130
S. Grzeszczyk and K. Jurowski
a new generation of polycarboxylate-based superplasticizers, much more effective,
and in result the development of self-compacting concrete technology [4, 5].
A progress in development of underwater concrete technologies is associated with
the use of achievements from the self-compacting concrete technology. Modern technologies of underwater concrete work involve meeting specific requirements by the
concrete mix. The mix should have proper rheological properties that guarantee
flowability of the mixture over time and demonstrate the least washout [6–8]. Therefore, application of the self-compacting concrete technology to obtain underwater
concrete, apart from addition of last-generation superplasticizers, requires application of the anti-washout admixture (AWA) preventing the washout of mix constituents
under water [9].
The paper presents test results from studies of own authors, aiming at increasing
of washout resistance of underwater concrete mixes by increasing amount of fine
particles in cement.
2 Role of Chemical Admixtures and Mineral Additives
in Shaping Underwater Concrete Properties
During underwater concrete placement, properties of the concrete mix are very
important. Its composition has to provide suitable rheological properties, as well
as the lowest washout as possible [10]. Application of self-compacting concrete for
underwater work became possible after development of not only the new-generation
polycarboxylate-based superplasticizers, but also introduction of a new type of AWA.
Viscosity enhancing chemical admixtures form a wide group of polymers. They
were divided into five groups according to Ramachadran’s classification [11]. Firstly,
there are synthetic and natural organic polymers soluble in water, then flocculants
soluble in water and organic material emulsions providing ultrafine particles. The
next group are large-surface non-organic materials swelling in water. The last group
are also large-surface materials increasing the share of fine particles, e.g. fly ash,
hydrated lime, diatomaceous earth. On the other hand, Kawai [12] presented AWAs
classification according to the type of polymer, dividing them into three groups. These
are natural polymers including starch, natural rubbers and plant protein, the next
group covers semi-synthetic polymers including starch decomposites and derivatives,
while the remaining group are synthetic polymers based on ethylene [13].
It is generally assumed that action of these admixtures consists in “cross-linking”
of binder particles by long chains of polymers. Chains of polymers interlace fine
particles of the cement, which in consequence increases viscosity of the paste (Fig. 1).
Underwater concrete mixes, with enhanced viscosity, have better stability, are capable
to fill out elements with dense reinforcement, without symptoms of segregation and
S. Grzeszczyk and K. Jurowski
a new generation of polycarboxylate-based superplasticizers, much more effective,
and in result the development of self-compacting concrete technology [4, 5].
A progress in development of underwater concrete technologies is associated with
the use of achievements from the self-compacting concrete technology. Modern technologies of underwater concrete work involve meeting specific requirements by the
concrete mix. The mix should have proper rheological properties that guarantee
flowability of the mixture over time and demonstrate the least washout [6–8]. Therefore, application of the self-compacting concrete technology to obtain underwater
concrete, apart from addition of last-generation superplasticizers, requires application of the anti-washout admixture (AWA) preventing the washout of mix constituents
under water [9].
The paper presents test results from studies of own authors, aiming at increasing
of washout resistance of underwater concrete mixes by increasing amount of fine
particles in cement.
2 Role of Chemical Admixtures and Mineral Additives
in Shaping Underwater Concrete Properties
During underwater concrete placement, properties of the concrete mix are very
important. Its composition has to provide suitable rheological properties, as well
as the lowest washout as possible [10]. Application of self-compacting concrete for
underwater work became possible after development of not only the new-generation
polycarboxylate-based superplasticizers, but also introduction of a new type of AWA.
Viscosity enhancing chemical admixtures form a wide group of polymers. They
were divided into five groups according to Ramachadran’s classification [11]. Firstly,
there are synthetic and natural organic polymers soluble in water, then flocculants
soluble in water and organic material emulsions providing ultrafine particles. The
next group are large-surface non-organic materials swelling in water. The last group
are also large-surface materials increasing the share of fine particles, e.g. fly ash,
hydrated lime, diatomaceous earth. On the other hand, Kawai [12] presented AWAs
classification according to the type of polymer, dividing them into three groups. These
are natural polymers including starch, natural rubbers and plant protein, the next
group covers semi-synthetic polymers including starch decomposites and derivatives,
while the remaining group are synthetic polymers based on ethylene [13].
It is generally assumed that action of these admixtures consists in “cross-linking”
of binder particles by long chains of polymers. Chains of polymers interlace fine
particles of the cement, which in consequence increases viscosity of the paste (Fig. 1).
Underwater concrete mixes, with enhanced viscosity, have better stability, are capable
to fill out elements with dense reinforcement, without symptoms of segregation and