Outline � Overview of LC-HPC � Specifications and their application Program Background and � Where we stand Introduction to Specifications 9 th Annual Meeting - Construction of Crack-Free Concrete Bridge Decks July 19, 2011 Kansas City, MO Scope of Work Bridges Low-Cracking High Performance Concrete Primarily composite steel girder (LC-HPC) Bridge Decks bridges Full-depth slabs 23 LC-HPC decks (28 placements) ( p ) completed through 2010 Removable forms 1 LC-HPC deck to be constructed this Matching bridges to serve as a control year where possible (Phase I) More to be let in MN Why LC-HPC? Why LC-HPC? Negative impact of cracks on concrete in the decks. Negative impact of cracks on corrosion Negative impact of cracks on corrosion performance of both conventional and epoxy-coated reinforcement. Cracks 1
Factors that affect cracking Our goal � Age � Eliminate cracking in bridge decks � Deck type � Cement paste content � Compressive strength � To do this, we need to minimize � Air content � Air content cracking due to cracking due to � Slump � Plastic shrinkage � Settlement over reinforcing bars � Temperature � Thermal contraction � Construction date � Drying shrinkage � Curing � Construction techniques Bridge Deck Type Age 0.90 1.20 ck Density, m/m 2 0.80 0.70 1.00 Age Corrected 0.60 0.51 0.49 ensity, m/m 2 0.44 0.50 0.80 0.40 0.33 0.30 0.60 0.20 0 20 Crack De Cra 0.10 0.40 0.00 7% SFO 5% SFO CO MONO 0.20 Bridge Deck Type 0.00 Number of (9) (18) (30) (16) 0 25 50 75 100 125 150 175 200 225 250 275 Bridges Bridge Age, months Number of (9) (36) (52) (32) Surveys Monolithic Paste Content Slump 0.87 0.90 0.90 Uncorrected 0.80 ack Density, m/m 2 0.80 0.73 ack Density, m/m 2 0.68 Adjusted for Water Content 0.70 0.70 0.60 Age Corrected 0.60 Age Corrected 0.51 0.50 0.50 0.40 0.40 0.31 0.30 0.19 0.30 0.22 0.16 0.20 0.18 0.19 Cra Cra 0.20 0 20 0 15 0.15 0.10 0.11 0.10 0.00 0.00 26 27 28 29 38 (1.5) 51 (2.0) 64 (2.5) 76 (3.0) Percent Volume of Water and Cement, % Slump, mm (in.) Number of Number of (8) (16) (4) (5) (5) (20) (5) (1) Placements Placements Number of (16) (31) (8) (11) Number of (10) (40) (11) (3) Surveys Surveys Monolithic Monolithic 2
Compressive Strength 0.90 0.80 ack Density, m/m 2 0.70 0.60 Age Corrected 0.49 0.50 0.40 0.26 0.30 0.16 0.20 0 20 Cra 0.10 0.00 31 (4500) 38 (5500) 45 (6500) Compressive Strength, MPa (psi) Number of (7) (12) (10) Placements Number of (13) (24) (23) Surveys Monolithic High Air Temperature Air Content 0.90 0.90 0.80 ck Density, m/m 2 0.80 2 /m 0.70 0.70 ack Density, m 0.60 0.60 Age Corrected Age Corrected 0.50 0.44 0.50 0.38 0.37 0.37 0.40 0.40 0.33 0.30 0.30 0.19 Cra Crac 0.20 0.13 0.20 0 20 0.10 0.10 0.00 0.00 5 (41) 15 (59) 25 (77) 35 (95) 4.5 5.5 6.5 High Air Temperature, C (F) Air Content, % Number of Number of (4) (15) (9) (4) (7) (19) (5) Placements Placements Number of Number of (8) (31) (17) (9) (14) (40) (10) Surveys Surveys Monolithic Monolithic Date of Construction - Conventional Overlays Date of Construction - Monolithic 0.90 0.81 0.90 0.80 2 0.80 /m 2 0.70 /m ack Density, m 0.70 ck Density, m 0.60 Age Corrected 0.53 0.60 Age-Corrected 0.50 0.50 0.50 0.40 0.40 0.30 0.24 0.30 Crac Cra 0.16 0.20 0.20 0.10 0.10 0.00 0.00 1985-1987 1990-1992 1993-1995 1984-1987 1990-1993 Date of Construction Date of Construction Number of Number of (6) (7) (6) (17) (3) Bridges Bridges (12) (16) Number of Number of (6) (36) (6) Surveys Surveys 3
Date of Construction - Silica Fume Overlays Control of early evaporation and 0.87 0.90 improved curing 0.80 2 /m 0.70 ck Density, m 0.55 0.60 ge Corrected 0.48 0.50 0.42 0.40 0.30 A Crac 0.20 0.10 0.00 1990-1991 1995-1996 1997-1998 2000-2002 Date of Construction Number of (2) (10) (8) (10) Bridges Number of (6) (20) (16) (10) Surveys Control of early evaporation and improved curing - 7 Silica Fume Overlays MONO CO Subdecks 6 0.90 0.87 5% SFO Subdecks 0.80 2 /m 0.70 5 7% SFO Subdecks 0.61 sity, m 0.58 0.60 lump, in. d te 0.48 c 0.50 rre en 0.39 4 o 0.40 C kD e g g ck 0.30 0 30 Sl A A ra 3 0.20 C 0.10 0.00 2 NONE R1, R2 R3 R4, R5, R6 R8, R9 Special Provision, (R#) 1 Number of (2) (4) (5) (9) (10) 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Bridges Number of Placement Date (6) (8) (10) (18) (10) Surveys Overall Approach 10 Work to reduce plastic, settlement, thermal MONO 9 CO Subdecks and drying shrinkage cracking 8 5% SFO Subdecks 7 7% SFO Subdecks ump, in. Low cement & water contents 6 5 Low slump Low slump Slu 4 High strength is not good 3 Low evaporation rate 2 Construction methods and materials matter 1 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 More early cracking means more total Placement Date cracking 4
LC-HPC Specifications Concrete temperature control � Optimized Aggregate Gradation � Low-absorption Aggregate 55 – 70 ° F � 1 inch Max Size Aggregate � Cement Content ≤ 540 lb/yd 3 50 – 75 ° F if approved by Engineer pp y g � w/c ratio = 0.43 – 0.45 � Air Content of 8 ±1 ½ % � Designated slump 1 ½ – 3 in. (4 3½ in. max) � Controlled temperature � Improved curing Cold-weather concreting Alternatives to Pumping Maintain temperature of both Concrete Buckets � girders and deck. Conveyor Belts � 5
Consolidation Requirements Placing Vertically mounted internal gang vibrators � Air cuff/bladder valve on pump or limit drop with conveyor � Filling end walls and diaphragms ahead of slab Concrete Finishing Curing � General Rule: Less is More � Presoaked burlap � Pan or burlap drag � Timely placement � Bullfloating only if � Constantly wet Constantly wet needed needed � Water is not a finishing � Spray hoses aid! � Soaker hoses � 14 days Three work bridges. Four rolls of pre-cut, Cost effectiveness pre-soaked burlap, two on each side � Cost of equipment: approximately $5000 � Cuts work crew to handle burlap on day of placement from 11 to 5 � Contractor added power to move the work bridges between first and second deck 6
Construction Schedule Curing � Qualification Batch & Slab Followed by curing compound to slow the rate of evaporation � Bridge Construction Specifications Concrete Testing & Acceptance � Clearly define 07-PS0167 Construction testing schedule 07-PS0166 Concrete ahead of time 07-PS0165 Aggregates 07 PS0165 Aggregates � Communicate C i t how out-of-spec concrete will be handled 7
Where we stand � We’ve now evaluated those � LC-HPC decks are working technologies for durability and are � Current provisions, however, don’t prepared to recommend their adoption encompass all of the technologies that � Ready for some more decks! can be brought to bare can be brought to bare � We chose not to propose those technologies until we were assured that they posed no durability problems Questions This year’s crack surveys � Adherence to the rules... The University of Kansas The University of Kansas David Darwin, Ph.D., P.E . JoAnn Browning, Ph.D., P.E. Deane E. Ackers Distinguished Professor Professor Director, Structural Engineering & Materials Laboratory Dept. of Civil, Environmental & Architectural Engineering Dept. of Civil, Environmental & Architectural Engineering 2142 Learned Hall 2142 Learned Hall Lawrence, Kansas, 66045-7609 Lawrence, Kansas, 66045-7609 (785) 864-3723 Fax: (785) 864-5631 (785) 864-3827 Fax: (785) 864-5631 jpbrown@ku.edu daved@ku.edu 8
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