Lecture topic1 concrete_aug2015_part2
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TOPIC 1: CONCRETE PART 2 MAK/BLD62003/MAC2015/SABD 1
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Transcript of Lecture topic1 concrete_aug2015_part2
TOPIC 1: CONCRETE
PART 2
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CEMENT TOPIC 1: CONCRETE
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CEMENT
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• A binding agent of any material that will bond two or more adhesive substances together (i.e fine sand and coarse aggregates together in concrete).
• Is a hydraulic binder (hardens when water is added).
• Sets after few hours when mixed with water. Hardens in few days into a solid & strong material.
• Construction term: Portland Cement
• Composition: Lime (60-65%); Silica (10-25%); Iron Oxide (2-4%); Aluminium (5-10%).
• 27 types of common cement; group into 5 categories & 3 strength classes: ordinary, high and very high.
TYPES OF CEMENT
TYPE I: ORDINARY (Normal cement)
TYPE II: MODIFIED (Moderate Sulfate Resistance – slow
reacting)
TYPE III: HIGH EARLY STRENGTH (fast setting)
TYPE IV: LOW HEAT HYDRATION (low heat generation)
TYPE V: HIGH SULFATE RESISTING
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TYPES OF CEMENT
•Used in general construction
•Should not be used where concrete will be in contact with high-sulfate soils or will be subject to high temperature during hydration.
TYPE I
•Used for precaution against moderate sulfate attack concentrations
•Generates less heat of hydration & cures at slower rate than Type I.
•I.e: marine conditions, sewage treatment works
TYPE II
•Tp produce concrete that sets faster than normal, permitting earlier form removal & speed up the construction: (i) early form removal is required; (ii) concrete must be put into service quickly; (iii) in cold weather to reduce time taken for protection against low temperatures.
•More economical than Type I.
TYPE III
•For large construction building foundation projects i.e dams)
•Amount of heat generated during hydration must be kept minimum.
•Slower rate of getting the required strength
TYPE IV
•More resistant to deterioration caused by sulfates & alkalis in the soil
•Slower rate of strength compared to Type I. TYPE V
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CONCRETE MATERIALS M
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MATERIAL STANDARD
(I) Portland Cement
• Types I, II, III, IV, V ASTM C 150
• Types IA, IIA, IIIA (air
entraining)
ASTM C 150
• Pozzolan & blast furnace ASTM C 595
(II) Ready mix concrete ASTM C 94
(III) Aggregates
• Normal weight ASTM C 33
• Light weight ASTM C 330
(IV) Admixtures
• Air-entraining agents ASTM C 260
• Accelerators: calcium
chloride
ASTM C 98
TYPES OF CEMENT
ALUMINOUS CEMENT
WHITE PORTLAND CEMENT
NATURAL CEMENT
LIMESTONE
GYPSUM CEMENT
OXYCHLORIDE CEMENT
MASONRY CEMENT/ MORTAR
FLY ASHES
SILICA FUME (MICROSILICA)
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ALUMINOUS CEMENT
Aluminous cement + aluminous (bauxite) +
calcareous (limestone)
Early hardening & early strength
Resistant to sulfate
Very expensive
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WHITE PORTLAND CEMENT
Architectural application
Used in precast wall & facing
panels, terrazzo, stucco, cement
paint, tile grout & decorative
concrete.
General purpose cement
White in color
Composed of limestone, silica &
iron
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PORTLAND BLAST FURNACE
SLAG CEMENT
Granulated & selected blast-furnace slag (obtain by
rapidly chilling or quenching molten slag in water,
steam or air) is added to & ground along with portland
cement.
Slag constituent must be 25 & 65% of the total weight of
the portland cement.
Usually available only in areas where it can be obtained
economically, such as near blast furnace sites.
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PRODUCTION OF PORTLAND CEMENT M
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Mixing limestone with shale, clay or
blast furnace slag in proper
proportions.
Burn mixture in a rotary kiln @
1482 degree Celcius to fuse it into
clinker (19mm in diameter)
Clinker is cooled & then pulverized
together with a small amount of
gypsum (slow the stetting time)
Then portland cement is produced.
Portland cement + water = a paster
if formed which first sets (becomes
stiff) & hardens into solid mass.
NATURAL CEMENT
For mortar
Admixture in Portland Cement
From natural materials
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LIMESTONE
For example: marble, chalk, coral & shell
For mortar application
White in color
Chalk is porous and often has high moisture content
that leads it to its use in the ‘semi-dry/wet’
manufacturing process of making cement.
This particular process represents some 16% of total
production.
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GYPSUM CEMENT
From gypsum mineral which contains
crystalline calcium sulfate dehydrate
E.g white powder which is also known as
cement plaster
Set rapidly & achieve high early strength of
concrete
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OXYCHOLRIDE CEMENT
Dense, hard, crystalline structure
Better bonding compared to Portland Cement
Floor application
Moderate resistant to water
Cannot be exposed to wet condition
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FLY ASHES
Used as admixtures for Portland Cement
Example: Pozzolan (type of silica)
Has higher cured strength than concrete
containing only portland cement, aggregate &
water.
Decreases the heat of hydration which is
important in mass concrete structures.
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SHALE
Shale is a pure sedimentary rock made of very fine silt, clay
and quarz.
Shale falls in the category of mudstones.
Its grain size is less than 1/256mm.
Shale is distinguished from other mudstones because it is
fissile and laminated.
Clays, mudstones and shales are very widely distributed in the
UK.
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WATER
Mixing water should be clean & free from
oil, alkali & acid.
Water that is fit to drink is suitable for
concrete use.
Water with excessive quantities of sulfates
should be avoided.
React with cement to form a bonding agent
Serves as lubricant to carry cement paste
into small pores
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WAYS OF CONTROLLING WATER CONTENT
For low quality concrete Specify that the concrete is to be a stiff mix with only
sufficient water to enable the material to be placed in position without difficulty.
For good quality concrete Specify the use of slump test.
For high quality concrete The sand content is dealt because the volume of sand
varies according to its water content.
Completely dry or completely wet has the same volume but wet sand has higher volume.
Water content must be carefully controlled for high quality concrete.
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AGGREGATE
WHAT IS AGGREGATE:
A broad category of coarse particulate material – sand, gravel, crushed stone, slag, recycled concrete.
A component of composite materials: concrete & asphalt concrete.
Constitutes of 60 – 75% of the volume of water.
Thus, cost & quality of concrete depends on aggregates used in it.
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AGGREGATES M
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Both fine & coarse aggregates should be uniformly
graded from their finest particles up to the largest.
This could be achieve by having least amount of
portland cement plaster to surround aggregate & fill
all spaces between particles.
Should be clean & free from loam, clay etc because
these objects are porous, have low resistance to
weathering & low strength & could cause defects.
TYPES OF
AGGREGATE
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AGGREGATE
FUNCTIONS OF AGGREGATE: M
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Functions of
Aggregate
STRENGTH
Add strength to overall composite
material
(Act as reinforcement)
FILLING
Make mixtures more compact – Facilitate specific applications
(drainage, weatherproofing & heat retention)
EMBELLISHMENT
Aesthetic qualities
(Sand – brightness; Local chippings – colors to concrete
& its products i.e tinted, interlocking paving,
industrialized slabs, panels & road paving)
SUPPORT
Prevent settling under building or road
(Used as base material under foundations, roads, buildings
etc)
FINE, COARSE & WELL GRAINED AGGREGATES
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VARIOUS SIZES OF AGGREGATES
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VARIOUS SHAPES OF
AGGREGATES
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SAND M
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• Granular material composed of finely divided rock and mineral particles.
• Defined by size (finer than gravel and coarser than silt)
• Size of sand grains: 0.0625mm – 2mm (diameter)
• Gravel: 2mm – 64mm
• Silt: 0.004mm - 0.0625mm
• Sand feels gritty; Silt feels like flour (Urquhart, 1959)
• Silica (Silicon dioxide : i.e quartz): most common mineral resistant to weathering.
CORRECT & INCORRECT WAY IN
ASSEMBLYING
MORTAR
Mortar is the material that
sticks two masonry units
together
Composed of: Portland cement,
hydrated lime, sand & water
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WHAT IS MORTAR?
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• Mortar is a paste used to bind blocks together while filling the spaces between them.
• It is used most commonly in the masonry trade to bind stone, brick or concrete blocks during building construction.
• It can also be used to repair when the original application has crumbled or washed away.
• It is a combination of sand, a binder such as lime or concrete, and water.
• It is applied as a thick paste and sets hard. • It creates a tight seal between bricks to
prevent the entry of air and moisture into the structure.
• It bonds with any joint reinforcements, anchor bolts or metal ties, and compensates for size variations in the bricks to create an aesthetically pleasing and structurally sound building.
Type Avg
Compressive
Strength
Use
M 2500 psi Masonry below grade and in
contact with earth
S 1800 psi Where maximum flexural
strength is required (winds
>80 mph)
N
750 psi General use in exposed
masonry above grade;
parapets, chimneys, and
ext. walls subjected to
severe weathering
O 350 psi Solid unit load-bearing walls
Where compressive
strength < 100 psi
TYPES OF MORTAR
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MORTAR
MORTAR BASICS
PROPERTIES
• Have a tendency to
shrink very little
• High degree of resistance
to moisture penetration
FUNCTIONS
JOINTS
• Brick masonry mortar made of
Portland cement, hydrated lime,
and sand (stone masonry uses
white Portland cement [non
staining].
• Re-tempering – adding water to
the mortar mix to maintain
consistency.
• Mortar mix should be used
within 2 – 2 ½ hours after initial
mix is prepared.
• Efflorescence – the soft white
powder appearing on the face of
brick; caused by salts in the
brick or mortar brought to the
surface.
• Possess adequate strength to
resist forces applied to it
• Provide aesthetic qualities to
the structure through the use of
color and type of joint
• Joint sizes vary
• Facing brick – 3/8”
to ½”
• Building brick – ½”
• Glazed brick – 1/4 “
• Although many types of
joints exist , the most
weatherproof &
recommended are: V-
shaped, Weathered, &
Concave
• Joints may be formed by
using a trowel, steel rod,
or specialized tools
TYPES OF JOINTS
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TYPES OF MORTAR JOINTS
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COMPARISON BETWEEN CONCRETE &
MORTAR
MORTAR
Mortar is used to hold building materials such as brick or stone together.
It is composed of a thick mixture of water, sand, and cement. The water is used to hydrate the cement and hold the mix together.
The water to cement ratio is higher in mortar than in concrete in order to form its bonding element.
When mixed, it is a much thicker substance than concrete, making it ideal as a glue for building materials like brick.
Because mortar must be replaced every 25-50 years, it isn’t practical for structural projects.
CONCRETE
Concrete is a mixture of sand, cement, and water, but it also contains rock chippings or gravel which makes it much stronger and more durable than mortar.
Because it needs a low water to cement ratio, it is much thinner when mixed, making it difficult to use as a bonding element.
Concrete is used in structural projects and is often reinforced with steel rebar to maintain its structural integrity as the soil beneath it settles.
It is best used for support, such as beams, walls, or other building foundations.
So essentially, what is the difference between mortar and concrete?
While a hydrated cement mixture forms the base of both materials, the rock chipping in cement makes it much stronger for use in structural projects, and mortar is thicker, which makes it a better bonding element.
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ADMIXTURES M
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A material other than water,
aggregates & portland
cement(ASTM C125).
Used as an ingredient of concrete
& added to the batch immediately
before or during is mixing.
Benefit: Improve concrete quality,
manageability, acceleration or
retardation of setting time among
other properties that could be
altered to get specific results.
Concrete mixes today contain one
or more admixtures.
Source:
http://www.ce.memphis.edu/1101/n
otes/concrete/PCA_manual?Chap06
Set-Retarding
Air-Entrainment
Water-Reducing
Accelerating
Shrinkage Reducing
Super Plasticizers
Corrosion-inhibiting
WHAT IS ADMIXTURES CATEGORIES OF
ADMIXTURES
TYPES OF ADMIXTURES
Set-Retarding
Air-Entrainment
Water-Reducing
Accelerating
Shrinkage Reducing
Super Plasticizers
Corrosion-inhibiting
MAK/BLD62003/MAC2015/SABD
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CONCRETE ADMIXTURES:
SET RETARDING
Admixtures that delay the setting time of
concrete = retarders.
Used to overcome the accelerating effect on high
temperatures during the summer.
To delay the initial set of concrete when difficult
or unusual conditions of placement are required.
Examples: Lignosulfonic acid & its salt;
hydroxylated, carboxylic acids & their salts.
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CONCRETE ADMIXTURES:
AIR ENTRAINING
Used to improve durability of concrete exposed to a combination of moisture.
Cycles of freezing & thawing is an air-entrainment agent.
It is a mechanism in which air-entrained concrete resists the disruptive effects of frost action – is in the large no. of minute air bubbles that are distributed uniformly throughout the cement paste.
Entrainment of the air may be produced by means of air-entraining admixtures added to the concrete ingredients before or during the mixing of concrete, or the use of air-entraining Portland cement.
Materials used: natural wood resins, fats & oils that have been chemically processed.
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CONCRETE ADMIXTURES:
ACCELERATING
Used to achieve high early strength & to shorten
the time of set.
High early strength results in earlier removal of
forms, reduction of required time for curing &
protection, earlier use of a structure & partial
compensation for the retarding effect of cold
weather.
Chemicals used: organic compounds of
triethannolamine & calcium chloride.
MAK/BLD62003/MAC2015/SABD
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CONCRETE ADMIXTURES:
SUPER PLASTICIZERS
Do more for concrete than make it more workable
under shovel, vibrator, float & trowel.
By making concrete fully plastic with less water,
the water-cement ratio can be kept low & the
concrete’s compressive strength kept high.
Several ingredients serve to plasticize a concrete
mix: slag cement, fly ash, mircosilica & air-
entraining agents.
MAK/BLD62003/MAC2015/SABD
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Further reading on Admixtures:
http://www.authorstream.com/Presentation/lavan
yakaransingh-1955952-admixtures-concrete/
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PLASTICIZER
Do more for concrete than make it more
workable under shovel, vibrator, float &
trowel.
By making concrete fully plastic with less
water, the water cement ratio can be kept
low & the concrete compressive strength
kept high.
For example: slag cement, fly ash,
microsilica & air-entraining agents.
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COLORING AGENTS
Pigments added to concrete to produce color
Should be colorfast, chemically stable & have
no diverse effect on the concrete
Are generally inorganic oxides of synthetic
type.
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CEMENT
MANUFACTURING PROCESS
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CEMENT PRODUCTION PROCESS
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VIDEO 1
CEMENT PRODUCTION PROCESS
VIDEO 2
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CEMENT PRODUCTION PROCESS
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VIDEO
http://www.lafarge-
na.com/wps/portal/na/en/2_2_1-
Manufacturing_process
CEMENT PRODUCTION PROCESS
1 Extraction
Materials are extracted / quarried / recovered and transported to the cement plant.
2 Crushing and milling
The raw materials, limestone, shale, silica and iron oxice are crushed and milled into fine powders.
3 Mixing and preheating
The powders are blended (the ‘raw meal’) and preheated to around 900° C using the hot gases from the kiln. The preheating burns off the impurities.
4 Heating
Next the material is burned in a large rotary kiln at 1500° C. Heating starts the de-carbonation where CO2 is driven from the limestone. The partially fused resulting is known as clinker. A modern kiln can produce around 6000 tons of clinker a day.
CaCO3 (limestone) + heat -> CaO (lime) + CO2
5 Cooling and final grinding
The clinker is then cooled and ground to a fine powder in a tube or ball mill. A ball mill is a rotating drum filled with steel balls of different sizes (depending on the desired fineness of the cement) that crush and grind the clinker. Gypsum is added during the grinding process to provide means for controlling the setting of the cement.
The cement is bagged transported for concrete production.
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REFERENCES
Urquhart, L.C (1959) Civil Engineering Handbook. McGrawHill Book Company.
Lyons, A., 2010. Materials for Architects & Builders. 4th ed. Oxford: Elsevier Ltd.
2. Allen, E. and Iano, J., 2009. Fundamentals of Building Construction: Materials and Methods. 5th ed. Hoboken: John Wiley & Sons Inc.
3. Emmitt, S. and Gorse, C.A., 2010. Barry’s Advanced Construction of Buildings. 2nd ed. Oxford: Blackwell Publishing Ltd.
4. Everett, A., 1994. Mitchell’s Materials. 5th ed. Oxford: Addison Wesley Longman Limited.
5. Foster, J.S., 2000. Mitchell’s Structure & Fabric Part 1. 6th ed. London: Pearson Education.
6. Foster, J.S. and Harington, R., 2007. Mitchell’s Structure & Fabric Part 2. 7th ed. London: Pearson Education.
7. Taylor, G.D., 2002. Materials in Construction: Principles, Practice and Performance. 2nd ed. Oxford: Longman.
Secondary References:
1. Brooks, A.,1998. Cladding of Building. 3rd ed. Oxford: E & FN Spon.
2. Mat Lazim Zakaria, 2005. Bahan and Binaan. 2nd ed. Kuala Lumpur: Dewan Bahasa dan Pustaka.
3. Neville, A.M., 2000. Properties of Concrete. 4th ed. Harlow: Pearson Education Limited.
4. Stulz, R. and Mukerji, K., 1993. Appropriate Building Materials. Oxford: Intermediate Technology Publications.
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