migration of water,
cement grains and other fine-grain factions from the concrete mix, thus increasing
its resistance to washout.
6 Conclusions
The washout resistance of underwater concrete mixes is mostly shaped by chemical
admixtures that increase viscosity. In most cases, these are synthetic and natural
organic polymers soluble in water. Polymer chains intertwine cement grains and
other fine particles present in cement paste, thereby leading to the increase in the
paste’s viscosity and reduction in of concrete mix washout.
In order to ensure greater washout resistance of underwater concrete mixtures, it
is recommended to use anti-washout admixtures in combination with fine particles
introduced with mineral additives with a high specific surface.
It was demonstrated that the washout resistance of an underwater concrete mix
based on cement containing blast-furnace slag improves along with the increase in the
slag’s fine particles content (especially smaller than 20 µm) and with its increasing
quantity in cement. It allows to reduce the concrete mix washout even by about 70%.
The washout resistance of an underwater concrete mixture can also be improved
by introducing a small quantity of SiO 2 nanoparticles. The addition of 0.5% nanoparticles in relation to the cement’s weight reduces the concrete mixes’ washout by as
much as 40%.
S. Grzeszczyk and K. Jurowski
clear improvement of the resistance to washout is observed in concrete mixes, where
the cement with addition of the slag (F) with higher specific surface area was applied.
This slag contains almost twice as many particles with diameter below 5 µm and
almost three times more particles below 10 µm than the slag (C). In this case the
washout of the concrete mix with the slag content of 50% by mass is only 0.9%.
Therefore, it may be concluded that the increase of fine particles in the concrete
mix, due to introduction of the slag to cement, causes higher resistance to washout,
the larger quantity of fine particles is (below 20 µm)—Fig. 2. Comparison of washout
of concrete mixes MF50 and MC50, that contain the same amount of the slag (50%
by mass), shows that the washout of the mix containing finer slag particles, and thus
a higher content of fine particles, is lower by 1.0% point.
Reduction of underwater concrete washout together with the increase of fine
particle content in CEM I, caused by addition of the slag and with introduction of
nanoparticles, can be explained if we take into account the chemical structure of AWA
used, determined in the previous study [21]. This phenomenon is closely related to the
chemical structure and mechanism of action of the AWA applied, in the liquid phase
environment of the concrete mix. Nanoparticles and fine particles of the blast furnace
slag, due to their size, have possibility to get located in the formed dense lattice of
developing ether chains of ethylene polyoxide and methyl cellulose chains, due to
hydration of ether groups occurring in both chains. It hinders migration of water,
cement grains and other fine-grain factions from the concrete mix, thus increasing
its resistance to washout.
6 Conclusions
The washout resistance of underwater concrete mixes is mostly shaped by chemical
admixtures that increase viscosity. In most cases, these are synthetic and natural
organic polymers soluble in water. Polymer chains intertwine cement grains and
other fine particles present in cement paste, thereby leading to the increase in the
paste’s viscosity and reduction in of concrete mix washout.
In order to ensure greater washout resistance of underwater concrete mixtures, it
is recommended to use anti-washout admixtures in combination with fine particles
introduced with mineral additives with a high specific surface.
It was demonstrated that the washout resistance of an underwater concrete mix
based on cement containing blast-furnace slag improves along with the increase in the
slag’s fine particles content (especially smaller than 20 µm) and with its increasing
quantity in cement. It allows to reduce the concrete mix washout even by about 70%.
The washout resistance of an underwater concrete mixture can also be improved
by introducing a small quantity of SiO 2 nanoparticles. The addition of 0.5% nanoparticles in relation to the cement’s weight reduces the concrete mixes’ washout by as
much as 40%.