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Lightweight Concrete for PBES Elements Reid W. Castrodale, PhD, PE Director of Engineering Carolina Stalite Company, Salisbury, NC Representing the Expanded.

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Presentation on theme: "Lightweight Concrete for PBES Elements Reid W. Castrodale, PhD, PE Director of Engineering Carolina Stalite Company, Salisbury, NC Representing the Expanded."— Presentation transcript:

1 Lightweight Concrete for PBES Elements Reid W. Castrodale, PhD, PE Director of Engineering Carolina Stalite Company, Salisbury, NC Representing the Expanded Shale, Clay and Slate Institute

2 2 LWA is a manufactured product LWA is not a new product LWA is a lighter rock LWA meets aggregate specifications LWA has higher absorption LWA is durable LWA typically costs more than NWA LWA can be used for internal curing LWA can be used as geotechnical fill Lightweight Aggregate (LWA)

3 3 LWC is not a new product LWC is made using same process and equipment LWC weighs less than NWC LWC has enhanced durability LWC typically costs more than NWC DOT specifications for LWC PBES applications for LWC Lightweight Concrete (LWC)

4 4 LWA is a manufactured product LWA is not a new product LWA is a lighter rock LWA meets aggregate specifications LWA has higher absorption LWA is durable LWA typically costs more than NWA LWA can be used as geotechnical fill for ABC projects Lightweight Aggregate (LWA)

5 5 LWA is a manufactured product Raw material is shale, clay or slate Expands in kiln at 1900 – 2200 deg. F Gas bubbles form in softened material Gas bubbles remain after cooling Clinker is crushed and screened

6 6 Stephen Hayde discovered that LWA could be manufactured from shale, clay and slate Observed that some bricks bloated during burning Began developing rotary kiln process in 1908 Patent for rotary kiln process was granted in 1918 First use of LWA was for LWC to build ships in World War I Launching of the USS Selma in June 1919 LWA is not a new product

7 7 Rotary kiln expanded LWA Specific gravity: 1.3 to 1.6 Normal weight aggregate Specific gravity: 2.6 to 3.0 Twice the volume for same mass Half the mass for the same volume Soil Gravel ESCS Agg. Limestone Sand 1 lb. of each aggregate LWA is a lighter rock

8 88 LWA satisfies typical specifications required of NWA for structural concrete LWA conforms to AASHTO M 195 gradations and other properties Coarse gradations are shown Several gradations of fine aggregate are available LWA meets aggregate specs ¾"½" 3/8 " 5/16 " Fines

9 9 Pores in LWA particles reduce density Result - increased absorption But pores are not all connected - Does not act like a sponge Absorption range for LWA in US: 6% to 40% 9 LWA has higher absorption An expanded slate LWA particle soaked in water with fluorescent yellow dye for 180 days, then split open. Absorption at the time of testing was 8% by mass. 0.73"

10 10 LWA is durable LWA is a vitrified ceramic material Hardness equivalent to quartz LWA meets requirements for LA abrasion test Freeze-thaw test for aggregate Soundness tests

11 11 LWA typically costs more Reasons for increased cost of LWA High-temperature processing Shipping from the manufacturing plant

12 12 LWA is a high-performance low-density geotechnical fill In-place density: 45 to 60 pcf Angle of internal friction: ≥ 40  Free draining Benefits for ABC projects Reduces settlement Reduces load on walls Fast installation - like 57 stone LWA as geotechnical fill

13 13 LWC is not a new product LWC is made using same process and equipment LWC weighs less than NWC LWC has enhanced durability LWC typically costs more than NWC DOT specifications for LWC PBES applications for LWC Lightweight Concrete (LWC)

14 14 Early use of LWC in a bridge project San Francisco-Oakland Bay Bridge Upper deck of suspension spans was built using 95 pcf all LWC in 1936 Lower deck was reconfigured for highway traffic using LWC in 1958 Both decks are still in service LWC is not a new product

15 15 When LWA is used to make LWC Can use same mix design procedures Same batch plants and mixing procedures Same admixtures Same placing and finishing methods Higher absorption of LWA requires prewetting, especially for pumping “Roll-o-meter” for measuring air content Can make self consolidating LWC, i.e., SCC LWC uses same processes

16 16 LWC weighs less than NWC All LWCSand LWCNWC 90 - 105 pcf110 - 125 pcf135 - 155 pcf LW FineNW Fine LW Coarse NW Coarse Specified Density Concrete (SDC) Density ranges shown are approximate Must add allowance for reinforcement (typ. 5 pcf)

17 17 Reduced weight of precast elements Affects handling, shipping and erection - Reduces costs - Improves safety Improves structural efficiency Reduces seismic loads Reduces foundation loads May get more concrete in a truck May get more pieces on a truck LWC weighs less than NWC

18 18 LWC has enhanced durability Improved bond between aggregate and paste Elastic compatibility Internal curing Reduced cracking tendency Improved resistance to chloride intrusion Enhanced resistance to freezing and thawing Good wear and skid resistance Alkali-silica reactivity (ASR) resistance Increased fire resistance Results in more durable concrete

19 19 Additional cost of LWC depends on Cost of LWA Cost of NWA being replaced Shipping cost for both aggregates Familiarity of contractor and concrete supplier with LWC - LWC is commonly used for building construction in most major metropolitan areas LWC typically costs more

20 20 Range of cost for sand LWC bridge deck Cost / SF assumes 9 in. thick deck (average) FHWA reports that average bridge unit cost in 2010 ranged from about $55 to over $500 / SF Sand LWC Premium / CYCost Prem. / SF $20 / CY$ 0.56 / SF $40 / CY$1.11 / SF $60 / CY$1.67 / SF LWC typically costs more

21 21 Range of cost for sand LWC bridge girders Assume $60 / CY cost premium for sand LWC Girder spacing assumed to be 10 ft Girder TypeCost Prem. / LFCost Prem. / SF PCBT-29$9.93 / LF$0.99 / SF PCBT-61$13.25 / LF$1.33 / SF PCBT-93$16.71 / LF$1.67 / SF LWC typically costs more

22 22 Increased cost is offset by potential savings Increased piece size - Fewer pieces = faster erection Reduced piece weight - Shipping and erection Reduced foundation loads Fewer truck loads in congested areas LWC can reduce the overall project cost LWC typically costs more

23 23 Example for NCDOT Mod BT-74 bridge girders Cost premium for sand LWC in girder - Assume $30 / CY = $6.83 / LF - Cost premium for LWC for 150 ft girder = $1,024 Cost reduction by using sand LWC girder - Shipping from plant to site = $811 NWC girder = 69 t; LWC girder = 58 t, or 11 t less - Drop 4 strands / girder @ $0.65 / LF ea. = $390 - Total cost reduction = $1,201 Net savings by using sand LWC girder$177 LWC typically costs more

24 24 Sand LWC for Bridge Decks TennDOT includes in Standard Specifications NCDOT, UDOT, etc. have standard special provisions Other states have project special provisions All LWC Special provisions have been developed for NCDOT Sand LWC for Girders GDOT has special provisions (10 ksi at 120 pcf) VDOT has special provisions (8 ksi at 125 pcf) INDOT allows in design manual (120-130 pcf) DOT Specifications for LWC

25 25 GDOT special provisions - 10 ksi sand LWC girders Maximum air-dry density is 120 pcf Size of LW coarse aggregate = ½ in. Minimum cement factor = 650 lbs/cy Maximum water-cement ratio = 0.330 Slump acceptance limits = 4½ ± 2½ in. Entrained air acceptance limit = 5 ± 1½ % Max. chloride permeability = 3,000 coulombs Same as for NW HPC, except density & aggr. size DOT Specifications for LWC

26 26 Prewetted LWA delivers curing moisture in NWC Replace a fraction of the NW sand with the same volume of prewetted fine LWA Water absorbed in the prewetted fine LWA Released over time into the concrete Does not enter into the mix water immediately Does not affect the w/cm Basic benefits of internal curing Increases cement hydration Allows more complete reaction of SCMs Internal Curing with LWA

27 27 More efficient use of cementitious materials Improves durability of NWC mixtures Reduces cracking tendency - Reduces shrinkage - Reduces curling and warping of slabs Improves robustness of concrete construction - More tolerant of inadequate external curing - More resistant to rapid temperature changes Reduces chloride penetration - Delays onset of corrosion Internal Curing with LWA

28 28 Internal Curing with LWA Denver Water Company – Lonetree Basin Tank #2 10 mg Concrete Water Storage Tank

29 29 Internal Curing with LWA Internal Curing vs. No Internal Curing – 1 day after placement Highlands Ranch, CO – 92  F ambient, 20% RH No conventional curing With internal curing Without internal curing

30 30 Internal Curing with LWA Indiana DOT Test in 2010 Internally cured slab had no visible cracks after 1 year Slab without IC was cracked after a few months

31 31 Internal Curing with LWA Indiana DOT Test in 2010 Preliminary observations after 1 year in service No difference in finishing was reported Compressive strength of IC concrete - 10% less at 1 day - About equal at 10 days - 20% stronger at 3 months Rapid chloride permeability tests for IC concrete - 10% lower charge passed at 28 days - Nearly 40% lower charge passed at 3 months

32 32 Actual and potential applications Precast foundation elements Precast pile & pier caps Precast columns Precast full-depth deck slabs Cored slabs & Box beams NEXT beams & Deck girders Full-span bridge replacement units with precast deck Bridges installed with SPMTs PBES applications for LWC

33 33 Mill Street Bridge, NH % Chng. Weight as Des. Chng. Weight as Built Chng. 150 pcf039 t025 t0 125 pcf17%32 t7 t20 t5 t 110 pcf27%28 t11 t18 t7 t Precast foundation elements – Project did not use LWC Comparison for abutment footings – Abutment walls have similar weights

34 34 Okracoke Island, NC Precast pile caps – Project did not use LWC End bent pile cap – 2 pieces – Size: 21 ft long x 3.67 ft x 3 ft – 3 pile pockets per piece Pile CapWeightChange% Chng. 150 pcf16 t00 125 pcf13 t3 t17% 110pcf12 t4 t27%

35 35 Lake Ray Hubbard, TX Precast pier caps Project did not use LWC Typical pier cap on 3 columns Size: 37.5 ft long x 3.25 ft x 3.25 ft Pier CapWeightChange% Chng. 150 pcf29 t00 125 pcf24 t5 t17% 110 pcf21 t8 t27%

36 36 Project did not use LWC Precast columns Max wt = 45 tons @ 150 pcf Max wt = 37 tons @ 125 pcf Using 128 pcf SDC could have eliminated pedestal for tall columns Precast caps Max wt = 78 tons @ 150 pcf Max wt = 65 tons @ 125 pcf Edison Bridges, FL

37 37 Deck replacement with full-depth precast deck panels in 1983 Sand LWC was used for panels Allowed thicker deck - Lower shipping cost & erection loads Allowed roadway widening with no super- or substructure strengthening - Reduced project cost and duration Sand LWC deck performed well until bridge was recently replaced to improve traffic capacity Woodrow Wilson Br, VA/DC/MD

38 38 Okracoke Island, NC Precast cored slabs – Project did not use LWC 21” deep by 3 ft wide – 30 and 50 ft spans Ext. 50 ft spanWeightChange% Chng. 150 pcf16.0 t00 125 pcf13 t3 t17% 125 pcf - Solid16.4 t0.4 t+3%

39 39 Okracoke Island, NC Precast barriers – Project was not designed with LWC Contractor proposed casting barriers on cored slabs in precast plant – Sand LWC was used for the barrier BarrierWeightChange% Chng. 150 pcf13.7 t00 125 pcf11.4 t2.3 t17% 110 pcf10.1 t3.6 t27%

40 40 Mill Street Bridge, NH Precast box beams – Project did not use LWC NWC box beam weight governed crane size with 2 crane pick – Using sand LWC for box beam would make beam pick nearly equal to NWC substructure elements Ext. Box BeamWeightChange% Chng. 150 pcf69 t00 125 pcf57 t12 t17%

41 41 NEXT F Beams Compare section weights for NEXT 36 F – NWC @ 155 pcf; Sand LWC @ 130 pcf – No max. span charts for sand LWC – 16% reduction in weight for same width sections – 12 ft wide LWC is lighter than 8 ft wide NWC 8 ft10 ft12 ft8 ft10 ft12 ft 16%

42 42 Compare section weights for NEXT 36 D – 12 ft width not used to limit weight of NWC section – Max. span charts are provided for sand LWC – 16% reduction in weight for same width sections – 12 ft LWC is lighter than 10 ft NWC 8 ft10 ft12 ft8 ft10 ft12 ft NEXT D Beams 16%

43 43 Deck Girders, NY Precast deck girder – Project did not use LWC 41” deep deck girders with 5 ft top flange – 87.4 ft long girders Girder & DeckWeightChange% Chng. 158 pcf45 t00 130 pcf37 t8 t18% NWC density was obtained from girder fabricator Specified concrete compressive strength = 10,000 psi

44 44 I-95 in Richmond, VA Prefabricated full-span units First project completed in 2002 Steel girders and sand LWC deck Max. precast unit weight for current project Deck densities do not include reinforcement allowance DeckWeightChange% Chng. 145 pcf132 t00 120 pcf116 t16 t12% 105 pcf106 t26 t20%

45 45 Deck replacement on existing truss Sand LWC precast deck units with steel floor beams Sand LWC density = 119 pcf Max. deck unit weight = 92 t Sand LWC saved about 14 t Existing deck was LWC Was in service 73 years Lewis & Clark Bridge, OR/WA

46 46 3300 South over I-215 – Built in 2008 Sand LWC used for deck Less deck cracking than bridges with NWC decks 3 bridges moved in 2011 Steel girder bridges with sand LWC decks 200 South over I-15 – 2 spans @ 3.1 million lbs Sam White Lane over I-15 – 2 spans @ 3.8 million lbs I-15 Southbound over Provo Center Street - 2 moves of 1.5 and 1.4 million lbs Bridges set with SPMTs, UT

47 47 Graves Ave. over I-4, FL Complete span replaced using SPMTs Project did not use LWC Comparison of weight for NWC and sand LWC Appendix C in FHWA “Manual on Use of SPMTs …” GirderDeckWeightChange% Chng. 152 pcf150 pcf1,282 t00 127 pcf120 pcf1,049 t233 t18% 127 pcf105 pcf996 t286 t22% Comparison with all LWC deck is not in Manual

48 48 LWC can be used to achieve both accelerated construction and longer-life structures For more information on LWA and LWC Contact Reid Castrodale: rcastrodale@stalite.com Visit: www.escsi.org


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