5. CONCRETE

concrete

a proportioned mixture of cement + aggregate + water

cement

a powder material which when combined with water possesses adhesive and cohesive properties

type of binder that hardens in place

aggregates

inert granular material such as sand and gravel which when mix with cement and water result in concrete

water

combines with the cement to form a paste, which coats and surround the inert particles of aggregates and upon hardening, binds 

concrete

is a plastic mass which can be cast, molded, or formed into predetermined size or shape

setting

is the term for the hardening of concrete. upon hydration of concrete, it becomes stone-like in strength, hardness and durability.

mortar, stucco, or cement plaster

when mixed with water, fine aggregate and a large aggregate of more than 6mm(1/4) is known as _____

plain or mass concrete

when without reinforcement it is called ___

fireproof construction

concrete provides ___ ____

reinforced concrete

concrete in which steel reinforcement is embedded in such a manner that the two materials act together in resisting forces

cement

a calcined mixture of clay and limestone, finely pulverized and used as an ingredient in concrete and mortar

• lime

• gypsum

• pozzolan cement

• portland cement

kind of cementing materials

lime

used by egyptians, greeks, and romans

made by calcination of limestone

gypsum

also used by egyptians, greeks, and romans

source of the word, ‘plaster’

can be more plastic if hydrated lime is added

plaster of paris

is pure gypsum

pozzolan cement

first developed by the Romans

mix with slaked lime with pozzolana (volcanic ash) which hardened underwater

portland cement

patented by John Aspdin in 1824

Type I: Normal

general purpose commonly used for structural work, bridges, pavements and concrete masonry units

Type II: Modified Portland Cement

generates less heat and at slower rate during the hydration process than Type I

used in structures in contact with ground water 

Type III: High Early Strength Cement

for use where high strength is desired at early periods, usually within a week or less

also used in cold weather construction to reduce time required for protection from low temperatures

Type IV: Low-heat Cement

generates less heat of hydration than normal Portland Cement

this is used in massive structures such as large gravity dams

Type V: Sulfate Resistant Cement

Used when high sulfate resistant attack is desired

gains strength at a slower rate than type 1

white portland cement

manufactured using selected raw materials so that the finished product will be white than gray

this is used for decorative architectural concrete, stucco, white or pigmented grout

air-entertaining portland cement (mayda lat usa same definition: Air-entertaining agents)

introduces minute air bubbles in the concrete mix to increase its resistance to freezing

makes the concrete more durable and lighter in color

fine aggregates

coarse aggregates

aggregates used in a concrete mixture can be:

fine aggregates

smaller than 6mm (1/4”) in diameter

example: sand

coarse aggregates

larger than 6mm (1/4”) in diameter

clean and free from injurious amount of oils, acids, alkali, organic material or other deleterious substances

water used in concrete mixing must be:

potable

clean enough to drink

admixtures

substances added to a concrete mix to alter or enhance a specific property

accelerators

used to speed up setting time and reduces the length of time for curing and protection

retarders

slows down the setting of a concrete mix in order to allow more time for placing and working the mix

reducers

reduces water requirements of concrete for a given consistency

also known as plasticizers

integral waterproofing compound

reduces the capillary attraction of the voids in the concrete and decreases water absorption of concrete or mortar

this does not render the concrete completely waterproof

example: sahara

colored pigments

used to give color to concrete floors

reinforcing bars

reinforcement changes the basic strength properties of concrete and consequently its behavior as a structural material

concrete

strong in handling compression forces, but very weak against tension

steel

strong in handling both compression and tensile forces

water-cement ratio

strength of a concrete mix is highly affected by how much water is added into the mixture.

amount of water used per bag of cement

6.5 gallons of water

average amount of water for ordinary job conditions

meow

the less water used in mixing, the better the quality of concrete

plastic and workable

the ideal mix is one that is ___

mix should NOT be too dry or too wet

1 (cement) :2 (sand) :4 (gravel) :6.5 (gallons of water)

proportion of concrete for 1 cubic foot

• 1 cubic foot = 1 cement

CLASS AA

CLASS A

CLASS B

CLASS C

CLASS D

types of concrete according to proportion

1: 1.5: 3 (CLASS AA)

for concrete under water, retaining walls

1: 2: 4 (CLASS A)

for suspended slabs, beams, columns, arches, stairs, walls of 100mm (4”) thickness

1: 2.5: 5 (CLASS B)

for walls thicker than 100mm (4”), footings, steps, reinforced concrete slabs on fill

1: 3: 6 (CLASS C)

for concrete plant boxes, and any non-critical concrete structures

1: 3.5: 7 (CLASS D)

for mass concrete works