COALESCENCE OFSILICA FUME, CALCIUM ALUMINATE AND ALUMINUM
OXIDEAND ITS EFFECT ON SOME MECHANICAL PROPERTIES OF NORMAL WEIGHT
CONCRETEChapter 1: IntroductionAdmixtures have been used in
concrete and mortar since at least the Roman Empire. The Romans
found that certain materials such as milk, blood and lard, as well
as organic materials such as molasses, eggs and rice paste allow
greater workability in cementitious mixtures. (Terry Harris and Ara
A. Jeknavorian, 2014). Chemical admixtures has five functions.
First, the water-reducing admixtures which reduce the water content
by 5 to 10 percent of the concrete mixture that attains the
required slump using less water. It indicates a lower water-cement
ratio that gives a high strength of concrete without adding more
cement. The second function is to slow down the pace of setting
time due to high temperature that may cause placing and finishing
difficult and it is called retarding admixture. Accelerating
admixtures tend to improve the concrete performance in an early
time. It gives early strength development, reduce hydration,
setting and curing time and speeds up the construction cycle. The
second to the last function is the superplasticizers which is a bit
related to the water-reducing admixture because it also reduce
water content on the mixture by 12-30 percent. This admixtures is
added on the jobsite that will improve those low to average slump
and water-cement ratio. The last function gives us a
corrosion-inhibiting admixtures that gives luxury to those water
exposed structures such as highway bridges, seaports, sea based
airports and structures that will highly exposed to chloride.
Silica fume also known as micro silica is a by-product of the
smelting process in the silicon and ferrosilicon industry.
By-products of the production of silicon metal and the ferrosilicon
alloys having silicon contents of 75% or more contain 8595%
non-crystalline silica. Silica fume has been recognized as a
pozzolanic admixture that is effective in enhancing the mechanical
properties to a great extent. By using silica fume, it is easier to
obtain compressive strengths of concrete. Addition of silica fume
to concrete improves the durability of concrete through reduction
in permeability and increase abrasion resistance of concrete.
Calcium Aluminate cement also known as High Alumina Cement or
(HAC)is a special cement compound that develops strength very
quickly. It is also a resistance to mild acids and alkalies;
sulfates, sea water, and pure water. They are similar to the more
familiar Portland cements in that they both require water for
hydration. HAC are rarely used for cast-in-place structural work,
except for emergency repairs and foundation construction. HAC are
not rapid setting. They are, however, rapid hardening; that is,
they will develop as much strength in 24 hours as Portland cement
concrete will achieve in 28 days. It should be cured for at least
24 hours, using a water spray or fog, ponding, wet burlap or a
curing membrane.Aluminumoxide is a common, naturally
occurringcompoundthats employed in various industries, most
particularly in the production ofaluminum. There are many
differentforms ofaluminumoxide, including both crystalline and
non-crystalline forms. Its crystalline form, corundum, its hardness
makes it suitable as an abrasive. In the present study, the
compressive strength of self-compacting concrete with different
amounts of aluminum oxide nanoparticles has been investigated.
Aluminum oxide nanoparticles having an average particle size of 15
nm were partially added to cement paste (Portland cement together
with super plasticizer) and the compressive strength of the
specimens has been measured. The results indicate that aluminum
oxide nanoparticles are able to improve compressive strength of
concrete and modify the negative effects of adding super
plasticizer. Aluminum oxide nanoparticle as a partial replacement
of cement up to 4 %wt. could accelerate CSH (calcium silicate
hydrate) gel formation as a result of increased amount of
crystalline calcium hydroxide at the early age of hydration. The
increased aluminum oxide nanoparticles' content of more than 4 %
wt., leads to reduced compressive strength because of unsuitable
dispersion of nanoparticles in the concrete matrix.1.1. The problem
and its background1.1.1. Background of the StudyConcrete plays an
important role in the societys infrastructure. It is the most
widely used structural material in the construction industry and
innovations are continuously being made to provide and perform the
structural function of the concrete and its properties. According
to The University of California Berkeley, it is estimated that the
present consumption of concrete in the world is of the order of 10
billion tonnes (12 billion tons) every year. Concrete is the most
construction choice material because of its properties that serve
the purposes of the structure.Concrete is a classic material in
construction industry, but it is not perfect. There are concrete
problems that are categorized in two basic types, the structural
strength and appearance. Majority of the structure like buildings,
bridges, dams and tunnels used concrete for its strength. Concrete
must possess a specified strength to perform its function as a
structural material and its mix design is related to its strength.
Another concrete problem is abrasion, it occurs due to sliding,
rubbing, skidding and scraping on the concrete surface. There are
certain number of factors that influenced the concrete abrasion
resistance such as concrete strength, aggregate properties,
finishing surface and type of hardeners. It is needed to determine
the appropriate mix proportions to produce an abrasion resistant
concrete. Another is a process called setting time of concrete, it
is significant because it denotes when the concrete can be properly
placed, consolidated and finished. It is based to the setting of
cement paste thus cement properties can greatly affect the setting
time of concrete. This are some properties of concrete that made
the construction industry to continue innovating a chemical
admixtures producing a well-developed concrete performance to
maximize the structural function of concrete.
1.1.2. Statement of the ProblemThis study is conducted to
determine if the three proportioned admixtures will help improve
the mechanical properties of normal concrete weight. In this
research the following questions are going to be answered: 1. How
much strength it will attain for both flexural and compressive
strength compare to the natural concrete
weight?CompressiveFlexural
Control4000 psi650 psi
Proportion 16000 psi750 psi
Proportion 26000 psi750 psi
Proportion 36000 psi750 psi
2. How it will affect the workability of concrete?3. Which
proportion of admixtures will give the best result?
1.2. Statement of the objectives1.2.1 General Objective/sThe
objective of the study is to identify what proportion of admixtures
such as Silica Fume, Aluminum Oxide and Calcium Aluminate with a
total of 12% by weight of cement will give the best effect on the
flexural and compressive strength of concrete.1.2.2 Specific
Objective/s1.2.2.1. To study and identify the effects on
compressive and flexural strength of concrete using the
proportioned admixtures. Compressive and FlexuralStrength
Control4000 psi
With Admixtures6000 psi
1.2.2.2To identify the right admixtures proportion that will
sustain a higher concrete properties on the 7th, 14th and 28th day
of curing.
1.1. Significance of the studyThe study is significant to the
following:1.3.1. To the construction industry:This study will be
helpful to the construction industry such as Residential, Light
commercial, Industrial, Heavy civil, Superstructure and
Substructure. In a way that it will provide better method of
producing innovative concrete mixtures and develop sustainable
mixtures for future generations to come. High performance
materials, mixtures were added to reduce cross sections and the
volume of concrete it produced. Our target or aim in the study is
to achieve a compressive strength of 6000psi or even higher that
can be used or sufficient in certain structural elements like
slabs, beams, retaining wall and foundation after achieving its
28th day of curing. As part of the fastest growing industry
Concrete must keep evolving to satisfy the increasing demands of
all its users. They are also intended to increase the durability of
concrete structures to minimize the maintenance needs of concrete
especially to the construction industry.1.3.2. To the consumer
group:This study will be beneficiary to the owner which their
ultimate objective is to get the greatest possible return on
investment during the lifetime of the construction. For the
contractor because they are capable to determine how much its use
would save on the final total cost of the structure and for the
concrete producer due to the highest standards of concrete mixtures
it has produced.This is to ensure that the structures built will
last for years to come, a long term economic benefit solutions to
the consumer and it requires less maintenance costs than most other
materials used in different construction projects.1.2. Scope and
DelimitationsThis study aims to identify the effects of the
coalescence of admixtures on some mechanical properties of a normal
weight concrete by using combination of admixtures: silica fume,
calcium aluminate, and aluminum oxide. In this research it will be
observed if the mechanical properties of normal concrete shall be
improved based on the particular mix proportions that the
researchers will use. This study is limited to the determination of
the parameters in a particular mix proportion of 1:1.5:3 and water
cement ratio of 0.57 with the target mean strength of 10000 psi.
The produced concrete will be tested with different composition,
such concrete itself, and concrete with 12% of admixtures by weight
of concrete. The admixtures will vary from 3 different percentage
of the admixtures. Concrete + admixtures of silica fume with 6%,
calcium aluminate with 4%, and aluminum oxide with 2%; and concrete
+ admixtures of silica fume with 4%, calcium aluminate with 6%, and
aluminum oxide with 2%; and concrete + admixtures of silica fume
with 4%, calcium aluminate with 4%, and aluminum oxide with 4%. The
specimen will be tested on its 7th, 14th and 28th day of curing
using Universal Testing Machine (UTM), to be able to know its
flexural and compressive strengthincluding slump test and unit
weight.The study is delimited to the setting time of concrete,
bleeding, segregation, hydration, air entrainment, fire resistance,
thermal mass, freeze thawing and chemical properties of a concrete.
1.3. Definition of terms Coalescence - to come together to form one
group or mass Abrasion -is the process of scuffing, scratching,
wearing down, marring, or rubbing away. It can be intentionally
imposed in a controlled process using an abrasive. Abrasion can be
an undesirable effect of exposure to normal use or exposure to the
elements. Superplasticizers - also known ashigh range water
reducers, are chemical admixtures used where well-dispersed
particle suspension is required. Alkalies -is abasic,ionicsaltof
analkali metaloralkaline earth metalchemical element. Silica fume -
is a byproduct of producing silicon metal or ferrosilicon alloys.
Calcium Aluminate cement - is a unique class of cement that is
different than ordinary Portland cement (OPC), particularly due to
the chemical make-up. CAC contains a far greater amount of alumina
and a far less amount of silica. Cementitious - having the
properties ofcement Pozzolanic Cement admixtures Dispersion - the
scattering of the values of a frequency distribution from an
average
Chapter 2: Review of Related literature2.1 Related StudiesIn an
article entitled The effect of aluminum oxide nanoparticles on the
compressive strength and structure of self-compacting concrete
published by Magazine of Concrete Research (2011).It was stated in
the present study, that the compressive strength with different
amounts of aluminum oxide nanoparticles has been investigated.
Aluminum oxide nanoparticles having an average particle size of 15
nm were partially added to cement paste (Portland cement together
polycarboxylatesuperplasticizer) and the compressive strength of
the specimens has been measured. The results indicate that aluminum
oxide nanoparticles are able to improve compressive strength of
concrete and modify the negative effects of adding
polycarboxylatesuperplasticiser. The increased aluminum oxide
nanoparticles' content of more than 4 % weight, leads to reduced
compressive strength because of unsuitable dispersion of
nanoparticles in the concrete matrix.2.1.1 Related StudiesIn 2014,
Aysu published an article entitled CALCIUM ALUMINATE CEMENT. The
article made a research about the setting time of calcium aluminate
cement and it is similar to Portland cement. The test was done by
using the Vicat needle method on a paste at standard consistence.
According to the research, the British and European Standard
requires that the initial setting time shall be not less than 2
hour, and the final setting time not more than 8hour. In comparison
made by the research with Portland cement and Calcium Aluminate
cement the initial and final setting time is much shorter for the
Calcium Aluminate cement; this may be prominent in concretes and
mortars. Decreasing lime-to-alumina ratio, the setting time of
calcium aluminate phases result to progressively longer. It has
been observed that the setting time increases when pastes mixed in
small quantities with temperature up to about 27C, further
increased in temperature decreases the setting time. However, the
effect is less noticeablein concrete mixed in normal quantitiesdue
to the range of effects including self-heating and the heating due
to the friction during mixing of the aggregates present in the
concrete. The setting time can also be adjusted by the use of
admixtures and additives.2.1.3. Related StudiesThere are some
studies on the effect of adding aluminum oxide nanoparticles to
cementing materials. Based on the article of Mohammad Reza, et.al
(2012), Aluminum Oxide Nanoparticles in Cement Mortar when adding
aluminum oxide nanoparticles up to 3% of weight, each of the
compressive, tensile, and flexural strengths increased. When the
amount of nanoparticles added was more than 5% of weight, the above
strengths decreased to less than the strength of ordinary cement
mortar.
2.2 Related StudiesAccording to the study of M. Mazloom, et.al
(2004) entitled Effect of Silica fume on Mechanical Properties of
High- strength Concrete presents the results of experimental work
on short- and long- term mechanical properties of high- strength
concrete containing different levels of silica fume. They have
investigated the effects of binder systems containing different
levels of silica fume on fresh and mechanical properties of
concrete. Their work focused more on concrete mixes having a water
ratio of 0.35 and a constant total binder content of 500 kg/m3.
They used different percentages of silica fume like 0%, 6%, 10% and
15%. In their study it has been observed that the increase of
percentages of silica fume will also increase the compressive
strength of concrete in 28 days but the workability of concrete
decrease.
Chapter 3: Materials and Methods3.1 Materials3.1.1
AdmixturesAdmixtureSource of material
Silica fumeAngono, Rizal
Calcium AluminateAngono, Rizal
Aluminum OxideFairview, Quezon City
3.1.2 AggregatesCoarse AggregatesSizeSource of material
3/4Balintawak, QC
3/8Balintawak, QC
Fine AggregatesSource of material
Bistay SandBalintawak, QC
3.1.3 Binding MaterialBrandSource of material
Lafarge Fortune Type 1Maypulo, Batangas
3.1.4 WaterPotable water 3.2 Mix
proportionsMixtureWater/Cementratio*Silica Fume*Calcium
Aluminate*AluminumOxide
Control0.57NoneNoneNone
P10.576%4%2%
P20.574%6%2%
P30.574%4%4%
*Percentage of admixtures is by weight of cement.
3.3 Method of testingI. ASTM C 143 03 Standard Test Method for
Slump of Hydraulic- Cement ConcretePROCEDURE1. Take a sample from
freshly mixed concrete mixture that will represent the entire
batch. 2. Dampen the cone mould, base plate and tampering rod. Set
the cone over the base plate and place it over a smooth, moist,
non-absorbent, level surface large enough to accommodate both the
slumped concrete and the slump cone. The cone should be clamped on
both sides and stand or foot must be on the base plate to hold the
cone firmly.3. Fill the cone in three layers and each layer is
approximately 1/3 full of its volume. After filling the 1st layer
rod the layer with 25 strokes using 5/8-inch diameter x
24-inch-long hemispherical tip steel tamping rod. Uniformly
distribute the rodding in the entire cross section of the layer.
Repeat the process for the 2nd and 3rd layer with the same number
of strokes. 4. Remove the excess concrete on the tip of the cone
using tamping rod as a screed. Clean overflow from base of cone.5.
Slowly lift the mould within 5 seconds from the concrete in a
vertical direction and avoid lateral motions. Note that the sample
must obtain a passing slump of 4 inches.
II. ASTM C 192 06 Standard Practice for Making and Curing
Concrete Test Specimens in the LaboratoryPROCEDUREMaking of molds1.
Mold specimens as near as practicable to the place where they are
to be stored during the first 24 h. If it is not practicable to
mold the specimens where they will be stored, move them to the
place of storage immediately after being struck off. Place molds on
a rigid surface free from vibration and other disturbances. Avoid
jarring, striking, tilting, or scarring of the surface of the
specimens when moving the specimens to the storage place.2. Place
the concrete in the molds using a scoop, blunted trowel, or shovel.
Select each scoopful, trowelful, or shovelful of concrete from the
mixing pan to ensure that it is representative of the batch.3. Move
the scoop or trowel around the top edge of the mold as the concrete
is discharged in order to ensure a symmetrical distribution of the
concrete and to minimize segregation of coarse aggregate within the
mold. Further distribute the concrete by use of a tamping rod prior
to the start of consolidation. In placing the final layer the
operator shall attempt to add an amount of concrete that will
exactly fill the mold after compaction. Do not add
non-representative samples of concrete to an underfilledmold.4.
Make specimens in layers as indicated in Table 1.
5. Preparation of satisfactory specimens requires different
methods of consolidation. The methods of consolidation are rodding,
and internal or external vibration (refer to table 1).6. After
consolidation strike off the specimen with a trowel or float, then
trowel the minimum amount required to form the concrete in the
opening concentrically with the rest of the specimen. Use a screed
curved to the radius of the specimen to more precisely shape and
finish the concrete in the opening.Curing 1. Cure the specimen on
the 7th, 14th and 28th day.
III. ASTM C39 / C39M Standard Method of Test for Compressive
Strength of Cylindrical Concrete Specimens PROCEDURE1. Compression
tests of moist-cured specimens shall be made as soon as practicable
after removal from moist storage.2. Test specimens shall be kept
moist by any convenient method during the period between removals
from moist storage and testing. They shall be tested in the moist
condition.3. Zero Verification and Block Seating - Prior to testing
the specimen, verify that the load indicator is set to zero. In
cases where the indicator is not properly set to zero, adjust the
indicator. As the spherically-seated block is brought to bear on
the specimen, rotate its movable portion gently by hand so that
uniform seating is obtained.4. Apply the load continuously and
without shock.5. During application of the first half of the
anticipated loading phase, a higher rate of loading shall be
permitted. Apply the higher loading rate in a controlled manner so
that the specimen is not subjected to shock loading.6. Do not
adjust the rate of movement (platen to crosshead) as the ultimate
load is being approached and the stress rate decreases due to
cracking in the specimen.Apply the compressive load until the load
indicator shows that the load is decreasing steadily and the
specimen displays a well-defined fracture pattern.
Chapter IVPresentation, Analysis and Interpretation of Data4.1
Physical Properties of AggregatesPhysical Properties
Coarse AggregatesSand
3/43/8
Specific Gravity2.692.852.78
Unit Weight (Rodded)
Trial 11558.57 kg/m31805.36 kg/ m31597.5 kg/ m3
Trial 21564.29 kg/ m31839.64 kg/ m31608.93 kg/ m3
Unit Weight (Loose)
Trial 11411.79 kg/ m31612.5 kg/ m31474.64 kg/ m3
Trial 21360.36 kg/ m31681.07 kg/ m31497.5 kg/ m3
Absorption1.15% 1.0%1.63%
Moisture Content1.22%1.0%7.21%
Fineness Modulus3.041.4%2.75%
4.2 Concrete Mix DesignCylindrical MoldBatch Mix Design
ContentControlP1P2P3
Cement (kg)
Water (kg)
3/4 Gravel (kg)
3/8 Gravel (kg)
Sand (kg)
Admixture
Silica Fume (kg)
Calcium Aluminate (kg)
Aluminum Oxide (kg)
Beam MoldBatch Mix Design
ContentControlP1P2P3
Cement (kg)
Water (kg)
3/4 Gravel (kg)
3/8 Gravel (kg)
Sand (kg)
Admixture
Silica Fume (kg)
Calcium Aluminate (kg)
Aluminum Oxide (kg)
4.3Concrete SlumpAdmixture ProportionsSlump (mm)
Control101.6
P1101.6
P2203.2
P3254
4.4Cost AnalysisContentUnitQuantityCost (php)Total Cost(php)
3/4 Gravelbag2830840
3/8 Gravelbag1230360
Sandbag4123943
Cementbag72201540
Silica Fumekg.1148528
Calcium Aluminatekg.1545675
Aluminum Oxidekg.6120720
TOTAL
5606
4.5Compressive Strength Results
7th Day Compressive Strength Test ResultsCOMPRESSIVE STRENGTH
(MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
14th Day Compressive Strength Test ResultsCOMPRESSIVE STRENGTH
(MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
28th Day Compressive Strength Test ResultsCOMPRESSIVE STRENGTH
(MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
4.6Flexural Strength Results7th Day Flexural Strength Test
ResultsFLEXURAL STRENGTH (MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
14th Day Flexural Strength Test ResultsFLEXURAL STRENGTH
(MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
28th Day Flexural Strength Test ResultsFLEXURAL STRENGTH
(MPa)
ADMIXTURE PROPORTIONTRIAL 1TRIAL 2TRIAL 3AVERAGE
CONTROL
P1
P2
P3
Chapter VSummary, Findings and Conclusion5.1 Summary of
Findings1. The proportion that gave the best compressive and
flexural strength was the proportion 3 which compose of 4% of
Silica Fume, 4% of Calcium Aluminate and 4% of Aluminum Oxide. 2.
Concrete with proportioned admixtures highly affects the
workability of concrete especially if same water content for the
normal weight of concrete is used. 3. Aluminum Oxide is a hard to
find additive and a little bit expensive than other admixtures.
Conclusion: The investigation on the effects of coalescence of
admixtures on compressive and flexural strength, the researchers
concluded the following:
1. The compressive strength of normal weight concrete with
admixtures failed to have a higher strength than the conventional.
Proportion 3 which has equal percentages of admixtures gave closer
results.2. None of the concrete with admixtures attained the 28th
day required compressive strength of 28 Mpa set by ACI 318.
Proportion 3 delivered the highest result with a compressive
strength of ____ Mpa, but still failed to meet minimum required
compressive strength. However the control concrete gave a ___ Mpa
which passed the ACI compressive strength requirement.
Recommendation:Based on the conclusions drawn, the following were
recommended:1. The 12% by weight of cementcoalescence of silica
fume, calcium aluminate and aluminium oxide is not recommended for
concrete as an additive for strength acceleration as it produced a
below minimum compressive and flexural strength requirement
provided by the ACI. 2. For further studies the higher percentage
of the aluminium oxide the higher strength it will produce.3. For
further studies, reduced the amount of water per batch mix if these
3 admixtures will be use so that workability will be attained. 4.
Explore other mechanical properties of concrete, test for the
concrete initial and final setting time. 5. For further research,
we recommend to use a new admixture into the mix such as calcium
carbonate or fly ash replacing the aluminium oxide since it is a
little bit expensive than those two and might give greater results.
Also with replacing the aluminium oxide use a total 14% of
admixtures by weight of cement.
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