Itroduction on Mass Concrete, Plum Concrete, RMC; Manufacture Process of RMC, Places of uses of different types of concrete, etc...

1. Mass Concrete
RMC
Plum Concrete
Created By:
Jay S. Singhania
En No:146490306107
Civil-B Sem-5th
Sir BPTI, BVN

2.  Mass Concrete is a concrete having considerable
dimensions that may get affected by thermal behaviour
of concrete. E.g.. Concrete Dam.

3.  In the design of a concrete dam, strength of concrete in
initial stage is less important.
 The primary considerations are given to the aspect of
how to reduce the heat of hydration, or if certain amount
of heat is generated, how to absorb such inside heat
from the concrete mass to reduce the adverse effect in
the form of cracks.
 The pouring of concrete in such large sections like dams
need the primary understanding of the thermal
behaviour mainly w.r.t. heat of hydration.

4.  Fitz Gibbon discovered from his research work that
temperature difference of 200C or more between the inner
and outer surfaces of the concrete causes cracks,
assuming the coefficient of thermal expansion of concrete
as 10 * 10-6 per 0C.
 At 200C temp. difference, the differential strain would
come to be 200 *10-6 which is considered as the realistic
tensile strain at cracking.

5.  Therefore, there is a need for controlling the heat of
hydration in concrete and also not allowing the concrete
surface to cool down rapidly.
 If the surface is insulated, the difference in temperature
between the interior and the exterior is reduced,
improving the cracking behavior of concrete.
 The retention of formwork and its retention properties
may be made use of to reduce the temperature difference
between the interior and exterior surfaces.

6. Fitz Gibbon estimated that the temperature rise under
adiabatic condition is 120C per 100gm of cement per cubic
metre of concrete, regardless of the type of cement used,
for cement contents between 300-600kg/m3.

9. The thermal changes due to heat of hydration will only be
important for first few days in normal structures but may last for
longer time in large mass concrete.
In India, in certain states or cities, the change of ambient
temperature in day and night could be as high as 300C and the
actual temperature change in concrete surfaces is much more
than 300C.
The seasonal variations could be as large as 400C, which is still of
higher range in middle east countries.

10. The change in diurnal or seasonal temperatures
mentioned above makes the concrete to expand and
contract.
Since the structures are not free to expand and contract
on account of restraint at support in case of roof slabs and
sub-grade reaction in case of pavements, a considerable
tensile stress more than the tensile strength is generated
resulting in cracks in concrete.

11. The tensile stress will be much higher in case of stronger
concrete with higher modulus of elasticity and higher
degree of variation of temperature.
No doubt concrete of higher compressive strength will
have higher tensile strength to withstand the higher tensile
stress.
But due to lower value of creep of such concrete, a small
extent of stress relaxation takes place and as such, the
stronger concrete will crack more than the weaker
concrete, from this consideration.

12. ∞Temperature rise varies by many parameters:
i. Cement composition, fineness, and content
ii. Aggregate content and CTE (Coefficient of Thermal
Expansion)
iii. Section geometry
iv. Placement & ambient temperatures
∞Most temp rise occurs in first 1-3 days after placement.

13. Stepstocontrol/minimizeheatofHydrationinMassConcrete
• Use of chilled water and ice flakes can be done in place of
normal water which will help decrease the heat of hydration to
some extent.
• Concrete should be poured in layers of equal depths so that
each layer may get some time to release the initial heat of
hydration.
• Use of chilled aggregates can be made to control/minimize the
heat of hydration in mass concrete structures.

15. • Post-Cooling utilizes cold water flowing throughpipes
embedded into the concrete. This helps to transfer heat
fromthe core, and reduce the temperature difference.

18. READY MIXED CONCRETE
(RMC)
¶ It is a concrete whose ingredients/ constituents
are weight-batched at the batching plant, mixed
at the plant itself or during the transit in
transit/truck mixers, and transported to the
construction site and delivered in a ready to use
condition, thus known as Ready Mixed Concrete
(RMC).
¶ RMC is not considered only as a product but
service-based product, as combination of 40% of
product and 60% of service.
¶ Delivery of such concrete is a science in itself.

19. ¶ This technique is very useful in the diverse
conditions when the site is at congested areas,
and also saves consumer botheration of
procurement, storage and handling of concrete
materials.
¶ This technique is becoming more popular because
of its low cost, durability and its ability to be
customized for different applications.
¶ Concrete quality in terms of its properties or
composition and quantity or volume required for
the particular applications is specified by the
customers.
¶ This technique can also be used for small works
and also when concrete is to be placed at
intervals.
¶ Usual cost of the RMC is higher than the site-
mixed concrete, but this may be offset by the
savings in the cement content, site organization

22. Threeprincipalcategoriesof RMCare:
i. Theplantmixedconcrete(Central mixedconcrete)
ii. Thetransitmixedconcrete
iii. Theshrinkmixedconcrete
• In plant mixed type, mixing is done at central batching plant, and mixed concrete is transported in
agitator trucks/ transit mixers, which keep on revolving at 2-3 revolutions per minute to prevent
segregationandstiffeningof themix.
• In transit mixed type or truck mixed type, materials are batched at the central batching plant and
mixed in the truck during the transit or immediately before discharging the concrete on the site.
Thistechniquepermitslongerhaulandlessvulnerableincaseof delay.
• In shrink mixed type, materials are partially mixed at the batching plant to increase the capacity of
theagitatortrucksandthe finalmixingiscompletedendroute.

24. ₤Maintaining the workability of the concrete mix and avoid
the hardening/ stiffening of the mix is the main problem in
the transportation of concrete.
₤Concrete stiffens with time and handling of RMC often takes
longer time.
₤Safe haul time shall be limited to 90 minutes or 300
revolutions (whichever is less).
₤Agitating up to 6 hours may not adversely affect the strength
of the concrete, provided that the mix should remain
sufficiently workable for full compaction.

25. Present high-tech RMC plants give facilities
for testing and give accurate results.
In RMC production, quality control begins
right from the beginning of the process i.e.
from receiving the raw materials and other
ingredients before using for the work, and
materials are used on work-site only after the
approval from the quality control department.
Basic properties of concrete such as slump,
compacting factor, strength, air content, unit
weight, etc. are tested from batch-batch to
ensure best quality control and thus required
modifications are made.

26.  Today RMC plants are expanding at a fast rate i.e. 25-30%andthere are over 100
RMC plants operating in the differentparts of the country.
 In our country, only 6-7%of total concrete productiongoes to RMCplants, as
against 80-85%in USA.
 Today, many tries are made by cement manufacturers, leading Indian
constructional companies, constructional equipment rental companies and raw
material suppliers to establish newer RMC plants in India.
 Also many foreignRMCgroups are trying for Indianpartners to set up RMC
plants in India as a joint venture.

27.  Ahlcon Ready MixedConcrete is the largest producer and supplier of RMC
in India withmore than20 plantsoperating all overthe country, all
equipped with state-of-the art equipment and machinery and strong R and
D backupsupport.
 It produces a hugerangeof productssuchas concreteof all grades from
M7.5 onwards, highperformance concrete of grade M50 onwards, concrete
with 40 mm size down aggregates, fiber-reinforced concrete, colored
concrete and concrete of any mix design as per client specification and
necessity, and covers various constructional requirements.

28. Ahlcon RMC has worked by setting up special project-based
plants for its clients such as DRMC, IRCON, Senbo, DDAetc,
and has pumpedfor 2000-3000 m3 continuously successfully.

31. Plum Concrete
Idea of use of aggregates as a filler inert material can
be extended to the inclusion of the large stones up to
300 mm size in normal concrete, increasing the yield
of concrete for given volume of cement. This type of
concrete is known as ‘PLUM CONCRETE’ or
‘CYCLOPEAN CONCRETE’.

32. Here, the plums used can be as large as 300 mm size
and this type of concrete can be used in large concrete
mass.
The size of plum used should be limited to of the
least dimension to be concreted.
Plums’ volume should not exceed 20-30%of the total
volume of the finished concrete, with being properly
dispersed throughout the concrete mass.
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33. Plum concreting is achieved by placing a layer of
normal concrete first, then placing plums, followed by
another layer of concrete and so on.
Care must be taken to prevent air traps below the
stone surfaces.
Plums have no adhering coating and thus preventing
possibilities of cracking of concrete and discontinuities
between plums, also giving consistency in
permeability.