Implementation of

LADOTD Mass

Concrete & Maturity

Testing Specifications Presented by

Mark A. Cheek, PE, FACI

Vice-President

LTC 2018

Definition of mass concrete

“any volume of concrete with dimensions large enough to

require that measures be taken to cope with generation of

heat from hydration of the cement and attendant volume

change to minimize cracking”

– American Concrete Institute (ACI 207.1R-05)

What is mass concrete?

Not all mass concrete placements are enormous pours!

For most state DOT’s, it is defined as any concrete placement

where the smallest dimension exceeds 3-4 ft.

Even thin placements like slabs and columns can qualify

ACI 301-10 commentary provides the following recommended limits:

Thickness ≥ 4 ft

Cementitious content ≥ 660 pcy

Industry Trends

Larger concrete elements in structural applications

Flowable / SCC

High-strength concrete

Rapid construction

Service life requirements

All of these are leading to more concrete placements

being mass concrete. If not properly considered, can

contribute to an increased risk of thermally induced

damage!

Why do we care?

High internal concrete temperatures can

cause delayed ettringite formation (DEF)

High temperature differentials within a

concrete placement can cause thermal

cracking

Early Ages Late Ages

6

Hot CoolCool Cool

Typical Specification Limits

Maximum Temperature:

Typical maximum temperatures range from 154°F to

160°F.

If SCM’s are used, limits sometimes increase to

170°F or higher.

Maximum Temperature Differential:

Typical limits range from 35°F to 38°F.

More advanced modeling techniques allow for this to

exceed typical limits (Performance based)

7

Thermal Control Plans Placement plans developed to decrease the risk of

thermal issues. Typically include:

Thermal modeling

Mix design

Concrete & ambient temperature

Element dimensions

Thermal control measures

Detailed placement plan

Mix design

Thermal control measures

Embedded thermocouples to monitor

placement8

Concrete Mix Design

Limit cementitious materials content

Use supplementary cementitious materials

Use fly ash and slag to lower temperature rise

Fly ash up to 40-50% replacement typical

Slag up to 70% replacement typical

Silica fume can increase the temperature rise

9

Thermal Control Measures

Passive: Surface insulation

Blankets, form liners, foam insulation

Precool the concrete Ice, cold water, liquid nitrogen

Active: Cooling Tubes

Passive measures typically require

longer periods until the placement

can be accessed than active control

measures

10

LOUISIANA Standard Specifications

for

Roads and Bridger

2016

901.12 MASS CONCRETE

901.12.1 Description

Mass concrete is defined as a structural concrete

placement having a least dimension of 48 inches or

greater, or if designated on the plans or in the project

specifications as being mass concrete. Drilled shafts are

exempt from mass concrete requirements.

901.12.2 General

Submit proposals for the mass concrete mix design,

analysis, temperature monitoring, and control, including

insulation and methods, to the Department for review and

acceptance a minimum of 30 days prior to the placement of

any mass concrete.

901.12.3 Materials

The structural class designation for mass concrete is Class

MASS (A1, A2, or A3) as shown in Table 901-3.

901.12.3.1 Cement/Cementitious Combination

Use Type II portland cement. Replace portland

cement with fly ash at 20 percent to 50 percent by

weight or replace with slag cement at 50 percent to

70 percent by weight or a ternary mix meeting

specification requirements. Certify that the

cementitious combination generates a heat of

hydration of not more than 70 calories/gram (290

kJ/kg) at 7 days as determined by ASTM C186.

901.12.4 Construction

Produce a structure free from thermal cracks. Place mass

concrete continuously to eliminate cold joints.

Control differential temperatures by appropriate use of insulated

forms, curing blankets, or other acceptable methods.

If during the first 48 hours after placement, the temperature

differential nears 35 ºF (20 ºC), take corrective measures

immediately to remain within the limits. Furthermore, revise the

plan to maintain the limits on differential temperature on any

remaining placements of mass concrete. Obtain the engineer's

acceptance of the revised plan prior to implementation.

Strength gain and cooling of the mass concrete placements can

take a long time. Take all such time and strength considerations

into account when planning construction activities.

901.12.4.1 Analysis and Monitoring

Submit an analysis to the engineer of the projected thermal

developments within the mass concrete elements for the

anticipated concrete and ambient temperatures, along with

the proposed mix design and construction methods.

Include a copy of model results, with site and element

specific data, and any electronic files. Describe the

measures and procedures intended to maintain, monitor,

and control the temperature differential between the interior

and exterior of the mass concrete elements. A maximum

temperature during curing of 160 º F (70 º C) and a

maximum differential temperature of 35 °F (20 °C) is

allowed. An abbreviated submittal may be allowed for

previously approved mass concrete mix designs.

901.12.4.2 Monitoring Devices

Provide temperature-monitoring devices to record

temperature development between the interior and the

exterior of the element at points acceptable to the engineer.

Monitor a minimum of two independent sets of interior and

exterior points for each element to provide redundancy.

Locate the monitoring points at the geometric center of the

element for the interior point and two inches from the

surface along the shortest line from the geometric center to

the nearest surface of the element for the exterior point.

Monitoring devices shall be automatic sensing and recording

instruments that record information at a maximum interval of

one hour. Calibrate monitoring devices to the manufacture’s

recommendations. These devices shall operate within the

temperature range of 0 to 180 ºF (-18 to 82 ºC) with an

accuracy of ± 2 ºF (±1 C). Take readings and record the

temperature data at intervals no greater than 6 hours to

ensure that the automatic devices are working properly and

that the temperatures are within allowable limits. The intervals

of one and six hours shall begin immediately after casting is

complete and shall continue until the maximum temperature

differential is reached and begins to drop. Transmit these

readings to the engineer daily.

Prior to the placement of mass concrete, perform a test of the

automatic and manual thermal sensing and recording

equipment to ensure they are operational.

Macarthur Interchange

Completion - Phase 1B

(H.009933)

Mass Elements

- 31 Footing (range in height from 5’

to 8’)

- 37 Pier Placements (range in width

from 5’ to 25’)

- 10 out of 39 Caps (range in depth

from 4’ to 7.5’)

Mix Design Cement Type I/II 162 lbs/yd3

Slag Cement Grade 100 379 lbs/yd3

Water 238 lbs/yd3

Coarse Aggregate 1879 lbs/yd3

Fine Aggregate 1164 lbs/yd3

Air Content 5%

Chemical Admixtures

ASTM C 494 Type A, HRWR

W/CM 0.44

Thermal Model

for

5’ Thick Footing

Installation

Geometric center of the element for the

interior point

Two inches from the surface along the

shortest line from the geometric center to

the nearest surface of the element for the

exterior point.

At each location use a minimum two

logger.

Logger Types

Cable Lengths 4ft to 200ft

MAT-02-1H180D

MAT-02-1M2D

TPL-02-1H28D

TPL-02-15M28D

Insulation

Insulation Recommendations

Install blankets preferable before placement

Blankets must completely cover all portions of

the formwork and any portion that extends

above or beyond the limits of the placement

Blankets should be held tightly against the

formwork to prevent air movement between the

blankets and forms

Protruding steel should be insulated

Insulation for the placement should extend a

minimum of 3 ft. onto any adjoining existing

concrete

Monitoring

Field Monitoring

Remote Monitoring

Watch real time in your office

Email and Text notifications

Maturity Meters for Any-Time

Strength Measurements

Brief History of the Maturity Method

The “maturity concept” was proposed in the late 1940s and early 1950s

as a technique to account for the combined effects of time and

temperature on the strength development of a concrete mixture (Nurse

1949; McIntosh 1949; Saul 1951).

Carino and Tank

Specifications

ACI

301 Standard Specifications for Structural

Concrete (paragraph 2.3.4)

318 Building Code Requirements for

Structural Concrete (paragraph 6.2)

Specifications

ACI

228.1R In-place Methods of Estimating Concrete Strength (paragraph 2.7)

306 Cold Weather Concreting (paragraph 6.4)

Specifications

FHWA

SA-97-105 Guide to Non-destructive Testing

of Concrete

ASTM

C 1074 Practice for Estimating Concrete

Strength by the Maturity Method

Used by DOT’sState

Allows Mat

Alabama X

Alaska X

Arizona X

Arkansas X

California X

Colorado X

Conneticut X

Delaware X

Florida X

Georgia X

Hawaii X

Idaho X

Illinois X

Indiana X

Iowa X

Kansas X

Kentucky X

Louisiana

Maine X

Maryland X

Massachusetts X

Michigan X

Minnesota X

Mississippi X

Missouri X

Montana X

Nebraska X

Nevada X

New Hampshire X

New Jersey X

New Mexico X

New York X

North Carolina X

North Dakota X

Ohio X

Oklahoma X

Oregon X

Pennsylvania X

Rhode Island X

South Carolina X

South Dakota X

Tennessee X

Texas X

Utah X

Vermont

Virginia X

Washington X

West Virginia X

Wisconsin X

Wyoming X

District of Columbia X

Benefits of Using the Maturity

Method (to the project)

Accelerate construction schedules

Reduce man-hours

Reduce test specimen cost

=

Remove shoring and re-shoring sooner

Allows earlier form removal and with confidence

that the operation is safe; rented forms can be returned sooner

Post-tensioning tendons can be stressed earlier

Open roadways to traffic in less time

Engineering Benefits of Using the

Maturity Method

Provides a better representation of in-place

concrete strength gain (compressive or flexural)

than laboratory or field cured specimens

Enables any-time in-place strength

measurements

Enables in-place strength measurements at

“lowest strength (youngest concrete)” locations

Enables in-place strength measurements at

“critical stress” locations

Maturity Rule

“Concrete of the same mix at the same

maturity (reckoned in temperature-time)

has approximately the same strength

whatever combination of temperature and

time go to make up that maturity.”

A.G.A. Saul, 1951

Maturity Functions

Temperature-time Factor (Nurse-Saul)

M = Σ (Ta – To ) Δt

Equivalent age (Arrhenius)

te = Σe –Q[ 1/Ta – 1/Ts ] Δt

Nurse – Saul Function

(Temperature – time factor)

M = Σ (Ta – To ) Δt

M = the temperature – time factor (TTF) at age t, degree – hours

Ta = average concrete temperature during time interval, Δt

Δt = a time interval, hours

To = 0˚ C or 32˚F

Datum Temperature

To = 0˚C

Traditionally, the datum temperature has

been the temperature below which strength

gain ceases, which has been assumed to be

about 0°C (32°F)

In-Place Concrete Temperature (Ta)

Ambient conditions

Types & amounts of cementitious

materials

Admixtures

Size and shape of the structure

Formwork & Insulation

Implementing the Concrete

Maturity Method

Strength-Maturity Relationship

y = 734.43Ln(x) - 3685.9

R2 = 0.9931

1000

1500

2000

2500

3000

3500

4000

500 5500 10500 15500 20500 25500

Maturity Index (TTF) (C-hrs)

Co

mp

ressiv

e S

tren

gth

(p

si)

1. Develop a mixture specific calibration curve

2. Embed maturity loggers into plastic concrete

3. Take maturity (TTF) measurements

4. Use the calibration curve to estimate strength from maturity (TTF) measurements

Laboratory Test Data

Developing a mixture specific curve

Developing a mixture specific curve

Strength - Maturity Relationship

1000

1500

2000

2500

3000

3500

4000

500 5500 10500 15500 20500 25500Maturity Index (TTF) (C - hrs.)

Co

mp

ressiv

e S

tren

gth

(p

si)

1 Day

3 Day

28 Day

7 Day

14 Day

Strength-Maturity Relationship

1000

1500

2000

2500

3000

3500

4000

500 5500 10500 15500 20500 25500

Maturity Index (TTF) (C-hrs)

Co

mp

res

siv

e S

tre

ng

th (

ps

i)

Y = 734.43Ln(x) – 3685.9

R2 = 0.9931

Maturity equation – defines the strength-maturity

relationship (logarithmic best fit curve)

Y = 734.43Ln(x) – 3685.9

The R2 value indicates the reliability of the

strength-maturity relationship

R2 = 0.9931

Using the Strength-Maturity

Relationship CurveStrength-Maturity Relationship

3000

3500

4000

4500

5000

5500

6000

500 5500 10500 15500 20500 25500

Maturity Index (TTF) (C-hrs)

Co

mp

res

siv

e S

tre

ng

th (

ps

i)

4029 °C-H

4450 psi

Utilizing Maturity for form

Removal

On average forms were removed 4 days

earlier!

Warm weather – removed in 5 days

Cold weather – removed in 7 days

Questions