drying shrinkage of high performance lightweight...
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DRYING SHRINKAGE OF HIGH PERFORMANCE LIGHTWEIGHT CONCRETE
By
PRAFULL VIJAY
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE IN CONSTRUCTION MANAGEMENT
UNIVERSITY OF FLORIDA
2017
© 2017 Prafull Vijay
To my family and friends who believed in my ability to work hard and always supported me throughout my studies
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ACKNOWLEDGMENTS
First and foremost, I would like to thank my thesis committee members, Dr. Larry
C. Muszynski, Dr. R. Raymond Issa, and Dr. Ravi Srinivasan for their continual
guidance through the process of this research. Their expertise in the field of Concrete
Technology and its application in the construction industry helped provide the
framework for this investigation. For their advice and direction, I am grateful.
I would like to thank the University of Florida Rinker School of Construction
Management and its faculty for giving me the intellectual tools to be successful in the
industry.
Finally, I would like to thank my family and friends for their support in everything I
have accomplished so far. Without you I would not have been able to achieve my goals.
I feel secure knowing I have such great people on whom I can depend.
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TABLE OF CONTENTS page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 7
LIST OF FIGURES .......................................................................................................... 8
ABSTRACT ................................................................................................................... 11
CHAPTER
1 INTRODUCTION .................................................................................................... 12
1.1 Background ....................................................................................................... 12 1.2 Problem Statement ........................................................................................... 12
1.3 Definition and Terminologies ............................................................................ 13 1.3.1 Internal Curing ......................................................................................... 13
1.3.2 Drying Shrinkage ..................................................................................... 13 1.3.2 Plastic Shrinkage ..................................................................................... 13
1.4 Scope of Study ................................................................................................. 14
2 LITERATURE REVIEW .......................................................................................... 15
2.1 Overview ........................................................................................................... 15 2.2 Shrinkage in Lightweight Aggregates and their Benefits ................................... 16 2.3 Use of Natural Pozzolans and Internal Curing as a Combination: Significant
Aid to shrinkage ................................................................................................... 17 2.4 Fly ash in Lightweight Aggregate Concrete and its Shrinkage Problems .......... 17
2.5 Early Age Shrinking and Surface Sealers ......................................................... 18 2.6 Internal Curing at Microscopic Level through X-Ray Absorption ....................... 19
3 METHODOLOGY ................................................................................................... 21
3.1 Overview ........................................................................................................... 21
3.2 Experimental Tests and Methods ..................................................................... 21
3.3 Phase I: Preliminary Tests for the Determination of the Mix Design ................. 23
3.3.1 Preparation of Samples ........................................................................... 23 3.3.2 Slump Test .............................................................................................. 26 3.3.3 Unit Weight of Concrete .......................................................................... 29 3.3.4 Compressive Strength ............................................................................. 31
3.4 Phase II: Main tests to Determine the Drying Shrinkage of High Performance Lightweight Aggregate Concrete .................................................... 33
3.4.1 Preparation of Samples ........................................................................... 33 3.4.2 Air Content .............................................................................................. 35
3.4.3 Drying Shrinkage ..................................................................................... 37
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3.4.4 Split Tensile Strength .............................................................................. 40
3.4.5 Compressive Strength ............................................................................. 42
4 RESULTS ............................................................................................................... 43
4.1 Physical Properties of Concrete ........................................................................ 43 4.2 Mechanical Properties of Concrete: .................................................................. 45 4.3 Drying Shrinkage .............................................................................................. 51
5 CONCLUSION ........................................................................................................ 58
5.1 General ............................................................................................................. 58 5.2 Physical Properties ........................................................................................... 58
5.3 Mechanical Properties ...................................................................................... 58
6 RECOMMENDATIONS AND SUGGESTIONS ....................................................... 59
LIST OF REFERENCES ............................................................................................... 60
BIOGRAPHICAL SKETCH ............................................................................................ 62
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LIST OF TABLES
Table page 3-1 Mix Design Proportion for the saturated surface dry coarse aggregates for
preliminary samples ............................................................................................ 23
3-2 Physical and Mechanical Properties of preliminary concrete batches ................ 33
3-3 Mix design proportion for the saturated surface dry coarse aggregates for main samples ..................................................................................................... 34
4-1 Physical Properties of prepared batches of concrete ......................................... 43
4-2 Compressive Strength of the main samples ....................................................... 45
4-3 Split Tensile Strength of the main samples ........................................................ 47
4-4 Percentage of Split Tensile to Compression ....................................................... 49
4-5 Specimen Reading for 10,000 psi 1st batch ........................................................ 51
4-6 Specimen Reading for 4,500 psi 1st batch .......................................................... 52
4-7 Specimen Reading for 10,000 psi 2nd batch ....................................................... 52
4-8 Specimen Reading for 4,500 psi 2nd batch ......................................................... 53
4-9 Specimen Reading for 10,000 psi 3rd batch ........................................................ 54
4-10 Specimen Reading for 4,500 psi 3rd batch .......................................................... 54
4-11 Average Percentage shrinkage of the main concrete samples for Drying Shrinkage Test ................................................................................................... 55
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LIST OF FIGURES
Figure page 2-1 Conceptual illustration of the differences between external and internal
curing. ................................................................................................................. 18
3-1 Research Methodology process ........................................................................ 22
3-2 Prepared concrete in the cylindrical mold .......................................................... 24
3-3 Cast cylinder samples kept for 7-day curing ...................................................... 24
3-4 Concrete mixer .................................................................................................. 25
3-5 Concrete Cylinder mold ..................................................................................... 25
3-6 Slump cone container ........................................................................................ 26
3-7 Slump cone container and tampering rod .......................................................... 27
3-8 Figure showing the way slump was being tested ............................................... 27
3-9 Figure showing the method to measure slump .................................................. 28
3-10 Slump values for different mix designs .............................................................. 28
3-11 Unit Weight Test ................................................................................................ 29
3-12 Recently smoothed surface of fresh concrete for Unit Weight test .................... 30
3-13 Graph showing the unit weight test results for different mix designs ................. 30
3-14 Graph showing the 7 -day compressive strength of different mix design ........... 31
3-15 Forney Pilot Testing Machine ............................................................................ 32
3-16 Cylinder in Compression ................................................................................... 32
3-17 Moist aggregates in the upright concrete mixer before the addition of cement .. 34
3-18 Freshly prepared concrete from the moist aggregates after the addition of cement ................................................................................................................ 34
3-19 Cast samples kept in saturated calcium hydroxide for curing ............................ 35
3-20 Air Content Apparatus ....................................................................................... 36
3-21 Test showing the air content of freshly prepared batch of concrete................... 37
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3-22 Two gang mold of size ....................................................................................... 38
3-23 Prisms kept in saturated calcium hydroxide water for moist curing ................... 39
3-24 Prepared prisms of size ..................................................................................... 39
3-25 Prisms with the gage studs ................................................................................ 40
3-26 Split Tensile Strength Testing ............................................................................ 41
3-27 Fracture Point .................................................................................................... 41
3-28 Compressive Strength Testing .......................................................................... 42
4-1 Graph showing the slump results for different mix designs ............................... 44
4-2 Graph showing the unit weight results for different mix designs ........................ 44
4-3 Graph showing the air content results for different mix designs ........................ 45
4-4 Graph showing the 7-day and 28-day compressive strength values of main samples .............................................................................................................. 46
4-5 Fracture Point or Yield Point (Compressive Strength Test) ............................... 46
4-6 Graph showing 7-day Compressive Strength range and average ..................... 47
4-7 Graph showing 28-day Compressive Strength range and average ................... 47
4-8 Figure showing the 7-day and 28-day split tensile strength values of main samples .............................................................................................................. 48
4-9 Fracture Point or Yield Point (Split Tensile Strength) ........................................ 48
4-10 Proportions of aggregate as shown in the cylinder split in two equal halves in split tensile testing .............................................................................................. 49
4-11 Graph showing 7-day Split Tensile Strength range and average....................... 49
4-12 Graph showing 28-day Split Tensile Strength range and average..................... 50
4-13 Graphical Representation for specimen reading 10,000 psi 1st batch ............... 51
4-14 Graphical Representation for specimen reading 4,500 psi 1st batch................. 52
4-15 Graphical Representation for specimen reading 10,000 psi 2nd batch ............... 53
4-16 Graphical Representation for specimen reading 4,500 psi 2nd batch ................. 53
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4-17 Graphical Representation for specimen reading 10,000 psi 3rd batch ............... 54
4-18 Graphical Representation for specimen reading 4,500 psi 3rd batch ................. 55
4-19 Length change value graphical representation for 4,500 psi specimen ............. 55
4-20 Length change value graphical representation for 10,000 psi specimen ........... 56
4-21 Comparator Reading ......................................................................................... 56
4-22 Graphical representation and comparison of drying shrinkage values of all prepared batches ................................................................................................ 57
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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science in Construction Management
DRYING SHRINKAGE OF HIGH PERFORMANCE LIGHTWEIGHT CONCRETE
By
Prafull Vijay
August 2017
Chair: Larry Muszynski Co-chair: Raymond R. Issa Major: Construction Management
The subject of this thesis is to utilize high performance lightweight aggregate
concrete that has robust mechanical and physical properties which are achieved by
having a high cement content, while keeping its drying shrinkage low as opposed to the
usual pattern of high cementitious content concrete having significant drying shrinkage
that leads to cracking.
Two different mix designs were selected with two different proportions of all the
ingredients, which were 8,000 psi and 10,000 psi inch for the preliminary tests. Based
on results of the slump, unit weight and compressive strength tests, 10,000 psi inch mix
design was chosen and then another mix design along, 4,500 psi was selected for the
main tests like slump, unit weight, air content, compressive strength, split tensile and
drying shrinkage.
A total of 60 samples were poured, cured and tested: 24 for drying shrinkage and
36 for compressive strength and split tensile. The samples had the following properties:
Slump value ranging from 1 inch to 6.5 inches, Unit weight from 113.8 lbs./ cu. ft. to
128.0 lbs./ cu ft., air content ranging from 1.5% to 3.5%.
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CHAPTER 1 INTRODUCTION
1.1 Background
Lightweight Aggregate Concrete (LWAC) is a necessity in today’s construction
world where sustainability is prioritized. Lightweight aggregate is not only
environmentally sustainable but it is also a cost-effective way of building structures.
Unlike conventional aggregates, the materials used to manufacture lightweight
aggregates are by-products that are usually considered useless in various other
industries, but which are very useful for lightweight aggregates. Also as technology in
construction is shifting to the development of high rise buildings in densely populated
urban areas, problems arise due to the massive weight that each building foundation
must support. On the other hand, lightweight concrete elements can be used to solve
the problem of heavy loads on foundations and this research will be increasingly of
greater importance. High strength lightweight concrete will be useful in making
structures like floating islands on which aircraft can land and take off easily and which
can even support small cities. In other words, structures that can bear shock loads and
have high strength to weight ratios can be manufactured with this process
1.2 Problem Statement
The objective of this research will be to evaluate the drying shrinkage potential of
high strength lightweight concrete having compressive strengths ranging from 6,000 psi
to 10,000 psi. Generally, lightweight aggregate is made up of clay or shale which helps
in reducing the self-weight of the concrete. As the high strength of concrete demands a
large amount of cementitious material, it creates shrinkage problem in these types of
concrete. There are various types of shrinkage like drying shrinkage, plastic shrinkage,
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autogenous shrinkage and chemical shrinkage. All of these types of shrinkage can lead
to cracks in concrete in early age and also in later age. The reason behind shrinkage is
high-water cement ratio or high cementitious content which reduces the moisture
amount in concrete leading to development of cracks in it. For this, a method known as
“Internal Curing” has been used which has the potential to solve the problem of
shrinkage. It is a way of transferring moisture through aggregates to paste or mortar.
Also, it will reduce the significant waste of water and use of large spaces as required in
conventional methods of curing like jute bag curing, water curing and steam curing.
1.3 Definition and Terminologies
1.3.1 Internal Curing
Internal curing is defined as the movement of moisture from pre-wetted
aggregates to the cement paste or mortar through capillary actions between paste and
aggregate. It is a way to ensure that the concrete will have enough water to prevent the
deleterious effects of shrinkage by providing a continuous supply of water, thus keeping
the water-cement ratio stable.
1.3.2 Drying Shrinkage
It is defined as the contraction in concrete due to loss of capillary moisture. It
develops some tensile stress which leads to cracks in concrete before concrete face
any loading.
1.3.2 Plastic Shrinkage
It is defined as the loss of moisture in concrete due to external factors like high
temperature, high rate of evaporation, etc. It causes the concrete to lose all moisture
before it sets.
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1.4 Scope of Study
The area of the study for this research is to utilize lightweight aggregates and
incorporate them in high strength lightweight concrete which will help reduce the
concrete drying shrinkage by providing moisture through capillary action of aggregates
known as internal curing method. The aggregates will be utilized so that they can
achieve a compressive strength as required for high impact loads in massive
construction. This research will investigate the effects of cement content on drying
shrinkage for high strength lightweight concrete in the construction industry.
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CHAPTER 2 LITERATURE REVIEW
2.1 Overview
Lightweight Aggregate Concrete (LWAC) is not the latest innovation in the
concrete industry. In fact, it has been used since antiquity. Due to its minimal weight
and high strength factors, lightweight concrete is preferred more than the conventional
concrete. Numerous papers have been published to acquaint the construction industry
with the beneficial aspects of lightweight concrete like the use of these innovative
concrete in tall structures, floating docks and so forth. Today, one of the major concerns
in the concrete industry for lightweight concrete is generally its shrinkage problem with
the demand of high strength. High strength LWAC demands more cementitious material
which will increase the water-cement ratio and thus increased drying shrinkage and
plastic shrinkage. This consequently, leads to cracks in the concrete a dire problem in
need of a solution. However, much research has been done on internal curing which
has explained how it works, how it reduces the cost of manufacturing lightweight
aggregate, and also how it will increase the strength of the concrete. The motivation for
this study was to obtain data that will help us deal with the shrinkage problem of high
strength, lightweight concrete by developing internal curing technique. In addition, this
study will measure the adsorption potential of manufactured lightweight aggregates,
which will transfer the water for curing internally from aggregates to concrete or mortar.
The strength of these lightweight aggregates and their strength in concrete has also
been discussed.
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2.2 Shrinkage in Lightweight Aggregates and their Benefits
Every perfect concrete structure has some amount of shrinkage in it. Though the
amount varies with the water-cement ratio, external factors during curing like ambient
temperature, the amount of cement, etc. lead to the loss of water in concrete. However
internal curing helps improve the shrinkage by transfer of moisture or hydration of the
concrete through pre-wetted aggregates. Dayalan J, Buellah. M (2014) studied that
ameliorated hydration greatly reduces the cracks in concrete because of internal
hydration. They also showed that compressive strength also gets improved by internal
curing by not a marginal difference but a good significant amount. They used expansive
shale as lightweight aggregates as a replacement for coarse aggregate by 10%, 15%,
20% and 25%, which increases the degree of hydration resulting in solid microstructure
resulting in better curing for the lightweight aggregate concrete. They also performed
compressive tests on the concrete made with these artificial aggregates which revealed
that concrete had more strength after 21 and 28 days than after 7 days due to internal
curing which was not the case in conventional curing. Their concrete samples
possessed a higher relative humidity in the pore structure, which reduced the internal
drying. This created a stronger and more durable concrete.[1] Cortas, R. et al. (2014)
studied the early age properties showed that the behavior of concrete depends on the
amount of water added to the concrete mortar during mixing i.e. the water content of
concrete. The tests that they conducted showed that concrete containing aggregates
with intermediate saturation showed early stage behavior that was different from the
samples with low or high saturation. It essentially had the highest autogenous shrinkage
and plastic shrinkage as compared to the other different saturated shrinkage samples.
The explanation lay in the amount of water in the intermediate saturated sample. Also, it
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cannot take benefits from aggregates through internal curing like in the case of high
saturated samples[2]. De la Varga, I. et al. (2012) found that low water-cement ratio
increases the physical and mechanical properties of concrete although at the same time
it increases the shrinkage problem, but can be reduced by the technique of internal
curing. Therefore, it will be an aid to self-desiccation through the process of internal
curing, which will greatly decrease autogenous shrinkage and cracking potential
speeding up the reaction of fly ash as shown in Figure 2-1. The results satisfied the
objective of the study, showing that the compressive strength increased with a reduction
in the water-cement ratio. [3].
2.3 Use of Natural Pozzolans and Internal Curing as a Combination: Significant Aid to shrinkage
Natural pozzolans are abundant natural substances generally found in the earth
like volcanic glass and pumice, etc. Natural pozzolans are significant replacements to
Ordinary Portland Cement (OPC). They improves workability and compressive strength
of concrete as well as reduces permeability of concrete, improving its durability. The
only factor that affects the use of Natural Pozzolans over OPC is that they require
hydration of concrete for a longer time which can be fulfilled with internal curing method
[4]. Moreover, it is not only mechanical properties that improve through this combination,
but also the concrete becomes less permeable at the pore level structure, consequently
leading to the reduced percolation and ingress of chloride ions, which would reduce the
durability of the concrete especially in reinforced concrete structures [5].
2.4 Fly ash in Lightweight Aggregate Concrete and its Shrinkage Problems
Use of fly ash, especially in relatively high concentrations, exerts significant
influence on the physical and mechanical properties of concrete. High Volume Fly Ash
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(HVFA) is on its way to be preponderant in the construction of bridges and in sidewalks.
By including fly ash in optimum quantities, constructors can fashion concrete that has a
lower self-weight and higher strength. Fly ash is also environmentally sustainable to
produce. However, use of HVFA presents serious risks for shrinkage and cracking
problems at early age strength, issues that are usually addressed by the use of internal
curing method. This method greatly reduces problems stemming from autogenous
shrinkage.
Figure 2-1.Conceptual illustration of the differences between external and internal curing. [Source: De la Varga, I. et al. (2012). “Application of internal curing for mixtures containing high volumes of fly ash.” Cement & Concrete Composites, 34(9), 1001–1008.]
2.5 Early Age Shrinking and Surface Sealers
Shi, X. et al. (2015) showed that surface sealers greatly benefit concrete in early
stage growth as early age drying greatly reduces any advantages of using internal
curing to reduce shrinkage and cracking. Proper surface sealers in conjunction with
internal curing not only improves the shrinkage process, but also increases the 28-day
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compressive strength and the split tensile strength. It preserves moisture content, which
mitigates the moisture loss and shrinkage in the concrete, and preserves the benefits of
internal curing, which itself reduces the amount of water that dry mortar will absorb.
2.6 Internal Curing at Microscopic Level through X-Ray Absorption
Internal curing is one of the best techniques for overcoming plastic and drying
shrinkage problems and a large body of research explains its mechanism and its
benefits as well as its limitations. However, very little research exists to illustrate this at
the microscopic level until Henkensiefken, R. et al. (2011) showed that the mechanisms
at the microscopic level by using the "X-Ray Adsorption" method. This works on the
principle that less dense material absorbs fewer X-rays and reflects more of them.
Therefore, as soon as water levels fall in the Lightweight Aggregate sample, the
sample's rate of X-ray adsorption falls in tandem. X-ray adsorption also measures the
distance water has traveled from aggregates to mortar.
While internal curing is a way of transferring moisture from LWA to paste, there is
a way of reverse this process when aggregates with respectively different moisture
contents are used. Some aggregates were oven-dried, for example, with a certain
moisture content and they were capable of drawing water from paste prior to setting and
returning it after setting when the paste required it. This greatly reduces the need to pre-
wetting the aggregates and it improves the mechanical properties by a significant
margin (chiefly, a higher compressive strength) due to the high hydration value and low
permeability (conductivity), which lead to more durable concrete.
While internal curing is overall a better method than conventional curing, it
sometimes carries non-negligible downsides, like loss of mass or reduced air
permeability. However, with the usage of the correct sizes and types of aggregate
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material, this can be overcome. Sometimes, by introducing the internal water as a
curing reservoir, strength and durability of concrete can be affected in a negatively, but
not devastatingly so. The advantages outnumber the disadvantages, resulting in the
general recommendation to use internal curing in high strength lightweight aggregate
concrete.
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CHAPTER 3 METHODOLOGY
3.1 Overview
The objective behind this study is to find out that if there is a significant drying
shrinkage difference between high strength lightweight concrete and normal weight
lightweight concrete. Pre-wetted aggregates are used for internal curing before they are
incorporated into concrete. The pores in the aggregates are the medium through which
moisture moves from the aggregates to the mortar. The experimental procedure in this
study is as follows. Concrete specimens were prepared with different types of materials
using different mix designs. Each of these concrete samples were compared in order to
determine which would be better suited in actual field service. Based on results, it can
be deduced which technique and which materials are more effective in reducing
shrinkage for high performance concrete. A High Performance Concrete (HPC) is a
conventional concrete by definition, but it has a different mix proportion using the same
materials to obtain a better workability, durability and strength required for the structural
and environmental need of the structure or project. The principal difference between
normal and high performance concrete is that ability of the latter to combine workability,
strength and performance.
3.2 Experimental Tests and Methods
Six different concrete specimens, were tested to measure their physical and
mechanical characteristics. These tests were performed in accordance with the
procedures of the American Society of Testing Materials (ASTM) which specified the
specimen size, the conditions of testing and curing, for example. The samples were
made to test their Compressive Strength (ASTM C 39), Split Tensile Strength (ASTM C
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496) and Drying Shrinkage Capacity (ASTM C 157). These specimens were cured for
the standardized testing periods which were 3,7,14 and 28 days. The durability of
concrete is usually associated with plastic and drying shrinkage. Thus, it is very
important to have a good durability for a high-performance concrete because drying
shrinkage greatly affects the strength and durability of concrete. Generally, high-
performance concrete has a water content less than 0.4 to make the concrete more
durable. To maintain the low water content problem, the superplasticizer is used while
manufacturing the high-performance concrete.
For each test six samples were prepared for each of the 6 types, giving 36
individual specimens, the mechanical properties of the specimen wereanalyzed and
their results will be plotted on a strength v/s time graph and shrinkage at standard
curing days at the 3 day, 7 day, 14 day and 28 day marks. The research methodology
process is shown in Figure 3-1
Figure 3-1. Research Methodology process
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3.3 Phase I: Preliminary Tests for the Determination of the Mix Design
This part describes about the all the tests performed for the determination of the
mix design that was used in further tests for the determination of the compressive
strength, split tensile, drying shrinkage and other properties of concrete to analyze the
lightweight concrete performance. As, discussed in the chapter 2, the objective of this
research is to utilize lightweight concrete which has low drying shrinkage and has the
high performance in its physical and mechanical properties.
3.3.1 Preparation of Samples
Following is the notation for the two different mix designs used for the
manufacturing of preliminary samples to determine the mix design for further
investigation like drying shrinkage and other mechanical and physical properties:
• 8,000 psi strength concrete with coarse aggregate size of ½ inch – 8,000 A
• 10,000 psi strength concrete with coarse aggregate size of ½ inch – 10,000 A Table 3-1. Mix Design Proportion for the saturated surface dry coarse aggregates for
preliminary samples (per cubic yard)
Mix ID Cement (Portland) (lbs)
Water (lbs) Coarse Aggregate (lbs)
Fine Aggregate (lbs)
Admixture – ADVA 140 (mL)
8,000 A 796.9 255.0 907.2 1259.9 4779.0 10,000 A 907.4 245.0 907.2 1327.4 5427.0
NOTE: ADVA is a high-range water reducing liquid admixture.
The freshly prepared concrete batches were tested for slump and unit weight test
in accordance with ASTM C 143 and ASTM C 138 respectively.
These samples were cast in cylindrical molds of diameter of 4 inches and height
of 8 inches. A tamper rod of diameter 3/8 inches, a 78 Hz frequency vibrating table was
used for compaction. The curing and casting of samples were done in accordance with
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ASTM C 192. The samples were cured for 7 days and their compressive strength was
tested in accordance with ASTM C 39.
Figure 3-2. Prepared concrete in the cylindrical mold (Photo courtesy of author)
Figure 3-3. Cast cylinder samples kept for 7-day curing (Photo courtesy of author)
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Figure 3-4. Concrete mixer (Photo courtesy of author)
Figure 3-5. Concrete Cylinder mold (4”x 8” in size) (Photo courtesy of author)
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3.3.2 Slump Test
The slump test was performed as per ASTM C 143 (Standard Test Method for
Slump of Hydraulic-Cement Concrete). The freshly prepared concrete batch was poured
into the mold in the shape of frustum of a cone with an 8-inch diameter base, a 4-inch
diameter top, measuring 12 inches in height as shown in Figure 3-6.
Figure 3-6. Slump cone container (side view and top view) (Photo courtesy of author)
The concrete that was poured in the mold held firmly on a flat surface in three
layers and after each layer was compacted by a tampering rod of 3/8 inch of diameter
by 25 times uniformly over cross section of frustum. When the frustum was filled with
concrete, the excess concrete was scraped off and the top surface was smoothened by
the tampering rod. The mold was held down completely during the filling of concrete and
immediately after the mold was lifted directly upwards in a stable manner. The slump
was determined by measuring the distance between the top of the mold and the new
central position of concrete specimen as shown in Figure 3-3 and 3-4.
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Figure 3-7. Slump cone container and tampering rod (Photo courtesy of author)
Figure 3-8. Figure showing the way slump was being tested (Photo courtesy of author)
28
Figure 3-9. Figure showing the method to measure slump (Photo courtesy of author)
Following is the graph showing the slump values for the above mentioned mix
designs mentioned.
Figure 3-10. Slump values for different mix designs
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9
0
2
4
6
8
10
12
Samples
Slu
mp
Val
ue
(in
ches
)
MiX ID
Slump (inches)
8000 psi with 1/2 inch aggregate
10000 psi with 1/2 inch aggregate
29
3.3.3 Unit Weight of Concrete
This test was performed as per ASTM C 138 [Standard Test Method for Density
(Unit Weight), Yield, and Air Content (Gravimetric) of Concrete]. The freshly prepared
batch of concrete was poured in three equal fractions into the cylindrical container made
up of steel, compacted by the tamper rod and the sides of cylinder was tapped 10 times.
After filling of concrete in the cylinder, extra concrete was scrapped off and the top
surface was smoothed using the flat strike off plate as shown in Figure 3-4. The weight
of the container was noted before and after being filled with concrete.
Figure 3-11. Unit Weight Test (weight measure) (Photo courtesy of author)
The unit weight of the concrete was calculated using the equation 3-1.
D = 𝑀𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒−𝑀𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑒𝑟
𝑉𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑒𝑟 (3-1)
• Mconcrete – Mass of container filled with concrete
• Mcontainer – Mass of container
• Vcontainer – Volume of container
• D – Unit weight of concrete
30
Figure 3-12. Recently smoothed surface of fresh concrete for Unit Weight test (Photo courtesy of author)
Following is the graph of unit weight values for the mentioned two mix designs.
Figure 3-13. Graph showing the unit weight test results for different mix designs
123.8
117.4
114
116
118
120
122
124
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Samples
Un
it W
eigh
t V
alu
e (l
bs/
cu.f
t.)
Mix ID
Unit Weight (lbs/cu.ft.)
8000 psi with 1/2 inch aggregate
10000 psi with 1/2 inch aggregate
31
3.3.4 Compressive Strength
The compressive strength was done according to ASTM C 39 (Standard Test
Method for Compressive Strength of Cylindrical Concrete Specimens). The
compressive strength was tested with the “Forney FX 250-Pilot Model” of capacity
300,000 lbsf. The machine was set to a constant load of 7 lbs/sec.
The compressive strength [(C) in psi] was determined by the following formula:
C = 𝑃 (𝐿𝑜𝑎𝑑 𝑖𝑛 𝑙𝑏𝑠)
𝐴 (𝐶𝑟𝑜𝑠𝑠−𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 𝑖𝑛 𝑠𝑞𝑢𝑎𝑟𝑒 𝑖𝑛𝑐ℎ) (3-2)
The specimens were cured for 7 days in a saturated calcium hydroxide solution tank.
Following is the graph of 7-day compressive strength:
Figure 3-14. Graph showing the 7 -day compressive strength of different mix design
8041.68
10165.31
0.00
2000.00
4000.00
6000.00
8000.00
10000.00
12000.00
Samples
Co
mp
ress
ive
Stre
ngt
h V
alu
e (p
si)
Mix ID
7 - Day Compressive Strength (psi)
8000 psi with 1/2 inch aggregate
10000 psi with 1/2 inch aggregate
32
Figure 3-15. Forney Pilot Testing Machine (Photo courtesy of author)
Figure 3-16. Cylinder in Compression (Photo courtesy of author)
33
Hence, it was decided to proceed with the 10,000 psi lightweight concrete with ½
inch aggregate for further investigations into aspects like physical, mechanical
properties and drying shrinkage potential.
Following is the tabulation of respective properties of the concrete.
Table 3-2. Physical and Mechanical Properties of preliminary concrete batches
Mix ID Slump (in inches) Unit Weight (in lb/cu. ft.) Compressive Strength (in psi)
8000A 11.00 123.8 8040
10000A 9.00 117.4 10170
3.4 Phase II: Main tests to Determine the Drying Shrinkage of High Performance
Lightweight Aggregate Concrete
This section describes the tests that were done on two different mix designs for
4,500 psi and 10,000 psi using ½ inch aggregate to determine their drying shrinkage,
compressive strength at 7 and 28 days, split tensile strength at 7 and 28 days, air
content and other physical and mechanical properties explained in detail below. As,
mentioned earlier this research focused on the performance of the concrete and the
same time analyzed its shrinkage capacity.
3.4.1 Preparation of Samples
Two different mix designs were taken into consideration and three different
batches of each mix design were made, on three separate days, for a total for six
batches. Following are the IDs and their notations for both mix designs:
• 10A, 10B, 10C: Concrete producing compressive strength of 10,000 psi.
• 4.5A, 4.5B, 4.5C: Concrete producing compressive strength of 4,500 psi.
Note: A, B, C are the batches for each mix design.
Following is the content and their proportion for each mix design:
34
Table 3-3. Mix design proportion for the saturated surface dry coarse aggregates for main samples (per cubic yard)
Mix ID Cement (Portland) (lbs)
Water (lbs)
Coarse Aggregate (lbs)
Fine Aggregate (lbs)
Admixture – ADVA 140 (mL)
10A, 10B, 10C 907.4 245.0 907.2 1327.4 5427.0 4.5A ,4.5B, 4.5C 715.0 295.0 900.0 1235.0 -
The freshly prepared concrete batches were tested for slump, unit weight test
and air content in accordance with ASTM 143, ASTM 138 and ASTM 173 respectively.
Figure 3-17. Moist aggregates in the upright concrete mixer before the addition of
cement (Photo courtesy of author)
Figure 3-18. Freshly prepared concrete from the moist aggregates after the addition of cement (Photo courtesy of author)
35
Figure 3-19. Cast samples kept in saturated calcium hydroxide for curing (Photo courtesy of author)
These samples were cast in cylindrical molds with a diameter of 4 inches and
height of 8 inches, and tested for compressive strength with a split tensile strength in
accordance with ASTM C 39 and ASTM C 496 and in a two gang mold with a 2- square
inch cross-section and a length of 11 ¼ inches. Their drying shrinkage was tested as
per California Test 537, “Method of Test for the Drying Shrinkage of Lightweight
Concrete.” A tamper rod of diameter 3/8 inches, a 78 Hz frequency vibrating table was
used for compaction. The curing and casting of samples was done in accordance with
ASTM C 192. The cylinders were cured for 7 days and 28 days for split tensile strength
and compressive strength and the prisms were cured for 7 days, 14 days, 28 days and
35 days.
3.4.2 Air Content
This test was performed as per ASTM C 173 (Standard Test Method for Air
Content of Freshly Mixed Concrete by the Volumetric Method). The freshly prepared
batch of concrete was poured in the measuring container of the air content apparatus in
two equal layers rodded 25 times each and tapped with a mallet around the side of the
36
container 10 times. The extra concrete was scrapped off with a flat smoothened plate
until it was flush with the top of the measuring bowl. The top meter of the inside of the
container, including the gasket was wetted. Water was added until it appeared at the
graduated neck of the top section. As soon as it matched the zero level, the addition of
water stopped.
The top meter of the container was inverted and shaken for 2-3 times in 45
second sessions with 5-seconds intervals between. It was rolled by holding the neck of
the section at an angle of 45° in ¼ to ½ revolutions back and forth.
After few minutes of stabilization of the liquid, the air content was calculated by
observing the markings of the water level and using the following formula:
A = AR – C + W (3-3)
• Where A = Air Content, %
• AR = Final meter Reading, %
• C = Correction Factor
• W = Number of calibrated cups of water added to meter.
Figure 3-20. Air Content Apparatus (Photo courtesy of author)
37
Figure 3-21. Test showing the air content of freshly prepared batch of concrete (Photo courtesy of author)
As, there was no addition of alcohol and the air content did not exceed 9% of the meter-
long section giving a value of zero for C and for W.
3.4.3 Drying Shrinkage
This test was performed as per California Test 537, “Method of Test for the
Drying Shrinkage of Lightweight Concrete.” The freshly batch prepared concrete was
molded in the two gang molds.
When the specimen was demolded after 24 hours, it was measured by a length
comparator apparatus and that reading was noted as “initial CRD”. The samples were
kept in a moist atmosphere for 23 ½ ± ½ hours before demolding and then the samples
were wet cured for 7 days and then dry cured for 7 days, 14 days and 28 days.
At 7 days, 14 days and 28 days of drying (14 days, 21 days and 35 days after
demolding) they were again measured with the length comparator apparatus and the
38
readings were noted as new CRD values at different ages. The length change (ΔLx) was
calculated as follows:
ΔLx = 𝐶𝑅𝐷−𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝐶𝑅𝐷
𝐺 x 100 (3-4)
Where,
• CRD – difference between the specimen reading and the reference bar reading at any age
• Initial CRD - difference between the specimen reading and the reference bar just after demolding
• G – gage length (10 inches)
• ΔLx – Length change of specimen in %
Figure 3-22. Two gang mold of size (2”x2”x11¼“) (Photo courtesy of author)
39
Figure 3-23. Prisms kept in saturated calcium hydroxide water for moist curing (Photo courtesy of author)
Figure 3-24. Prepared prisms of size (2”x2”x11¼”) (Photo courtesy of author)
40
Figure 3-25. Prisms with the gage studs (Photo courtesy of author)
After getting all the values of length change (ΔLx) the drying shrinkage values
were reported as the difference of length at 7 days and 21 days.
3.4.4 Split Tensile Strength
The split tensile strength test was performed as per ASTM C 496 (Standard Test
Method for Splitting Tensile Strength of Cylindrical Concrete Specimens). The
compressive strength was tested with the “Forney FX 250/300 testing machine”. The
machine was set to a constant force of 100 psi/min – 200 psi/min.
The split tensile strength [(T) in psi] was determined using the following formula:
T = 2𝑃
𝜋𝑙𝑑 (3-5)
Where,
• P = Max. Load before specimen breaks (lbs.)
• l = Length of specimen (inches)
• d = Diameter of specimen (inches)
41
Figure 3-26. Split Tensile Strength Testing (Photo courtesy of author)
The specimens were cured for 7 days and 28 days in a saturated calcium
hydroxide solution tank. Following is the graph of 7-day and 28-day split-tensile strength
values.
Figure 3-27. Fracture Point (Photo courtesy of author)
42
3.4.5 Compressive Strength
The specimens were cured for 7 days and 28 days in a saturated calcium
hydroxide solution tank. Following is the graph of 7 days and 28 days compressive
strength:
Figure 3-28. Compressive Strength Testing (Photo courtesy of author)
43
CHAPTER 4 RESULTS
In this study, the test results were reported in Microsoft Excel. The various tests
that were performed on concrete samples were split tensile, compressive strength,
drying shrinkage and plastic shrinkage.
Often, in concrete research studies, these data are compared with a benchmark
to find out whether the objectives have been successfully achieved or not. It is easier to
understand the results in a graphical form rather than from a table.
The visualization also helps in better understanding stress formation in concrete
in a space-time configuration. There are many different combinations of such simulation
graphical representations, like stress-strain formation over time and space
configuration, or over amount of materials added, or different curing conditions for
different durations.
4.1 Physical Properties of Concrete
Freshly prepared batches of concrete were tested for their physical properties
and after testing had the following values as shown in Table 4-1
Table 4-1. Physical Properties of prepared batches of concrete
Mix ID Slump (in inches) Unit Weight (in lbs/cu. ft.) Air Content (in %)
4.5 A 6.50 124.6 1.50
4.5 B 6.25 122.8 1.50
4.5C 4.00 116.8 1.50
10 A 1.00 113.8 3.50
10 B 4.50 128.0 2.50
10 C 1.50 127.0 2.75
44
Following is the graphical representation of those values:
Figure 4-1. Graph showing the slump results for different mix designs
Figure 4-2. Graph showing the unit weight results for different mix designs
1.00
4.50
1.50
6.506.25
4.00
1ST BATCH 2ND BATCH 3RD BATCH
Slu
mp
(in
che
s)
Samples
Slump Test
10,000 psi
4,500 psi
113.8
128.0127.0
124.6
122.8
116.8
1ST BATCH 2ND BATCH 3RD BATCH
Un
it W
eig
ht
(lb
./cu
. ft
.)
Samples
Unit Weight Test
10,000 psi
4,500 psi
45
Figure 4-3. Graph showing the air content results for different mix designs
The above values clearly indicate that the workability for the 10B and 4.5C batch
was well above board as the values of slump was very near to the required value.
Additionally, the value of unit weight for the corresponding batch also fell within
acceptable parameters. According to ASTM C 138, the required unit weight values for
the slump ranging from 3 inches to 6 inches should be 115 lbs./ cu. ft. to 155 lbs./ cu. ft.
which specimens did.
The air content values for the corresponding batch also indicate that the concrete
was well compacted and has fewer pores as compared to the other batches.
4.2 Mechanical Properties of Concrete:
Table 4-2. Compressive Strength of the main samples
Mix ID 7- Day (Min)
7-Day (Max)
7-Day (Avg)
28-Day (Min)
28-Day (Max)
28-Day (Avg)
4.5A 4250.00 5810.00 4,720.00 6280.00 7260.00 6,770.00
4.5B 4630.00 4820.00 4,730.00 7100.00 7240.00 7,170.00
4.5C 5590.00 5710.00 5,650.00 7610.00 7950.00 7,780.00
10 A 9210.00 10060.00 9,640.00 9880.00 10030.00 9,950.00
10 B 10540.00 9700.00 10,200.00 10020.00 10150.00 10,080.00
10 C 8540.00 9090.00 8,820.00 9920.00 10110.00 10,020.00
3.50
2.502.75
1.50 1.50 1.50
1ST BATCH 2ND BATCH 3RD BATCH
Air
Co
nte
nt
(%)
Samples
Air Content Test
10,000 psi
4,500 psi
46
Figure 4-4. Graph showing the 7-day and 28-day compressive strength values of main samples
Figure 4-5. Fracture Point or Yield Point (Compressive Strength Test) (Photo courtesy of author)
0
2000
4000
6000
8000
10000
12000
0 7 2 8
CO
MP
RES
SIV
E ST
REN
GTH
(IN
PSI
)
TIME (IN DAYS)
COMPRESSIVE STRENGTH
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
47
Figure 4-6. Graph showing 7-day Compressive Strength range and average
Figure 4-7. Graph showing 28-day Compressive Strength range and average
4000.00
5000.00
6000.00
7000.00
8000.00
9000.00
10000.00
11000.00
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
CO
MP
RES
SIV
E ST
REN
GTH
(P
SI
MIX ID
7-Day Compressive Strength and Average
7 (Avg.)
6000.00
6500.00
7000.00
7500.00
8000.00
8500.00
9000.00
9500.00
10000.00
10500.00
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
CO
MP
RES
SIV
E ST
REN
GTH
(P
SI)
MIX ID
28-Day Compressive Strength Range and Average
28 (Avg.)
48
Table 4-3. Split Tensile Strength of the main samples
Mix ID 7- Day (Min)
7-Day (Max)
7-Day (Avg)
28-Day (Min)
28-Day (Max)
28-Day (Avg)
4.5A 320 355 335 420 460 440
4.5B 315 345 330 420 480 450
4.5C 385 385 385 385 420 405
10 A 525 565 545 375 445 410
10 B 460 630 545 455 575 515
10 C 485 510 495 440 480 460
Figure 4-8. Figure showing the 7-day and 28-day split tensile strength values of main
samples
Figure 4-9. Fracture Point or Yield Point (Split Tensile Strength) (Photo courtesy of author)
0
100
200
300
400
500
600
700
0 7 2 8
SPLI
T-TE
NSI
LE S
TREN
GTH
(IN
PSI
)
TIME (IN DAYS)
SPLIT-TENSILE STRENGTH
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
49
Figure 4-10. Proportions of aggregate as shown in the cylinder split in two equal halves in split tensile testing (Photo courtesy of author)
Figure 4-11. Graph showing 7-day Split Tensile Strength range and average
300.00
350.00
400.00
450.00
500.00
550.00
600.00
650.00
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
SPLI
T TE
NSI
LE S
TREN
GTH
(P
SI)
MIX ID
7-Day Split Tensile Strength Range and Average
7 (Avg.)
50
Figure 4-12. Graph showing 28-day Split Tensile Strength range and average
Table 4-4. Percentage of Split Tensile to Compression
Mix ID Average Split Tensile
Test (psi) Average Compression
Test (psi)
Average Percentage of split tensile
to compression (%)
Days 7 28 7 28 7 28
4.5 A 337.20 438.00 4720.00 6767.50 7.14 6.47
4.5 B 329.70 450.80 4730.00 7167.85 6.97 6.29
4.5 C 386.00 402.85 5650.00 7783.61 6.83 5.18
10 A 544.70 410.60 9640.00 9952.26 5.65 4.13
10 B 544.50 515.72 10120.00 10080.74 5.38 5.12
10 C 496.50 460.20 8820.00 10016.10 5.63 4.59
According to ASTM C 157 State of California, the concrete batches that were
prepared were used for multiple purpose. A fraction of the freshly prepared batch was
used for measuring slump, unit weight and air content. When the tests were completed,
the used concrete for slump and unit weight test was returned to the remaining concrete
in the mixer. However, the portion that was used for measuring air content, discarded.
The concrete was remixed briefly before the fabrication of specimens. The concrete in
350.00
400.00
450.00
500.00
550.00
600.00
650.00
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
SPLI
T TE
NSI
LE S
TREN
GTH
(P
SI)
MIX ID
28-Day Split tensile Strength Range and Average
28 (Avg.)
51
then used for casting cylinders for compressive strength and split tensile strength tests
and prisms for drying shrinkage tests.
Following are the values of specimen readings for drying shrinkage test for each
batch of prepared mix design. Each batch had four samples totaling 24 samples and
then their average value was plotted against time (in days).
4.3 Drying Shrinkage
Table 4-5. Specimen Reading for 10,000 psi 1st batch
Mix ID 10,000 psi 1st batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.1321 0.1308 0.1288 0.1275 0.1261
Sample 2 0.0359 0.0356 0.0809 0.0943 0.0300
Sample 3 0.2060 0.2055 0.1446 0.1434 0.1430
Sample 4 0.1893 0.1888 0.1293 0.1277 0.1267
Average 0.1408 0.1402 0.1209 0.1232 0.1065
Figure 4-13. Graphical Representation for specimen reading 10,000 psi 1st batch
y = -0.0086x + 0.152
0.0000
0.0500
0.1000
0.1500
0.2000
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
10000 psi 1st batch
Linear (10000 psi 1st batch)
52
Table 4-6. Specimen Reading for 4,500 psi 1st batch
Mix ID 4500 psi 1st batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.2338 0.2333 0.2331 0.2312 0.2304
Sample 2 0.2631 0.2626 0.2612 0.2596 0.2587
Sample 3 0.2331 0.2328 0.2295 0.2304 0.2294
Sample 4 0.2543 0.2539 0.2536 0.2515 0.2507
Average 0.2461 0.2457 0.2444 0.2432 0.2423
Figure 4-14. Graphical Representation for specimen reading 4,500 psi 1st batch
Table 4-7. Specimen Reading for 10,000 psi 2nd batch
Mix ID 10000 psi 2nd batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.1780 0.1775 0.1755 0.1749 0.1740
Sample 2 0.1357 0.1351 0.1335 0.1327 0.1319
Sample 3 0.1991 0.1986 0.1977 0.1964 0.1961
Sample 4 0.1989 0.1986 0.1963 0.1958 0.1956
Average 0.1779 0.1775 0.1758 0.1750 0.1744
y = -0.001x + 0.2473
0.2400
0.2425
0.2450
0.2475
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
4500 psi 1st batch
Linear (4500 psi 1st batch)
53
Figure 4-15. Graphical Representation for specimen reading 10,000 psi 2nd batch
Table 4-8. Specimen Reading for 4,500 psi 2nd batch
Mix ID 4500 psi 2nd batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.1207 0.1200 0.1175 0.1173 0.1160
Sample 2 0.2037 0.2031 0.2016 0.2008 0.2000
Sample 3 0.1911 0.1904 0.1884 0.1874 0.1870
Sample 4 0.1789 0.1786 0.1757 0.1736 0.1728
Average 0.1736 0.1730 0.1708 0.1698 0.1690
Figure 4-16. Graphical Representation for specimen reading 4,500 psi 2nd batch
y = -0.001x + 0.179
0.1700
0.1725
0.1750
0.1775
0.1800
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
10000 psi 2nd batch
Linear (10000 psi 2nd batch)
y = -0.0013x + 0.175
0.1600
0.1700
0.1800
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
4500 psi 2nd batch
Linear (4500 psi 2nd batch)
54
Table 4-9. Specimen Reading for 10,000 psi 3rd batch
Mix ID 10000 psi 3rd batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.2305 0.2300 0.2265 0.2259 0.2252
Sample 2 0.1949 0.1944 0.1906 0.1890 0.1899
Sample 3 0.1850 0.1845 0.1815 0.1802 0.1800
Sample 4 0.2057 0.2052 0.2010 0.2004 0.1997
Average 0.2040 0.2035 0.1999 0.1989 0.1987
Figure 4-17. Graphical Representation for specimen reading 10,000 psi 3rd batch
Table 4-10. Specimen Reading for 4,500 psi 3rd batch
Mix ID 4500 psi 3rd batch
Sample No. Day-1 Day-7 Day-14 Day-21 Day-35
Sample 1 0.1970 0.1966 0.1944 0.1936 0.1920
Sample 2 0.2100 0.2096 0.2074 0.2067 0.2059
Sample 3 0.1386 0.1381 0.1360 0.1350 0.1343
Sample 4 0.1959 0.1955 0.1930 0.1927 0.1912
Average 0.1854 0.1850 0.1827 0.1820 0.1809
y = -0.0015x + 0.2056
0.1900
0.1950
0.2000
0.2050
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
10000 psi 3rd batch
Linear (10000 psi 3rd batch)
55
Figure 4-18. Graphical Representation for specimen reading 4,500 psi 3rd batch
Table 4-11. Average Percentage shrinkage of the main concrete samples for Drying Shrinkage Test
Mix ID 7-Day (in %) 14-Day (in %) 21-Day (in %) 35-Day (in %)
4.5AB 0.004 0.017 0.029 0.038
4.5CD 0.006 0.022 0.038 0.047
4.5EF 0.004 0.029 0.039 0.050
10AB 0.007 0.016 0.035 0.044
10CD 0.005 0.022 0.030 0.035
10EF 0.005 0.041 0.050 0.053
NOTE: The above data for each mix design at any age is an average value of
four specimens.
Figure 4-19. Length change value graphical representation for 4,500 psi specimen
y = -0.0012x + 0.1868
0.1750
0.1800
0.1850
0.1900
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SPEC
IMEN
REA
DIN
GS
(IN
CH
ES)
TIME (DAYS)
SPECIMEN READING
4500 psi 3rd batch
Linear (4500 psi 3rd batch)
0
0.01
0.02
0.03
0.04
0.05
0.06
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SHR
INK
AG
E (
%)
TIME (DAYS)
PERCENTAGE SHRINKAGE OF 4,500 PSI SPECIMENS
4500 psi 1st batch
4500 psi 2nd batch
4500 psi 3rd batch
Average
56
As, we can see that the graph is increasing with time for all specimens at
different rate. This indicates that the prism is shrinking. The actual value of specimen
length readings with the comparator apparatus is described in Appendix A. For each
mix design their readings is explained by their graphs which have a trendline equation
that predicts the nature and the shrinkage amount for future.
Figure 4-20. Length change value graphical representation for 10,000 psi specimen
Following are the picture showing the different comparator readings at different
ages for one of the samples.
Figure 4-21. Comparator Reading a)- at age – 7 days, b)- at age – 14 days, c)- at age – 21 days (Photo courtesy of author)
0
0
0
0
0
0
0
D A Y - 1 D A Y - 7 D A Y - 1 4 D A Y - 2 1 D A Y - 3 5
SHR
INK
AG
E (%
)
TIME (DAYS)
PERCENTAGE SHRINKAGE OF 10,000 PSI SPECIMENS
10000 psi 1st batch
10000 psi 2nd batch
10000 psi 3rd batch
Average
(a) (b) (c)
57
Drying Shrinkage is a value determined by taking difference of percentage
shrinkage value of 7 days and 21 days (Table 4-11)
Following is the graph representing the drying shrinkage of all prepared batches:
Figure 4-22. Graphical representation and comparison of drying shrinkage values of all
prepared batches
0.029
0.025
0.045
0.025
0.0330.035
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
1st batch 2nd batch 3rd batch
DR
YIN
G S
HR
INK
AG
E V
ALU
ES (
IN %
)
SAMPLES
DRYING SHRINKAGE
10,000 psi
4,500 psi
58
CHAPTER 5 CONCLUSION
5.1 General
It can be said that all of samples of all mix designs used in the research showed
good results for fresh concrete as well as hardened concrete. Their physical and
mechanical properties such as slump, unit weight, air content, like compressive
strength, split tensile and drying shrinkage potential are discussed below.
5.2 Physical Properties
The slump value ranged from 1 to 6.5 inches for all samples with an average
value of 3.59 inches. In case of unit weight tests, most samples had unit weights within
acceptable boundaries. As per the data collected by the National Ready Mixed
Concrete Association (see ASTM 138), the unit weight for the concrete having slump
values between 3 and 6 inches should be between 115 and 155 pounds per cubic foot.
The air content of the 10,000 psi samples had values ranging from 2.5% to 3.5%.
However, the air content of the 4,500 psi samples was more uniform with a value of
1.5%. The air content value depended on the amount of fine aggregates and the
amount of water in concrete.
5.3 Mechanical Properties
The compressive strength of every sample reached minimum requirements, but
also produced consistent compressive strength. The split tensile strength also shows
the reliable results as per the ASTM Test standards. On a per batch basis, drying
shrinkage does not differ significantly for the 4,500-psi light weight concrete vs. 10,000
psi light weight concrete at 14 days of drying.
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CHAPTER 6 RECOMMENDATIONS AND SUGGESTIONS
There were some recommendations and suggestions were suggested based on
the results and literature review for this research before it goes to field. The air content
results for some samples were not at all consistent. Further research is recommended
for the air content testing particularly for air-entrained concrete. As there was not any
research that was done on plastic shrinkage, further research on restrained plastic
shrinkage test should be conducted using various methods described by ASTM. A long-
term study is suggested to analyze the drying shrinkage potential for the lightweight
concrete prisms. Based on the results, the use of high cementitious lightweight concrete
should be allowed for the field application and testing.
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LIST OF REFERENCES
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ASTM C138/C138M-17a Standard Test Method for Density (Unit Weight), Yield, and Air
Content (Gravimetric) of Concrete, ASTM International, West Conshohocken, PA, 2017, https://doi.org/10.1520/C0138_C0138M-17A
ASTM C173/C173M-16 Standard Test Method for Air Content of Freshly Mixed Concrete
by the Volumetric Method, ASTM International, West Conshohocken, PA, 2016, https://doi.org/10.1520/C0173_C0173M-16
ASTM C39/C39M-17a Standard Test Method for Compressive Strength of Cylindrical
Concrete Specimens, ASTM International, West Conshohocken, PA, 2017, https://doi.org/10.1520/C0039_C0039M-17A
ASTM C496/C496M-11 Standard Test Method for Splitting Tensile Strength of Cylindrical
Concrete Specimens, ASTM International, West Conshohocken, PA, 2004, https://doi.org/ 10.1520/C0496_C0496M-11
ASTM C157/C157M-08(2014) e1 Standard Test Method for Length Change of Hardened
Hydraulic-Cement Mortar and Concrete, ASTM International, West Conshohocken, PA, 2014, https://doi.org/10.1520/C0157_C0157M-08R14E01
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BIOGRAPHICAL SKETCH
Prafull Vijay grew up in Jaipur, India, where he was born in 1994, to Sanjay Vijay
and Asha Vijay. He graduated from VIT University in Vellore, India in 2015 with a
Bachelor in Technology (the Indian equivalent of a B.S.), majoring in civil engineering.
Later that same year, he enrolled into the M.E. Rinker School of Construction
Management at the University of Florida, studying for a Master of Science in
Construction Management, which he completed in the summer of 2017. He secured a
professional appointment as a project engineer in Orlando with Turner Construction, a
commercial company, where he works in renovation and small-scale division projects.