Internal CuringUsing Prewetted Lightweight

Aggregates

Presented to:ACIA Concrete WorksSeptember, 2012

Jeff Speck, P.E., FACIV.P. Sales & Marketing

Big River Industries, Inc.

Improving Concrete Durability and SustainabilityUsing Internal Curing

The Expanded Shale, Clay & Slate Institute (ESCSI) is a Registered Providerwith The American Institute of Architects Continuing Education Systems(AIA/CES). Credit(s) earned on completion of this program will be reported toAIA/CES for AIA members. Certificates of Completion for both AIAmembers and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be anapproval or endorsement by the AIA of any material of construction or anymethod or manner of handling, using, distributing, or dealing in any material orproduct. Questions related to specific materials, methods, and services will beaddressed at the conclusion of this presentation.

INTERNAL CURING USINGPREWETTED LIGHTWEIGHTAGGREGATE

Internal Curing using prewetted lightweight aggregate

Course Description

• This program introduces the concept of using prewetted lightweightaggregate to provide internal curing for normal weight concrete.

• It reviews significant research results, details specific benefits provided byinternal curing, and provides examples of current use projects locatedthroughout the United States.

• Discussion includes how the benefits of internal curing make concrete amore sustainable material.

Learning Objectives1. Recall how internal curing of normal weight concrete using ESCS lightweight

aggregate works to increase concrete durability by lowering the concretepermeability and reduce its shrinkage.

2. Estimate the amount of lightweight aggregate needed to provide the properamount of internal curing in a concrete mix design.

3. Recall examples of current use of internal curing on projects constructedthroughout the United States.

4. Analyze how the improved permeability and shrinkage properties affect life cyclecost of the structures.

5. Evaluate how internal curing makes concrete sustainable through improvedperformance and longevity and potential reduction of cement along with increaseduse of supplementary cement materials like fly ash and slag.

INTERNAL CURINGUSING PREWETTEDLIGHTWEIGHT AGGREGATE

Concrete 101: Concrete is a mixture of hydrauliccement, water, aggregates, and other materials (e.g.,admixtures, SCMs, etc.)

INTERNALCURING USINGPREWETTED LIGHTWEIGHTAGGREGATEConcrete 101: Quality concrete requires a good mixture

design, proper batching and mixing, efficient transport,proper placement, and quality finishing

Concrete 101: All of the above can be ruined byimproper curing.

Curing is one of seven essential procedures“that make concrete capable of providingdecades of service with little or nomaintenance.”

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

INTERNALCURING USINGPREWETTED LIGHTWEIGHTAGGREGATE

ACI: “supplying water throughout a freshlyplaced cementitious mixture using reservoirs, viapre-wetted lightweight aggregates, that readilyrelease water as needed for hydration or to replacemoisture lost through evaporation or self-desiccation[1]”

INTERNALCURING USINGPREWETTED LIGHTWEIGHTAGGREGATE

What is LWA?• Expanded shale, clay and slate

(ESCS)

• Structural, ceramic aggregateproduced in a rotary kiln

• Less than half the unit weightof ordinary aggregate

• Complies with ASTM C-330 and C-331

Expanded at2000° F

In low w/c, high performance mixtures the densemicrostructure can limit the depth of water penetrationThese mixtures are also prone to self desiccation (Internaldrying)

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

• Use fine aggregate to distribute water• Help satisfy increased water demand from SCM’s• Works even at moderate 0.40 – 0.48 w/cm

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

INTERNAL CURING USING PREWETTED LIGHTWEIGHTAGGREGATE

It’s All About the Distribution Henkensiefken (2008)

Coarse LWA

Fine LWA

Hydration Age Estimated TravelDistance for Water

< 1 day 20 mm1 day to 3 days 5 mm3 days to 7 days 1 mm

> 28 days 0.25 mm

Clogging theCapillaries

WithProducts ofHydrationRestrictsthe Flowof Water

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

INTERNAL CURING USING PREWETTED LIGHTWEIGHTAGGREGATE

• Benefits• Less shrinkage, less cracking• Improved 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

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Extensive Lab Research

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

121 Citations as ofDecember 2011

NIST – Internal Curing “home page”

http://ciks.cbt.nist.gov/lwagg.html

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Google ‘bentz internal curing’

Internal Curing Research

The first published recognition of the internal curing potential oflightweight aggregates was likely that of Paul Klieger in 1957,who wrote “Lightweight aggregates absorb considerable waterduring mixing which apparently can transfer to the paste duringhydration.” Klieger, P., Early High Strength Concrete for Prestressing,Proceedings World Conference on Prestressed Concrete, SanFrancisco, CA, A5-1 to A5-14, July 1957.

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Internal Curing ResearchRobert Philleo stated in 1991; “Either the basic nature ofPortland cement must be changed so that self-desiccation isreduced, or a way must be found to get curing water into theinterior of high-strength structural members. The latter ispossible through the use of saturated lightweight aggregate.However, people striving for high strengths are not eager to uselightweight aggregate. A partial replacement of fine aggregatewith saturated lightweight fines might offer a promisingsolution.” Philleo, R.E., Concrete Science and Reality, Materials Scienceof Concrete II, Eds. J. Skalny and S. Mindess, American CeramicSociety, Westerville, OH, 1-8, 1991.

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

A History of Internal Curing - 1• Klieger 1957 - LWA can provide moisture to the cement as it

hydrates

• Bloem 1965 - LWA may have the beneficial effect of supplyingcuring water internally

• Philleo 1991 - improved strength and durability due to release ofwater from LWA.

• Holm et al. 2004 - anecdotal evidence of reduced plastic shrinkagecracking in LWA

• RILEM 2002 – SOTA Early Age Cracking

A History of Internal Curing - 2• Bentz & Snyder 1999, Jensen & Hansen 2001 - benefits of LWA

for improved curing, specifically designed to improve the curing

• RILEM 2007 – IC: SOTA Review/Conference

• Bentz and Weiss 2010 – IC LWA: SOTA

• RILEM 2011 – SAP – SOTA Review

• TRB 2012 – IC Applications/Workshop

• ACI Fall 2012 – IC Session - Toronto

B

Fundamental Volume Change• Le Chatelier• 1850-1936• Volume of the reactants

larger than the volumeof the products

• Chemical Shrinkage

+ =

B

Chemical shrinkage is “the volume reduction associatedwith the hydration reactions in a cementitious material”

ChemicalShrinkage

Measured by Absorptionof External Water

(after Jensen & Hansen 2001)

Cement

Water (Pore Soln.)

0 20 40 60 80 100Degree of Hydration (%)

0

20

40

60

80

100

Volume (%)

Hydration Ceases

CapillaryWater

Hydration Product

Gel

HydrationProduct

Solid

Unhydrated Cement

Chemical Shrinkage

(after Powers)

Early Age Shrinkage in Cement Paste

• Initially we have cementparticles in water

• As these particles begin toreact (hydrate) the volumeof the system is reduced

Early Age Shrinkage in Cement Paste

• As theseparticleshydrate thevolume isreduced

• Since it is a

fluid, thesystemcollapses

Early Age Shrinkagein Cement Paste

• Once thesystem ‘sets’it can notcollapse toaccount forshrinkage

• Therefore

vapor filledvoids mustform

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Mixture Proportions of

the Fine AggregateIn a Yard of Concrete

Natural

Sand

10-25% LWAS 75-90% Natural Sand

For Internal Curing Replace a Portion of Natural SandWith Lightweight Aggregate Sand (LWAS)

LWAS

The “Bentz Equation” Typically replace ~400 lbs of concrete sand with equalvolume of lightweight fines

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Cement Paste Cement PasteLWA

• 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?

ESCS AbsorptionINTERNAL CURING USING PREWETTED LIGHTWEIGHTAGGREGATE

ESCS AbsorptionINTERNAL CURING USING PREWETTED LIGHTWEIGHTAGGREGATE

0 6 12 18 24 30 36 42 48Elapsed time (h)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized water absorption

(Mass of water/24h absorption)

StaliteUteliteSlagTXI - BoulderTXI - StreetmanNorliteBuildexSoliteHaydite

INTERNAL CURING USING PREWETTED LIGHTWEIGHTAGGREGATE

Typical Desorption for LWA - Virtually all moisture available at 94% RH Castro (2011)

More Hydration

0.40 0.425 0.45 0.475 0.50

Degree ofhydration(%)

█ Mixture with internal curing

█ Mixture without internal curing

0% 20% 40% 60% 80%

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

Test Slabs 15’ long with end restraintCuring: 2 days sealed, then 730 F @ 50% RH Schlitter (2010)

Less Shrinkage; Less Cracking

Schlitter (2010)

Plain 0.30 Concrete0.6 mm wide crackobserved @ 12 days

IC 0.30 Concrete0.4 mm wide crackobserved @ 43 days

Less Shrinkage; Less Cracking

Byard (2010)

0204060800

0

20

20

40

40

60

60

80

80

ICControl Control ICTime to Cracking, hoursTime to Cracking, hours

Time to Cracking, hours

Delayed Cracking - Summer curing temp. profile for expanded shale IC mix Byard (2010)

Internal Curing vs. No Internal Curing Denver Water Test Slabs – 92oF ambient, 20% RH

No conventional curing

Internal Curing No Internal Curing

Denver Water – 1300 yard slab pour

Change Order to include walls and columns

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)

Transport Properties: Reduced Conductivity

Castro (2011)

0.20 0.25 0.30 0.35 0.40water - cement ratio

0

2

4

6

8

10

12

14

16

18

20

Conductivity, (10-3 S/m) Mortar - 28 d

LWA 12% - 28 dLWA 24% - 28 d

0.23 0.29

• Results on saturatedsamples,

• w/c = 0.30• IC reduces the

overallconductivity.

Lower Chloride Permeability

0.40 0.425 0.45 0.475 0.50

Chargepassed(coulombs)

█ 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

Paving in Texas

UP RR Intermodal FacilityConstructed 2005 250,000 yd3 IC project lowslump pavement

Visual inspectionsAt 6 months one crackAt 5.5 yrs minuscule plastic ordrying shrinkage cracks

NY: 16 built or under construction as of 2012

IN: 33 bridges

INTERNAL CURING USING PREWETTEDLIGHTWEIGHT AGGREGATE

Bridges in New York & Indiana

Service Life Prediction– NRC Canada

Cusson (2010)

Initial & Life Cycle Cost– NRC Canada

Cusson (2010)

FHWA Unit Cost Data for entire bridgehttp://www.fhwa.dot.gov/bridge/nbi/unit_cost.cfm

For 2010 Fed Aid: Avg = $156/sf; Max = 558; Min = 57For Non-Fed Aid: Avg = $142/sf; Max = 380; Min = 54

Say premium for IC is $10/CY (assumption)Assume 9” deckCompute 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 veryminor – less than ½ of 1%, at worst!

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

Specifying Internal Curing

• Specification Will Include:

• Lightweight aggregate meets ASTM C330

• Lightweight aggregate meets new ASTM C1761,“Specification for LWA for IC of Concrete”

• C 330 Grading: fine aggregate 4.75 mm x 0

• Provide 7 lb. IC water per 100 lb. cement

• Pre-wet min three days / as recommended

• Verify degree of desorption

• Everything else the same – this is NWC

ResearchersDale BentzChemical EngineerNational Institute of Standards & Technology100 Bureau Drive Stop 8615Gaitherburg, MD 20899(301) 975-5865dale.bentz@nist.govhttp://concrete.nist.gov/bentz

Jason WeissProfessorPurdue University – School of Civil Engineering550 Stadium Mall DriveWest Lafayette, IN 47907(765) 494-2215wjweiss@purdue.eduhttp://cobweb.ecn.purdue.edu/~wjweiss

Anton SchindlerHRC Director/Associate ProfessorAuburn University238E Harbert Engineering CenterAuburn, AL 36849(334) 844-6263

ReferencesByard, B. & Schindler, A. (2010). Cracking Tendency of LightweightConcrete, 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. WestLafayette: Purdue University. Cusson, D., Lounis, Z., & Daigle, L. (2010). Benefits of Internal Curing onService Life and Life-Cycle Cost of High-Performance Concrete BridgeDecks – A Case Study. Cement and Concrete Composites, 32. Espinoza-Hajazin, G., & Lopez, M. (2010) Extending Internal Curing ToConcrete Mixtures With W/C Higher Than 0.42. Construction & BuildingMaterials, Elsevier Ltd. Golias, M. (2010). The Use of Soy Methyl Ester-Polystyrene Sealants andInternal Curing to Enhance Concrete Durability, M.S. Thesis. WestLafayette: Purdue University.

References (cont’d)Henkensiefken, R. (2008). Volume Change and Cracking in InternallyCured Mixtures Made with Saturated Lightweight Aggregate Under Sealedand Drying Conditions, Presented at ACI Fall Convention, St. Louis, MO. Henkensiefken, R., Bentz, D., Nantung, T., & Weiss, J. (2009). VolumeChange and Cracking in Internally Cured Mixtures Made with SaturatedLightweight Aggregates under Sealed and Unsealed Conditions. Cement andConcrete Composites , 31 (7), 426-437. Schlitter, J., Kenkensiefken, R., Castro, J., Raoufi, K., Weiss, J., &Nantung, T. (2010). Development of Internally Cured Concrete forIncreased Service Life. Joint Transportation Research Program. WestLafayette: Purdue University. Wei, Y., & Hansen, W. (2008). Pre-soaked Lightweight Fine Aggregates asAdditives for Internal Curing in Concrete. In D. Bentz, & B. Mohr (Ed.),Internal Curing of High-Performance Concretes: Laboratory and FieldExperiences (pp. 35-44). Farmington Hills: American Concrete Institute.

Questions?

This concludes the American Institute of ArchitectsContinuing Education Systems Course

Jeff.Speck@Riverlite.com