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 Sal Villalobos Rob Rodden Zach Grasley Others students Hector Figueroa Victor Cervantes

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

Project Objectives Concrete properties Long-term perfor- mance at ORD Material constituents and mix design Analysis of existing concrete mix designs Laboratory tests Optimal joint types and spacing. Modeling Test for material properties

FY Accomplishments 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 Tech Notes (TN) - TN21: An Overview of Ultra-Thin Whitetopping Technology TN23: TN23: Effect of Large Maximum Size Coarse Aggregate on Strength, Fracture and Shrinkage Properties of Concrete TNXX: Effects of Concrete Materials and Geometry on Slab Curling TNYY: Concrete Saw-Cut Timing Model TNZZ: Functionally Layered Concrete Pavements

Presentation Overview Large-sized coarse aggregate mixtures Saw-cut timing model Slab Curling Field Demo Project Recycled Concrete Aggregate

Crack width, cw Dowels deemed necessary Aggregate Interlock Joints Reduced LTE with small maximum size CA

Larger maximum size CA Larger aggregate top size increases aggregate interlock and improves load transfer Crack width, cw Aggregate Interlock Joints

Why Larger Size Coarse Aggregate? Potential benefits Less paste  lower cementitious content  Shrinkage Higher toughness  Fracture and crack propagation resistance Increase roughness of joint surfaces  Increased load transfer between slabs  Reduced # of dowels Durability (??)  D-cracking Cost - Effectiveness

Experimental Design Effect of aggregate size (1.0” vs. 1.5”) Effect of 1.5” coarse aggregate: Total cementitious content:  688 lb/yd 3, 571 lb/yd 3, 555 lb/yd 3 and 535 lb/yd 3 Water / cementitious ratio:  0.38 versus 0.44 Fly Ash / cementitious ratio:  14.5% versus 0% Effect of coarse aggregate cleanliness

Mix Design Results

Phase II Mix Summary Larger-size coarse aggregate Effect of larger-size coarse aggregate on strength

Drying Shrinkage – Phase II Effect of larger-size coarse aggregate on shrinkage

Fracture Energy Results-Phase II Age = 28-days Effect of larger-size coarse aggregate on fracture properties

PCC Mix Design – Phase II Summary* Larger aggregates reduce strength by 20%, but… 28-day G F similar  similar cracking resistance Larger aggregates reduce concrete brittleness 1-day fracture energy  with larger MSA  greater joint stiffness / performance No significant shrinkage difference TN23 – April 2006 *Roesler, J., Gaedicke, C., Lange, Villalobos, S., Rodden, R., and Grasley, Z. (2006), “Mechanical Properties of Concrete Pavement Mixtures with Larger Size Coarse Aggregate,” accepted for publication in ASCE 2006 Airfield and Highway Pavement Conference, Atlanta, GA.

Saw-Cut Timing Model Concrete E and fracture properties(c f,K IC ) at early ages. Develop curves of nominal strength vs notch depth for timing. d a Notch depth (a) depends on stress, strength, and slab thickness (d) Stress = f(coarse aggregate,  T,RH)

Saw-Cut Timing and Depth Saw cut depth / timing – EXPERIENCE Fracture properties at early ages Critical Stress Intensity Factor (K IC ) Critical Crack Tip Opening Displacement (CTOC C ) form this type of specimen Wedge Splitting Test (WST)  need geometric factors d a

Saw-Cut Timing and Depth Objectives Develop a FEM Model for WST specimens Integrate measured fracture properties with a Size Effect Model  (after Zollinger et al. 2001) Effect of coarse aggregate size, cementitious content and age on timing/depth Determine saw cut depth for different pavement thicknesses

Saw-Cut Timing and Depth Process FRACTURE PROPERTIES Wedge Split Test FEM Model Saw Cut Depth Model Concrete Mix Aggregate sizeAggregate size Cementitious contentCementitious content Crack Propagates

WST setup and specimen 30mm 57mm 2mm Notch detail  = a/b 200 mm 205mm 200 mm 80mm 40mm 80mm a b t Wedge Split Testing

FEM Model Special Mesh around crack tip Q8 elements Symmetry and BC considerations 200 mm 100 mm Saw-Cut Timing and Depth

Saw-cut timing and depth FEM Model Results Determination of Fracture parameters

Saw-cut timing and depth FEM Model Results Determination of Fracture parameters

SEM Model (Bazant) Saw-Cut Depth Model Nominal Strength vs Notch Depth Chart

Concrete Saw-cut timing and depth Mix proportions Aggregate gradations

Concrete Fracture Properties Critical Stress Intensity Factor (K IC ) Critical Crack Extension (c f )

Westergaard Slab Curling Curling Stress in Concrete Slab Saw cut Depth

Saw Cut Depth Charts Low Cementitious Content

Saw Cut Depth Charts High Cementitious Content

Summary of Notch Depth Requirements

Saw-cut timing and depth Summary Saw cut depth increases with concrete age  dramatic increase in depth after 10 to 12 hr. Larger maximum aggregate size increases saw cut depth  High cementitious materials especially

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 Effects of materials and slab geometry on moisture and temperature curling       Time Stress after Grasley (2006) & Rodden (2006)

Field vs Lab Field Lab

RH Profile - Lab

STD Cube Moisture Stresses

Summary of Curling Moisture profile effects Temperature Set temperature Shrinkage Reducing Admixtures Fiber Reinforced Concrete

Joint Type Analysis How can we choose dowel vs. aggregate interlock joint type & joint spacing? Need to predict crack width & LTE Shrinkage, zero-stress temperature, creep Aggregate size and type (G F ) Slab length & base friction If we use aggregate interlock joints there is a significant cost savings h

Field Demo Project

Joint Opening Measurement

Two week joint opening

Concrete Free Shrinkage

Dong/Zach formula

Slab Lift-Off (Curling)

Step 1: Predict crack opening, w Step 2: Predict differential deflection, δ diff Step 3: Determine LTE Inputs: RH, T, L, E, , C Inputs: w, CA topsize,  Step 4: Acceptable LTE? Inputs: δ free, δ diff,  Inputs: FAA recommendation Base friction Curling (thermal and moisture) Steel reinforcement Crack spacing Drying shrinkage Temperature drop Restraints *after Zollinger Crack Width Model Approach

Recycled concrete aggregate (RCA)

RCA Slight strength reduction Higher shrinkage potential Lower modulus Lower concrete density Potential cost saving ++ Can RCA (coarse) provide similar mechanical properties for airfield rigid pavements as virgin aggregates?

Use of RCA for OMP RCA may lead to cost savings Disposal, trucking, aggregate costs RCA may increase shrinkage? RCA less stiff than natural aggregate RCA can shrink more than natural aggregate Shrinkage may be same or reduced if RCA is presoaked to provide internal curing

UIUC First Trial RCA from Champaign recycling plant Concrete came from pavements, parking garages, etc. Mix of materials with unknown properties Material washed, dried, and sieved to match natural fine aggregate Soaked for 24 hrs, surface dried, and then 100% replacement of natural fine aggregate

Saturated RCA vs Lab Aggregates Similar autogenous shrinkage curves

Mechanical Property Test Plan Simple lab crusher Three Point Bend (TPB) test  Fracture properties (Spring 2006) Full-scale crushing at contractor Fracture / strength properties Shrinkage (Summer 2006)

Sample Preparation 1. Crush Process

Sample Preparation (Con’t) 2. Gradation3. Mixture Design

Sample Preparation (Con’t) P 50 mm CMOD 600mm 700mm 150mm 80 mm 4. Dimensions

Sample Preparation(Con’t) 3 beams Tested 7 day Position control displacement CMOD = 3 Max 3 Cycles Load – CMOD curve

Test

Plain Concrete Fracture Behavior PCC RCA

FRC Fracture Behavior FRC RCA w/ Fibers

Fracture Energy

Results (Con’t) RCA Virgin RCA Virgin

Results

RCA vs FRCA

Summary of Fracture Properties

Fracture Energy

Initial Findings RCA reduce the concrete fracture energy by 50% RCA does not affect the fracture energy in fiber reinforced concrete (peak load still less)

Summer 2006 RCA Concrete Mixtures Type of Coarse AggregateVirgin (V)Recycled (R)V & R FibersYesNoYesNo Mix IDVFVPRFRPMP Mix date Mixturelb/yd 3 Water308 Cement Type I607 Coarse Aggregate1645 Fine Aggregate1360 Synthetic Fibers3---3 BSG SSD = 2.42 AC = 5.7%

RCA Tests Fresh properteis Slump, Density, Air Compressive Strength (7 days) Split Tensile (7 days) Three Point Bending at 7days G F G f CTOD c Drying Shrinkage – 28 days

RCA Summary to Date Optimization of RCA gradation may lead to reduction in overall shrinkage Other concerns: Reduced concrete strength and modulus Potential for ASR from RCA? Source of chlorides to cause corrosion of dowels? Future work - use RCA with known properties Try different gradations Measure strength/fracture properties also

Work remaining for FY2006 Joint type and size analysis – con’t Saw-cut timing model - TN Materials and geometry effects on curling - TN Functionally-layered concrete pavements - TN Recycled concrete aggregate – con’t P h Botto m layer Top layer aoao h1h1 h2h2

QUESTIONS Thanks!