High
strength concrete
High Strength
Concrete (HSC) or sometimes referred to as High Performance Concrete
can generally be described as concrete which has a strength greater
than concrete used for conventional structural work. In the work
done with Super-Pozz®, HSC is classified as concrete with a minimum
compressive strength of 60 MPa.
One of the basic
principles of HSC is the need for proper packing of particles. The
purpose is to obtain the smallest possible volume of empty or water-filled
space in the material. The ideal particle size distribution of
Super-Pozz®
is such that it efficiently fills void spaces between the aggregates
and cementitious components of the mixture. The end result is a
mix, which exhibits lower water demand, which leads to improved
durability and strength gain.
HSC normally requires
high cement contents, high-range water reducing admixtures and highly reactive
mineral additives. The use of Super-Pozz® is beneficial because
it produces concrete with a lower w/c ratio and can also provide a reduction
in HRWR. The added advantage is an improvement in durability, reduction
in shrinkage, reduced bleeding, improved slump retention and ease of placement
of the concrete.
Research and experience
has showed that the use of Super-Pozz® coupled with silica fume
has a great potential for achieving very high strengths, particularly over
longer periods. Blends of Super-Pozz® with silica fume are found
complementary in that Super-Pozz® provides the water reduction
and workability and silica fume promotes accelerated hydration; both products
synergising to improve the overall strength gain profile of a mix.
Super-Pozz®
incorporates into the concrete mix easily which reduces the risk of having
a non-homogeneously mixed concrete after placement.
Self-Compacting Concrete (SCC)
Self-compacting concrete
(SCC) is defined by Khayat, Hu and Monty as a "highly flowable, yet
stable concrete that can spread readily into place and fill the formwork
without any consolidation and without undergoing any significant separation".
The main characteristic of the fresh concrete is to have a high slump-flow
measurement with no segregation. With Super-Pozz®, due to its
ideal particle shape and fineness, it disperses easily into the concrete
resulting in major improvements in the workability and rheology of the mix.
The use of Super-Pozz® in SCC creates a cohesive, yet workable
mix without the need of modifying the water and/or admixture content. Super-Pozz®
also reduces segregation and bleeding, which improves the bond between paste
and aggregate as well as producing a less permeable concrete.
Ready-mix concrete
The use of
Super-Pozz® can be effective in enhancing the properties of concrete,
both in its fresh and hardened state. Due to the lower water demand
required, Super-Pozz can beneficially be used to:
- Lower the w/b
ratio
- Use of more cost
effective admixtures dosages, or
- A combination
of the above
Super-Pozz® can
be stored in silos and handled in the same manner as cement.
Super-Pozz®
in concrete assists with the placement and compaction, which is
as a result of the material being totally spherical. Due to the
ideal particle shape and size, Super-Pozz® fulfils an actively enhancing
role unlike other ultra-fine materials, which tends to generally
stiffen up the concrete mix. In addition, Super-Pozz® also aids pumpability
and reduces pumping pressures, which allows for a major cost savings
on equipment maintenance.
Durability
The durability of a product
can be measured by its ability to remain serviceable for a required period
of time (years,decades or even centuries). The environment to which cementitious
products are exposed to needs to be taken into consideration when doing
mix designs. Super-Pozz® as a mineral additive can effectively
be used where typical aggressive environments such as chloride attack, alkali
aggregate, silica reaction, and sulfate attack conditions exist. Other durability
tests on concrete include permeability, abrasion resistance, carbonation
rates, where Super-Pozz®
improves the performance of concrete.
Pump
concrete
Generally, the workability
of Super-Pozz® concrete is improved due to the fact that
there are a number of very fine, solid, spherical particles introduced in
the mix. These small spheres act like miniature ball bearings allowing the
concrete to exhibit better workability characteristics when energy is introduced
into the mix. As a result of the Super-Pozz® addition,
the workability is increased resulting in improved compatibility and pumpability
of the mix. The improved compaction has the further advantage of increasing
durability and resistance against penetration by aggressive chemicals. Another
major benefit with the addition of Super-Pozz® in pumped
concrete is that pumping pressures can be reduced thus allowing major cost
savings on equipment maintenance.
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