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Concrete (PCC) Mixture Designs for O’Hare Modernization Program. Principal Investigators Prof. Jeff Roesler Prof. David Lange. PROJECT GOAL
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Concrete (PCC) Mixture Designs for O’Hare Modernization Program Principal Investigators Prof. Jeff Roesler Prof. David Lange PROJECT GOAL Investigate cost-effective concrete properties and pavement design features required to achieve long-term rigid pavement performance at Chicago O’Hare International.
Acknowledgements Principal Investigators • Prof. Jeff Roesler • Prof. David Lange Research Students • Cristian Gaedicke • Victor Cervantes
Former OMP Research Students • Sal Villalobos – CTL, Inc. (Chicago area) • Civil engineer • Robert Rodden – American Concrete Pavement Association (Chicago area) • Technical director • Zach Grasley – Texas A&M • Materials professor
Project Objectives • Develop concrete material constituents and proportions for airfield concrete mixes • Strength • volume stability • fracture properties • Develop / improve models to predict concrete material behavior • Crack width and shrinkage • Evaluate material properties and structural design interactions • joint type & joint spacing (curling and load transfer) • Saw-cut timing
FY2005-06 Accomplishments www.cee.uiuc.edu/research/ceat • Tech Notes (TN) - • TN2: PCC Mix Design • TN3: Fiber Reinforced Concrete for Airfield Rigid Pavements • TN4: Feasibility of Shrinkage Reducing Admixtures for Concrete Runway Pavements • TN11: Measurement of Water Content in Fresh Concrete Using the Microwave Method • TN12: Guiding Principles for the Optimization of the OMP PCC Mix Design • TN15: Evaluation, testing and comparison between crushed manufactured sand and natural sand • TN16: Concrete Mix Design Specification Evaluation • TN17: PCC Mix Design Phase 1
FY2006 Accomplishments www.cee.uiuc.edu/research/ceat • Tech Notes (TN) - • TN21: An Overview of Ultra-Thin Whitetopping Technology • TN23: Effect of Large Maximum Size Coarse Aggregate on Strength, Fracture and Shrinkage Properties of Concrete • TN24: Concrete Saw-Cut Timing Model • TNXX: Recycled Concrete Aggregate Concrete (80%) • TNYY: Functionally Layered Concrete Pavements (70%) • TNZZ: Properties of concrete containing GGBFS • TNAA: Effects of Concrete Materials and Geometry on Slab Curling (40%)
Presentation Overview • 2006 Topics – TN & Brown Bag • Large-sized coarse aggregate mixtures • Slab Curling –theoretical analysis • Saw-cut timing model • Recycled Concrete Aggregate • P-501 Accomplishments • P-501 Remaining Items • Field Demo Project • Future Work
Phase II Mix Summary Effect of larger-size coarse aggregate on strength Larger-size coarse aggregate
Drying Shrinkage – Phase II Effect of larger-size coarse aggregate on shrinkage
Fracture Energy Results-Phase II Effect of larger-size coarse aggregate on fracture properties • Age = 28-days
P-501 Accomplishments • No fly ash replacement ratio • ASTM C157 <0.045% at 28-days* • MSA 1.5 inch* • Design strength 650 psi and specified strength =620 psi • Min. cement content =535 lb/yd3 • Min. w/cm 0.4 & max 0.45
P-501 Remaining Issues • Nominal vs. Maximum Size Aggregate • Combined Gradation • ASTM C1157 – blended cements • Performance spec • Air content • 5.5% for 1.5inch MSA • Slag
Saw-Cut Timing and Depth • Process • Concrete Mix • Aggregate size • Cementitious content Crack Propagates FRACTURE PROPERTIES Wedge Split Test FEM Model Saw Cut Depth Model
Recycled Concrete Aggregate (RCA) Objectives Determine the fracture properties of concrete • virgin and recycled coarse aggregate • w/ and w/o structural fibers • Effects of concrete drying shrinkage with recycled coarse aggregate
Results – Virgin vs RCA • Similar peak loads • Virgin GF is 1.6 times larger than RCA GF
Results – Virgin FRC vs RCA FRC • Similar peak loads • Similar softening curves • Similar GF
Concrete Slab Behavior • Curling stresses • temperature • moisture • Joint Opening • Load transfer • Dowel vs. no dowel
Hygro-thermal Strain (1) • Quantify the drying shrinkage due to RH change • Micro-mechanical model: modified Mackenzie’s formula
Hygro-thermal Strain (2) • Kelvin-Laplace equation
Slab-base friction L: joint spacing Expansion caused by friction (after K.P. George)
Field Validation • Field data: three concrete slabs were cast on 06/22/06 at ATREL • Slab size: 15’x12’x10’’, BAM • Temp., RH measured @ surface, 1’’,3’’,5’’,7’’ and 9’’ at 15-min. interval • Two LVDTs installed in each joint to measure joint opening
Material inputs • Setting temp. T= 50°C (122°F) • =5.75 x 10-6/°F (10.35 x 10-6/°C) • K=2.12 x 106 psi • Ks=3.77 x 106 psi • E=4.03 x 106 psi • Unit weight =149 pcf • Friction coeff. = 2.5 • Data set: 0:08a.m. on 07/01/06 –12:38p.m. on 07/13/06 at 15-min. interval
Concrete Pavement / Material Interaction • Hygro-thermal effects on slab behavior • Curling & joint opening (slab sizes) • Dowel • Construction practices (curing, temp, mix components) • Early & long age • Material effects (e.g.) • Combined gradation* • Slag • High early strength/stiffness • FRC
Surface Energy Balance Solar radiation Reflected radiation Convection Wind Conduction PCC slab BAM ASB Subgrade Conduction
N-layer Heat Transfer Model Layer 1 Layer 2 Layer n B.C.s • Governing PDE
QUESTIONS • www.cee.uiuc.edu\research\ceat • Thanks!
Curling Questions • How does shrinkage effect slab size? • What are the combined effect of moisture/temperature profile? • What is the role concrete creep? • How do other concrete materials behave – FRC & SRA?
Slab Curling Stress s s s s Time • Effects of materials and slab geometry on moisture and temperature curling after Grasley (2006) & Rodden (2006)
Field vs Lab Lab Field
Introduction • By product of the steel industry • Produced in blast furnaces • Highly cementitious • Hydrates similarly to Portland cement
Production Iron blast furnace slag is quenched… it is then ground to a fine power
Pros and Cons Improves workability Lower water demand Higher paste volume Higher strength potential Using 120 grade Longer setting time Decreased permeability Performs well in freeze thaw tests Reduces the effects of ASR Reduced heat of hydration* More susceptible to drying shrinkage Slower strength gain* Cons Pros
Slag Activity Index ASTM C989 • Higher grade GGBFS can be used in larger percentages • Improves early and ultimate performance