Using Prewetted Lightweight Aggregates - Louisiana ... the... · Using Prewetted Lightweight Aggregates ... Improving Concrete Durability and ... [ACI 201 2R-08, Guide to Durable

Internal Curing Using Prewetted Lightweight Aggregates

Presented to:

LA DOTD Transportation Conference

February, 2013

Jeff Speck, P.E., FACI

V.P. Sales & Marketing

Big River Industries, Inc.

Improving Concrete Durability and

Sustainability Using Internal Curing

Curing is one of seven essential

procedures “that make concrete capable

of providing decades of service with

little or no maintenance.”

[ACI 201 2R-08, Guide to Durable Concrete]

INTERNAL CURING USING PREWETTED LIGHTWEIGHT AGGREGATE

ACI: Internal Curing: “supplying water

throughout a freshly placed cementitious

mixture using reservoirs, via pre-wetted

lightweight aggregates, that readily release

water as needed for hydration or to replace

moisture lost through evaporation or self-

desiccation [1]”


What is LWA? • Expanded shale, clay and

slate (ESCS)

• Structural, ceramic aggregate produced in a rotary kiln

• Less than half the unit weight of ordinary aggregate

• Complies with

ASTM C-330 and C-331

Expanded at

2000° F

• Use fine aggregate to distribute water

• Help satisfy increased water demand from SCM’s

• Works even at moderate 0.40 – 0.48 w/cm



It’s All About the Distribution

Henkensiefken (2008)

Coarse

LWA

Fine LWA

Hydration Age Estimated Travel

Distance for Water

< 1 day 20 mm

1 day to 3 days 5 mm

3 days to 7 days 1 mm

> 28 days 0.25 mm

Clogging the Capillaries

With Products of Hydration Restricts the Flow of Water

Bentz, D., Koenders, S., Monnig, S., Reinhardt, H., van Breugel, K ., Ye, G.


• Benefits • Less shrinkage, less cracking

• Improved fluid transport properties

• lower water absorption

• lower chloride permeability & penetration

• More hydration & SCM reaction

• less cement or more strength

• Results • More durable structures achieving extended

service life

• Improved economics

• Increased sustainability


Extensive Lab Research


121 Citations as of December 2011

Stress Development Mechanisms


Why Does Concrete Crack?

Restraint + Volume Change = Stress

Occurs When Tensile Stress Exceeds

Tensile Capacity

Stress Development Mechanisms


• Early-Age Volume Change Occurs Because of

• Thermal effects

• Temperature changes due to hydration

• Coefficient of thermal expansion

• Decrease of internal relative humidity

• Drying due to atmospheric conditions

• Self-desiccation (autogenous shrinkage)

Thermal Effects INTERNAL CURING USING PREWETTED LIGHTWEIGHT AGGREGATE

Self-Desiccation


Self-Desiccation


Self-Desiccation


Self-Desiccation


The “Bentz Equation”

𝑀𝐿𝑊𝐴 =𝐶𝑓 ∗ 𝐶𝑆 ∗ α𝑚𝑎𝑥

𝑆 ∗ 𝝓𝐿𝑊𝐴

~ 7 lb of internal curing water needed per 100 lb

cement


Mixture Proportions of the Fine Aggregate In a Yard of Concrete

Natural Sand

10-25% LWAS 75-90% Natural Sand

For Internal Curing Replace a Portion of Natural Sand

With Lightweight Aggregate Sand (LWAS)

LWAS

Cement Paste Cement Paste LWA

Sealed - SRA

Unsealed - Plain Unsealed - SRA

Sealed - LWA

Unsealed - LWA

Sealed - Plain Sealed - SRA


Sealed - LWA

Unsealed - LWA

Sealed - Plain

0.1 1.0 10.0 100.0 1000.0

Kelvin Radius (nm)

30

40

50

60

70

80

90

100

Rela

tiv

e H

um

idit

y (

%)

= 72 x 10-3 N/m (Plain)

= 36 x 10-3 N/m (~5% SRA)

20 40 60 80 100

Relative Humidity (%)

-5000

-4000

-3000

-2000

-1000

0

Sh

rin

kag

e S

train

()

w/c = 0.30

w/c = 0.30+5%SRA

Menisci Radius (nm)

r1 r1 r2

r3 r3 r4

Sealed - SRA


Sealed - LWA

Unsealed - LWA

Sealed - Plain Sealed - SRA


Sealed - LWA

Unsealed - LWA

Sealed - Plain

0.1 1.0 10.0 100.0 1000.0

Kelvin Radius (nm)

30

40

50

60

70

80

90

100

Rela

tiv

e H

um

idit

y (

%)

= 72 x 10-3 N/m (Plain)

= 36 x 10-3 N/m (~5% SRA)

20 40 60 80 100

Relative Humidity (%)

-5000

-4000

-3000

-2000

-1000

0

Sh

rin

kag

e S

train

()

w/c = 0.30

w/c = 0.30+5%SRA

Menisci Radius (nm)

r1 r1 r2

r3 r3 r4

• Largest pores will empty first

• The saturated LWA provides water to the paste and keeps

a large pore full

Why can LWA be used for IC?

More Hydration

0.40 0.425 0.45 0.475 0.50

Degre

e o

f hydra

tion

(%

)

█ Mixture with

internal curing

█ Mixture without

internal curing

0%

2

0%

4

0%

6

0%

8

0%

Water / cement ratio

Espinoza-Hajazin (2010)

Degree of hydration of cement @ 90 days, cured @ 50%

RH

Higher Compressive Strength

- Portland Cement Mortar @ 0.30 & 0.50 w/c

Sealed Curing 50% RH Curing

Golias (2011)

Less Shrinkage; Less Cracking

Schlitter (2010)

Plain 0.30 Concrete

0.6 mm wide crack

observed @ 12 days

IC 0.30 Concrete

0.4 mm wide crack

observed @ 43 days

0 20 40 60 80

Time to Cracking, hours

Control IC

Delayed Cracking

- Summer curing temp. profile for expanded shale

IC mix

Byard (2010)

Reduced Warping – 80% Reduction

Wet base, 7 day cure then 73oF @ 50% RH on slab surface Wei (2008)

Lower Absorption

28 day curing Henkensiefken (2009)

Lower Chloride Permeability

0.40 0.425 0.45 0.475 0.50

Charg

e p

assed (

cou

lom

bs)

█ Mixture with

internal curing

█ Mixture without

internal curing

0

water / cement ratio

1200

2400

3600

Espinoza-Hajazin (2010)

Chloride ion permeability @ 90 days, cured @ 50%

RH

Internal Curing vs. No Internal Curing

Denver Water Test Slabs – 92oF ambient, 20% RH

No conventional curing

Internal Curing No Internal Curing

Denver Water – 10 million gallon tank

– 1300 yard slab pour

Change Order to include walls and columns


– 1300 yard slab pour


– Contractor requested change order to use IC mix

for ring girder, columns and walls



– 8” thick PT roof slab placed monolithically


Denver Water - Conclusions

• Using IC resulted in an 80% reduction in

shrinkage cracks compared to similar size

tanks built previously

• Based on the Lonetree Basin project

success, IC will be used for:

• 2 more 10 MG tanks will be built this

year

• Three 15 MG tanks are planned for 2014

Paving in Texas

UP RR Intermodal Facility Constructed 2005

250,000 yd3 IC project low slump pavement

Visual inspections At 6 months one crack At 5.5 yrs minuscule plastic or drying shrinkage cracks

NY: 16 built or under construction as of 2012

IN: 33 bridges


Bridges in New York & Indiana


Indiana Bridges NE of Bloomington

• Replacement of two bridges ¼ mile apart

• Prestressed concrete box beams

• Composite RC deck

• 8” thick at centerline, 4½” thick at edge



InDOT 2010



InDOT 2010

Standard External Curing

(wet burlap) – Both Bridges



InDOT 2010

Plain Concrete Deck at

One Year



Plain Concrete Deck at

One Year

Longitudinal and

Transverse crack



IC Concrete Deck at

One Year

No Cracks

Texas State Highway 121

1300 CY, 5 miles of CRCP, Class P


SR-121

Crack Spacing of IC Section at 10 months


SR-121

Crack Width (% of total at 10 months)


Conclusions


• The use of saturated LWA for internal curing delays the occurrence of early-age cracking in bridge deck and pavement applications

• This is because the use of LWA for IC:

• Decreases or eliminates stresses due to autogenous shrinkage effects

• Decreases the modulus of elasticity

• Decreases the coefficient of thermal expansion

• This improved cracking performance may be in the form of: reduced number of cracks and/or decreased crack widths.

Say premium for IC is $10/CY (assumption)

Assume 9” deck

Compute premium per SF of bridge deck:

$10/CY (0.75 CF/SF) (1CY/27CF) = $0.28/SF

Compare to Fed Aid unit costs for entire bridge:

Avg = $156/SF 0.28/156 = 0.18%

Max = $558/SF 0.28/558 = 0.05%

Min = $57/SF 0.28/57 = 0.49%

The cost of IC, compared to total bridge cost, is very minor – less than ½ of 1%, at worst!

Cost of Internal Curing

Summary:

• Less shrinkage, less cracking

• More hydration & SCM reaction

• Improved transport properties

• Lower water absorption

• Lower chloride permeability & penetration

• Increased durability

• Significant increase in service life

• Significant life cycle cost reduction

• Increased sustainability

Researchers

Dale Bentz Chemical Engineer

National Institute of Standards &

Technology

100 Bureau Drive Stop 8615

Gaitherburg, MD 20899

(301) 975-5865

[email protected]

http://concrete.nist.gov/bentz

Jason Weiss Professor

Purdue University – School of Civil

Engineering

550 Stadium Mall Drive

West Lafayette, IN 47907

(765) 494-2215

[email protected]

http://cobweb.ecn.purdue.edu/~wjweiss

Anton Schindler HRC Director/Associate Professor

Auburn University

238E Harbert Engineering Center

Auburn, AL 36849

(334) 844-6263

References

Byard, B. & Schindler, A. (2010). Cracking Tendency of Lightweight

Concrete, Research Report. Auburn University: Highway Research

Center.

Castro, J. (2011). Moisture Transport in Cement-Based Materials:

Application to Transport Tests and Internal Curing, Ph.D. Thesis. West

Lafayette: Purdue University.

Cusson, D., Lounis, Z., & Daigle, L. (2010). Benefits of Internal Curing

on Service Life and Life-Cycle Cost of High-Performance Concrete

Bridge Decks – A Case Study. Cement and Concrete Composites, 32.

Espinoza-Hajazin, G., & Lopez, M. (2010) Extending Internal Curing

To Concrete Mixtures With W/C Higher Than 0.42. Construction &

Building Materials, Elsevier Ltd.

Golias, M. (2010). The Use of Soy Methyl Ester-Polystyrene Sealants

and Internal Curing to Enhance Concrete Durability, M.S. Thesis. West


References (cont’d)

Henkensiefken, R. (2008). Volume Change and Cracking in Internally

Cured Mixtures Made with Saturated Lightweight Aggregate Under

Sealed and Drying Conditions, Presented at ACI Fall Convention, St.

Louis, MO.

Henkensiefken, R., Bentz, D., Nantung, T., & Weiss, J. (2009). Volume

Change and Cracking in Internally Cured Mixtures Made with

Saturated Lightweight Aggregates under Sealed and Unsealed

Conditions. Cement and Concrete Composites , 31 (7), 426-437.

Schlitter, J., Kenkensiefken, R., Castro, J., Raoufi, K., Weiss, J., &

Nantung, T. (2010). Development of Internally Cured Concrete for

Increased Service Life. Joint Transportation Research Program. West


Wei, Y., & Hansen, W. (2008). Pre-soaked Lightweight Fine Aggregates

as Additives for Internal Curing in Concrete. In D. Bentz, & B. Mohr

(Ed.), Internal Curing of High-Performance Concretes: Laboratory and

Field Experiences (pp. 35-44). Farmington Hills: American Concrete

Institute.

In the words of Jason Weiss

IC is “ready to go, NOW!”

“The research has been done; it’s time to

stop talking about it and start making use of

it.”

- – Jason Weiss at TRB, January, 2013

Questions?

[email protected]

Documents

Using Prewetted Lightweight Aggregates - Louisiana ... the... · Using Prewetted Lightweight Aggregates ... Improving Concrete Durability and ... [ACI 201 2R-08, Guide to Durable