EXPERIENCE WITH SUPERPAVE MIXTURES Construction Conference Robert Lee and Paul Hoelscher

Transcription

1 EXPERIENCE WITH SUPERPAVE MIXTURES 2014 Construction Conference Robert Lee and Paul Hoelscher

2 Table of Contents 1 Introduction Statewide Average Binder Contents 7 3 Statewide Overlay Test Results Aggregate Quality Design Requirements Pay Adjustment Factors Mix Cost 19 2

3 Introduction The Choice 3

4 Dense-Graded Hot-Mix Asphalt Typical Use Can be used for a variety of applications ranging from new construction to overlays Applied on high volume and low volume roads Used as base, intermediate, and surface layers Advantages Lower initial cost More experience & familiarity Disadvantages Cannot accommodate high AC contents No stone on stone contact Low texture of dense graded surface mixtures (Type D, and F) Can either be rut resistant or crack resistant, but not both 4

5 SuperPave Mixtures Typical Use Versatile mix used for a variety of applications ranging from high volume to low volume roadways; from new construction to overlays. Used as base, intermediate and surface layers. Advantages Can be used on medium to high volume roadways. The binder content can be adjusted by adjusting the N-des level. Stone on stone contact The coarse surface texture can be beneficial for wet weather traction. Disadvantages More difficult to compact. May have intermediate temperature tenderness (tender-zone). Gradation is not as gap graded as an SMA mixture. More susceptible to cracking and water infiltration than SMA mixtures 5

6 WHY? Longer Pavement Life Higher Asphalt Content Higher VMA Requirement Consistency With The SGC Stone on Stone Aggregate Structure 6

7 Binder Content - Statewide Averages Mix Type Dense-Graded SuperPave Type A Type B Type C Type D

8 Overlay Test Influence of Binder Content 1000 Overlay Test Median Average Number of Cycles %-3.9% 4.0%-4.9% 5.0%-5.9% 6.0%-6.9% 7.0%-7.9% >8.0% 8

9 Overlay Test Influence of Mix Type 500 Number of Cycles Median Average 0 Dense Graded Superpave 9

10 Aggregate Quality Requirements Property Superpave Dense-Graded Coarse Aggregate SAC As shown on plans As shown on plans Deleterious material, %, max Decantation, %, max Micro-Deval abrasion, %, max Note 1 Note 1 Los Angeles abrasion, %, max Magnesium sulfate soundness, 5 cycles, %, max Coarse aggregate angularity, 2 crushed faces, %, min Flat and elongated 5:1, %, max Fine Aggregate Linear shrinkage, %, max 3 3 Combined Aggregate 3 Sand equivalent, %, min Used to estimate the magnesium sulfate soundness loss in accordance with Section Coarse Aggregate. 2. Only applies to crushed gravel. 3. Aggregates, without mineral filler, RAP, RAS, or additives, combined as used in the job-mix formula (JMF). 10

11 Statewide Bituminous Rated Source Quality Catalog 15 out of 98 sources would be affected by aggregate requirements 11

12 Mixture Design Requirements - Master Gradation Limits SP-C Type C 70 Percent Passing Sieve Size 12

13 Mixture Design Requirements - Master Gradation Limits SP-D Type D Percent Passing Sieve Size 13

14 Design Requirements VMA SP-A Base SP-B Intermediate SP-C Surface Design VMA, % Minimum SP-D Fine Mixture Production (Plant-Produced) VMA, % Minimum A Coarse Base B Fine Base C Coarse Surface D Fine Surface F Fine Mixture Design VMA, % Minimum Production (Plant-Produced) VMA, % Minimum Proposed VMA in 2014 Spec Book

15 Design Requirements - Gyratory Compactor TGC 4 Specimens 5.8 Angle Can Adjust Lab Molded Density SGC 6 Specimens 1.25 Angle Density Curve Can Adjust # of Gyrations Specimen Size 15

16 Laboratory Mixture Design Properties Mixture Property Superpave Requirement Dense-Graded Requirement Target laboratory-molded density, % Design gyrations (Ndesign) 50 - Indirect tensile strength (dry), psi Dust/asphalt binder ratio

17 Production Pay Adjustment Factors Production Pay Adjustment Factor Superpave Dense-Graded Absolute Deviation from Target Lab-Molded Density 17

18 Placement Pay Adjustment Factors Placement Pay Adjustment Factor Superpave Dense-Graded In-Place Air Voids 18

19 Average Mix Cost $86.40 $ / Ton $ Dense Graded SuperPave 19

20 Kent Stonewall Haskell Borden Scurry Fisher Jones ABILENE EXPERIENCE WITH SUPERPAVE Howard Mitchell Nolan ABILENE Taylor Callahan 2014 Construction Conference Paul Hoelscher

21 Table of Contents 1 Overview 22 2 Issues Encountered 23 3 Goals 24 21

22 Brief Overview History of Superpave Usage in the Abilene District Began Transition in early 2000 s Migrated from SP-A to SP-B Migrated from SP-C to SP-D Reasons for moving from Conventional Mixes to Superpave Desire to Increase Performance Life Desire to Increase Durability Bill Hale Wanted To Development of General Notes and Spec Requirements Migrated from 100 gyrations to 75 gyrations Impacts of Hamburg Specifications Typical PG Grades (PG70-22/Surface, PG64-22/Base) Stone on stone contact below Reference Zone 22

23 Issues Encountered Tender Zone During Compaction A temperature range during the cooling process of the mat in which the mix becomes tender. Excessive rolling in the Tender Zone can cause mat to shove and crack 23

24 Have Goals been Met? Performance Life 10 years on average before sealcoating Performance No rutting issues Mixes still crack eventually 24

25 Questions? 25