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The Compatibility and Efficiency of Low Alkali South African Cements with New Generation Super Plasticisers
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5/28/2018 The Compatibility and Efficiency of Low Alkali South African Cements with New Generation Super Plasticisers
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The Compatibility and Efficiency of Low Alkali South African
Cements with New Generation Super Plasticisers
By
Mikhail Bramdaw
(200823954)
A Project Investigation Report submitted to the Faculty of Engineering and the
Built Environment as partial fulfilment of the requirements of the degree
BACCALAUREUS INGENERIAE
In
CIVIL ENGINEERING SCIENCE
At
UNIVERSITY OF JOHANNESBURG
STUDY LEADER: Mr Jannes Bester
7 December 2011
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i
ANTI-PLAGIARISM DECLARATION
Title: Mr.
Full name: Mikhail Bramdaw
Student number: 200823954
Course: Civil Project Investigation 4B (PJS 4B)
Lecturer: Mr Jannes Bester
Plagiarism is to present someone elses ideas as my own. Where material written by other
people has been used (either from a printed source or from the internet), this has been
carefully acknowledged and referenced. I have used the Harvard Convention for citation and
referencing. Every contribution to and quotation from the work of other people in this essay
has been acknowledged through citation and reference. I know that plagiarism is wrong.
I understand what plagiarism is and am aware of the Universitys policy in this regard. I know that I would plagiarise if I do not give credit to my sources, or if I copy sentences
or paragraphs from a book, article or Internet source without proper citation.
I know that even if I only change the wording slightly, I still plagiarise when usingsomeone elses words without proper citation.
I declare that I have written my own sentences and paragraphs throughout my essay and Ihave credited all ideas I have gained from other peoples work.
I declare that this assignment is my own original work. I have not allowed, and will not allow, anyone to copy my work with the intention ofpassing it off as his or her own work.
SIGNATURE .DATE..
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ii
Abstract
In South Africa little testing has been done on the compatibility or efficiency of polymer
based super-plasticisers with South African manufactured cements. This investigation project
aimed to show that the cements tested were compatible with these new super-plasticisers
despite being produced from different manufactures. It also aimed to show that efficiency and
compatibility of the cement-super-plasticiser combination is dependent on the alkali content
of the cement.
The investigation was done by choosing three cements from different manufactures and
testing these cements against three different polymer based super-plasticisers. For each of the
cement-super-plasticiser combinations different dosages of the admixture were tested. Theconcrete mixes were tested for workability and strength to give an indication of the
compatibility as well as the efficiency of the cements with the super-plasticisers.
The workability of the concrete was measured using the slump test, slump retention test and
the Tattersall Two-Point Tester. The results from these tests gave insight into the concrete
behaviour in the fresh state.
The strength of the concrete was measured using the compressive strength test at 3 days. The
strength is the most important characteristic of hardened concrete and therefore was a crucial
property to investigate.
The tests concluded that cement with lower alkali content was less sensitive to changes in
super-plasticiser type and changes in dosage. This cement was also more efficient than the
other two cements with higher alkali content. It also showed that a super-plasticiser based on
phosphonate polymers is better suited for slump retention ability, while a polycarboxylate
polymer super-plasticiser is better suited for its efficiency in providing a mix with a better
slump and higher strength.
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iii
Acknowledgements
I acknowledge the following individuals for their help and guidance which aided in the
completion of this report:
Mr Jannes Bester (University of Johannesburg, APK)Study Leader Salome Potgieter (University of Johannesburg, APK) - for assisting with research at the
UJ library
Ansie Martinek, Martha de Jager and Susan Battison (C&CI)for assisting with researchat the C&CI library
Nick Sfarnas (University of Johannesburg, DFC) for assisting with the use of theTattersall Tester and testing facilities at the Doornfontein laboratory
Petrus Jooste (C&CI) for providing information on how to calibrate and operate theTattersall Tester
Amit Dawneerangen (Afrisam, Roodepoort) for assisting with the chemicalcomposition test and general guidance.
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iv
Table of Contents
ANTI-PLAGIARISM DECLARATION .................................................................................... i
Abstract ......................................................................................................................................ii
Acknowledgements .................................................................................................................. iii
Table of Contents ...................................................................................................................... iv
List of Tables ........................................................................................................................... vii
List of Figures ........................................................................................................................ viii
List of Symbols .......................................................................................................................... x
Chapter 1 .................................................................................................................................... 1
Introduction ................................................................................................................................ 1
1.1 Problem Definition........................................................................................................... 1
1.2. Aim ................................................................................................................................. 2
1.3. Objectives ....................................................................................................................... 2
1.4. Limitations ...................................................................................................................... 2
1.5. Methodology ................................................................................................................... 3
1.6. Layout of this Project Investigation ................................................................................ 4
Chapter 2 .................................................................................................................................... 5
LITERATURE REVIEW .......................................................................................................... 5
2.1 Concrete Properties .......................................................................................................... 5
2.1.1. Rheology .................................................................................................................. 5
2.1.1.1. Slump and Slump Retention ................................................................................. 6
2.1.1.2. Plastic Viscosity .................................................................................................... 7
2.1.1.3. Air Content............................................................................................................ 7
2.1.2. Strength .................................................................................................................... 8
2.2. Super-plasticisers ............................................................................................................ 8
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v
2.3. Cement Composition ...................................................................................................... 9
2.4. Rheological Tests .......................................................................................................... 11
2.5. Tattersall Two-Point Tester .......................................................................................... 12
Chapter 3 .................................................................................................................................. 17
Experimental Design ................................................................................................................ 17
3.1. Requirements ................................................................................................................ 17
3.2. Materials ....................................................................................................................... 17
3.3. Mix Design.................................................................................................................... 19
3.4. Grading Analysis .......................................................................................................... 20
3.5. Tests .............................................................................................................................. 22
3.6. Efficiency Rating System ............................................................................................. 23
3.7. Expected Results ........................................................................................................... 23
Chapter 4 .................................................................................................................................. 24
Test Results .............................................................................................................................. 24
4.1. Slump Test .................................................................................................................... 24
4.2. Slump Retention............................................................................................................ 27
4.3. Plastic Viscosity ............................................................................................................ 32
4.3.1. Calibration.............................................................................................................. 32
4.3.2. Results .................................................................................................................... 33
4.4. Air Content.................................................................................................................... 38
4.5. Hardened Density.......................................................................................................... 41
4.6. Strength ......................................................................................................................... 44
4.7. Efficiency ...................................................................................................................... 47
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vi
Chapter 5 .................................................................................................................................. 49
Conclusions .............................................................................................................................. 49
5.1. Summary of work ......................................................................................................... 49
5.2. Main conclusions .......................................................................................................... 49
5.2.1. Slump ..................................................................................................................... 49
5.2.2. Slump Retention..................................................................................................... 50
5.2.3. Plastic Viscosity ..................................................................................................... 51
5.2.4. Air Content............................................................................................................. 51
5.2.5. Hardened Properties ............................................................................................... 51
5.3. Suggestions for further work ........................................................................................ 52
5.4. Outcomes satisfied ........................................................................................................ 52
Bibliography ............................................................................................................................ 54
Appendix AChemical Test Results ...................................................................................... 56
Appendix BTattersall Two Point Test Results..................................................................... 57
Appendix CPictures Taken During Practical ..................................................................... 100
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vii
List of Tables
Table 2.1: Rheology of Cement Paste, Mortar and Concrete................................................... 7
Table 2.2: Viscosities of Selected Materials........................................................................... 16
Table 3.1: Chemical Composition of Cements....................................................................... 18
Table 3.2: Mix design Results for a 1000 litre mix................................................................ 19
Table 3.3: Mix design Results for a 20 litre mix.................................................................... 20
Table 3.4: Grading results for andesite crusher sand.............................................................. 20
Table 3.5: Tests performed during practical........................................................................... 22
Table 4.1: Slump Test Results for CEM A............................................................................. 24
Table 4.2: Slump Test Results for CEM B............................................................................. 25
Table 4.3: Slump Test Results for CEM C............................................................................. 26
Table 4.4: Readings from Tattersall Tester for Calibration with Canola Oil......................... 32
Table 4.5: Calibration Data for Tattersall Tester.................................................................... 32
Table 4.6: Example of Tattersall Result Calculation.............................................................. 34
Table 4.7: Tattersall ResultsCEM A................................................................................... 35
Table 4.8: Tattersall ResultsCEM B................................................................................... 36
Table 4.9: Tattersall ResultsCEM C................................................................................... 37
Table 4.10: Air Content Results for CEM A.......................................................................... 38
Table 4.11: Air Content Results for CEM B.......................................................................... 39
Table 4.12: Air Content Results for CEM C........................................................................... 40
Table 4.13: Density Results for CEM A................................................................................. 41
Table 4.14: Density Results for CEM B................................................................................. 42
Table 4.15: Density Results for CEM C................................................................................. 43
Table 4.16: Strength Results for CEM A................................................................................ 44
Table 4.17: Strength Results for CEM B................................................................................ 45
Table 4.18: Strength Results for CEM C................................................................................ 46
Table 4.19: Efficiency Rating Table for CEM A.................................................................... 47
Table 4.20: Efficiency Rating Table for CEM B.................................................................... 47
Table 4.21: Efficiency Rating Table for CEM C.................................................................... 48
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viii
List of Figures
Figure 2.1: Effect of super plasticizing admixture................................................................... 9
Figure 2.2: Classification and Composition % of South African cements.............................. 10
Figure 2.3: Tattersall Two Point Tester Apparatus Motor and Processing Unit..................... 12
Figure 2.4: Tattersall Two Point Tester Apparatus Sample Holder and Impeller................... 13
Figure 2.5: Tattersall Two Point Tester Impeller Blade.......................................................... 13
Figure 2.6: Sample Holder Showing the Filling Mark............................................................ 14
Figure 3.1: Grading curve for andesite crusher sand............................................................... 21
Figure 4.1: Slump Test Results for CEM A............................................................................ 24
Figure 4.2: Slump Test Results for CEM B............................................................................ 25
Figure 4.3: Slump Test Results for CEM C............................................................................ 26
Figure 4.4: Slump Retention CEM A with SP A.................................................................... 27
Figure 4.5: Slump Retention CEM A with SP B..................................................................... 27
Figure 4.6: Slump Retention CEM A with SP C..................................................................... 28
Figure 4.7: Slump Retention CEM B with SP A.................................................................... 28
Figure 4.8: Slump Retention CEM B with SP B..................................................................... 29
Figure 4.9: Slump Retention CEM B with SP C..................................................................... 29
Figure 4.10: Slump Retention CEM C with SP A................................................................... 30
Figure 4.11: Slump Retention CEM C with SP B................................................................... 30
Figure 4.12: Slump Retention CEM C with SP C.................................................................. 31
Figure 4.13: Graph of Calibration Results to Calculate G...................................................... 33
Figure 4.14: Tattersall Test Graph for Calculation of h......................................................... 34
Figure 4.15: Tattersall TestCEM A..................................................................................... 35
Figure 4.16: Tattersall TestCEM B..................................................................................... 36
Figure 4.17: Tattersall TestCEM C..................................................................................... 37
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Figure 4.18: Air Content Results for CEM A......................................................................... 38
Figure 4.19: Air Content Results for CEM B......................................................................... 39
Figure 4.20: Air Content Results for CEM C......................................................................... 40
Figure 4.21: Density Results for CEM A................................................................................ 41
Figure 4.22: Density Results for CEM B................................................................................ 42
Figure 4.23: Density Results for CEM C................................................................................ 43
Figure 4.24: Strength Results for CEM A............................................................................... 44
Figure 4.25: Strength Results for CEM B............................................................................... 45
Figure 4.26: Strength Results for CEM C............................................................................... 46
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x
List of Symbols
gValue related to shear stress (Nm)
hValue related to plastic viscosity (Nms)
FForce (N)
GCalibration Constant Based on Newtonian Fluid (m3)
K - Calibration Constant Based on non-Newtonian Fluid
NSpeed of Impeller Blades (1/s)
TTorque (Nm)
Shear Stress (N/m2= Pa)
- Plastic Viscosity (Ns/m2= Pa.s)
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1
Chapter 1
Introduction
1.1 Problem Definition
Recently in South Africa and particularly in the Gauteng region there was a focus on the
rehabilitation of road infrastructure using concrete. Due to this, a mix design was created with
the use of new generation polymer based super-plasticisers and microfibers to produce an
ultra-thin, high strength concrete for the use in concrete pavements. Therefore, it was made
possible for parts of the national highway system to be upgraded using this ultra-thin, high
performance concrete.
The N12 highway was one of the highways that were being upgraded with the use of ultra-
thin concrete pavements. After placement of the concrete, a section on the N12 highway
failed and the reason for failure was unknown. The mix design for this concrete mix was
done in Pretoria. When the mix was tested in the laboratory, the mix passed all tests.
However, when put in place on the N12 highway, the concrete failed. Investigations were
done into what had caused the failure and it was accepted that the failure could possibly be
related to the chemical compatibility of the cement with the super-plasticiser.
Cements produced in different parts of South Africa have slightly altered chemistries, thus
the reaction between the cement and the super-plasticiser may not always be the same. The
altered chemistries of cements with the same specified class suggests that the failure was due
to a different reaction with the cement.
A different chemical reaction would cause a change in how the admixture reacts with the
cement and affect the efficiency of the super-plasticiser. This in turn will affect the rheology
i.e. viscosity, slump and slump retention of the concrete. These properties of fresh concrete
are vital to the design of an ultra-thin pavement mix as the concrete needs to be self-
compacting and remain pumpable for a reasonable period of time.
An investigation will be done into the compatibility and efficiency of three selected
admixtures with three cements. Particular attention will be placed on the effect that the mix
combinations have on the workability and slump retentions. Each of the nine combinations of
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cement with super-plasticiser will be tested at varying admixture dosages ranging from 0.4%
- 1.2% of cementitious material in increments of 0.2%.
1.2. Aim
The aim of this project investigation was to determine, by laboratory work, whether the
compatibility of cements with polymer based super-plasticisers remained the same (with
regard to rheology and strength) regardless of where and by whom it is manufactured and
regardless of the alkali content of the cement. The project also aimed to show the effect that
alkali content and dosage has on the efficiency of the cement with super-plasticiser
combination.
1.3. Objectives
The objectives of this project investigation report are as follows:
1. Evaluate the compatibility and efficiency of each mix with regards to rheology(Slump, Slump Retention, Plastic Viscosity and Air Content)
2. Evaluate the compatibility and efficiency of each mix with regard to Density andStrength.
In order to check the compatibility of the cement with the super-plasticiser the test results
was required to show that the cement performed similarly regardless of which super-
plasticiser was being tested with the cement. Large variations in results for a given property
of the concrete mix or a test that cannot yield a result would indicate incompatibility of the
cement with super-plasticiser combination.
A rating system was used to evaluate the efficiency of the selected super-plasticisers and
cements. This is further described in the experimental design section of this project
investigation report (Chapter 3).
1.4. Limitations
For the purposes of this report, the compatibility of the cements with super-plasticisers were
evaluated with regard to slump, slump retention, viscosity, air content, hardened density and
3-day strength. Other concrete properties were not investigated.
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Only one type of aggregate was used which was andesite from the Eikenhoff quarry. The
coarse aggregate used was 19mm stone and the fine aggregate used was unwashed crusher
sand.
The three cements that were chosen were all CEM II type cements. This aided in creating a
standard mix design which provided data to fairly compare the cements, of the same
classification, to each other.
Each of the cement with super-plasticiser combinations were tested at 5 different dosages of
super-plasticiser. These dosages were 0.4%, 0.6%, 0.8%, 1.0% and 1.2% of the cementitious
material.
1.5. Methodology
A literature review was done to gather information regarding polymer based super-
plasticisers and cement composition (with focus on the alkali content) and the effect they
have on the properties of concrete mixes. Thereafter, research was done to determine how to
measure the rheology of the concrete mixes. From the literature review the Tattersall Two-
Point Tester was chosen to measure the concretes workability and therefore more research
was done on how to calibrate and operate the Tattersall Two-Point Tester.
From the recommendations by the sponsor of this project, it was decided that three CEM II
cements from different manufactures be used in the mixes. A mix design was created using
the Cement and Concrete Institute method for mix design. This mix would be used to
evaluate the concrete properties of each combination by using the same mix design for all
tests that followed. Each of the three cements were analysed to show their chemical
compound composition. This was used to show how alkali content affects the compatibility
and efficiency of the cements with the polymer based super-plasticisers.
An investigation into the workability and strength of each concrete mix was then evaluated
by the following tests: the slump test, the slump retention test, the air content test, the
Tattersall Two-Point Test and the 3 day compressive strength cube test.
From the results obtained the efficiency of each mix was analysed using an efficiency rating
system. The ratings from this system made it possible to draw conclusions between the alkali
content of the cement, the dosage of the super-plasticiser and the efficiency of the mix.
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1.6. Layout of this Project Investigation
Chapter 2 consists of an overview of the literature found and judgements made based on this
literature. It was also stated how this literature is necessary for the completion of the report.
Particular attention was paid to the cement alkali content and the methods for working with
the Tattersall Two Point Tester.
Chapter 3 follows with a summary of the experimental design. The 5 mix designs are stated
for each of the 5 dosages that were tested. This is then followed by the tests that were
performed during the practical. This chapter includes a description of the rating system used
to evaluate efficiency of the products.
Chapter 4 provides a summary of all the test data, and then followed by a more specific
summary of the data gathered per test. Also included in this chapter are the calibration results
for the Tattersall Two Point Tester. Included in this section is an example of the calculations
that were done to obtain the results.
Chapter 5 summarises the findings and results of this investigation along with
recommendations for further work. This chapter discusses the relationship found between the
alkali content of the cements with the results obtained from the testing that was done.
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Chapter 2
LITERATURE REVIEW
2.1 Concrete Properties
Before the investigation could be carried out, it was important that an understanding be
gained for what the concrete properties that will be investigated are, and how they would
most likely be affected. By understanding what these properties are and how they change
depending on the mix design makes it easier to draw conclusions about how the super-
plasticisers are affecting the concrete. The concrete properties that will be investigated are
rheology, and strength.
2.1.1. Rheology
In order to evaluate a concrete mixs rheology, an understanding for this term needs to be
gained. Rheology is the science of the deformation and flow of matter. (Banfill, 2003) In
other words rheology refers to the fresh properties of a concrete mix, specifically the
workability of the concrete as well as the workability retention. The use of ultra-thin, high
strength concrete in pavements requires that the concrete that is being placed is pumped and
is self-compacting. This leads to the rheological requirements for the concrete to be
important. The concrete is required to have a workability that lends itself to being pumped
easily.
High workability can be achieved in different ways. The easiest and most cost effective
method of increasing the workability and flow of the mix is to increase the water to cement
ratio (W/C) so that the mix contains a higher percentage of water in the mix design. This
method, although easy, comes at the cost of a reduction in strength. The loss of strength
makes the mix unsuitable for the use in pavements as a high strength concrete is required.
A second method of increasing the workability of the concrete mix is with the use of an
admixture. Admixtures such as plasticisers and super-plasticisers, also known as water
reducers, work by redistributing the cement particles evenly. (Addis, 2008) The even
distribution of cement particles allow for the concrete to flow easier.
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By assessing the rheology of each mix, it will then be possible to see how the super-
plasticiser affects each of the three different cements. The rheology will be assessed by
investigating the slump and slump retention, viscosity and air content of the concrete.
2.1.1.1. Slump and Slump Retention
The slump test is a commonly used test that is done to assess the workability of a concrete
mix. This test is used, as the apparatus needed for the test is relatively cheap compared to
other tests and is easier to perform than the other tests. Results from the slump test are also
immediately available as the reading is just measured with a ruler. However, although this
test is simple and easy to perform, it is also prone to inaccuracies.
The slump test is sensitive to operator technique, whether it is intended or not. (Tattersall,
1991) The slump test also has a very limited range. Slumps of highly workable mixes cannot
be evaluated as they simply collapse and slumps of low workability concrete cannot be
evaluated as they all give roughly the same result. (Tattersall, 1991) Although the test is not
suitable for highly workable concrete, it was specified by the sponsor that a slump of between
125mm and 175mm be achieved, therefore, the mix design was adjusted accordingly.
Slump retention is the ability of the concrete mix to maintain its workability over a period of
time. This is important for the use in ultra thin high strength concrete, as the concrete mix is
required to retain its workability for long periods of time so that it can be pumped without the
concrete starting to harden.
Generally, super-plasticisers increase slump loss in comparison to an equivalent plain mix
with no admixture. The lower the W/C ratio of the concrete mix, the higher the slump loss.
(Felekoglu & Sarikahya, 2008) However, it was suggested by the sponsor of the super-
plasticisers used that the new polymer based super-plasticisers would allow the concrete toretain its slump for a time of two hours. This is supported by work done by Felekoglu and
Sarikahya were they state that the polycarboxylate based super-plasticisers are able to extend
the flow retention of concrete mixes. (Felekoglu & Sarikahya, 2008) The slump retention
may last for about two hours. After this time period, the concrete mix will return to its
original state of workability. (Holcim South Africa, 2006)
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2.1.1.2. Plastic Viscosity
The term viscosity refers to a how a fluid reacts to force that is applied to it. It gives an
indication of the frictional forces within the fluid. These frictional forces will slow down the
movement of the fluid. Therefore a higher viscosity correlates to higher frictional forces in
the fluid, therefore this results in the fluid moving slower when a force is applied to it as
compared to a fluid with a lower viscosity. (Serway & Jewett, 2004)
This means that a highly workable mix will have a low viscosity since it requires a low force
applied to in to cause it to continue to flow. This property defines the rheology of the
concrete much better than the slump as it more accurately defines how the mix will behave
with the application of a force.
Table 2.1: Rheology of Cement Paste, Mortar and Concrete (Banfill, 2003)
Material Cement Paste,
Grout
Mortar Flowing
Concrete
Self-compacting
Concrete
Concrete
Yield Stress
N/m2
10-100 80-400 400 50-200 500-2000
Plastic Viscosity
Ns/m2
0.01-1 1-3 20 20-100 50-100
Structural
Breakdown
Significant Slight None None None
2.1.1.3. Air Content
The air content refers to the amount of air that is present in the concrete when the concrete is
in its fresh state. The air in the concrete often takes the form of tiny air bubbles. These air
bubbles significantly increase the workability of the concrete. (Tattersall, 1991) The air
content will be measured to show if the super-plasticisers are entraining the same amount of
air into each concrete mix.
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2.1.2. Strength
The strength of the concrete in its hardened state is probably the most important property of
concrete as it is a substance used for its structural characteristics. Often, to increase strength,
the water-cement ratio is reduced but this will then decrease the workability. (Addis, 2008)
Therefore it is necessary to use a super-plasticiser to reverse this effect of a reduction in
workability.
2.2. Super-plasticisers
According to Rivera-Villarreal, super-plasticisers are divided into four main groups:
1.
Sulfonated Naphthalene-Formaldehyde Condense (SNF)2. Sulfonated Melamine-Formaldehyde Condense (SMF)3. Modified Lignosulfonates (MLS)4. Others; including polyacrylates, polystyrene sulfonates and polycarboxylate polymers
(PCP)
(Rivera-Villarreal, 1999)
The super-plasticisers that were chosen to be used in the experiment are polycarboxylate
based polymers. Polycarboxylate polymers produce maximum water reduction among the
different super-plasticisers groups. The water reduction can be as much as 20 to 35%. This
makes it well suited for concretes that require a high fluidity and flow retention. (Marais,
2009)
Another property of the PCP super plasticizer is the early strength development. (Marais,
2009) These properties of the PCP makes it well suited for the use in ultra thin concrete
pavements as the early strength development means that the road can be opened to the public
quickly, and the high reduction in water means that the W/C ratio can be reduced leading to
an increase in concrete strength.
The PCP super-plasticiser products are known to be sensitive to cement chemistry and
therefore the performance of the admixture will differ with different cements. (Marais, 2009)
It is important to do trial mixes to observe the effectiveness of the admixture as under dosing
will lead to having a mix that is not as fluid as required, while an overdose will cause a lack
of cohesiveness and may lead to segregation.
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Figure 2.1: Effect of super plasticizing admixture. (Addis, 2008)
2.3. Cement Composition
The type of cement as classified according to SANS 50197: Composition, specification and
conformity criteria for common cements. However, these classifications are general and the
actual percentages of clinker, GGBS, limestone and fly ash differ within these classes. This
means two cements of the same classification made by different manufactures can have
different chemical compositions.
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Figure 2.2: Classification and Composition % of South African cements. (Holcim South
Africa, 2006)
In the study done by Schober and Mder on the compatibility of polycarboxylate super-
plasticisers with cements and cementious blends, it was shown that a low-alkali cement was
more compatible than the higher alkali cements with the super-plasticisers that were tested.
(Schober & Mder, 2003) Work done by Golaszewski and Szwabowski supports the idea that
lower alkali cements are better suited for use with the polymer based super-plasticisers.
(Golaszewski & Szwabowski, 2002)
The level of alkali found in cement is determined by evaluating the amount, by percentage, of
alkali metal compounds that are present in the cement. The alkali metal compounds that are
found in cements are Na2O (Sodium oxide) and K2O (Potassium oxide). (Holcim South
Africa, 2006)
The percentages of these compounds in the cement are then converted to a Na2Oeq(Sodium
oxide equivalent). This is done by the use of the following formula:
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This formula is derived using the molar mass of the compounds to relate them to each other.
In order for the cement to be classified as a low alkali cement the Na2Oeqis required to have a
value of less than 0.6%. (Holcim South Africa, 2006)
2.4. Rheological Tests
Work done by Tattersall, G.H. suggests that the most effective way of evaluating the
rheology or workability of a concrete mix is by using a two-point tester. He recommends this
test as it overcomes the inaccuracies of the other standard tests for measuring workability.
(Tattersall, 1991)
Rheology is not a measurable characteristic of concrete; however, there are many different
tests which give an indication as to the behaviour of the mix in terms of its rheology. The
most effective way in South Africa to test the rheological behaviour of concrete mixes is with
the use of the Tattersall Two Point Tester. (Jooste, 2006)
Fortunately, the apparatus for the Tattersall Two-Point Test was available for use during this
practical, therefore it was decided that this apparatus would be employed to evaluate the
rheology of the concrete mixes.
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2.5. Tattersall Two-Point Tester
Figure 2.3: Tattersall Two Point Tester Apparatus Motor and Processing Unit.
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Figure 2.4: Tattersall Two Point Tester Apparatus Sample Holder and Impeller.
The tester measures pressures in the transmission when turning an impeller in the mix at
different speeds. Plotting the relationship between the torque and the speed allows for the
calculation of yield stress and plastic viscosity. (Jooste, 2006)
Figure 2.5: Tattersall Two Point Tester Impeller Blade.(Jooste, 2006)
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Figure 2.6: Sample Holder Showing the Filling Mark. (Jooste, 2006)
The Tattersall Tester uses the principle that concrete acts as a Bingham Fluid. (Tattersall,
1991) From this principle the equation that the machine was based on was calculated.
Where:
T = Torque (Nm) g = A value relative to shear stress (Nm) h = A value relative to plastic viscosity (Nms) N = Speed of the Impeller Blades (1/s)
From the values of g and h the shear stress and plastic viscosity can be calculated using the
following formulae:
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Where:
= shear stress (N/m2) = plastic viscosity (Ns/m2= Pa.s) = Calibration Constant based on a Newtonian fluid (m3) = Calibration Constant based on a Non-Newtonian fluid (pseudo plastic fluid)
Tattersall G.H. suggests that the calibration of the machine is not required for the practical
use in the industry. The calibration of the machine is done using a linear relationship and
therefore the values for g and h would be sufficient for comparative testing. Tattersall goes on
to propose that the calibration of the machine would be too time consuming and thus not be
justified for use in practice. He suggests that by standardising the shape and dimensions of
the sample holder and impeller will eliminate the need for calibration. (Tattersall, 1991)
For this investigation project the actual plastic viscosity was recommended as a value of
interest by the sponsor and so the necessary calibration was done. This investigation only the
viscosity of the concrete was required so the calibration constant of G was calculated and the
calculation of K was not done. Canola oil was used to calibrate the machine as the plastic
viscosity was known for two different temperatures (shown in Table 2.3) and the substance
was easily available.
Water was not used to calibrate the machine as, even though it is a Newtonian fluid, it proved
difficult due to the fact that the Tattersall Testers force readings only give a reading to two
decimal points. Therefore a value for G was calculated as a zero value since the change in
force was not visible.
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Table 2.2: Viscosities of Selected Materials (The Physics Hypertextbook, 2011)
Viscosities of Selected Materials (note the different unit prefixes)
simple liquids T() (mPa s) gases T() (Pas)alcohol, ethyl (grain) 20 1.1 air 15 17.9
alcohol, isopropyl 20 2.4 hydrogen 0 8.42alcohol, methyl (wood) 20 0.59 helium (gas) 0 18.6
blood 37 34 nitrogen 0 16.7
ethylene glycol 25 16.1 oxygen 0 18.1
ethylene glycol 100 1.98
freon 11 (propellant) 25 0.74 complex materials T() (Pa s)freon 11 (propellant) 0 0.54 caulk 20 1000
freon 11 (propellant) +25 0.42 glass, room temperature 10 10
freon 12 (refrigerant) -15 ?? glass, strain point 10.
freon 12 (refrigerant) 0 ?? glass, annealing point 10.
freon 12 (refrigerant) +15 0.20 glass, softening 10.
glycerin 20 1420 glass, working 10glycerin 40 280 glass, melting 10
helium (liquid) 4 K 0.00333 honey 20 10
Mercury 15 1.55 ketchup 20 50
milk 25 3 lard 20 1000
oil, vegetable, canola 25 57 molasses 20 5
oil, vegetable, canola 40 33 mustard 25 70
oil, vegetable, corn 20 65 peanut butter 20 150250
oil, vegetable, corn 40 31 sour cream 25 100
oil, vegetable, olive 20 84 syrup, chocolate 20 1025
oil, vegetable, olive 40 ?? syrup, corn 25 23
oil, vegetable, soybean 20 69 syrup, maple 20 23oil, vegetable, soybean 40 26 tar 20 30,000
oil, machine, light 20 102 vegetable shortening 20 1200
oil, machine, heavy 20 233
oil, motor, SAE 10 20 65
oil, motor, SAE 20 20 125
oil, motor, SAE 30 20 200
oil, motor, SAE 40 20 319
propylene glycol 25 40.4
propylene glycol 100 2.75
water 0 1.79
water 20 1.00
water 40 0.65
water 100 0.28
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Chapter 3
Experimental Design
3.1. Requirements
For the purpose of this investigation, a large amount of practical testing was required. A mix
design was calculated and from there, testing could be done on the rheology and strength of
the concrete. The same mixing drum was used and the mixer was run for 5 minutes for each
batch. This was done to ensure that the mixing energy stays constant for each batch as super-
plasticisers are sensitive to a variation in mixing energy.
The Method for addition of the super-plasticisers was kept constant for each batch. The
super-plasticisers were added by mixing the fluid with 1 litre of the mixing water and then
adding the solution to the mix. The super-plasticisers were all added at 1 minute after mixing
had commenced in order to eliminate any additional variables.
Tests that were performed in this investigation were the slump test, slump retention test, a
viscosity test (using the Tattersall Two-Point Tester), an air content test and a 3 day
compressive strength cube test.
3.2. Materials
All aggregate used was andesite aggregate from the Eikenhoff quarry.
Coarse aggregate19mm stone Fine aggregateunwashed crushed sand
Cements from different manufactures that were used are specified as follows:
CEM ACem II A-L 42.5 N CEM BCem II A-M (V-L) 42.5 N CEM CCem II A-M (V-L) 42.5 N
A chemical analysis was carried out in order to determine the chemical compounds found in
each of the cements. The test also showed the amount of each of the compounds found in the
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cement as although the cements may be classified as the same category of cement the
composition may differ. From these results the cements can then be classified according to
the alkali levels in the cement. The table provided below shows the results of the chemical
analysis.
Table 3.1: Chemical Composition of Cements
TestCEM A CEM B CEM C
% % %
L.O.I. 1.71 4.40 4.41
SiO2 29.02 23.47 24.75
Al2O3 10.82 6.42 8.97
CaO 50.83 61.78 57.17
Fe2O3 3.38 2.66 3.25
MgO 1.85 1.80 1.64
TiO2 0.78 0.47 0.71
Mn2O3 0.22 0.10 0.14
Na2O 0.23 0.15 0.17
K2O 0.40 0.51 0.24
P2O5 0.25 0.10 0.16
*Na2Oeq 0.50 0.49 0.32
* Note: Sodium Oxide Equivalent = % Na2O + (0.658 * % K2O)
Super-plasticisers that were used are from the same manufacturer and are specified as
follows:
SP A, which is a new generation polymer super-plasticiser based on modifiedphosphonates.
SP B, which is a new generation polymer super-plasticiser based on polycarboxylateand modified phosphonates.
SP C, which is a new generation polymer super-plasticiser, based on modifiedpolycarboxylates.
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3.3. Mix Design
A mix design was created using the method set out by the Cement and Concrete Institute.
From the resulting mix design a trail mix was done with CEM A and SP A at a dosage of
0.8%. The mix was adjusted until a slump of 150mm was obtained. The following values for
the material properties were used in the calculation of the mix design:
RDsand= 2.92 (Holcim South Africa, 2006) RDstone= 2.92 (Holcim South Africa, 2006) RDcement= 3.1 FM = 3.1 (Grading Analysis Section 3.4) CBD = 1640 kg/m3 K = 0.94 (Addis, 2008)
Table 3.2: Mix design Results for a 1000 litre mix
Mix Design
1
Mix Design
2
Mix Design
3
Mix Design
4
Mix Design
5
W:C 0.45 0.45 0.45 0.45 0.45
Water (L) 180 180 180 180 180
Cement (Kg)* 400 400 400 400 400Sand (Kg) 1050 1050 1050 1050 1050
Stone (Kg) 780 780 780 780 780
Admixture (L)* 1.6 2.4 3.2 4.0 4.8
* Note: Although the admixtures and cements are different in each of the nine mix
combinations, the quantity remains constant to show the difference in rheology and to
eliminate additional variables.
Note: The Admixture dosages for mixes 1, 2, 3, 4 and 5 were 0.4%, 0.6%, 0.8%, 1.0%, and
1.2% respectively.
After the mix design was calculated, the mix was resized to a batch volume of 20litres or
0.02m3. This was to accommodate as much of the testing as possible with a single batch.
However, due to the quantities required for each test, two batches of concrete were made for
each of the mixes.
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Table 3.3: Mix design Results for a 20 litre mix
Mix Design
1
Mix Design
2
Mix Design
3
Mix Design
4
Mix Design
5
W:C 0.45 0.45 0.45 0.45 0.45
Water (L) 3.6 3.6 3.6 3.6 3.6Cement (Kg)* 8 8 8 8 8
Sand (Kg) 21 21 21 21 21
Stone (Kg) 15.6 15.6 15.6 15.6 15.6
Admixture (L)* 0.032 0.048 0.064 0.080 0.096
3.4. Grading Analysis
Table 3.4: Grading results for andesite crusher sandParticle size
(mm)
Mass Retained
sieve (g)
Cumulative %
Retained by Sieve
Cumulative% Passing
Sieve
9.5 0.00 0 100
6.7 4.20 0.2 99.8
4.75 27.27 1.5 98.5
2.36 566.46 28.5 71.5
1.18 499.32 52.3 47.7
0.6 312.60 67.2 32.8
0.425 113.29 72.6 27.4
0.3 96.51 77.2 22.8
0.15 144.76 84.1 15.9
0.075 69.23 87.4 12.6
pan 264.35 100 0
Total 2097.99 *310.8
FM = 310.8 100 FM = 3.1
* Note: Sum of the standard sieves up to and including the 0.15mm sieve.
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Figure 3.1: Grading curve for andesite crusher sand
0
10
20
30
40
50
60
70
80
90
100
0.01 0.1 1 10
Cumu
lative%ofmasspassingSieve
Particle Size (mm)
Grading Curve for Andesite Crusher Sand
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3.5. Tests
The following tests were performed during the investigation:
Table 3.5: Tests performed during practical
Test performed SABS/SANS Number Comments
Slump Test SABS Method862-1:1994 The Slump Test is known to
be sensitive to operator
technique therefore the same
operator was used for all the
slump tests that were
performedSlump Retention Test SABS Method862-1:1994 The slump test was re-
performed at 30min intervals
after the original slump test
up to a time of 120min.
Plastic Viscosity
Tattersall Two-Point Test
n/a The test to measure plastic
viscosity was done according
to the method described in
the literature review.
Calibration Data found in
Section 4.3.1
Air Content Test SANS 6252 Method A. A correction was made for
the air trapped in the
aggregate according to the
standard.
Strength Test SABS 860:1994,
SABS 861-2:1994,
SABS 861-3:1994,
SABS 863:1994,
SANS 0100-2:1992
During the strength test the
mass of each cube was
measured and used to
calculate density
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3.6. Efficiency Rating System
The efficiency for each of the tests was evaluated in terms of the most efficient combination
of cement and super-plasticiser. The best performer of each result was given a value of 1 with
the remaining results receiving a value proportional to 1 depending on how close the result
was to the best result. An Example is shown below:
Best Result of Slump Test, CEM CSP C @ 1.2% = 175mm
Another Result, CEM ASP C @ 1.2% = 170mm
Therefore, CEM CSP C @ 1.2% = 1
And, CEM ASP C @ 1.2% = 170mm/175mm = 0.971
The slump retention data was evaluated slightly differently. The value given to each of the
slump retention test results were calculated as follows:
3.7. Expected Results
During the testing, it was expected that the chosen low alkali cements will behave similarly,
in all tests, regardless of which manufacturer made the cement. During the testing it was
expected that the low alkali cement would be less sensitive to changes, in dosage and super-
plasticiser type, when considering its compatibility with the super-plasticisers. The cements
with higher alkali content are expected to show signs of lower efficiency with the given
super-plasticisers. Although the cements with higher alkali content may work effectively with
a given super-plasticiser at a given dosage, it may not be compatible at a different dosage.
It was expected that SP A would be the weakest in terms of slump and viscosity and the best
in terms of the slump retention ability. SP C would be the opposite of SP A, with SP B beingan intermediate super-plasticiser between the two extremes.
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Chapter 4
Test Results
4.1. Slump Test
Table 4.1: Slump Test Results for CEM A
Cem A
SP A SP B SP C
Dosage % Slump (mm) Dosage % Slump (mm) Dosage % Slump (mm)
0.4 100 0.4 100 0.4 110
0.6 140 0.6 145 0.6 155
0.8 150 0.8 155 0.8 1601.0 155 1.0 160 1.0 165
1.2 Segregation 1.2 165 1.2 170
Figure 4.1: Slump Test Results for CEM A
90
100
110
120
130
140
150
160
170
180
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Slump(mm)
Dosage %
Slump - CEM A
SP A
SP B
SP C
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Table 4.2: Slump Test Results for CEM B
Cem B
SP A SP B SP C
Dosage % Slump (mm) Dosage % Slump (mm) Dosage % Slump (mm)
0.4 105 0.4 110 0.4 1200.6 145 0.6 145 0.6 155
0.8 145 0.8 150 0.8 160
1.0 145 1.0 150 1.0 165
1.2 160 1.2 155 1.2 Segregation
Figure 4.2: Slump Test Results for CEM B
90
100
110
120
130
140
150
160
170
180
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Slump(mm)
Dosage %
Slump - CEM B
SP A
SP B
SP C
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Table 4.3: Slump Test Results for CEM C
Cem C
SP A SP B SP C
Dosage % Slump (mm) Dosage % Slump (mm) Dosage % Slump (mm)
0.4 145 0.4 150 0.4 1600.6 145 0.6 150 0.6 160
0.8 155 0.8 160 0.8 165
1.0 160 1.0 165 1.0 170
1.2 165 1.2 170 1.2 175
Figure 4.3: Slump Test Results for CEM C
90
100
110
120
130
140
150
160
170
180
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Slump(mm)
Dosage %
Slump - CEM C
SP A
SP B
SP C
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4.2. Slump Retention
Figure 4.4: Slump Retention CEM A with SP A
Figure 4.5: Slump Retention CEM A with SP B
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Figure 4.6: Slump Retention CEM A with SP C
Figure 4.7: Slump Retention CEM B with SP A
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Figure 4.8: Slump Retention CEM B with SP B
Figure 4.9: Slump Retention CEM B with SP C
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Figure 4.10: Slump Retention CEM C with SP A
Figure 4.11: Slump Retention CEM C with SP B
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Figure 4.12: Slump Retention CEM C with SP C
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4.3. Plastic Viscosity
4.3.1. Calibration
Table 4.4: Readings from Tattersall Tester for Calibration with Canola Oil
Temperature (C) Speed (RPM) Speed (1/s) Force (N) Torque (Nm) Slope (Nms)
25
40 0.67 0.54 0.0540
0.0091636
45 0.75 0.55 0.0550
50 0.83 0.56 0.0560
55 0.92 0.56 0.0560
60 1.00 0.57 0.0570
65 1.08 0.58 0.0580
70 1.17 0.59 0.0590
75 1.25 0.59 0.0590
80 1.33 0.60 0.0600
85 1.42 0.61 0.0610
90 1.50 0.62 0.0620
Temperature (C) Speed (RPM) Speed (1/s) Force (N) Torque (Nm) Slope (Nms)
40
40 0.67 0.50 0.05
0.0076364
45 0.75 0.50 0.050
50 0.83 0.51 0.051
55 0.92 0.51 0.051
60 1.00 0.52 0.052
65 1.08 0.53 0.053
70 1.17 0.54 0.054
75 1.25 0.54 0.054
80 1.33 0.55 0.055
85 1.42 0.55 0.055
90 1.50 0.56 0.056
Table 4.5: Calibration Data for Tattersall Tester
Temperature (C) Temperature (K) Viscosity (Pa.s) T/N (Nms)
25 298.15 0.057 0.009164
40 313.15 0.033 0.007636
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Figure 4.13: Graph of Calibration Results to Calculate G
From the results G = 0.0636 m3
4.3.2. Results
The reading from the Tattersall Two Point Tester gives two sets of data, firstly the speed
which the user inputs as revolutions per minute and secondly the force exerted on the motor
as Newtons. The values are then converted to a speed as revolutions per second and a torqueby multiplying the distance of the load cell to the centre of the motor.
These calculated values are then plotted on a graph showing Torque (Nm) on the y-axis and
Speed (1/s) on the x-axis. The gradient of a best-fit linear line is the value of h (Nms). The h
value is then converted to a viscosity value () by dividing h by the calibration constant G
which was calculated above.
Due to the large number of mixes which were tested, each result was not included in this
section of the report. An example of one of the calculations is shown below in table 4.6 and
figure 4.14. The remaining calculations can be found in appendix B.
y = 0.0636x
0.007000
0.007500
0.008000
0.008500
0.009000
0.009500
0 0.02 0.04 0.06
Calculation of G
Calibration
Linear (Calibration)
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Table 4.6: Example of Tattersall Result Calculation
N (RPM) N (1/s) F (N) T (Nm) G (m) h (Nms) (Pa.s)
40 0.67 6.23 0.623 0.06364 2.6604 41.8063
45 0.75 8.13 0.813
50 0.83 10.88 1.088
55 0.92 12.12 1.212
60 1.00 15.32 1.532
Figure 4.14: Tattersall Test Graph for Calculation of h
Below is a summary of the results of the Tattersall Two Point Test in terms of the viscosities
that were calculated.
y = 2.6604x - 1.1634
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
1.800
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Torque(Nm)
Speed (1/s)
Tattersall Test - CEM A - SP A @ 0.4%
Series1
Linear (Series1)
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Table 4.7: Tattersall Results CEM A
Cem A
SP A SP B SP C
Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s)
0.4 41.8063 0.4 35.3194 0.4 31.96290.6 35.1120 0.6 27.2109 0.6 23.1189
0.8 29.0400 0.8 25.5703 0.8 20.1206
1.0 26.9657 1.0 25.2497 1.0 19.9886
1.2 Segregation 1.2 24.9291 1.2 19.7434
Figure 4.15: Tattersall Test CEM A
0.0000
5.0000
10.0000
15.0000
20.0000
25.0000
30.0000
35.0000
40.0000
45.0000
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Viscosity(Pa.s
)
Dosage %
Tattersall Test - CEM A
SP A
SP B
SP C
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Table 4.8: Tattersall Results CEM B
Cem B
SP A SP B SP C
Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s)
0.4 40.4297 0.4 33.1886 0.4 30.20910.6 33.2829 0.6 27.6069 0.6 22.2514
0.8 29.0740 0.8 24.8349 0.8 20.2526
1.0 26.2869 1.0 22.3080 1.0 19.0646
1.2 25.0046 1.2 Segregation 1.2 18.7251
Figure 4.16: Tattersall Test CEM B
0.0000
5.0000
10.0000
15.0000
20.0000
25.0000
30.0000
35.0000
40.0000
45.0000
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
V
iscosity(Pa.s
)
Dosage %
Tattersall Test - CEM B
SP A
SP B
SP C
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Table 4.9: Tattersall Results CEM C
Cem C
SP A SP B SP C
Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s)
0.4 31.6046 0.4 29.7189 0.4 22.45890.6 28.0594 0.6 26.3434 0.6 21.3840
0.8 27.6257 0.8 24.0240 0.8 19.1589
1.0 25.1743 1.0 22.9114 1.0 18.5366
1.2 23.8543 1.2 20.8371 1.2 17.5560
Figure 4.17: Tattersall Test CEM C
0
5
10
15
20
25
30
35
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
V
iscosity(Pa.s
)
Dosage %
Tattersall Test - CEM C
SP A
SP B
SP C
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4.4. Air Content
Table 4.10: Air Content Results for CEM A
Cem A
SP A SP B SP C
Dosage % Air Content % Dosage % Air Content % Dosage % Air Content %
0.4 2 0.4 2.2 0.4 1.8
0.6 2.1 0.6 2.2 0.6 1.8
0.8 2.2 0.8 2.5 0.8 1.9
1.0 2.4 1.0 2.5 1.0 2.1
1.2 Segregation 1.2 2.6 1.2 2.1
Figure 4.18: Air Content Results for CEM A
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
AirContent%
Dosage %
Air Content - CEM A
SP A
SP B
SP C
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Table 4.11: Air Content Results for CEM B
Cem B
SP A SP B SP C
Dosage % Air Content % Dosage % Air Content % Dosage % Air Content %
0.4 2.1 0.4 2.2 0.4 2
0.6 2.1 0.6 2.2 0.6 2.1
0.8 2.2 0.8 2.4 0.8 2.1
1.0 2.3 1.0 2.5 1.0 2.2
1.2 2.3 1.2 Segregation 1.2 2.3
Figure 4.19: Air Content Results for CEM B
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
AirConte
nt%
Dosage %
Air Content - CEM B
SP A
SP B
SP C
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Table 4.12: Air Content Results for CEM C
Cem C
SP A SP B SP C
Dosage % Air Content % Dosage % Air Content % Dosage % Air Content %
0.4 1.6 0.4 1.7 0.4 1.5
0.6 1.6 0.6 1.7 0.6 1.7
0.8 1.7 0.8 1.7 0.8 1.7
1.0 1.7 1.0 1.9 1.0 1.8
1.2 1.8 1.2 1.9 1.2 1.9
Figure 4.20: Air Content Results for CEM C
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
AirConte
nt%
Dosage %
Air Content - CEM C
SP A
SP B
SP C
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4.5. Hardened Density
Table 4.13: Density Results for CEM A
Cem A
SP A SP B SP C
Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage % Density (kg/m)
0.4 2415 0.4 2410 0.4 2435
0.6 2410 0.6 2405 0.6 2430
0.8 2410 0.8 2395 0.8 2430
1.0 2400 1.0 2395 1.0 2420
1.2 Segregation 1.2 2390 1.2 2410
Figure 4.21: Density Results for CEM A
2385
2390
2395
2400
2405
2410
2415
2420
2425
2430
2435
2440
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Density
(kg/m)
Dosage %
Density -CEM A
SP A
SP B
SP C
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Table 4.14: Density Results for CEM B
Cem B
SP A SP B SP C
Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage %Density
(kg/m)0.4 2420 0.4 2415 0.4 2420
0.6 2420 0.6 2410 0.6 2415
0.8 2410 0.8 2410 0.8 2415
1.0 2405 1.0 2395 1.0 2405
1.2 2405 1.2 Segregation 1.2 2400
Figure 4.22: Density Results for CEM B
2390
2395
2400
2405
2410
2415
2420
2425
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Density(kg/m)
Dosage %
Density - CEM B
SP A
SP B
SP C
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Table 4.15: Density Results for CEM C
Cem C
SP A SP B SP C
Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage %Density
(kg/m)0.4 2435 0.4 2430 0.4 2440
0.6 2430 0.6 2430 0.6 2435
0.8 2430 0.8 2420 0.8 2435
1.0 2420 1.0 2415 1.0 2430
1.2 2415 1.2 2415 1.2 2425
Figure 4.23: Density Results for CEM C
2410
2415
2420
2425
2430
2435
2440
2445
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Density(kg/m)
Dosage %
Density - CEM C
SP A
SP B
SP C
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4.6. Strength
Table 4.16: Strength Results for CEM A
Cem A
SP A SP B SP C
Dosage % Strength (MPa) Dosage % Strength (MPa) Dosage %Strength
(MPa)
0.4 16.0 0.4 15.0 0.4 18.5
0.6 16.0 0.6 15.0 0.6 18.0
0.8 15.5 0.8 14.5 0.8 17.0
1.0 15.0 1.0 13.0 1.0 17.0
1.2 Segregation 1.2 12.0 1.2 17.0
Figure 4.24: Strength Results for CEM A
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Strength(MP
a)
Dosage %
Strength - CEM A
SP A
SP B
SP C
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Table 4.17: Strength Results for CEM B
Cem B
SP A SP B SP C
Dosage % Strength (MPa) Dosage % Strength (MPa) Dosage %Strength
(MPa)0.4 16.5 0.4 16.0 0.4 17.0
0.6 16.0 0.6 15.5 0.6 16.5
0.8 15.0 0.8 14.0 0.8 16.5
1.0 14.0 1.0 13.5 1.0 16.0
1.2 13.0 1.2 Segregation 1.2 16.0
Figure 4.25: Strength Results for CEM B
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Stre
ngth(MPa)
Dosage %
Strength - CEM B
SP A
SP B
SP C
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Table 4.18: Strength Results for CEM C
Cem C
SP A SP B SP C
Dosage % Strength (MPa) Dosage % Strength (MPa) Dosage %Strength
(MPa)0.4 18.0 0.4 18.5 0.4 19.0
0.6 18.0 0.6 18.5 0.6 18.5
0.8 18.0 0.8 18.0 0.8 18.5
1.0 17.5 1.0 18.0 1.0 18.0
1.2 17.0 1.2 17.5 1.2 18.0
Figure 4.26: Strength Results for CEM C
16.5
17.0
17.5
18.0
18.5
19.0
19.5
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Stre
ngth(MPa)
Dosage %
Strength - CEM C
SP A
SP B
SP C
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4.7. Efficiency
Table 4.19: Efficiency Rating Table for CEM A
CEM SPDosage
% SlumpSlump
Retention ViscosityAir
content Workability Density StrengthHardened
Properties
A A 0.4 0.57 0.85 -0.38 0.77 1.81 0.99 0.84 1.83
A A 0.6 0.80 0.96 0.00 0.81 2.57 0.99 0.84 1.83
A A 0.8 0.86 0.97 0.35 0.85 3.02 0.99 0.82 1.80
A A 1.0 0.89 0.97 0.46 0.92 3.24 0.98 0.79 1.77
A A 1.2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
A B 0.4 0.57 0.85 -0.01 0.85 2.26 0.99 0.79 1.78
A B 0.6 0.83 0.93 0.45 0.85 3.06 0.99 0.79 1.78
A B 0.8 0.89 0.90 0.54 0.96 3.29 0.98 0.76 1.74A B 1.0 0.91 0.91 0.56 0.96 3.34 0.98 0.68 1.67
A B 1.2 0.94 0.94 0.58 1.00 3.46 0.98 0.63 1.61
A C 0.4 0.63 0.59 0.18 0.69 2.09 1.00 0.97 1.97
A C 0.6 0.89 0.65 0.68 0.69 2.91 0.95 0.95 1.90
A C 0.8 0.91 0.69 0.85 0.73 3.19 1.00 0.89 1.89
A C 1.0 0.94 0.76 0.86 0.81 3.37 0.99 0.89 1.89
A C 1.2 0.97 0.76 0.88 0.81 3.42 0.99 0.89 1.88
Table 4.20: Efficiency Rating Table for CEM B
CEM SPDosage
%Slump
Slump
RetentionViscosity
Air
contentWorkability Density Strength
Hardened
Properties
B A 0.4 0.60 0.86 -0.30 0.81 1.96 0.99 0.87 1.86
B A 0.6 0.83 0.93 0.10 0.81 2.67 0.99 0.84 1.83
B A 0.8 0.83 0.93 0.30 0.85 2.90 0.99 0.79 1.78
B A 1.0 0.83 0.97 0.50 0.88 3.18 0.99 0.74 1.72
B A 1.2 0.91 0.97 0.58 0.88 3.34 0.99 0.68 1.67
B B 0.4 0.63 0.82 0.11 0.85 2.40 0.99 0.84 1.83
B B 0.6 0.83 0.90 0.43 0.85 3.00 0.99 0.82 1.80B B 0.8 0.86 0.93 0.59 0.92 3.30 0.99 0.74 1.72
B B 1.0 0.86 0.97 0.73 0.96 3.51 0.98 0.71 1.69
B B 1.2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
B C 0.4 0.69 0.54 0.28 0.77 2.28 0.99 0.89 1.89
B C 0.6 0.89 0.71 0.73 0.81 3.14 0.99 0.87 1.86
B C 0.8 0.91 0.75 0.85 0.81 3.32 0.99 0.87 1.86
B C 1.0 0.94 0.82 0.91 0.85 3.52 0.99 0.84 1.83
B C 1.2 0.94 0.91 0.93 0.88 3.67 0.98 0.84 1.83
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Table 4.21: Efficiency Rating Table for CEM C
CEM SPDosage
%Slump
Slump
RetentionViscosity
Air
contentWorkability Density Strength
Hardened
Properties
C A 0.4 0.83 0.93 0.20 0.62 2.57 1.00 0.95 1.95
C A 0.6 0.83 0.97 0.40 0.62 2.81 1.00 0.95 1.94
C A 0.8 0.89 0.94 0.43 0.65 2.90 1.00 0.95 1.94
C A 1.0 0.91 0.97 0.57 0.65 3.10 0.99 0.92 1.91
C A 1.2 0.94 0.97 0.64 0.69 3.25 0.99 0.89 1.88
C B 0.4 0.86 0.90 0.31 0.65 2.72 1.00 0.97 1.97
C B 0.6 0.86 0.93 0.50 0.65 2.94 1.00 0.97 1.97
C B 0.8 0.91 0.91 0.63 0.65 3.11 0.99 0.95 1.94
C B 1.0 0.94 0.94 0.69 0.73 3.31 0.99 0.95 1.94
C B 1.2 0.97 0.94 0.81 0.73 3.46 0.99 0.92 1.91
C C 0.4 0.91 0.75 0.72 0.58 2.96 1.00 1.00 2.00C C 0.6 0.91 0.78 0.78 0.65 3.13 1.00 0.97 1.97
C C 0.8 0.94 0.79 0.91 0.65 3.29 1.00 0.97 1.97
C C 1.0 0.97 0.85 0.94 0.69 3.46 1.00 0.95 1.94
C C 1.2 1.00 0.86 1.00 0.73 3.59 0.99 0.95 1.94
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Chapter 5
Conclusions
5.1. Summary of work
A research investigation or literature review was carried out which allowed for all the
necessary information for this project to be collected. This was followed by the calculation of
the mix designs.
Five mix designs were created using the Cement and Concrete Institute method for mix
design which was then used to evaluate the mixes. These mix designs were then used for all
tests that followed.
Each mix batch was mixed as two 20litre mixes and that concrete was then used to perform
the practical tests required. The slump test, slump retention test, viscosity test, air content test
were then performed.
The remained of the mix was then placed in cubes and left to cure for 3 days in order to
perform the cube strength test. After 3 days the cubes were weighed and crushed and their
strengths were recorded.
5.2. Main conclusions
Incompatibility due to overdosing only occurred with CEM A and SP A as well as with CEM
B and SP B both at a 1.2% dosage. Incompatibility due to under-dosing occurred for CEM A
and CEM B when the super-plasticiser was used at a 0.4% dosage.
The results showed that the slump test alone is not sufficient to specify the workability. A
low slump that is not pumpable can still be classified as a pumpable mix by viscosity. It is
therefore suggested that in future mixes are specified according to both slump and viscosity.
5.2.1. Slump
The general trend amongst the slump test results is that as the dosage of the super-plasticiser
increases the slump also increases. SP C consistently gave higher values for the slump, for all
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three cements, showing that it is more efficient at increasing slump than the other two super-
plasticisers
From the results obtained in this investigation it can be said that the three chosen cements are
compatible with the chosen super-plasticisers for dosages of between 0.6% and 1.0%. At a
dosage of 0.4% the two cements, CEM A and CEM B, with higher alkali contents had low
slumps and were no longer classified as pump-able slumps.
At the highest dosage tested of 1.2% CEM A and CEM B also proved to be incompatible
with SP A and SP B respectively. CEM B had a large increase in slump with SP A at a
dosage of 1.2%. This may indicate that at higher dosages the mix possibly will segregate and
be incompatible.
CEM C which had the lowest alkali content, showed compatibility for all the dosages tested
(0.4% to 1.2%). The slumps that were produced from the tests with the different super-
plasticisers all remained in the pump-able zone for slump tests, between 125mm and 175mm.
In figure 4.3 it can be seen that the change in dosage had similar affects on the slump for each
of the super-plasticisers tested. This result reinforces the robustness of the cement as
regardless of which of the polymer super-plasticisers it is being used with, the slump will
behave in a similar manner when increasing the dosage.
In terms of efficiency CEM C with SP C proved to be the most efficient. This was an
expected result as SP C was specified by the supplier as being the strongest in terms of
increasing the slump of a mix. From the information gathered in the literature review it was
also expected that the lower alkali cement would be more efficient.
5.2.2. Slump Retention
The slump retention was the best with SP A. This was true for all the cements, reinforcing the
fact that the low alkali cements have a similar compatibility with the super-plasticisers. SP C
had a loss in slump after 120 minutes. This is not as a result of the compatibility or efficiency
of the super-plasticiser with the chosen cements but rather the design of the super-plasticiser
by the manufacturer.
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The super-plasticiser that was based on the modified phosphonates polymer was more
efficient at retaining the slump. The polycarboxylate polymer super-plasticiser was not as
efficient in retaining the slump as it was designed to retain its slump up to 90 minutes.
5.2.3. Plastic Viscosity
Although when the super-plasticiser was used at a dosage of 0.4% with CEM A and CEM B
were not pumpable according to the slump test, it did fall into the category of pumpable
concrete when it was evaluated according to viscosity.
From the graphs of the Tattersall Two Point Tester Viscosity results it can be seen that the
shape of the graphs for CEM A and CEM B show a curve that flattens as dosage increases.
This suggests that the cement-super-plasticiser combination is reaching its limit in terms of
efficiency.
CEM C did not level off as the dosage was increased therefore it suggests that the cement
would still have an increase in efficiency for some dosages higher than 1.2%. The differences
in viscosity between super-plasticisers for CEM C were not as large as for the other two
cements, this shows that the cement is less sensitive than the other two higher alkali cements.
5.2.4. Air Content
The results for air content shows that CEM C had consistently lower amounts of air than the
other two cements. This may be signs of the difference in chemical reaction when the super-
plasticiser reacts with CEM C as opposed to the other two cements.
The higher air content in CEM A and CEM B did not relate to better values in viscosity or
slump as CEM C was still more efficient in this respect.
5.2.5. Hardened Properties
The density and strength were very similar in the results that they produced. This was to be
expected as a cube with a higher density should have more material in the cube giving it a
higher strength.
CEM C did not show a large variance in strength between the super-plasticisers. The cement
also proved to be more efficient and yielded results which showed CEM C had a higher
strength as compared to the CEM A or CEM B equivalents.
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5.3. Suggestions for further work
An investigation should be done into the use of these super-plasticisers with cements that are
more sensitive to changes than the low alkali cements that were used in this investigation.
Cements with higher alkali content may show a greater variance in results for a given super-
plasticiser. Also the test should be done with a varying W/C ratio to observe what effect it has
on compatibility.
Due to the Tattersall Two-Point Tester not having a definitive user manual, it is
recommended that an investigation in order to develop a standard test procedure. Also an
investigation should be done to produce a software program, which is compatible with the
Tattersall Two-Point Tester, to make data capture and calculations quicker and easier.
From the results of this report it is evident that the slump test alone is not accurate enough to
define concrete with a high workability. The Tattersall Two-Point Tester is too big to be used
on site and it requires a power source which may not be available on site. It is therefore
recommended that an investigation be done into a more suitable method for analysing
workability both in the lab and on site.
5.4. Outcomes satisfied
ECSA outcome 1: Competence to formulate and solve the Project Investigation problem
creatively and innovatively.
This was done by the selection of the necessary tests to be done. I.e. Tattersall Two Point
Test and the Air Content Test as well as creating a suitable mix design to use as a standard.
The use of the Efficiency Rating System aided in achieving the outcome.
ECSA outcome 2: Competence to apply relevant knowledge of mathematics, basic sciences
and/or engineering sciences to solve the Project Investigation problem.
The use and calibration of the viscosity test (Tattersall Two-Point Tester). This was also
shown during the mix design calculations, grading curve, Strength test results and the
graphing and reporting of captured data.
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ECSA Outcome 4: Competence to design and conduct investigations and/or data analyses.
This was shown in the tests that were performed during this investigation and the literature
researched. The use of spreadsheets to capture and evaluate the results obtained in the tests.
Conclusions and recommendations based on the results.
ECSA outcome 5: Competence to use relevant and appropriate engineering methods, skills
and tools as required by the Project Investigation problem.
All the tests that were performed were done according to engineering standards. This was
also shown during the mix design calculations, grading curve, Strength test results.
ECSA outcome 6: Competence to communicate effectively, both in writing and orally.
This report serves to represent written communication. A lot of the background information
obtained in order for testing to be done successfully was gathered by communications with
professionals in industry either by e-mail, telephonically or in person. An oral presentation
was done as well as a poster.
ECSA outcome 8: Competence to work effectively as an individual.
The structure of this project investigation set out by the university required that the project bean individual project.
ECSA outcome 9: Competence to engage in independent learning through well developed
learning skills?
The Tattersall Two-Point Tester and the Air Entrainment Meter were two pieces of apparatus
that was not used before. Therefore it was necessary for research to be done in order to
successfully use them.
ECSA Outcome 10: Critical awareness of the need to exercise judgment and take
responsibility within own limits of comp