Enhancing Durability Of Everyday Concrete
Amol Anand Patil, Product Manager-Admixture System, BASF India Limited
Self consoliditated Concrete (SCC) has tremendous
benefits over traditional vibrated concrete to increses
overall efficiency and durability of concrete. To design
SCC as per EFNARC guidelines requre miminum 500 – 650 Kg/
m3 fines in the mix, which is not available in M20 to M30 grade
of concrete. In today’s context of everyday concrete, almost 70
-80% of the traditional vibrated concrete classes are between
M20 to M35 MPa. To convert these strength classes to classical
SCC is a big challenge, especially to maintain balance between
stability and fluidity of the concrete. This paper is about smart
materials that can be used to enhance the concreting process
and achieve maximum durability of everyday concrete. Smart
Dynamic Concrete (SDC) is an innovative concept in concreting
and it is possible to achieve self-consolidation properties using
a lower amount of cementatious material without detrimental
effect in everyday concrete.
It is essential that every concrete structure should continue
to perform its intended function that is maintaining its required
strength and serviceability, during the specified or traditionally
expected service life. It follows that concrete should be able to
withstand the processes of deterioration to which it is expected
to be exposed. Such concrete is said to be durable.
Cause of Inadequate Durability
Inadequate durability manifests itself by deterioration, which
can be due to either external factors or internal causes within the
concrete itself. The various actions can be physical, chemical, or
mechanical. It should be observed that the physical and chemical
processes of deterioration can act in a synergistic manner. For
these reasons, it is sometimes difficult to assign deterioration
to a particular factor, but quality of concrete in the broad sense
of the word, though with a special reference to permeability,
nearly always enters the pictures. Indeed, with the expectation
of mechanical damage, all the adverse influences on durability
involve the transportation of fluids through the concrete. For this
reason, the consideration of durability requires an understanding
of the phenomena involved.
Transportation of Fluid in Concrete
There are three fluids, particularly relevant to durability,
which can enter concrete; water, pure or aggressive ions,
carbon dioxide and oxygen. They can move through the
concrete in different ways, but all transportation depends
primarily on the structure of the hydrated cement paste. As
stated earlier, the durability of concrete largely depends on
the ease with which fluids, both liquids and gases, can enter
into, and move through, the concrete; this is commonly
referred to as permeability of concrete. Now, strictly speaking,
permeability refers to flow through the porous medium.
The movement of various fluids takes place not only by
flow through the system but also by diffusion and sorption.
Nevertheless, the commonly accepted term ‘permeability’ will
be used for the overall movement of fluids into and through
concrete excepted where, for clarity, distinctions between the
various types of flow to be made.
Challenges in Day to Day Concrete
It is not enough that a concrete mix is correctly designed,
transportation, placing and compaction, it is of utmost
importance that the concrete must be placed in a systematic
manner to yield optimum results. As stated earlier the
permeability is a major factor for durability of concrete and
it is related to density of concrete. The density of the concrete
is majorly affected due to the improper compaction of
concrete.
The creation of durable concrete structure requires adequate
compaction by skilled workers. However, a gradual reduction in
skilled workers and the availability of workers in a construction
industry has led to reduction of quality of construction. One
solution for the achievement of durable concrete structure
independent of construction of quality of work is the use of selfconsolidate
concrete, which can be compacted into every corner
of formwork, purely by means of its own weight and without
the need of vibrating compaction. The necessity of these typesof concrete is proposed by Prof. Okamura in 1986. Studies to
develop self-compacted concrete, including fundamental study
of workability of concrete have been carried out by Ozawa and
Meakawa at university of Tokyo (Ozawa 1989, Okamura 1993
and Meakawa 1999).
Self consolidated Concrete (SCC) has tremendous benefits
over traditional vibrated concrete as it increases overall
efficiency and durability of concrete. But the picture is quite
different in a day to day concrete requirement. Why this big
difference? In today’s context of everyday concrete, almost
70 -80% of the traditional vibrated concrete classes are
between M20 to M35 MPa. The usage of SCC in day to day
concrete requirement is limited because of several reasons as
follows.
I. The increase the initial cost since SCC has a higher unit content
of powder compared to the traditional concrete.
II. The sensitivity of SCC to variation in the mix proportion can
lead to higher production cost. The variation in moisture
content of the aggregate, especially of the sand cans
significantly the stability of SCC.
When concrete producers have to supply self consolidated
concrete, they deliver much higher strength than ordered.
This is due to higher fine content necessary for achieving the
particular properties of SCC. Those fines are usually provided
by cement and pozzolanic material that is readily available at
batching plants. The excess of cement content and extra amount
of fines required for SCC requirement compliances as per
EFNARC guidelines increase production cost. The reduction of
total fine content and of cement content would lead to decrease
in unit cost of SCC as long as self-compaction properties are
maintained. SCC is used for conditions, where a high density of
reinforcement is used and high strength is required. The use of
SCC goes through the designer specification, when the reliability
of design characteristics and durability has to be assured in the
concrete structure. The high fines content SCC has a higher
plastic viscosity and which are suitable for heavily reinforced
structure, and they have more than 350 Kg/m3 of steel as per
JSCE recommendation.
In today’s context of everyday concrete, almost 70 -80%
of the traditional vibrated concrete classes are between M20
to M35 MPa. To convert these strength classes to classical
SCC is a big challenge, especially to maintain balance between
stability and fluidity of the concrete. Smart Dynamic Concrete
(SDC) is an innovative concept in concreting and it is possible
to achieve self-consolidation properties using a lower amount
of cementatious material (fine) without detrimental effect in
everyday concrete.
Smart Dynamic Concrete is characterized by higher
yield value and lower plastic viscosity and is suitable for light
reinforced structure, where the amount of reinforcement is less
than 100 kg/m3 and classified as Rank 3 in JSCE recommendation.
This type of concrete is typically of a structure, where concrete
of strength M20 to M35 is used - this is a major grade used in
construction sites. Therefore, this diffusion of self compacted
concrete should be increased; it is in this sector that the industry
should focus its resources to find innovative approach to increase
durability of day to day concrete.
Concept of Smart Dynamic Concrete
The Smart Dyanamic concept is suitable to upgrade high
slump concrete to a higher performance level with selfcompacting
characteristics and is as easy to produce as standard
concrete. It allows the ready mix industry to reach better
construction process economy, higher concrete durability and
increased energy efficiency in order to save time and money and
reduce CO2 emissions.
MasterMatrix is the essential component of the Smart
Dynamic Concrete concept. It consists of water soluble polymer
witch modifies the rheological properties of concrete mix.
Tailored-mode of action when used in conjunction with one
of our MasterGlenium product, MasterMatrix brings a level of
viscosity to the mix that allow the right balance between fluidity,
passing ability and resistance to segregation apparently opposing
properties to be achieved.
Mechanism of Action
Comparison of Traditional Vibrated Concrete versus Smart Dynamic Concrete.
Conclusion
– Smart Dynamic Concrete is designed to upgrade high slump concrete to become self-compacted concrete
– The centerpiece of this concept is MasterMatrix, a high performance viscosity modifying agent (VMA) which allows for a quantum leap in concrete robustness.
– Smart Dynamic Concrete combines the advantages both traditional vibrated and self-compacting concrete.
– Smart Dynamic Concrete improves durability criteria over traditional vibrated concrete.
– This concept makes unique mix design optimization (by reducing fines) possible.
– Smart dynamic Concrete adds economical, ecological and ergonomic values to concrete and has the potential to move the market up to the next level of advanced construction practice. (Amol Anand Patil, Business Development manager in BASF India limited, more than 14 years of experience in the concrete industry and has worked for development of high performance concrete, Geopolymer concrete and reactive powder concrete.)
References:
1. Adam M Neville, “Properties of concrete”.
2. Hibimo, M Okuma M and Ozawa k (1998) “Roll of viscosity agent in self-compacting concrete”, Proceeding of the sixth East Asia conference on structural Engineering and construction, 1313-1318.
3. Meakawa K and Ozawa K (1999), “ Self compacting high performance concrete”, social Institute Japan 20-32
4. Okamura H, Meakawa K and Ozawa K (1993), “High performance concrete”, Gihodo Publishing.
5. Bruno D’Souza and Hironoba Yamamiya, “ Application of Smart dynamic Concrete”, Third International conference on sustainable construction material technology, http: www. claises.info/proceedings.in
6. Nilotpal Kar and David Firth, “ Smart Dynamic Concrete” – Economic, Ergonomic and Ecological Technology, IQA- CCAA construction material industry conference, Melbourne Victoria.
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