03 Water and Admixture-1
03 Water and Admixture-1
03 Water and Admixture-1
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Water
Usually water is specified only in terms of
quantity rather than quality
A good concrete mix usually have about 140 to
200 liters / cu.m. but depend on size of aggregates
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Water
NSCP 426.4.1.3 Water
426.4.1.3.1 Compliance Requirements:
(a) Mixing water shall conform to ASTM C1602M;
(b) Mixing water, including that portion of mixing
water contributed in the form of free moisture on
aggregates, shall not contain deleterious amounts
of chloride ion when used for prestressed
concrete, for concrete that will contain aluminum
embedments, or for concrete cast against stay-in-
place galvanized steel forms.
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ASTM C1602 / C1602M - 18
Standard Specification for Mixing Water Used in the
Production of Hydraulic Cement Concrete
It defines sources of water and provides requirements and
testing frequencies for qualifying individual or combined
water sources. Mixing water shall consist of: batch water,
ice, water added by truck operator, free moisture on the
aggregates, and water introduced in the form of
admixtures. Potable and non-potable water is permitted to
be used as mixing water in concrete. The following are
concrete performance requirements for mixing water:
compressive strength and time of set. Density of water
shall be tested or monitored with a hydrometer. Optional
chemical limits for combined mixing water are given for:
chloride, sulfate, alkalis, and total solids.
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Seawater
Recently, there is an increase in study that explores the
possibility of using seawater for concrete mixing
A THESIS OPTION
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Seawater
Potential of seawater:
- Does not significantly reduce concrete strength
- Slightly accelerates the early strength of concrete
Minor concern/s:
- Slightly reduces the 28-day strength by 10-15%
- May cause efflorescence and persistent dampness
- Not advisable for plastering purpose
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Admixtures in Concrete
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NSCP 426.4.1.4 Admixtures
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Chemical Admixtures
- ACCELERATOR
- SET RETARDERS
- WATER-REDUCERS (PLASTICIZERS)
- SUPERPLASTICIZERS
- OTHERS
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Chemical Admixtures
ACCELERATOR
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Chemical Admixtures
SET-RETARDER
SET-RETARDER
Effects:
- reduce early strength
- rate of strength development increases in later ages
- eliminates/lessens the formation of cold joints
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cold
cold joints
joints
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Chemical Admixtures
WATER- REDUCERS
(or Plasticizers)
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Chemical Admixtures
WATER- REDUCERS
SOLUTION: PLASTICIZER!!
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Chemical Admixtures
WATER- REDUCERS
(or Plasticizers)
Three purposes:
- Same workability + lower w/c = higher strength
- Same workability + lower cement content = lower
heat of hydration
- Same w/c = increase workability
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Chemical Admixtures
WATER- REDUCERS
- Surface-active agents
creates repulsion effect between the particles and
results in stabilizing their dispersion
Effects:
Reduce water content
Increase workability
Improve hydration
Purpose:
- Produce flowing, self-leveling, self-compacting
concrete
- Produce high strength, high performance concrete
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Chemical Admixtures
SUPERPLASTICIZERS
Effects:
- Increase in early strength
- Workability is improved for a short duration
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Effect of superplasticizer in concrete (flowable, self leveling, self
compacting) and still achieves high strength
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Chemical Admixtures
Others
Air-Entraining (Gas-Forming)
Permeability Reducing (Air-Detraining)
Waterproofing
Expansion Producing
Anti-bacterial
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Mineral Admixtures
POZZOLAN
POZZOLANIC REACTION
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Mineral Admixtures
Effects of Pozzolan
Reduce bleeding and segregation
Reduce temperature rise
Natural
- Clays and shales
- Volcanic tuff and pumicites
Artificial
- Fly ash
- Blast furnace slag
- Silica fume
- Rice husk ash
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Mineral Admixtures
Natural Pozzolan
- either a raw or calcined natural material that has
pozzolanic properties
- volcanic ash or pumicite, opaline, metakaolin,
shales and some diatomaceous earths
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Mineral Admixtures
Artificial Pozzolan : Fly Ash
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Mineral Admixtures
Silica Fume
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Mineral Admixtures
Silica Fume
Available in:
As-produced silica fume
Thank you
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