COMPUTATIONAL RESEARCH AND THEORY FACILITY

LAWRENCE BERKELEY NATIONAL LABORATORY

Ana Lua

Melissa Meikle

Chwei Peng Tieng

Qudsia Wahab

April 22, 2014

CEE 165: Concrete Materials and Construction

Professor Monteiro

2

Abstract ...................................................................................................................................................... 3

Introduction ................................................................................................................................................ 4

Mix Design .................................................................................................................................................. 6

High Early Strength Concrete ......................................................................................................... 8

Fiber Reinforced Concrete .............................................................................................................. 9

Shotcrete ........................................................................................................................................ 10

Controlled Density Fill .................................................................................................................. 12

Reinforcement ........................................................................................................................................... 13

Mixing and Transportation ........................................................................................................................ 15

Placement .................................................................................................................................................. 16

Formwork .................................................................................................................................................. 17

Consolidation ........................................................................................................................................... 18

Curing ........................................................................................................................................................ 18

Finishing .................................................................................................................................................... 19

Conclusion ................................................................................................................................................. 21

Acknowledgements ................................................................................................................................... 21

References ................................................................................................................................................. 22

Appendix ................................................................................................................................................... 23

TABLE OF CONTENTS

3

The Computational Research and Theory (CRT) Facility at Ernest Orlando Lawrence Berkeley National

Laboratory is currently under construction with an expected completion date of late December 2014 or early

2015. This is a unique construction project due its location on a hillside, proximity to the Hayward fault, and

use to accommodate multimillion dollar supercomputers. DPR Construction is working as the construction

management firm on the project in combination with LBNL, the owner representative. Out of the approximate

twenty mix designs, four have been discussed extensively: high early strength, fiber reinforced concrete,

shotcrete, and controlled density fill. The mix designs commonly used Portland cement types I, II, and V with

coarse and fine aggregates, fly ash class F, and admixtures. DPR Construction has worked with two different

subcontractors to obtain the required concrete: CEMEX and Central Concrete. The centrally mixed concrete

has been delivered to the facility through concrete trucks and has been placed primarily through concrete

pumps, with select structures being casted using pneumatic guns for shotcrete placement. The facility’s

exposure to seismic risk necessitated heavy reinforcement in some locations of the building, and a variety of

rebar sizes are used, albeit not coated with epoxy. The majority of formwork used is made of Douglas. An

array of finishes have been specified for different levels or sections of the facility with practical and aesthetic

considerations in mind. In this project, there are no known quality assurance issues; however, quality control

problems have arisen throughout the construction of the facility. Overall, this high profile project, like any

other, has involved its fair share of construction issues but is well on its way to becoming a state-of-the-art

computing facility with LEED Gold certification.

ABSTRACT

4

Located on 200 acres in the hills above the

University of California, Berkeley campus lies the

Ernest Orlando Lawrence Berkeley National

Laboratory (LBNL), where multidisciplinary

scientific teams work together to solve global

problems in human health, technology, energy, and

the environment. Ernest Orlando Lawrence laid the

foundation of the laboratory’s creation and his legacy

of team science paved the way for discoveries that

led to 13 Nobel Prizes.

The Computational Research and Theory (CRT)

Facility continues this tradition and encourages

expertise coupled with an optimal environment to

advance research. The CRT Facility will bring

together the Computing Sciences Division within

LBNL for the first time, which includes: The

National Energy Research Scientific Computing

Center (NERSC), The Computational Research

Division, The Scientific Networking Division, and

Computational Science and Engineering at Berkeley

(CSE). Through these divisions, key research areas

including global climate change, fusion energy,

biological and environmental basic energy science,

and astrophysics are expected to greatly benefit from

the CRT Facility. Additionally, the facility’s close

location to the University of California, Berkeley will

enable students, scientists, and faculty a common

meeting place to discuss and carry out research in

science and computing.

Figure 1: Image of Rendered Project

The CRT Facility project, approximately 140,000

gross-square-feet with 4 levels, was broken into two

phases, site preparation involving rerouting utilities,

and excavation and construction. DPR Construction

won the construction management bid for the project

in 2007. After settling a litigation regarding the

buildings’ proximity to Strawberry Creek that put the

project on hold for two years and reevaluating the

budget, the budget became lower than expected in

2011 and construction finally began late that year.

With a budget of $125 million from University of

California and $19.8 million from Department of

Energy (DOE), the project is expected to be

completed by late December 2014 or early 2015 with

LEED accreditation of Gold. By incorporating

Berkeley’s climate, the CRT Facility is anticipated to

greatly improve the efficiency of energy for high-

performance computing and be among the forefront

of high-performance supercomputing research.

With a project of this magnitude and location, many

challenges arose. In regards to the location, the site is

located 100 yards away from the Hayward fault. The

Hayward fault is located along the topographic

interface between the gently sloping plain and hills,

and poses a significant ground-rupture and seismic

shaking hazard to LBNL.

Figure 2: Geographic Location of Hayward Fault

Souce: http://seismo.berkeley.edu/tour/tourmap.html

INTRODUCTION

5

In addition to the project’s close proximity to the

Hayward fault, the CRT Facility is uniquely located

on a hillside near the Blackberry entrance to the

laboratory. The steep hillside and small roads

presented many obstacles with excavation, step

footings, and tie-backs. The combination of these

caused the first 18 months of the project to be

dedicated solely to foundation work, which is

typically longer relative to most projects. The

foundation work was taken into special consideration

to ensure the building performs satisfactorily during a

seismic event, especially since the building will

contain a computing floor level that will house

multimillion dollar supercomputers. Having this

computing floor level with a seismically isolated

floor system makes this project unique and

innovative compared to other construction projects.

A construction project at LBNL also presents a

uniqueness in terms of safety regulations.

Supplementary to standard Occupational Safety and

Health Administration (OSHA) regulations, the

project must also follow DOE and LBNL policies

and coordinate with the City of Berkeley and

University of California. LBNL implements their

own safety inspectors that are on-site to ensure their

policies along with all other policies and regulations

are being met.

All four group members had the opportunity to

explore the CRT Facility construction site and learn

the procedures and processes involved in the creation

of the facility. Site visits were conducted in 2014 on

February 19th and 20th, and March 26th and 28th.

Through these site visits, contact with Tim Hart

(Structural Engineer and Consultant), Tim Kemper

(Construction Manager), Ian White (Project

Manager), Rory Shortreed (Inspector of Record)

from LBNL and Mike Miller (Project Engineer) from

DPR Construction assisted with providing

information on mix design, concrete transportation,

reinforcement, concrete placement, finishing, and

construction issues of the CRT Facility project.

6

For a project with several different needs, such as the

CRT Facility, it has been necessary for the contractor

to use a variety of unique concrete mix designs to

implement at different areas throughout the building.

Table 1 summarizes properties of the concrete

required for various locations.

Table 1: Required Concrete Properties for Different

Locations

Approximately 20 mix designs have been used for

different components of the building. Four mix

designs, including mixes for high early strength

concrete, fiber reinforced concrete, shotcrete, and

controlled density fill (CDF) are discussed in detail.

In these diverse concrete mixes, some of the

properties for cement, aggregate, and admixtures

overlap. With the exception of the fiber reinforced

concrete mix design, the concrete mixes are provided

by CEMEX at their Berkeley and Oakland mixing

plant locations. These mix designs were submitted

for review to satisfy the engineer of records

specifications.

Cement

Portland cement is a hydraulic cement capable off

setting, hardening, and remaining stable under water.

Through various tests, CEMEX had certified that the

Portland cement in all the mixes (except fiber

reinforced concrete mix) met or exceeded the

chemical and physical specifications of ASTM C-

150, ASTM C-1157, and AASHTO M 85. The

source of most of the cement was from the CEMEX

Construction Materials Pacific LLC plant in

Victorville, CA, which is located 340 miles from the

project site. This cement was then transported to the

mixing plants in Berkeley and Oakland, located 5

miles and 10.5 miles away respectively. According to

the Cement Mill Test Report provided by CEMEX

that compares the standard chemical and physical

requirements, high early strength concrete, shotcrete,

and CDF qualified as Type I, Type II, and Type V.

Aggregate

Aggregates are broken into two categories - coarse

and fine - and are used to provide dimensional

stability for concrete. The specifications for both

types of aggregates used in the project were provided

mostly to CEMEX by Thornton Tomasetti.The

aggregates for all of the mixes discussed in this

section except those for high early strength concrete

were mined in Eliot Quarry in Pleasanton, CA,

located 37 miles from the project site, and processed

in the Bay Area. The Eliot Quarry produces

MIX DESIGN

Location 28-Day

Strength (psi)

Slump +/- 1 (in)

Min – Max Fly Ash (%)

Footings / Grade Beams

3,000 4 20 - 40

Slab-on-Grade

3,000 2 - 4 15 – 25

Fiber Reinforced Slab

3,000 4 15 – 25

Walls / Columns

5,000 4 15 – 25

Elevated Beams, Slabs and Flll on Metal Deck at HPC Level

5,000 4 15 – 25

Fill on Metal Deck (Except for HPC Level)

4,000 2 – 4 -

Shotcrete for Temporary Walls

4,000 4 15 – 25

Cantilever Retaining Walls and Their Footings

4,000 4 15 – 25

7

greywacke and sandstone aggregates, an inexpensive

source of moderately shrinking aggregate that is

suitable to use for normal strength concrete. For high

early strength concrete, the aggregates were imported

over 1,000 miles away from Polaris’ Orca Quarry in

British Columbia, Canada to Pleasanton, CA. The

cost of the aggregates for all the mixes is unknown.

Admixtures

Admixtures are additions to the concrete mix other

than cement, water, and aggregates to improve or

modify some or several properties of concrete. In this

project, both types of admixtures were used: mineral

and chemical. The decision to incorporate admixtures

in the mix design and their proportions was made by

CEMEX and approved by Thornton Tomasetti based

on tests.

Mineral admixtures are fine-grained materials that

are added to the concrete mix in large amounts to

improve its properties. They are by-products of coal,

iron, steel, and other industries that reduce the

environmental impacts of dumping the waste into

landfills and streams. This environmental impact was

taken into consideration when selecting a mineral

admixture. In this project, fly ash was the mineral

admixture used in the fiber reinforced concrete,

shotcrete, and CDF mix designs to improve the

workability, durability, cohesiveness, and ultimate

strength of concrete. Fly ash was also used to assist

with the reduction of thermal cracking, bleeding, and

segregation. Most of the fly ash used in mix designs

was Class F (low calcium) Jim Bridger fly ash

provided by Headwaters Resources from Wyoming

located 1,105 miles away from the project site. The

choice to use fly ash, an increasingly common choice

in construction, came from a desire to receive LEED

certification points for the substitution of cement

with a mineral admixture; fly ash was deemed a

better choice than slag because it was less costly and

had a more predictable behavior.

Properties High Early

Strength Concrete Fiber Reinforced

Concrete Shotcrete

Controlled Density Fill

28-Day Compressive Strength (psi)

5,000 @ 3-days 3,000 5,000 100

w/c 0.39 0.55 0.42 0.86

Slump (in) 4 4 2 NA

Air Content (%) 2.5 7.6 2.5 10

Clinker Composition (%)

C3S 60 64 61 60

C2S 15 11 13 14

C3A 4 8 4 4

C4AF 11 8 11 12

Mix Material Percentage of Total Weight (%)

Cement 19 6 17 1

Fly Ash Class F 0 6 3 8

Coarse Aggregate 42 40 21 43

Fine Aggregate 33 41 50 39

Water 7 7 9 8

Table 2: Properties and Compositions of Four Different Mixes

8

Chemical admixtures can have different purposes

depending on the type used. The types of chemical

admixtures used in this project are Type A water-

reducing, Type D water-reducing and retarding, and

air-entraining. All of the chemical admixtures used in

the project were manufactured and supplied by Grace

Construction Products, W.R. Grace & Co. - Conn.

(W.R. Grace) and formulated to comply with

Specifications for Chemical Admixtures for

Concrete. W.R. Grace was located in Livermore, CA,

37 miles away from the project site. All of the

recommended dosages were followed.

Table 2, on the previous page, summarizes details

provided by manufacturers and general contractor of

these four diverse mixes. This table allows for the

comparison of properties and compositions between

the mixes.

These four mixes and their individual properties are

discussed extensively as follows.

High Early Strength

High early strength concrete is the type of concrete

that develops relatively high compressive strength in

a shorter span of time when compared to normal

strength concrete. On occasions, this concrete can be

used to accelerate a project’s schedule. As a result of

the higher early compressive strength, loads can be

applied sooner to the casted concrete, and the next

dependent task in the schedule can commence. Most

of these mixes are more expensive than typical

concrete mixes.

In this project, high early strength concrete was used

for walls of the CRT Facility footings with tiebacks

that required a compressive strength of 3,000 psi

within 7 days, and slabs on deck. This section will

specifically cover high early strength concrete used

for walls, which did not use the concrete properties

for its high early strength but rather used it for

scheduling purposes. The use of this concrete mix

design allowed for formwork to be removed after one

day, in addition to allowing the concrete to achieve

60-70% compressive strength gain in four days.

The concrete was specified to achieve a compressive

strength of 5,000 psi at three days [Table 2], after

which a compressive strength test was conducted to

verify this before proceeding with formwork

removal. The water-to-cement ratio, at 0.39

[Table 2], was relatively low compared to other

mixes, which can help assist with its high strength.

Table 3, below, describes the material composition of

high early strength concrete mix design.

Cement

The composition of C3S in cement used in the project

Material Description Source Oz/yd Weight (lb) Volume

(ft3)

Cement Type I/II/V CEMEX - 776.0 3.95

Coarse Aggregate

Orca ½” x #4 Polaris Minerals

Corp. - 1750.0 9.70

Fine Aggregate Orca Concrete

Sand Polaris Minerals

Corp. - 1365.2 7.87

Type A Water Reducer

WRDA 64 W.R. Grace 2.0 – 4.0 oz/

cwt C - -

Water - - 36.0 gal 300.4 4.81

Air - - - - 0.68

Table 3: Mix Design of High Early Strength Concrete

9

is somewhat high at 60% [Table 2], which assisted

with high early strength development. Although

sulfate resistance was not required for the concrete

walls, the mix contained less than 5% of C3A which

will provide high resistance against sulfate attacks.

Aggregates

Unlike the other mixes, aggregates in this mix were

from Orca Sand & Gravel in British Columbia,

Canada and supplied by Polaris Minerals Corp. ½” x

#4 gravel was used as coarse aggregate and concrete

sand was used as fine aggregate.

Mineral Admixture

No mineral admixtures were used in the high early

strength concrete mix, making it the only mix out of

the four discussed to not contain any fly ash. This is

because substitution of cement with fly ash will

reduce the amount of C3S in the mix, which is

responsible for high early strength development.

Although fly ash could be added instead of

substituted into the mix, this is likely not practical

since fly ash does not play an important role in high

early strength development and its addition would

increase costs without any energy savings.

Chemical Admixture

The high early strength was achieved by using a

Type A water-reducing admixture from Grace

Concrete Products, which produces concrete with 8-

10% less water. Since the amount of water reduction

is less than 15%, this admixture is simply a

plasticizer. This water-reducing admixture was used

to reduce the required amount of water, lowering the

water-to-cement ratio. This allowed for higher

strength without the addition of cement. The addition

of this admixture also increased the consistency of

the mix without the addition of cement, reducing the

amount of water needed for the same slump.

Concerns of corrosion from the use of admixtures is

eliminated through the use of this particular product,

which does not contain calcium chloride. For every

100 pounds of concrete, 3-6 ounces of the water-

reducing admixture was used.

Fiber Reinforced Concrete

Fiber reinforcement was used as a means to reduce

shrinkage cracking that often occurs in slabs with

large exposed surfaces. The proper use of these fibers

makes for efficient load distribution, and is typically

cheaper than placing reinforcement or wiremesh that

may be susceptible to corrosion. Due to scheduling

problems, the fiber reinforced concrete mix could not

be brought in by CEMEX and was instead brought in

by Central Concrete from San Jose. Table 4, below,

describes the material composition of fiber reinforced

concrete mix design.

Material Description Source lbs/cu

yd Weight

(lb) Volume

(ft3)

Cement Type II/V CalPortland - 243.0 1.24

Fly Ash Class F Four Corners Flyash Salt River Materials - 243.0 1.59

Coarse Aggregate Eliot 1” x #4 CEMEX - 1675.0 10.02

Fine Aggregate Top Sand

Vulcan Materials Company

- 812.0 4.94

Fine Aggregate Oakland Concrete Sand

Hanson Aggregates - 812.0 4.95

Fiber Reinforcement

MasterFiber M 70 BASF 0.75-1.50

- -

Water - - - 267.0 4.28

Table 4: Mix Design of Fiber Reinforced Concrete

10

Cement

Central Concrete chose a combination of Type II and

V cement, which was called “Mojave” by the

company they received it from, CalPortland located

527 miles away from the project in Mojave, CA. The

clinker composition was 64% C3S, 11% C2S, 8.3%

C3A, and 7.5% C4AF, which reveals a significantly

larger amount of C3A than found in any of the other

mix designs. The use of such a mix indicates that a

high heat of hydration was desired. Although using a

large amount of C3A can cause concerns of sulfate

attack, the location shows little possibility of sulfate

attack occurring.

Aggregate

The coarse aggregate, 1” x #4, were obtained from

Eliot Quarry in Pleasanton, CA.

Fine aggregates were Vulcan sand brought in from

Pleasanton, and Oakland concrete sand. Unlike the

other three mixes, two types of fine aggregates were

incorporated into the mix: top sand and concrete

sand. The top sand is processed in Pleasanton, CA

whereas the concrete sand is processed in Oakland,

CA.

Mineral Admixture

Fly ash was the only type of admixture used in the

mix design of fiber reinforced concrete. The fly ash

used was a Class F fly ash, a low calcium fly ash,

which is nonreactive on its own at ordinary

temperatures. The Four Corners Fly Ash is sourced

from Fruitland, New Mexico, located over 1,000

miles away from the CRT Facility job site. There was

a 15-25% fly ash content substitution for the fiber

reinforced concrete mix design.

Fibers

The fiber reinforced concrete was used for the

topping slab of the floors on top of their metal decks.

This was specified by the architect so as to control

the formation and propagation of any unsightly

cracks. The fibers, which were supplied by BASF

Corporation, were “MasterFiber M70”, a

monofilament microsynthetic fiber, and the fibers

increased the concrete’s tensile strength to about

25,000 psi. A low volume fraction of fibers was used

to have an efficient load distribution over the length

of the slabs. The plastic fibers were of uniform size,

with a diameter of 33 microns and a length of three

fourths of an inch. For every cubic yard of concrete, a

pound and a half of fibers were added, with around

27 pounds of fiber being added for every cubic yard

of concrete.

Shotcrete

Shotcrete is a technique used to apply concrete in

locations where thin sections are required and in

locations that are difficult to reach with typical

concrete placement methods. For the CRT Facility,

shotcrete was used to place the concrete on some

walls and stairs. This was chosen due to its

advantages of vertical placement and ability to travel

faster after placement. While two types of shotcrete

mixes were used for this project, the alternate

shotcrete mix design with Recover® will be

discussed here. CEMEX was responsible for

providing the mix design. Table 5 outlines properties

used in this mix.

Cement

The base cement phase composition consists of 61%

C3S, 13% C2S, 4% C3A, and 11% C4AF shown in

Table 2. This mix has a slightly higher C3S, lower

C3A, and slightly higher C4AF content relative to

normal strength concrete. The higher C3S content

alone provided higher heat of hydration and early

strength, while the lower C3A content offered a lower

heat of hydration. This cement composition qualified

as Type I, Type II, and Type V.

Aggregate

Both the coarse aggregate and fine aggregate, ⅜” x

11

#8 gravel and fine concrete sand respectively, were

sourced from Eliot Quarry in Pleasanton, CA. These

were approved and certified from tests conducted at

Aggregate Technical Services in the same region.

The coarse aggregate used was finer than the ones

used for high early strength concrete and fiber

reinforced concrete.

An interesting aspect to note is the fine/coarse

aggregate ratio, in which there is a disproportionately

high amount of fine aggregate compared to those

ratios used in the other mixes. From Table 2, it can

be seen that coarse aggregate constitutes only 21% of

the total mass of the mix, approximately half of the

percentages in the other mixes. The proportion of

fine aggregate is also relatively high at 50%. This

fine /coarse aggregate ratio is likely optimized to

reduce aggregate void content to increase the

workability -- and hence, pumpability -- of shotcrete,

while including cost considerations.

Mineral Admixture

Fly Ash Class F, low-calcium, was used in this mix

design for shotcrete. The Jim Bridges Fly Ash is

provided by Headwaters Resources, sourced from the

Jim Bridger Plant in Rocksprings, Wyoming. A small

amount of approximately 3% of fly ash was used

relative to the overall mix.

Chemical Admixtures

In this shotcrete mix design, a chemical admixture of

Type D, water-reducing and retarding, was used to

control the setting time in order to maintain the

workability and pumpability of the shotcrete. The

admixture product selected for this purpose was

Recover®, which was manufactured and supplied by

W.R. Grace. Recover® is an aqueous chemical

solution used to stabilize the hydration of Portland

cement and provide extra workability time by

preventing the concrete mix from reaching initial set

and setting for a given period of time. This retarding

admixture was used to lengthen the set time of

shotcrete, extending the required delivery time for

the shotcrete mix from 60 minutes to 90 minutes.

Another chemical admixture, Type A water-

reducing, was used to increase the concrete

consistency, achieve a higher compressive strength,

and save cement. While all three of these benefits

cannot be obtained at the same time, at most two can

be achieved. The water-reducing admixture selected

for this purpose was WRDA 64, also manufactured

and supplied by W.R. Grace. WRDA 64 is a polymer

based aqueous organic compound solution that

Material Description Source Oz/yd Weight (lb) Volume (ft3)

Cement Type I/II/V CEMEX 679.0 3.45

Fly Ash Class F Headwaters

Fly Ash Headwaters Resources

120.0 0.81

Coarse Aggregate Eliot 3/8” x

#8 CEMEX 821.0 4.91

Fine Aggregate Eliot Natural

Sand CEMEX 1953.8 11.81

Type A Water Reducer WRDA 64 W.R. Grace 2.0 – 4.0 oz/cwt C

Type D Water Reducer & Retarder

Recover W.R. Grace 13.6 oz

Water 40.0 gal 333.8 5.35

Air 0.67

Table 5: Mix Design of Shotcrete

12

produces a concrete with water content of 8 to 10%

in reduction, greater plasticity, and higher strength.

The recommended dosage was followed in this mix

with a dosage of 2.0 to 4.0 oz/cwt C. This low

viscosity liquid admixture was factory pre-mixed in

exact proportions to avoid mistakes and minimize

handling.

Controlled Density Fill

Self-consolidating concrete was not used in this

project due to budget constraints but there were

several concrete materials used that were self-

compacting or self-leveling. One of these was

controlled density fill (CDF), alternatively known as

controlled low-strength material (CLSM), flowable

fill, soil-cement slurry, unshrinkable fill, plastic soil

cement, or flowable mortar. CDF is a self-

compacting, cementitious material with similar

structural capacity to that of soil.

CDF was mainly used as a substitution to compacted

soil backfill. According to the American Concrete

Institute (ACI), CDF should have a compressive

strength lower than 1,200 psi. The CDF used in the

project had a compressive strength of 100 psi to

match the strength of soil backfill and also to allow

potential excavation. For this construction job, CDF

was specifically used to fill up over-excavated holes

that were dug to about 8 feet to the expected bottom

of the colluvial soil layer. Since the CDF mix was

highly flowable, its placement does not require much

labor or consolidation. CEMEX was responsible for

providing the CDF mix for this project. Table 6

shown below describes its material composition

below.

Cement

Compared to the other mixes, very small proportions

of cement were used in CDF. Cement only

constitutes 1% of the total mass of the mix,

compared to 6-19% for the other three. This was

because CDF only needs to achieve a compressive

strength of less than 300 psi to match the structural

capacity of soil.

Similar to high early strength concrete and shotcrete,

the cement qualifies as Type I, Type II, and Type V.

This suggests that the CDF has high sulfate

resistance, appropriate for its use as soil backfill

since it may be exposed to soil with high presence of

sulfates. Table 2 shows the clinker composition of

the mix juxtaposed with the other four mixes. The

composition of C3A is less than 5%, indicating that

the mix indeed has high sulfate resistance. Since C3A

produces the highest heat of hydration out of all the

clinkers, its low composition reduces the heat of

hydration of the mix. However, this may be offset by

the higher percentage of C3S which contributes to

Material Description Source Oz/yd Weight (lb) Volume (ft3)

Cement Type I/II/V Cemex 30.0 0.15

Fly Ash Class F Headwaters Flyash

Headwaters Resources

300.0 2.02

Coarse Aggregate Eliot 3/8” x #8 Cemex 1533.0 9.16

Fine Aggregate Eliot Natural Sand

Cemex 1388.5 8.39

Air Entrainer Daravair 1000 WR Grace 2.0 – 20.0 oz

Water 34.0 gal 283.7 4.55

Air 2.73

Table 6: Mix Design of Controlled Density Fill

13

high heat of hydration and early strength

development.

Aggregates

The aggregates used in the mix are ⅜” x #8 gravel as

coarse aggregate and concrete sand as fine aggregate,

both sourced from Eliot Quarry in Pleasanton,

CA. As with all the aggregates from this source, the

tests conducted by Aggregate Technical Services, the

#8 gravel and concrete sand showed that the sodium

sulfate soundness and alkali silica reactivity fell

within allowable limits.

Mineral Admixture

CDF was proportioned with fly ash to improve

workability and reduce bleeding, segregation or

settlement, which is important to produce self-

leveling concrete. Approximately 90% Fly Ash F was

used in this mix design. The maximum compressive

strength of the material was less than the one made

with larger proportions of Portland cement due to the

long term strength development. Fly ash constituted

8% of the total mass of the mix, thus, less cement

was required, resulting in lower costs and lower heat

of hydration which help achieve the required lower

compressive strength of 100 psi.

Chemical Admixture

Chemical admixture was used to entrain air into CDF

which produces a specified air content of 10% by

volume. Air entraining admixture in CDF controls

strength development, improves workability, and

reduces the water content, bleeding, shrinkage and

settlement. In this mix, Daravair 1000, manufactured

and supplied by W.R. Grace, was used. It is a liquid

air-entraining admixture that increases the plasticity

and workability of concrete. Daravair 1000 also

increases the durability of concrete by increasing

resistance to freezing and thawing.

Concrete is a great construction material that has a

high compressive strength, but is approximately ten

times weaker in tension. This is the reason why

concrete is frequently reinforced. Reinforcement,

typically steel, is required in concrete structures to

prevent cracks from initiating and propagating, to

reduce concrete thickness, and to increase the tensile

strength.

Different bar sizes are used for reinforcement of the

structural components of buildings. The ASTM

specifications for each rebar require identification

marks to be rolled into the surface of the bar to

denote the producer’s mill designation, bars size,

type of steel, and minimum yield strength.

Figure 3: Labeling on Reinforcement Bar

In order to prevent rebars from corroding, epoxy

coating is required or a minimum cover over the

rebars has to be maintained as indicated in the code.

In this project, epoxy coating was not used, which is

standard practice in California because it is believed

that the bond between bar and concrete is better

without coating. According to Hart (Structural

Engineer and Consultant), corrosion is not a concern

in this project because a concrete cover of 3 inches is

provided as recommended by the code and the

climate in this region is not as moist compared to

REINFORCEMENT

14

other regions. However, in a meeting with Miller

(Project Engineer), he expressed that there might be

some issues with corrosion due to the difficulty of

maintaining a 3 inch cover on heavily reinforced

walls.

Figure 4: Heavily Reinforced Walls

During construction, some locations had concrete

cover of only 1 or ¾ of an inches. This was a critical

concern because the purpose of the concrete cover is

to provide reinforcing bars with sufficient

embedment to enable the rebars to be stressed

without slipping. As a result, close inspection was

conducted to ensure corrosion and rebar slippage

would not become an issue.

To resolve the lack of clear cover, DPR Construction

consulted with Thornton Tomasetti to approve areas

where less coverage would be acceptable. In these

areas, an extra layer of waterproofing was added to

accommodate for the coverage that was less than 3

inches. In other locations, subcontractors solved the

problem by applying crowbars to wrench the rebar

back into its place. The concrete cover issue confused

some subcontractors since the ACI 318-11 code

expressed a concrete cover that was less than the

cover desired per Thornton Tomasetti’s request. In

addition to a cover smaller than specified, the loss of

concrete cover occurred in places where all the

reinforcement was packed into the walls, which

provided the opportunity for rebar to shift out of

alignment. One case that illustrates a similar issue

was on the computing floor level. The reinforcement

in the slab was placed too high and caused the top

concrete layer to spall off.

Figure 5: Concrete Layer

LBNL believes this will be fixed by patching the

area. When the area is patched, the method should be

done with caution to avoid and eliminate thermal

mismatch, cracking, elastic mismatch, and mismatch

in strength. The combination of these obstacles that

arose caused a delay in the CRT Facility project

schedule due to the large amount of time lost having

to redo and properly fix the placement of

reinforcement.

15

CEMEX was responsible for the majority of the

concrete used in the project and delivered the

concrete from their central mixing plants in Berkeley

and Oakland, situated approximately 5 miles and

10.5 miles away from the job site, respectively. Most

of the mixes used in the project were transported and

derived from the Berkeley plant with the exception of

the shotcrete mix which was obtained from Oakland.

The other concrete mixes were supplied from Central

Concrete in San Jose, located 46 miles away from the

site, in the case of fiber reinforce concrete and one

other mix that was switched from CEMEX due to

delivery issues. This shift in mixing plant assisted

with the project schedule to avoid delays pertaining

to delivery.

Figure 6: Concrete Truck

Despite the specification stating for concrete in

trucks to be delivered within the standard 90 minutes,

DPR Construction adhered to a more stringent

requirement of 60 minutes for concrete delivery time.

According to DPR project engineer, Mike Miller,

meeting this requirement was especially crucial for

shotcrete, where they have confronted issues of

shotcrete setting in the hose that only had a 2 or 3

inch diameter as opposed to 4 inches. As part of their

quality control, the loading, departure, arrival, and

unloading times for each batch of concrete were

recorded in concrete tags as shown in Fig. 7 below:

MIXING AND TRANSPORTATION

Figure 7: Concrete Tag

Ensuring timely transportation of concrete - and

consequently, obtaining the correct quantity of

concrete for placement - constituted some of the

major challenges in the project. As a result of the

stringent delivery time requirement, a number of

concrete trucks that failed to arrive within 60 minutes

after loading had to be turned around. This not only

delayed the start of the next activity but also incurred

additional cost: a single turn around for a cement

truck with a 9 cubic yard capacity costs $1,000. The

issue of delayed transportation resulting in the

unsatisfactory concrete workability for placement

was dealt with through the use of an alternate

shotcrete mix described earlier. This mix

incorporated a Type D retarder, W.R. Grace

Recover® to extend the setting time. This allowed

for the required delivery time to be extended from 60

minutes to 90 minutes. In the case where trucks went

past the 90 minute limit, they were refused and asked

to leave the job site.

The topography of the site also presented another

challenge in terms of transportation. The location of

LBNL in the hills created concerns of concrete in the

cement truck falling out due to the steep slope. As a

precaution, concrete trucks were limited to transport

8 instead of 9 cubic yards of concrete.

16

Concrete Pumps

The concrete used in the project was placed primarily

through the use of pumps attached to the concrete

truck, performed by CF&T Concrete Pumping. The

pumps delivered concrete from the central discharge

to the formwork. The main advantage in using this

method for the project was that pipes occupied

minimal space. DPR project engineer Mike Miller

described how space was limited such that tailgating

(placing concrete directly from the truck into the

formwork) was not possible and pumps had to be

used to keep the road leading to the job site available

for use. The pipe lengths could also be adjusted and

extended to deliver concrete to formwork in required

places, hence eliminating the need for conveyor belts.

Figure 8: Concrete Truck with Pump

As part of quality control, American Concrete

Institute (ACI) recommends performing the slump

test at the end of the pipeline. This is to provide

information on whether retempering should be

performed within controlled limits. Flat slump tests

were performed in this project and the workability of

the concrete mix was analyzed from the diameter

covered by the concrete after the test was performed.

Due to stringent quality control in this project, the

flat slump test was performed at both the truck and

the end of the pipeline. However, this raised

manpower issues as it required two inspectors on site

instead of one.

Figure 9: Workers Handling Pump

Pneumatic Guns

For some parts where concrete was not cast-in place,

pneumatic guns were used to deliver shotcrete,

concrete that’s ‘shot’ at high velocity onto a surface

using a hose. Dees-Hennessey Inc. was

subcontracted to perform the placement of shotcrete.

Pneumatic guns were used for the vertical

application of shotcrete on walls and to produce a

good finish. The shotcrete was placed in 300MDO

formwork. Guide wires, which are tensioned wires,

were utilized to control the thickness of the shotcrete

wall. Panels 18” x 18” for testing were specified to

be used for aggregate size greater than ⅜” per UBC

section 1922.

The use of shotcrete was unique because the quality

of the work depends on the skill of the nozzlemen.

For this reason, they must be certified and approved

to perform the task. Typically, they are approved by

demonstrating their shotcrete ability on a series of

test panels that are evaluated on their consistency and

quality. One occurrence of a construction issue with

shotcrete involved the certification but not approval

of a nozzleman who was operating and placing

concrete. When this was discovered, the unapproved

nozzleman was replaced with an approved one to

complete the remaining shotcrete. Due to this

happening while in the middle of shotcreting a series

of stairs, the problem was solved by replacing the

operator to continue the process and submitting a

Request For Information (RFI) change order.

PLACEMENT

17

Formwork was required to prevent leakage of cement

mortar and to provide concrete with resistance against

spreading and shifting. In this project, the majority of

the formwork used was made out of wood and a

select few out of metal.

Wood

Most of the formwork utilized in the project was

made out of Douglas fir of either Medium Density

Overlaid (MDO) or Hard Density Overlaid (HDO).

The following types of formwork have been

specified:

For exposed concrete, plywood that complies

with U.S. Product Standard PS-1, HDO

Plyform Class 1, Exterior Grade, or better is

specified.

For panel forms, an exterior grade plywood

with sealed edges of at least ⅝” thick, PS 1

grade Plyform Class I and II B-B Exterior or

HDO Exterior is specified.

For columns, a brand of formwork specialized

for columns, SONOTUBE, or an equivalent

product is specified.

HDO formwork is supposed to provide superior

concrete finish and has been specified for exposed

surfaces. However, according to the general

contractor, there is minimal visible differences

between concrete surfaces from MDO formwork and

HDO formwork. Despite its higher cost, HDO was

still preferred as it allows for higher number of reuse.

The wood formwork in this project was reused up to

a maximum of two to three times. Before reuse,

formwork has to be straight and free from nails, dirt,

and hardened concrete. Reuse of formwork with

repairs or patches was not allowed as this may affect

architectural concrete finish.

FORMWORK

Metal

The only metal formwork used in this project is Stay-

form®. It is a mesh-like leave-in-place form and is

used to make keyway for the next concrete pour. The

keyway allowed proper adhesion to the adjoining

wall and alleviated the effect of cold joints.

Figure 10: Metal formwork, Stay-form®, used for

keyway in Mechanical Level

Formwork Removal

The formwork in this project was typically kept on

for 7 to 14 days, and was tied into the 7-day test

strength. For high early strength concrete, formwork

could be removed as early as 3 days and a 3-day

strength test would be performed. Formwork for

structures such as elevated beams were left on for 14

days.

Different concrete structures must attain a certain

percentage of their ultimate strength before their

formwork can be removed. For vertical surfaces of

walls, columns, beams, and girders, the concrete must

attain a strength of 0.60 times the compressive

strength prior to form removal. For beams, soffits,

slabs, and girders, a strength of 0.75 times the

compressive strength was specified.

.

18

Vibrators were used to consolidate concrete,

including mat slabs and structural slabs. Exposed

concrete was vibrated with rubber type heads, which

is more protective for the formwork and creates

denser concrete with fewer voids to patch. The

majority of consolidation was executed using internal

vibration. Vibrating formwork was also utilized for

larger retaining walls.

Figure 11: Concrete Consolidation

Issues arose in the consolidation of concrete in

heavily reinforced grade beam. Internal vibrators

could not be used in these regions effectively. The

use of self-consolidating concrete was considered but

not used due to financial reasons. This construction

issue was solved by reducing the number of

reinforcement bars in the grade beam that was

designed conservatively due to the facility’s

proximity to an active fault.

CONSOLIDATION

Typically 28-day curing was specified, where

concrete was cured for 7-days before the addition of

curing compounds were applied either on the top

layer or mixed in with the concrete. Curing

compounds were used to protect fresh concrete from

direct sunshine and drying winds. The amount used

was per manufacturers’ recommendations, with the

exception of slabs-on-grade where 150% of the

manufacturer’s recommended application was

specified. During one of the site visits, a large

amount of excess water was discovered on one of the

floor levels after it had been cured for 7-days. This

violated the curing general requirement of avoiding

alternate wetting. Later, a leak in the waterline was

found by the LBNL maintenance crew, and it was

determined that this waterline had sprayed water on

the floor and caused the floor to become saturated

with the excess water. To ensure this would not

happen again, traps were installed to keep water out.

An exception to the 28-day requirement for curing

was the curing for the lightweight concrete fill used

on the roof. For the roof, 56-days was required

before load could be applied. However, the long

curing time created scheduling problems and due to

time constraints, a cover worth $100,000 was place

over the concrete to curb evaporation and hasten the

curing process.

Figure 12: Roof Covering to Reduce Curing Time

from 56-Days to 28-Days

CURING

19

trowel finish due to concerns of dusting caused by

potential movement of heavy objects on floor during

earthquake. Dusting may rise and affect the

building’s ductwork, along with the sensitive

equipment that will be brought into the Computing

Level.

Broom finish

Broom finish was to be applied to exterior concrete

platforms, steps, and ramps that have to be non-slip.

Broom finish was observed on the ramp in the

Mechanical Level.

Figure 15: Broom Finish

Trowel and Fine Broom Finish

Trowel finish followed by fine brooming was

required on surfaces where ceramic or quarry tile

will be installed with thin-set mortar.

Dry Shake Hardener, Wear-Resistant Finish

This finish was required for floor slabs at the loading

dock.

Rough Form Finish

Rough form finish achieved after the removal of

formwork, was to be performed on formed concrete

surfaces that will not be visibly exposed. Patchwork

was then applied to fix and hide defects.

Smooth Form Finish

Smooth form finish was to be achieved through the

use of chosen form facing material organized in an

orderly and symmetrical manner that minimizes

FINISHING

The project required different types of finish to be

applied for various types of surfaces as follow:

Float Finish

Application of such finish was to be done on

concrete slabs that will have trowel finish and other

finishes. Float finish was also required on slabs with

membrane or elastic waterproofing, membrane or

single-ply roofing, sand-bed terrazzo, or raised

access floor.

Figure 13: Float Finish

Trowel Finish

Trowel finish was required on concrete slabs that

will be visibly exposed and those with resilient

flooring, carpet, ceramic or quarry tile, paint, or other

thin film coats.

Figure 14: Trowel Finish

Compact power trowels were used on the project

when more ground needed to be covered. On the

Computing Level, float finish was preferred over

20

seams. This finish was is to be performed conducted

on surfaces expected to be exposed-to-view or

covered with a coating or covering material.

Some special areas also demanded architectural

finish, where a sealer was specified to provide a dust-

proof surface. Where appearance is an issue, mock-

ups were requested and joint alignment, finishing,

and spacing was checked and evaluated. Water wash

finish to reveal exposed aggregates were initially

considered but later abandoned due to cost

considerations.

Construction Joints

Construction joints serve the purpose of controlling

crack formation caused by tensile forces that develop

within the concrete due to restraints. Joints that were

seen cut into the concrete were manifested in some of

the large slabs in the project, such as those in the

Mechanical Level flooring as illustrated in Figure 16

below:

Figure 16: Construction Joint on Mechanical Level

Flooring

Reveals were also created on the walls of the

Mechanical Level, as illustrated in Figure 17 below.

According to DPR project engineer Mike Miller, the

reveals served to control cracks, although wall

reveals are usually imprinted for architectural

purposes. However, since the addition of

reveals increased costs, these were omitted from the

cooling tower, where crack formations are causing

current concern. Other concerns regarding cracking

include the concrete ramp in the Mechanical Level,

where construction joints were not added (Figure 18).

Figure 17: Reveal Control Joints on Walls in

Mechanical Level

Figure 18: Potential Problem Area at Ramp Due to

Absence of Contraction Joints

21

The CRT Facility at the Lawrence Berkeley National

Lab has been a fantastic example of both

commonplace construction practices and increasingly

familiar modern day innovations in the field of

concrete. The base of the concrete mix designs were

similar, with most of the Portland cement used able

to fall under the classification of either type I, II, or

V, the main aggregates used all came from

CEMEX’s Eliot Quarry, and the Class F fly ash all

coming from Headwaters Resource in Wyoming. The

real distinctions in the mix designs came from the use

of different types and amounts of admixtures. The

high early strength mix contained water-reducing

admixture as well as special aggregate from Polaris’s

Orca Quarry in British Columbia, the fiber reinforced

mix contained microsynthetic fibers, the shotcrete

mix contained a water-reducing and retarding

admixture as well as a high proportion of fine

aggregates compared to coarse, and the controlled

density fill mix contained an air-entraining admixture

coupled with a low cement content. The adjacent

Hayward fault made the use of reinforcing steel bars

necessary at several locations in the building. The

concrete was placed with pumps and pneumatic guns,

and finished in a multitude of different ways. The

CRT Facility has taken the 2,000 year old practice of

building with concrete to create a state-of-the-art

computing facility.

CONCLUSION ACKNOWLEDGEMENTS

We would like to express our very great appreciation

to the following people:

1. Professor Paulo J. M. Monteiro for expanding our

knowledge of concrete materials and construction.

2. Tim Hart, Structural Engineer and Consultant, for

having a meeting with us and discussing the

details of the project and reviewing some of the

construction problems.

3. Tim Kemper, Construction Manager, for providing

information on the mix design, concrete

transportation, reinforcement, concrete placement,

finishing, and construction issues.

4. Ian White, Project Manager, for providing a

detailed tour of the project.

5. Rory Shortreed, Inspector of Record, for answering

questions about the details of the construction

methods.

6. Mike Miller, Project Engineer, for answering

questions about concrete and discussing

construction issues.

22

"CEMEX Eliot Quarry." Structural Engineers Association of Northern California. Construction Quality Assur-

ance Committee, n.d. Web. <http://www.act-right.net/AggregateProject/ cemex-eliot.shtml>.

Draney, Brent. Presentation on Computational Research and Theory Facility (CRT): Networking and Security.

NERSC. February 2013. Web.

Mehta, P. Kumar; Monteiro, Paulo J. M. Concrete: Microstructure, Properties, and Materials. McGraw-Hill

Professional; 4th edition, 2013. Print.

Monteiro, P. (January - April 2014). Concrete Materials and Construction Lectures. Lectures conducted at

University of California, Berkeley.

Ragan, Steve. "A Cost-Effective Alternative to Compacted Soil Backfill." Graniterock. Graniterock, n.d. Web.

<http://www.graniterock.com/technical_notes/ cost-

effective_alternative_to_compacted_soil_backfill.html>.

Sloan, D., Wels, D. “The Hayward Fault.” Geological Society of America Field Guide 7 2006: 27-31. Web.

“The Computational and Research Facility: A Catalyst for Scientific Discovery.” Handout. Lawrence Berkeley

National Lab. Berkeley, CA. n.d. Web. April 2014.

"The Purpose of Joints in Concrete Slabs." Concrete Network. Concrete Network, n.d. Web.

<http://www.concretenetwork.com/concrete-joints/purpose.html>.

“UC Berkeley’s Computational Research and Theory (CRT) Facility.” Poster. Lawrence Berkeley National

Lab. Berkeley, CA. n.d. Web. April 2014.

REFERENCES

23

Fiber Reinforced Concrete

Mix Design ..................................................................................................................................... A

Trial Mixes ......................................................................................................................................B

Strength Gain...................................................................................................................................C

Cement ........................................................................................................................................... D

Coarse Aggregate ............................................................................................................................ E

Oakland Sand .................................................................................................................................. F

Vulcan Sand ................................................................................................................................... G

Fly Ash ........................................................................................................................................... H

Fiber Details .................................................................................................................................... I

Shotcrete

Mix Design ....................................................................................................................................... J

Hydration Stabilizer Admixture ..................................................................................................... K

Water Reducing Admixture ............................................................................................................ L

Controlled Density Fill

Mix Design ..................................................................................................................................... M

Mill Test Report ............................................................................................................................. N

Aggregates ...................................................................................................................................... O

Fly Ash ............................................................................................................................................ P

High Early Strength

Mix Design ..................................................................................................................................... Q

Trial Mixes ......................................................................................................................................R

Water Reducing Admixtures ........................................................................................................... S

APPENDIX