Internal Curing. Improving Concrete Durability and Sustainability Using Internal Curing. Using Prewetted Lightweight Aggregates

Transcription

1 Internal Curing Using Prewetted Lightweight Aggregates Improving Concrete Durability and Sustainability Using Internal Curing Presented to: LA DOTD Transportation Conference February, 2013 Jeff Speck, P.E., FACI V.P. Sales & Marketing Big River Industries, Inc.

2 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]

3 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 selfdesiccation [1]

4 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

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6 Expanded at 2000 F

7 Use fine aggregate to distribute water Help satisfy increased water demand from SCM s Works even at moderate w/cm

8 It s All About the Distribution Coarse LWA Fine LWA Henkensiefken (2008)

9 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.

10 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

11 Extensive Lab Research 121 Citations as of December 2011

12 Stress Development Mechanisms Why Does Concrete Crack? Restraint + Volume Change = Stress Occurs When Tensile Stress Exceeds Tensile Capacity

13 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)

14 Thermal Effects

15 Self-Desiccation

16 Self-Desiccation

17 Self-Desiccation

18 Self-Desiccation

19 The Bentz Equation M LWA = C f CS α max S φ LWA ~ 7 lb of internal curing water needed per 100 lb cement

20 For Internal Curing Replace a Portion of Natural Sand With Lightweight Aggregate Sand (LWAS) Natural Sand LWAS 10-25% LWAS 75-90% Natural Sand Mixture Proportions of the Fine Aggregate In a Yard of Concrete

21 Shrinkage Strain ( ) Why can LWA be used for IC? 0 0 w/c = 0.30 w/c = 0.30 w/c = %SRA w/c = %SRA r r r 2 r r 1 1 r 2 1 Shrinkage Strain ( ) Sealed - Plain Sealed - Sealed Plain - SRA Sealed - SRA Sealed - LWA Sealed - LWA -3000r 3 Cement -3000r 3 Paste r 4 LWA r 4 Cement r 3 Paste r 3 /m Largest pores will empty first /m The saturated LWA provides water to the paste and keeps a large pore full -5000

22 Degree of hydration (%) 0% 20% 40% 60% 80% More Hydration Mixture with internal curing Mixture without internal curing Espinoza-Hajazin (2010) Water / cement ratio Degree of hydration of 90 days, 50% RH

23 Higher Compressive Strength - Portland Cement 0.30 & 0.50 w/c Sealed Curing 50% RH Curing Golias (2011)

24 Less Shrinkage; Less Cracking Plain 0.30 Concrete 0.6 mm wide crack 12 days IC 0.30 Concrete 0.4 mm wide crack 43 days Schlitter (2010)

25 Delayed Cracking Time to Cracking, hours Control IC - Summer curing temp. profile for expanded shale IC mix Byard (2010)

26 Reduced Warping 80% Reduction Wet base, 7 day cure then 73 o 50% RH on slab surface Wei (2008)

27 Lower Absorption 28 day curing Henkensiefken (2009)

28 Charge passed (coulombs) Lower Chloride Permeability Mixture without internal curing Mixture with internal curing water / cement ratio Espinoza-Hajazin (2010) Chloride ion 90 days, 50% RH

29 Internal Curing vs. No Internal Curing Denver Water Test Slabs 92 o F ambient, 20% RH Internal Curing No Internal Curing No conventional curing

30 Denver Water 10 million gallon tank 1300 yard slab pour Change Order to include walls and columns

31 Denver Water 10 million gallon tank 1300 yard slab pour

32 Denver Water 10 million gallon tank Contractor requested change order to use IC mix for ring girder, columns and walls

33 Denver Water 10 million gallon tank

34 Denver Water 10 million gallon tank 8 thick PT roof slab placed monolithically

35 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

36 Paving in Texas Bridges in New York & Indiana UP RR Intermodal Facility Constructed 2005 NY: 16 built or under construction as of ,000 yd 3 IC project low slump pavement Visual inspections At 6 months one crack At 5.5 yrs minuscule plastic or drying shrinkage cracks IN: 33 bridges

37 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

38 Indiana Bridges NE of Bloomington InDOT 2010

39 Indiana Bridges NE of Bloomington Standard External Curing (wet burlap) Both Bridges InDOT 2010

40 Indiana Bridges NE of Bloomington Plain Concrete Deck at One Year InDOT 2010

41 Indiana Bridges NE of Bloomington Plain Concrete Deck at One Year Longitudinal and Transverse crack

42 Indiana Bridges NE of Bloomington IC Concrete Deck at One Year No Cracks

43 Texas State Highway CY, 5 miles of CRCP, Class P

44 SR-121 Crack Spacing of IC Section at 10 months

45 SR-121 Crack Width (% of total at 10 months)

46 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.

47 Cost of Internal Curing 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!

48 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

49 Researchers Dale Bentz Chemical Engineer National Institute of Standards & Technology 100 Bureau Drive Stop 8615 Gaitherburg, MD (301) Jason Weiss Professor Purdue University School of Civil Engineering 550 Stadium Mall Drive West Lafayette, IN (765) Anton Schindler HRC Director/Associate Professor Auburn University 238E Harbert Engineering Center Auburn, AL (334)

50 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 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 Lafayette: Purdue University.

51 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 ). Farmington Hills: American Concrete 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), 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 Lafayette: Purdue University.

52 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

53 Questions?