Concrete Compression Analysis

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Concrete Compression
Analysis

By

Anthony Avilla, Michael Sullivan, and Jeremy Brickman

ENGR 45, SRJC

12/5/05

What is Concrete Exactly?


Concrete

is a composite building material made from the combination of aggregate
and cement binder.



The most common form of concrete is Portland cement concrete, which consists of
mineral aggregate (generally gravel and sand), Portland cement and water.



The two major components of concrete are a cement paste and inert materials.



The cement paste consists of portland cement, water, and some air either in the form
of naturally entrapped air voids or minute, intentionally entrained air bubbles.



The inert materials are usually composed of fine aggregate, which is a material such
as sand, and coarse aggregate, which is a material such as gravel, crushed stone, or
slag.



In general, fine aggregate particles are smaller than 6.4 mm (.25 in) in size, and
coarse aggregate particles are larger than 6.4 mm (.25 in). Depending on the
thickness of the structure to be built, the size of coarse aggregate particles used can
vary widely. In building relatively thin sections, a small size of coarse aggregate, with
particles about 6.4 mm (.25 in) in size, is used. At the other extreme, aggregates up
to 15 cm (6 in) or more in diameter are used in large dams. In general, the maximum
size of coarse aggregates should not be larger than one
-
fifth of the narrowest
dimensions of the concrete member in which it is used.


History


The Assyrians and Babylonians used clay as cement.



The Egyptians used lime and gypsum cement.



The Roman Empire, cements made from pozzolanic ash/pozzolana and an
aggregate made from pumice were used to make a concrete very similar to
modern portland cement concrete.



In 1756, British engineer John Smeaton pioneered the use of portland
cement in concrete, using pebbles and powdered brick as aggregate.



In modern day mixtures use of recycled/reused materials for concrete
ingredients.

Mechanics


Concrete does not solidify because water evaporates, but rather cement
hydrates, gluing the other components together and eventually creating a
stone
-
like material.



During hydration and hardening, concrete needs to develop certain physical
and chemical properties, among others, mechanical strength, low permeability
to ingress of moisture, and chemical and volume stability.



The ultimate strength of concrete is related to water/cement ratio and the size,
shape, and strength of the aggregate used. Concrete with lower water/cement
ratio (down to 0.35) makes a stronger concrete than a higher ratio. Concrete
made with smooth pebbles is weaker than that made with rough
-
surfaced
broken rock pieces for example.

Properties


Composite



When set, has high compressive strength, low tensile strength



Brittle



Withstands high temperatures



Behaves as a ceramic

Properties

QUIKRETE
®

Fast
-
Setting
Concrete #1004
-
50

QUIKRETE
®

5000 High
Early Strength Concrete

Mix #1007


Mix meets or exceeds the strength
requirements of ASTM C387. It will achieve a
compressive strength of 2500 psi (17.3 MPa) at
7 days and 4000 psi (27.6 MPa) at 28 days
when tested in accordance with applicable
standards.

QUIKRETE
®

Concrete
Mix #1101 (Ready
-
To
-
Use)


QUIKRETE
®

Fiber
-
Reinforced
Concrete Mix #l006
-
60

Chemistry of Cement


H = H
2
O


C
3
S = 3CaO
.
SiO
2


C
2
S = 2CaO
.
SiO
2


C
3
A = 3CaO
.
Al
2
O
3


Cs = CaSO
4


Ch = Ca(OH)
2


C
4
AF = 4CaO
.
Al
2
O
3
.
Fe
2
O
3


2C
3
S + 6H



3Ch + C
3
S2H
3


2C
2
S + 4H



Ch + C
3
S2H
3


C
3
A + 10H + CsH
2



C
3
ACSH
12


C
3
A + 12H + Ch



C
3
AChH
12


C
4
AF + 10H + 2Ch



C
6
AFH
12

Chemical Reactions

Chemical Composition

Constituents and Nomenclature

Application of Concrete


Pavements


Building structures


Foundations


Motorways/roads


Overpasses


Dams


Parking structures


Bases for gates/fences/poles


Cementing bricks or blocks in walls


Any structure requiring high compressive strength and durability


Can be used for structures demanding high temperature performance


Although brittle, when cast around rebar, can be used in structures requiring
ductility or moderate tensile demands

Project Materials

What We Did!


Cut PVC pipe into 9 in. segments


Squared off bottom end of each segment


Determined directed ratio of water to concrete (by volume)


For each product of concrete, we mixed samples containing varying quantities
of water (at directed ratio, 15% higher, and 15% lower)


Poured samples into PVC casts


Allowed samples to set for five days


Removed PVC casts


Applied compression tests


Obtained and analyzed data

Compression Test

This is the apparatus that we used to test our concrete samples

for our compression analysis

0
100
200
300
400
500
600
700
800
Compression (psi)
Ready to
Use
High Early
Strength
Fiber
Reinforced
Fast
Setting
Compression Strength Relative to Water
Concetration
15% More
Ideal
15% Less
Our “ideal” water concentration samples should have theoretically had the greatest compression, but since they

did not, we should have added more water (such as 15% more) or until visually satisfying. Therefore giving the

“ideal” concentration the highest compression and the 15% more and 15% less, a lower compression result.

Some of our samples had so little water that they just crumbled under compression and gave no data reading.

Project Pictures

Strongest

Weakest

References

Shackelford, James F.
Introduction to Materials Science for Engineers, 6
th

Ed. Upper Saddle



River, New Jersey: Pearson Prentice Hall, 2005. (Pages 500


543)


http://en.wikipedia.org/wiki/Concrete


http://en.wikipedia.org/wiki/John_Smeaton


http://en.wikipedia.org/wiki/Portland_cement


http://www.quikrete.com


http://www.cement.org


http://www.concretenetwork.com


http://www.concrete.org.uk


http://encarta.msn.com/encyclopedia_761558777/Concrete_(construction).html