Concrete

Question 1

what is concrete made of?

Answer 1

agrregate ( rock, sand, gravel )
cement (80 % limestone + silica, sand, iron oxide)
water

Question 2

what is concrete?

Answer 2

structural material consisting of sggregate that is bondded together with cement and water

Question 3

Hydragtion

Answer 3

chemical reaction between cement and water whicg causes the cement to set and harden

Question 4

Cement production

Answer 4

raw material
cooking
admixture and grind

Question 5

Parts that make up concrete

Answer 5

1 part cement
2 parts sand
4 parts gravel
1/2 parts water

Question 6

workabiliy

Answer 6

property of fresh mixed concrete or mortar which determines the ease and homogeneity which can be mixed, placed, compacted and finished

Question 7

Slump test

Answer 7

most sisgnifacte peoperty is the amount of water used
aggregate = shape, size, grading, surface temperatureaa
ambient temperature = evaporationand hydration rate

Question 8

RATIO of concrete

Answer 8

0. 3 = mimiumum neede for hydration
1. 4 = high strength concrete
2. 6-0.7 = sonsidred normal
3. 8 = very wet varation

Question 9

Admixture

Answer 9

added in small proportions during the mix to produce some desired modifications of the properties of concrete

reduces setting time and accelerates early strength

water-reducing admixture = reduces the amount of water needed, lowers the water-cement ratio and increases strength

Question 10

compaction

Answer 10

expelling the entrapped air pockets
by hand = rodding, ramming, tamping
mechanical = vibrations ( internal, external, table, platform, surface)

Question 11

reinforcement

Answer 11

improve the tensile strength of concrete = metal, rod, wire, cable, mesh
Fibre reinforcement= glass, plastic, steel, graphite
less expensive than steel but shape, dimensions and length important

Question 12

concrete cover

Answer 12

the least distance between the installed reinforcement and outer surface of the concrete
protects the rebar
sufficient embedding for the rebar to function
thermal insulation

Question 13

Formwork

Answer 13

the structure used to contain the concrete and to mould it to required shape until it can support itself
falsework = holds the framework

Question 14

what are the qualities of framework

Answer 14

capable of resisting hydrostatic pressure of wet concrete
water resistant
light-weight
reusable

Question 15

concrete tie

Answer 15

tie holes left after breaking back or removing metal tie ends then patched with mortar or filled with plastic/ precast plugs prevents moisture from getting into the wall

Question 16

Control joint

Answer 16

sawed groove in a concrete slab used to regulate the location of cracking

Question 17

Expansion joint

Answer 17

separates concrete from other parts of the building and allows independent movement between adjoining members

Question 18

In situ concrete

Answer 18

pour the liquid material into the forms at the building site

Question 19

Pre-casted concrete

Answer 19

building component are maunfactured in a central plant and later brought to the building site for assembly

Question 20

uses of concrete

Answer 20

structure = frame
envelope = panels
slabs = floor and ceiling

Question 21

benefits of concrete

Answer 21

versatile
robust and durable = low maintenance
resistance to fire and flooding 
thermal mass = passive radiant cooling
inexpensive = limestone abundant
little production waste
integrity = structural expression
reflectivity = minimise urban heat island effect

Question 22

disadvantages of concrete

Answer 22

low tensile strength
low strength to weight ratio
construction = setting time
susceptible to cracking
sustainability

Question 23

environmental impact of concrete

Answer 23

high carbon dioxide emissions
reabsorb carbon dioxide over the course of 100 years on a more molecular level
recycle content
reduce energy consumption = thermal mass
durability = lifespan and maintenance issues
1/5 th of all waste in landfill = content/by-product