Evaluation of the Compressive Strength of Masonry Prisms

Filled With High Volume Mineral Admixture Grout

Constructed With Type N Mortar

Brice Emerson Somers

A project submitted to the faculty of

Brigham Young University

in partial fulfillment of the requirements for the degree of

Master of Science

Fernando S. Fonseca, Chair

Paul W. Richards

Mitsuru Saito

Department of Civil and Environmental Engineering

Brigham Young University

December 2012

Copyright © 2012 Brice Emerson Somers

All Rights Reserved

ABSTRACT

Evaluation of the Compressive Strength of Masonry Prisms

Filled With High Volume Mineral Admixture Grout

Constructed With Type N Mortar

Brice Emerson Somers

Department of Civil and Environmental Engineering, BYU

Master of Science

The Concrete Masonry Association of California and Nevada commissioned a research

project at Brigham Young University to analyze the compressive strength of masonry prisms that

were to be cast with grout that had a high quantity of the Portland cement replaced with mineral

admixtures. The laboratory research associated with this project involved a control group of

prisms cast with Portland cement-based grout, a test group with Class F fly ash replacing

determined percentages of cement , and a third test group that utilized Class F fly ash and ground

blast-furnace slag to replace Portland cement. In the test groups, the mineral admixtures replace

45%, 55%, 65%, 75% and 85% of the mix design cement by weight. Sufficient samples of each

mixture were cast to test prisms after 14, 28, 42, 56 and 90 days of curing.

Analyses of the test results indicated that the minimum required design strength for

masonry prisms could be achieved with all of the designs tested except for the design that had

65% of the Portland cement replaced with fly ash. Some of the blended cements attained higher

strengths than the control group and also gained strength at a similar rate. This research

indicated that there was no observed deficiencies with the high mineral admixture volume grouts

and that up to 85% of the Portland cement could be replaced with cementitous by-products if

compressive strength is the only consideration.

Keywords: fly ash, ground granulated blast-furnace slag, high cement replacement concrete,

masonry prism, compressive test

ACKNOWLEDGMENTS

The author would like to thank Dr. Fernando S. Fonseca for his assistance with the

experimental design and analysis of results. The author would like to thank Dr. Mitsuru Saito

and Dr. Paul W. Richards for their assistance in editing and for serving as committee members

for this project. Funding for this project was provided by the Concrete Masonry Association of

California and Nevada under the direction of Kurt Siggard. The author acknowledges Doyle

Hatfield Masonry for their help in creating the test samples. A special thanks is given to: Ash

Grove for their donation of sand and gravel, Quickcrete for their donation of premix mortar,

Amcor for their donation of concrete masonry units and Headwaters for their donation of fly ash

and ground granulated blast-furnace slag. Arthur Guo, Scott Watterson, Juan-Ma Salguero,

Robert Godfrey, and Tana Uyema, are acknowledged for their significant assistance with the

specimen preparation and testing. Finally, the author would like to thank his wife Morgan for

her continued support and understanding throughout the duration of this project.

v

TABLE OF CONTENTS

LIST OF TABLES ...................................................................................................................... vii

LIST OF FIGURES ..................................................................................................................... ix

1 Introduction ........................................................................................................................... 1

1.1 Problem Statement .......................................................................................................... 1

1.2 Scope ............................................................................................................................... 2

1.3 Outline of Report ............................................................................................................ 3

2 Background ........................................................................................................................... 5

2.1 Type N Masonry Mortar ................................................................................................. 5

2.2 Masonry Grout ................................................................................................................ 6

2.3 Portland Cement ............................................................................................................. 6

2.4 Mineral Admixtures ........................................................................................................ 7

2.4.1 Fly Ash ........................................................................................................................ 7

2.4.2 Ground Granulated Blast-Furnace Slag ...................................................................... 9

2.5 Chapter Summary ......................................................................................................... 10

3 Experimental Methodology ................................................................................................ 11

3.1 Mix Design ................................................................................................................... 12

3.2 Mortar and Hollow Prism Preparation .......................................................................... 13

3.3 Grout and Grouted Prism Construction ........................................................................ 17

3.4 Specimen Preparation ................................................................................................... 24

3.5 Specimen Testing .......................................................................................................... 25

3.6 Chapter Summary ......................................................................................................... 28

4 Results .................................................................................................................................. 29

4.1 Data Reduction ............................................................................................................. 29

4.2 Compressive Test Results ............................................................................................. 32

vi

4.3 Chapter Summary ......................................................................................................... 35

5 Conclusions and Recommendations .................................................................................. 37

5.1 Conclusions ................................................................................................................... 37

5.2 Recommendations ......................................................................................................... 38

REFERENCES ............................................................................................................................ 39

Appendix A: TWINING LABORATORY GROUT TEST INFORMATION ...................... 41

Appendix B: MATERIAL PROPERTY CHARTS ................................................................. 43

vii

LIST OF TABLES

Table 3-1: Components of Each Grout Type ................................................................................ 12

Table 3-2: Grout Slump Results ................................................................................................... 20

Table 4-1: Prism Compressive Strength at Each Time Interval in psi .......................................... 32

Table A-1: Twining Laboratories Grout Specimen Compressional Strength Data ...................... 41

Table A-2: Absorption, Density and Moisture Content of CMU Samples ................................... 41

Table A-3: Twining Laboratories Grout Compressive Strength Results ...................................... 42

viii

ix

LIST OF FIGURES

Figure 3-1: Mechanical Mixer for Mortar ................................................................................... 14

Figure 3-2: Hollow Prisms being Constructed with Type N Mortar ........................................... 15

Figure 3-3: Mortar Cube Casting ................................................................................................. 15

Figure 3-4: Mortar Flow Test ...................................................................................................... 16

Figure 3-5: Fog Room Curing of Mortar Cubes .......................................................................... 16

Figure 3-6: Curing of Hollow Prisms in Plastic Bags.................................................................. 17

Figure 3-7: Mechanical Mixer Used for Mixing Grout ............................................................... 18

Figure 3-8: Slump Test ................................................................................................................ 20

Figure 3-9: Flowable Type 4 Grout being Placed in Prism ......................................................... 21

Figure 3-10: Eight Inch Slump Grout Type 5 being Placed in Prism ........................................... 21

Figure 3-11: Casting of Grout Samples ........................................................................................ 22

Figure 3-12: Grout Sample after Removal from CMU ................................................................. 22

Figure 3-13: Grout Correlation Sample Mold .............................................................................. 23

Figure 3-14: Casting of Grout Correlation Sample ....................................................................... 23

Figure 3-15: Baldwin Compressive Testing Machine .................................................................. 26

Figure 3-16: Bearing Plates .......................................................................................................... 27

Figure 4-1: Stress-Strain Curve before Modification .................................................................. 31

Figure 4-2: Stress Strain Curve after Modification...................................................................... 31

Figure 4-3: Compressive Strength (psi) of CMUs, Mortar, and Hollow Prisms over Time ........ 33

Figure 4-4: Compressive Strengths (psi) of the Seven Prism Types over Time .......................... 33

Figure 4-5: Compressive Strengths (psi) over Time Excluding 28 Day Data ............................. 34

Figure B-1: Manufacturer Supplied CMU Properties ................................................................... 43

Figure B-2: Manufacturer Supplied Coarse Aggregate Properties ............................................... 44

Figure B-3: Manufacturer Supplied Fine Aggregate Properties ................................................... 45

x

1

1 INTRODUCTION

1.1 Problem Statement

The production of Portland cement has been indicated as one of the leading producers of

carbon dioxide in the world contributing about 5% of total carbon dioxide emissions. “Cement

plants and factories across the world are projected to churn out almost 5bn (billion) tons of

carbon dioxide annually… 20 times as much as… the entire UK” (1). Portland cement is the

most common binding agent used to create concrete but other cementitous materials can be used

to replace or supplement Portland cement in concrete. In Europe, cement replacement products

are used more commonly; for example, studies show that in Europe 88% of fly ash (FA)

produced is reused as compared to only 33% is reused in the United States (2).

Masonry grout is a low strength concrete that is highly flowable and has a small nominal

aggregate size. Construction of masonry buildings competes directly with buildings constructed

with solid concrete walls, known as concrete tilt-up buildings. Due to the fact that tilt-up

construction requires concrete that gains high strengths in a short period of time, itt is hoped that

this research will lead to improved sustainability in masonry construction and thus give it a

significant edge over tilt-up construction methods. High replacement of Portland cement will

reduce the cost of the masonry grout, reduce the carbon footprint of the production process,

dispose of industrial byproducts, and increase the sustainability of masonry construction.

2

According to design standards, the required compressive strength of masonry grout is

2000 pounds per square inch (psi). Engineers from The Concrete Masonry Association of

California and Nevada (CMACN) postulate that masonry construction can reach this strength

even when high percentages of Portland cement are replaced by mineral admixtures such as FA

and ground granulated blast-furnace slag (GGBS). CMACN commissioned Twining

Laboratories, in California, to perform research concerning the compressive strength of a variety

of masonry grout types. These grout types have high volumes of FA and GGBS replacing the

common Portland cement binding agent. That research has shown that an adequate grout

compressive strength can be reached with up to 80% of the Portland cement replaced with FA

and GGBS (see Appendix Table A-1). CMACN desires to conduct further research to show how

these types of grouts will perform when they are used to fill the hollow cores of cinder block

(also known as concrete masonry units (CMUs)) walls. The purpose of this research is to

evaluate the compressive strength achieved by masonry prisms. A masonry prism consists of

CMUs that are stacked as they would be in construction, with a layer of mortar in between rows,

and have the hollow core filled with grout.

1.2 Scope

To evaluate the effect that mineral admixtures have on compressive strength of CMU

prisms, this research involved compressive strength testing of prisms that were cast with seven

different grout designs. For a control group, the first design used only Portland cement as a

binding agent in the grout. The second, third, and fourth designs were be identical to the first

design except that Class F FA was used to replace the Portland cement at rates of 45%, 55%, and

65% respectively. The replacement of the Portland cement with mineral admixtures was be done

by weight. The fifth, sixth, and seventh mix designs used a combination of FA and GGBS to

3

replace Portland cement at rates of 65%, 75%, and 85% respectively. In order to evaluate the

effects that each component of the masonry prism had on the entire prism, samples of the type-N

mortar, individual CMUs, prisms with no grout (hollow prisms), and samples of grout were

tested. In order to track the effect that the mineral admixtures had on curing time and strength

gain, compressive strength testing was completed at 14, 28, 42, 56, and 90 days after casting.

Five samples were cast for each type of sample for each test day; approximately 195 samples

were tested for this research.

1.3 Outline of Report

The report consists of five chapters. Chapter 1 has presented an introduction and

explained the scope of the research project. Chapter 2 contains the results of a literature review

on the types and uses of laboratory compressive tests as well as properties of various mineral

admixtures. In Chapter 3, the mix design, specimen preparation and testing, and data analysis

procedures are presented. The test results are included in Chapter 4, while Chapter 5 contains

conclusions based on the results of the testing and recommendations for further research

pertaining to the topic.

4

5

2 BACKGROUND

The following sections include the results of a literature review conducted for this

research. A description of each type of material used in this research is given including masonry

mortar, masonry grout, and Portland cement. A description of the mix design is followed by a

discussion of mineral admixtures including FA and GGBS.

2.1 Type N Masonry Mortar

Mortar is typically a mixture of Portland cement, lime, sand, and water. Increased lime

content in mortar make the mix more workable and more ductile when cured. The purpose of

mortar is to bind masonry units together and, therefore, its most important property is adhesion

rather than compressive strength. Mortar for masonry is produced in several typical types

including type M, type S, and type N. Of these mortar types, type M has the least amount of

lime and type N has the most. Compressive strengths of mortar are low compared to other types

of concrete; after 28 days of curing they are typically 2500psi (17.2 MPa), 1800psi (12.4 MPa),

and 750psi (5.2 MPa), for types M, S, and N, respectively. This research project analyzed the

compressive strengths of masonry prisms constructed with type N mortar and will be compared

to the results of concurrent research that involves types M and S.

6

2.2 Masonry Grout

Masonry grout is a type of concrete that has high slump and small aggregate and is used

to fill the hollow cores of CMUs. Grout bonds CMUs together as well as bonding to any

reinforcing bars set in the grout. The high slump of masonry grouts is important so that the grout

can be flowable and fill the hollow cores without leaving voids in the masonry construction and

is important because the hydrophilic CMUs wick a significant amount of water out of the grout.

ASTM standards do not allow the use of superplasticizers in masonry grouts due to the fact that a

grout with reduced water content will suffer from extreme plastic shrinkage after the CMUs

remove water from the grout. When considering the bulk cross-sectional area of a masonry

prism, there is more grout than CMU. Since masonry design parameters are all derived from the

compressive strength of the masonry system (CMU, grout, and mortar), the grout plays a very

significant role in the compressive strength of the system.

2.3 Portland Cement

Portland cement is the most commonly known binding agent used to make modern

concrete. Portland cement was named after the limestone cliffs on the Isle of Portland in

England and was patented by Joseph Aspdin in 1824 (3). Portland cement is produced by

mining limestone and clay, grinding these materials, and placing them together in a kiln. In the

kiln, the raw materials melt and the silica, alumina, and calcium from the raw materials bond to

form clinker. After cooling, the clinker is ground together with gypsum and becomes known as

Portland cement.

Portland cement is classified into five subgroups depending on composition and fineness.

Types I and II are the most common, while types III through V are primarily used for specialty

projects that require increased set time, low heats of hydration, or additional resistance to sulfate.

7

The primary Portland cement reaction is the hydration reaction which occurs when

Portland cement comes in contact with water. In this exothermic reaction, the combination of

calcium, silica, and water, results in the formation of calcium silicate hydrate (C-S-H) and excess

calcium hydroxide (CH). Calcium hydroxide remains as a useless byproduct in the concrete

unless a pozzolanic reaction utilizes its chemical make-up to form more C-S-H. C-S-H gel is the

primary binding agent that gives concrete its strength. This gel binds together the aggregates

(sand and gravel) found in concrete and masonry grout.

2.4 Mineral Admixtures

The mineral admixtures that will be utilized in this study are Class F FA and GGBS.

Both of these products are known to react chemically and form bonding calcium silicate hydrate

(C-S-H) gels similar to those produced by Portland cement. History records the use of mineral

admixtures for their cementitous properties since the Greeks, who used a volcanic ash from the

island of Santorin as a binding agent (4). The Romans are said to have adopted and expanded

this Greek technology. Evidence that the Romans used mineral admixtures in their cements can

be found in old Roman buildings along the Rhine (5). Mineral admixtures can enhance the

performance of concrete and are known to enhance strength and strength gain properties,

increase density and durability, increase workability, and reduce heat of hydration.

2.4.1 Fly Ash

Fly ash is a by-product of the coal industry and is a mineral admixture known as a

pozzolan. The major component in a pozzolan is the glassy or amorphous silica that it contains.

The primary pozzolanic reaction occurs when the silica or siliceous materials in the pozzolan

react with the calcium hydroxide byproduct of the Portland cement. This reaction forms binding

8

C-S-H gels similar to those formed in the Portland cement reaction. Reactive alumina in

pozzolans can also react to form cementitous calcium aluminum hydrate gels.

As coal is burned in power plants, FA is produced and trapped from the gases in the flue.

Each year over 250 million tons of FA is produced in the U.S. alone (4). FA may be

characterized as Class C or Class F, depending on the type and composition of the coal that is

burned. Class F FA is produced from bituminous and subbituminous coals typically found east

of the Mississippi River, while Class C FA comes from the lignitic coals usually found in the

western United States (4). Due to the differences in chemical composition, Class C is self-

cementing because it contains some calcium hydroxides but has high heat of hydration which can

often be deleterious. Class F FA hydrates at lower temperatures but is not self-cementing, it can

only react with products of Portland cement hydration. If too high of a replacement ratio is used,

the Class F FA would not be able to completely react due to a deficiency in the calcium

hydroxide that is required for the FA to react.

Fly ash particles are finer than those of Portland cement, creating a more densely packed

concrete product and; therefore, the use of FA increases the durability of concrete products.

Pozzolanic reactions occur more slowly and often concretes with high volume fly ash (HVFA)

contents do not meet the design strength after the specified 28 day cure time. Concretes with FA

are known to gain strength for extended periods of time and some FA has been known to

continue gaining strength for an entire year after placement (6). Due to the fact that pozzolanic

reactions occur at varying rates, depending largely on the composition of the FA (6), determining

the percentage of the final strength that will be achieved after a 7- or 14-day cure is not usually

possible.

9

In 1999, FA was added to the approved material list for masonry grout via ASTM C476-

99 “Standard Specification for Grout for Masonry”. At this time, there was, however, a

maximum permissible amount of 40% FA when used with Portland cement. This restriction was

placed due to concerns that FA results in less bleed water and that grout with high FA content

may have difficulty bonding to the CMU face shells (7). Further research on the topic has since

led to replacing this standard with ASTM C476-10 which allows for the use of any quantity of

FA as long as the required compressive strength is met.

FA particles are smaller and more rounded than Portland cement particles. These shape

properties affect the properties of the plastic and cured grout mixture. FA is known to reduce

hydration heat, reduce problems caused by the alkali-silica reaction (ASR), improve workability,

reduce permeability of the final grout, and improve the grout’s resistance to sulfate attack (8).

Grout mixes with high volumes of FA will not be subject to many of the problems encountered

with typical concrete products.

2.4.2 Ground Granulated Blast-Furnace Slag

Ground granulated blast-furnace slag is a hydraulic cement similar to Portland cement,

which is produced in the steel manufacturing process. Blast-furnace slag is a waste or byproduct

that forms in a blast-furnace when iron ore, coke, limestone and other materials are smelted to

form iron. Slags reach temperatures of 2900 degrees Fahrenheit (1600 degrees Celsius) after

which they are broken up with water jets in a process called granulation. Granulated pieces of

slag are then rapidly cooled or “quenched” in water. If the slag is not quenched, it will not

become “glassy” or amorphous and will not form the calcium aluminosilicate glass which makes

it hydraulically active (4). After granulation, the slag particles are ground into a powder. Blast-

furnace slags that come from iron production have high contents of silica, lime, and alumina but

10

are not entirely self-cementing. GGBS must be activated by alkaline compounds, and this is

most commonly achieved by combining GGBS with Portland cement. Much higher proportions

of GGBS can be mixed with Portland cement than pozzolans such as FA (9) and it is commonly

accepted that a mixture of up to 80/20 (GGBS/Portland cement) can be used. When combined

with Portland cement, GGBS forms C-S-H through the primary hydration reaction as well as

through the primary pozzolanic reaction (4).

GGBS is known to increase the ultimate strength of blended cements; increase the

workability of the plastic mix; gain strength for long periods of time; double its 28-day strength

over the period of a decade; decrease heat of hydration; increase sulfate, ASR, and chloride

resistance; prevent efflorescence; and result in a more attractive finish surface (10). The

production of GGBS uses one third the amount of raw materials and less than half the energy

consumption than does the production of Portland cement (5). When GGBS is acquired as a

byproduct, it uses only about 8% as much energy as Portland cement and has a similar cost.

2.5 Chapter Summary

A masonry prism consists of 2 or more CMUs that are connected with mortar and whose

hollow cores are filled with masonry grout. In this study type N mortar will be used and the

grouts will contain water, sand, gravel, Portland cement, FA, and GGBS. Portland cement is the

most commonly known binding agent in concrete products but mineral admixtures such as FA

and GGBS can also be used to make concrete products. These mineral admixtures provide many

benefits such as increasing the durability and workability of concretes but also have drawbacks

such as lower strength and slower strength gain over time when compared to Portland cement.

11

3 EXPERIMENTAL METHODOLOGY

In this research, a full-factorial laboratory experiment including seven mix designs and

two different mineral admixtures at different replacement rates, with five replicates of each mix

design and for each cure date, was performed. For comparison, single CMU blocks, hollow

CMU prisms, filled prisms, grout samples, and mortar samples were made and tested. One grout

mix design contained typical Portland cement grout and was used as a baseline to which all other

results would be compared to. The samples were subjected to compressive strength tests after

14, 28, 42, 56, and 90 days of curing. ASTM requires a minimum test group size of three

replicates and in this research 4 specimens were typically tested for each group leaving one extra

prism for each test group. With four replicates of each of the seven mix designs there were 28

solid prisms to be tested for each of the 5 cure dates. Specimens of hollow prisms, single CMUs,

and mortar cubes were also tested on each cure date. Approximately 156 samples were tested for

this research. This chapter presents the procedures and protocols used during the research

project, including mix design, specimen preparation, compressive testing, and data analyses. All

ASTM cited in the remainder of this document are provided by ASTM Volume 4.02 Concrete

and Aggregates (11)

12

3.1 Mix Design

As previously mentioned, there will be seven different types of grout tested in this

research project. In order to have results that are easily comparable to research performed by

CMACN, the mix designs used in this project will have the same weights of sand, gravel, and

cementitous material per cubic yard as did CMACN’s grout research. The first type of grout will

have only Portland cement as a binding agent. This grout will be called Grout 1. All seven grout

types will have the same weight of cementitous materials. For the second grout type (Grout 2),

45% of the cementitous materials will be Class F FA and the remaining 55% will be Portland

cement. The third grout (Grout 3) will contain 55% Class F FA and 45%Portland cement. The

fourth grout (Grout 4) will contain 65% Class F FA and 35% Portland cement. The cementitous

materials for the fifth grout (Grout 5) will be composed of 25% FA, 40% GGBS, and 35%

Portland cement. Grout 6 will be composed of 25% FA, 50% GGBS, and 35% Portland cement

and Grout 7 will be composed of 25% FA, 60% GGBS, and 35% Portland cement. The

composition of materials by weight for each grout type is listed in Table 3-1.

Table 3-1: Components of Each Grout Type

Grout Type Sand

(lbs)

Gravel

(lbs)

Water

(lbs)

Cement

(lbs)

Fly

Ash

(lbs)

Slag

(lbs)

Water

Cement

Ratio

1 (Portland Cement) 1923.5 813.8 566.9 591.8

0.883

2 (45 % FA) 1923.5 813.8 566.9 325.5 266.3

0.883

3 (55% FA) 1442.6 610.3 425.2 199.7 244.1

0.883

4 (65% FA) 1346.4 569.6 396.8 145.0 269.3

0.883

5 (25% FA, 40% GGBS) 1346.4 569.6 356.2 145.0 103.6 165.7 0.785

6 (25% FA, 50% GGBS) 1413.8 598.1 373.8 108.8 108.8 217.5 0.785

7 (25% FA, 60% GGBS) 1413.8 598.1 373.8 65.3 108.8 261.0 0.785

13

3.2 Mortar and Hollow Prism Preparation

Concrete masonry units were acquired from Amcor Masonry who prepared a batch of

CMUs specifically for this project. Testing was performed in accordance with American Society

for Testing and Materials (ASTM) C140 which provides information relating to the conditions of

the CMUs. This information consisted of, but was not limited to, CMU dimensions, absorption

(percent of block weight absorbed), dry weight, density and moisture content. With materials on

hand, Doyle Hatfield Masonry sent a work crew to Brigham Young University’s civil

engineering structures lab and constructed the hollow masonry prisms. CMUs were bonded

together using type-N mortar manufactured by Quickcrete. The premix bags of mortar

manufactured by Quickcrete conform to ASTM standards C144 and C270, which specify

aggregate gradation and the properties of the materials used to create the mix. Doyle Hatfield

masonry workers mixed the mortar adding water until the appropriate consistency was reached in

general accordance with ASTM C305 “Standard Practice for Mechanical Mixing of …Mortars”.

The mixer used for the mechanical mixing of the mortar is shown in Figure 3-1. While the

masons used the mortar to construct prisms (Figure 3-2), mortar cubes were made for

compressive strength testing (Figure 3-3), samples of mortar were tested for flow (Figure 3-4),

and plastic mortar temperature was recorded in accordance with ASTM C109. The mortar flow

and temperature results are given in Table 3-2. Figure 3-5 shows that after casting, mortar cubes

were placed in a controlled environment fog room in accordance with ASTM C511. Figure 3-6

shows that upon completion of constructing the hollow prisms, the samples were placed in

plastic bags and left to cure for 24 hours in accordance with ASTM C1314.

14

Figure 3-1: Mechanical Mixer for Mortar

15

Figure 3-2: Hollow Prisms being Constructed with Type N Mortar

Figure 3-3: Mortar Cube Casting

16

Figure 3-4: Mortar Flow Test

Figure 3-5: Fog Room Curing of Mortar Cubes

17

Figure 3-6: Curing of Hollow Prisms in Plastic Bags

3.3 Grout and Grouted Prism Construction

The following day, the plastic bags were opened and the prisms were prepped to be filled

with grout. Prep work included removing any pieces of hardened mortar that had fallen inside of

the constructed prisms. The manufacturer material properties charts for the sand, gravel,

Portland cement, FA, GGBS, and mortar are found in Appendix B. These material data sheets

indicate that the materials conform to all pertinent ASTM standards for materials used in the

construction and testing of masonry prisms. Potable water was used for the grout in accordance

to ASTM C1602. Appropriate quantities of sand, gravel, Portland cement, and water were

weighed and placed in a 1 cubic yard cement mixer, shown in figure 3-7, to make the first batch

of grout.

18

Figure 3-7: Mechanical Mixer Used for Mixing Grout

For the first grout type, no mineral admixtures were used. It was estimated that

approximately one cubic yard of grout was needed to fill prisms for this and other concurrent

research. Prior to adding materials to the mixer, the mixer was washed out with potable water

and excess water was allowed to drain out of the mixer. This process ensures that the interior of

the mixer is in a surface saturated dry (SSD) condition. The SSD condition of the mixer

guarantees that the mixer will neither contribute nor remove water to the batched materials in the

mixing process. With the mixer prepared, an approximation of the weight of water that would be

required for the batch was made and one half of the water was placed in the mixer. With water

in the mixer, the mixer was turned on and, as it was mixing, sand and gravel were weighed and

added to the mixer incrementally. With all of the sand and gravel in the mixer, Portland cement

and the majority of the remaining water were placed in the mixer. It was found that the volume

of grout that was produced in the initial batches was too much and therefore, the volume of grout

was reduced by 25% when Grout 3 was batched.

19

Slump tests were performed in accordance with ASTM 172 on the Grout 1 and the water

was added incrementally until the target slump of nine inches was achieved. The water cement

ratio that was found through this method was held constant for Grouts 1-4. It was observed that

slump increased with the increasing quantities of mineral admixture. For Grout 5, Grout 6 and

Grout 7 the amount of water was reduced (thus reducing the water-cement ratio) in order to

produce grouts that had a slump less than eleven inches. ASTM C476 requires that masonry

grouts have a slump between eight and eleven inches and researchers in this project desired to

maintain the slump within these parameters when possible. The results of the slump tests for

each grout design can be seen in Table 3-2.

Single CMUs were also filled with grout for the purpose of creating grout samples. Due

to the large quantity of grout samples that would be broken, it was determined by researchers to

cast samples in single CMUs and later remove the grout centers with the use of a masonry saw.

Samples would not be saw-cut to the appropriate dimensions before compressive strength testing

as per typical ASTM C1019 methods but would be tested at the full size of the inside of the

CMU. Ten samples were cast according to typical ASTM C 1019 methods because ASTM

C1019 allows for a correlation to be made when test samples do not conform to the ASTM

specification. This correlation involves casting ten grout samples in a three inch by three inch

mold created by carefully placing 4 CMUs in a specified pattern. This mold is to be lined with a

permeable liner and an example of this mold is shown in figure 3-13. Figures 3-8 through 3-14

show different phases of the casting and testing process.

20

Figure 3-8: Slump Test

Table 3-2: Grout Slump Results

Grout Mix Slump (in) Temperature (°F)

1 9 68

2 9.5 70

3 10.5 69

4 Flowable 68

5 8 69

6 8.5 70

7 10.5 70

21

Figure 3-9: Flowable Type 4 Grout being Placed in Prism

Figure 3-10: Eight Inch Slump Grout Type 5 being Placed in Prism

22

Figure 3-11: Casting of Grout Samples

Figure 3-12: Grout Sample after Removal from CMU

23

Figure 3-13: Grout Correlation Sample Mold

Figure 3-14: Casting of Grout Correlation Sample

24

3.4 Specimen Preparation

When prisms and grout samples have reached the end of their curing time and are ready to

be broken, the ends of the specimen that will be in contact with the plates of the compressive

strength testing machine must be altered. If the sample were left as is, the highest points of the

jagged sample end would come into contact with the loading plates first. This would cause loads

to be concentrated on portions of the surface rather than distributed evenly over entire surface of

the sample. The effective bearing area of the sample would be decreased and would not be

calculable. In order to provide a surface that ensures that the load is transferred from the loading

plates to the entire cross-section of the sample, ASTM C617 requires that the sample is capped

with either molten sulfur or gypsum cement. These two capping methods provide a cap that

molds to the contours of the surface of the sample and cures to have a compressive strength

higher than that of the sample. For this research it was decided to use gypsum cement to cap the

samples.

Gypsum capping was performed in accordance with ASTM C140. Following this

procedure, an abrasive stone was rubbed over each sample end to remove loose protrusions from

the specimens to be capped. To cap the bottom side of the prism, a glass capping plate was

placed on the floor, a light coat of lubricating oil (WD-40 brand) was sprayed on the glass, and

gypsum cement capping material was spread evenly over the glass. Directly after the capping

compound was placed on the glass plate, the prism was placed on the capping compound. The

weight of the prism was sufficient to force the capping compound into the surface of the concrete

and assure that the thickness of the gypsum was less than 1/8 of an inch. When hollow CMUs

were capped it was necessary to press down on the CMU firmly to achieve the same effect. With

the bottom of the prism capped first, the top of the prism was capped next. After smoothing with

25

the abrasive stone, capping compound was placed evenly over the surface of the prism. After the

capping compound was placed, a glass capping plate was pressed firmly on the top of the

capping compound and a weight such as a CMU was placed over the plate.

The capping compound was allowed to cure for a minimum of 25 minutes before the

glass plates were removed from the specimen. When removing the glass plates it was common

to find that about 15% of the caps were broken or incomplete. Caps that were determined to be

deficient were removed and replaced. The deficiencies encountered included: caps not covering

the corners of the prism, caps that did not bond to the prism, caps that did not completely cover

the prism surface, caps that had large air bubbles, caps that were not perpendicular within .08

inches to the vertical axis of the prism, or caps that were broken when the glass plates were

removed. After the capping process was complete, capped prisms were allowed to cure

overnight to assure that caps would achieve the required strength.

3.5 Specimen Testing

After specimens were prepared with plaster caps, they were tested for compressive

strength. Compressive strength testing was performed using a Baldwin loading machine as can

be seen in Figure: 3-15. During testing, stress, strain, loading rate, and compressive resistance

were recorded by a software program called “Merlin" made by the Instron Corporation (12).

In order to have a backup of the most crucial data, sample dimensions and ultimate

compressive loads for each sample were also recorded by hand in a notebook. Due to the

antiquated nature of the computer and Merlin software that were used with the Baldwin machine,

there were a number of computer “crashes” and several sets of data were lost. Hand recorded

data from the notebook were used for those cases.

26

Figure 3-15: Baldwin Compressive Testing Machine

In order to conform to ASTM C1314 it was necessary to enlarge the effective bearing area

of the plates that the machine uses to load the specimens. The swivel plate on the lower head of

the Baldwin was nearly large enough for the specimens to fit on, having a radius that was only

about a quarter inch too small to fit the entire prism. In order to make sure that the corners of the

specimen were not hanging off of the bearing swivel by a quarter inch and conforming to ASTM

C1388, a steel plate with a thickness of 7/16 of an inch was placed on the existing swivel head.

On the top head of the machine, the existing swivel head had a smaller diameter and was too

small by two inches. In order to conform to ASTM C1388, the thickness of added plates must be

27

equivalent to the amount by which the existing bearing radius is too small. There were no steel

plates available that had a thickness of two inches or greater so it was necessary for researchers

to combine two steel plates. The first plate had a thickness of one and a half inches and the

second plate had a thickness of one half inch. These plates were welded to the existing top

swivel head of the machine so that researchers would not have to concern themselves with

centering the plates on each specimen before testing. Figure 3-16 shows a masonry prism being

tested for compressive strength as well as the placement and welds of the plates on the top and

bottom heads of the machine.

Figure 3-16: Bearing Plates

28

3.6 Chapter Summary

Specimens of hollow prisms, grouted prisms, mortar cubes, and grout were made. The

methodology for constructing the test samples and for testing the materials used adhered closely

to all pertinent ASTM standards so that this process would be standardized and repeatable.

Samples were tested for compressive strength after Curing for 14, 28, 42, 56, and 90 days.

29

4 RESULTS

This chapter discusses the manner in which the data from the compressive strength

testing of the samples were interpreted. First, it is described how simple statistics were applied

to the compressive strength results to determine if the data were valid. After validating the data,

a method for modifying the stress-strain curves was applied in order to remove extraneous

information that inherently occurs due to the imperfections of the testing process. Lastly this

chapter shows the performance of each specimen type in compressive testing and how the

strength of each sample type increased as cure time elapsed.

4.1 Data Reduction

A minimum of three samples were tested for compressive strength for each of the seven

prism types at each time interval (14, 28, 42, 46, 90 days) in accordance with ASTM C1314. For

most data sets there were four samples tested, providing the ability to remove data that were

deemed outliers. Outliers could not be removed from any groups that had only three samples in

order to conform to ASTM C1314. It was decided that for this research any value that was more

than one standard deviation from the group mean would be eliminated. This course of action

was chosen because samples that are more than one standard deviation from the group mean are

likely to have structural deficiencies such as void space in the grouted center or poorly placed

gypsum caps. Most all samples fell within one standard deviation and not many data were

30

removed. After eliminating outliers from any groups, the mean values for the group were

reported to be the compressive strength for the corresponding cure time and prism type.

Stress-strain curves were calculated by computer software for each sample tested. Due to

mechanical play or “slop” in the plates of the compressive testing machine and inconsistency in

the initial load applied to each sample before testing, there was significant variability in the

initial portion of the stress-strain curves that were generated. It was necessary to normalize these

curves so that they could be compared to each other. Normalization was accomplished by

assuming that any stress less than 1% of the maximum stress could be considered mechanical

settlement as the plates draw tight to the sample. When stresses were recorded less than this

amount both the stress and corresponding strain were removed from the curve. The averages of

the removed stresses and strains were used to plot a point that serves as the new origin for the

remaining curve. While there is still some apparent settlement after the normalization process,

settlement is dramatically reduced. For samples that had less settlement, the modified curve has

little to no flat portion at the beginning of the curve. In order to have uniformity in the stress-

strain curves, the end of the curve was truncated. This was accomplished by terminating the

curve after the stress has decreased to 50% of the maximum recorded stress. Figures 4-1 and 4-2

show the stress strain curve for one sample before and after modification respectively.

The data modification detailed above slightly alters the stresses, strains, and loads from

that outputted by the computer software. This slight altercation decreases the inherent error that

is caused by the inconsistency of the initial portion of the recorded stress-strain curve. The focus

of this research is to observe and report the findings concerning the compressive strength of each

sample. It was noted that the data modification resulted in an insignificant change in the

31

compressive strength of each sample. The compressive strengths reported in this section will be

the actual recorded compressive strengths, not the modified values.

Figure 4-1: Stress-Strain Curve before Modification

Figure 4-2: Stress Strain Curve after Modification

32

4.2 Compressive Test Results

ASTM C476 states that masonry prisms must have a compressive strength of 2000 psi at

28 days. As can be seen in Table 4-1, all seven grout types met this criteria except for the prisms

with Grout 4. ASTM C270 indicates that the minimum compressive strength for type N mortar

is 750 psi and, as can be seen in Table 4-1, the mortar cubes were much stronger than the

minimum. The hollow prisms and single CMUs had similar strength indicating that the thin

layer of weak mortar only has a slight effect on the strength of the system. Figure 4-3

graphically shows the compressive strength in psi of the hollow prisms, the CMUs, and the

mortar cubes. Figure 4-4 shows the compressive strength curves for the prisms with the seven

types of grout.

Table 4-1: Prism Compressive Strength at Each Time Interval in psi

GROUT TYPE Cure Time (DAYS)

14 28 42 56 90

1 3108.6 2702.4 3738.0 3748.8 3809.8

2 2397.4 2351.7 2891.6 3164.9 3188.5

3 2187.6 2132.5 2569.1 2686.4 3195.3

4 1984.0 1915.8 2340.8 2529.3 3052.0

5 2915.4 2751.3 3685.7 3699.1 4086.2

6 2803.0 2644.1 3242.0 3179.6 3557.0

7 2421.9 2462.7 3017.3 3221.9 3361.0

Hollow Prism 3192.4 3399.0 3393.7 3423.3 3458.0

CMU 3663.5 3366.6 2486.3 3963.7 2688.2

Mortar Cube 1266.4 1329.0 1636.1 1108.3 1108.3

33

Figure 4-3: Compressive Strength (psi) of CMUs, Mortar, and Hollow Prisms over Time

Figure 4-4: Compressive Strengths (psi) of the Seven Prism Types over Time

34

In these curves it can be observed that there was an apparent decrease in strength for all

seven prism types at the 28 day test time period. This is an unexpected result since it is

commonly known that concrete products gain strength over time. Researchers were unable to

determine what error might have caused these results but it is important to note that even with

this dip in strength, all prism types except for the Grout 4 group made strength at 28 days.

Figure 4-5 shows the strength gain curves for all seven prism types if the 28 day data were

eliminated. As is expected, the strength gain curve for the 100% Portland cement prisms has a

near level trajectory after 90 days but the prisms with FA and GGBS were continuing to gain

strength with time. A significant result is that mix number 5 gained early strength at a rate very

similar to the control group (100% Portland cement). It was not expected that a prism whose

grout has had 25% of the Portland cement replaced with FA and another 40% replaced with

GGBS gains strength as quickly as a Portland cement based grouted prism. This particular mix

also had a higher compressive strength at 90 days than the control group.

Figure 4-5: Compressive Strengths (psi) over Time Excluding 28 Day Data

35

4.3 Chapter Summary

Testing procedures provided stress-strain curves and ultimate compressive strength for

each sample. In test groups of four or more data for samples were discarded if the ultimate

compressive strength was more than one standard deviation from the group mean. Most data

were within one standard deviation. Stress-strain curves were modified to eliminate extraneous

data at the beginning and end of each curve. An inconsistency in the test results for the 28 day

tests was found and deemed to be insignificant due to the fact that all of the grout types except

for one still made strength.

36

37

5 CONCLUSIONS AND RECOMMENDATIONS

This chapter discusses the implications of compressive strengths attained by the masonry

samples tested in this study. A comparison is made between the compressive strength results of

the masonry prisms tested in this research and the masonry grout samples that were tested by

Twining Laboratories. Recommendations concerning further research that should be conducted

in order to ensure full confidence in the ability of these grouts to resist any possible load scenario

are made.

5.1 Conclusions

Compressive strength is the single most important design parameter in masonry design.

Other design parameters such as shear capacity and flexure are calculated based on the

compressive strength of the masonry prisms. Compressive strength testing of prisms is

commonly the only method used to ensure that materials used in construction meet the specified

design requirements.

Separate research performed concurrently with this research has confirmed that the

compressive strength of the grouts used to construct these masonry prisms were similar to the

grouts tested by Twining Laboratories (see appendix table A-3). Despite the fact that ASTM

C476 prohibits replacing more than 40% of Portland cement in masonry grout, this research has

shown that the required strength of 2000 psi can be met at 28 days when 45% and 55% of the

38

Portland cement is replaced with FA and when 65%, 75% and 85% is replaced with a mixture of

FA and GGBS. This research confirms that the performance of the prisms correlates to that of

the grout and that the use of high mineral admixture volume grouts is a viable method of

attaining the required compressive strength.

5.2 Recommendations

Further research should be conducted to determine if high mineral admixture volume

grouts differ from traditional grouts when tested for rebar pull-out strength, shear strength, and

flexural strength. The research performed in this study concentrated specifically on the

compressive strength of masonry prisms and it is possible that high volume of mineral admixture

in masonry grouts will change the way the system reacts in other loading conditions. In order to

ensure that design standards may be changed to allow the grout designs included in this study it

is necessary to ensure that they perform well to all potential loading scenarios.

39

REFERENCES

1. Adam, David: The unheralded polluter: Cement Industry Comes Clean on its Impact: in

Brussels The Guardian (newspaper), Thursday 11 October 2007. Accessed February 25,

2012. http://www.guardian.co.uk/environment/2007/oct/12/climatechange

2. Geertsema, Ari: Coal Products: Status and Future for the USA, University of Kentucky,

Center for Applied Energy Research. Accessed February 25, 2012.

http://www.flyash.info/2001/keynote/109geert.pdf

3. Mamlouk, Michael S. and Zaniewski, John P. Materials for Civil and Construction

Engineers Second Edition, Pearson Prentice Hall, Upper Saddle River, NJ 2006

4. Mindess, S., Young, J. F. and Darwin, D. Concrete, Second Edition. Prentice Hall, Upper

Saddle River, NJ, 2003

5. Swamy, R.M. Cement Replacement Materials, Surrey University Press, Blackie and Son

Ltd, 1986

6. Ferguson, G. and Levorson, S. M. Soil and Pavement Base Stabilization with Self-

Cementing Coal Fly Ash. American Coal Ash Association, Virginia, 1999.

7. Kang, Grace S. and Kren, Alan. Structural Engineering Strategies Towards Sustainable

Design September 10, 2007. Accessed February 25, 2012.

http://www.seaonc.org/pdfs/SESTSD%20final%20%20.pdf

8. ACI committee 232. Use of Fly Ash in Concrete, ACI Manual of Concrete Practice, reported

by American concrete institute, April 1996

9. Day, Ken W, Concrete Mix Design, Quality Control and Specification, E & FN Spon,

London, UK 1995

10. Whiting, David. Ground Granulated Blast-Furnace Slag, Federal Highway Administration,

USDOT. Accessed February 25, 2012.

http://www.fhwa.dot.gov/infrastructure/materialsgrp/GGBS.htm,

11. ASTM Volume 04.02, Concrete and Aggregates, ASTM International, West Conshohocken,

PA, 2010.

12. Merlin (Revision B) [software]. 825 University Ave.Norwood, MA 02062-2643:Instron

40

41

APPENDIX A: TWINING LABORATORY GROUT TEST INFORMATION

Table A-1: Twining Laboratories Grout Specimen Compressional Strength Data

Age

(days)

100%

Portland

Cement

(psi)

20% FA

Replacement

(psi)

30% FA

Replacement

(psi)

40% FA

Replacement

(psi)

50% FA

Replacement

(psi)

60% FA

Replacement

(psi)

50% FA &

GGBFS

Replacement

(psi)

60% FA &

GGBFS

Replacement

(psi)

70% FA &

GGBFS

Replacement

(psi)

80% FA &

GGBFS

Replacement

(psi)

7 2982.5 2780.0 2450.0 1540.0 1610.0 910.0 1890.0 2260.0 1940.0 1460.0

14 3285.0 2920.0 2970.0 2140.0 2090.0 1150.0 2890.0 3270.0 2770.0 1940.0

28 4062.5 3310.0 3830.0 2690.0 2880.0 1440.0 3310.0 3230.0 3410.0 2430.0

42 4175.0 3800.0 3880.0 3050.0 3130.0 1930.0 3660.0 4540.0 4210.0 2710.0

56 4300.0 4250.0 4650.0 3330.0 2960.0 2070.0 5010.0 4830.0 4260.0 3140.0

180 4120.0 5180.0 5670.0 4690.0 4330.0 3790.0 6210.0 6010.0 5260.0 3590.0

Table A-2: Absorption, Density and Moisture Content of CMU Samples

Wr,

Received

Weight

Wi,

Immersed

Weight

Ws,

Saturated

Weight

AbsorptionMoisture

Absorbed

Moisture

Content

(lb) (lb) (lb) (lb) (kg) (pcf) (g/cm3) (%) (%) (pcf) (g/cm

3) (%)

1 22.15 12.40 22.82 21.48 9.75 8.0 0.13 6.2 50.17 128.63 2.06 3.12

2 22.04 12.21 22.62 21.15 9.59 8.8 0.14 6.9 60.81 126.87 2.03 4.21

3 22.05 12.37 22.63 21.14 9.59 9.1 0.15 7.1 61.39 128.61 2.06 4.34

4 22.28 12.66 22.86 21.58 9.79 7.8 0.12 5.9 54.46 132.08 2.11 3.21

5 22.00 12.14 22.60 21.18 9.61 8.4 0.13 6.7 58.14 126.45 2.02 3.88

6 21.87 12.10 22.48 21.06 9.6 8.5 0.1 6.7 56.96 126.64 2.0 3.83

Averages 21.27 9.6 8.4 0.1 6.6 56.99 128.21 2.1 3.76

Wd, Dry

WeightSpecimen

#

DensityAbsorption

42

Table A-3: Twining Laboratories Grout Compressive Strength Results

43

APPENDIX B: MATERIAL PROPERTY CHARTS

Figure B-1: Manufacturer Supplied CMU Properties

44

Figure B-2: Manufacturer Supplied Coarse Aggregate Properties

45

Figure B-3: Manufacturer Supplied Fine Aggregate Properties