Update on New Era Testing. John Cunningham, Xuhao Wang, Peter Taylor

Transcription

1 Update on New Era Testing John Cunningham, Xuhao Wang, Peter Taylor 1

2 The Latest Technologies All in One 2 CP Tech Center

3 Who Needs More Testing? Performance Engineered Concrete Pavement Mixtures (AASHTO PP84) 3

4 Why Bother? Current approaches May not measure critical parameters Are often built around previous failures thereby introducing unintended consequences Limit innovation Need to deliver mixtures that meet needs, reliably 4

5 A Better Specification For measuring the things that matter Transport properties (everywhere) Aggregate stability (everywhere) Strength (everywhere) Cold weather resistance (cold regions) Shrinkage (dry regions) Workability (everywhere) 5

6 What Next? Understanding and education What and why Validate tests in the field Reliability Efficiency New tests 6

7 Transport (Resistance to Fluids) Resistivity Then calculate formation factor based on Moisture Temperature Geometry Curing conditions Ionic concentration of the pore solution 7

8 Transport (Resistance to Fluids) Drop Test Assess the quality of paste in an exposed surface at a local scale of less than 0.5 in 2 20µL Measure time to loose sheen 8

9 Transport (Resistance to Fluids) Drop Test Calibration (56 days) 9

10 Transport (Resistance to Fluids) Drop Test Example results 10

11 Aggregate Stability AAR Follow PP65 D-Cracking Follow local practice (i.e., IPA in Iowa) 11

12 Strength Compressive or flexural 12

13 Cold Weather Resistance Freeze Thaw (air void system) Super air meter (SAM) AASHTO TP118 Pump to 3 pressures in 2 cycles Dial reports a SAM number 13 Ley 2016

14 Cold Weather Resistance Freeze Thaw (time to saturation) Absorption of water ASTM C

15 Cold Weather Resistance Resistance to salts Expansive calcium oxychloride formation From MgCl2 and CaCl2 Measure with low temperature differential scanning calorimetry (LT-DSC) 15

16 Cold Weather Resistance LT-DSC (AASHTO T365) results 16

17 Cold Weather Resistance Paste expansion test (ISU) assess the ability to resist oxychloride formation 17

18 Shrinkage Cracking risk Warping 18

19 Shrinkage Ring test - ASTM C1581 Assesses cracking risk Starts immediately 19

20 Shrinkage Dual ring test Measure both expansion and contraction Force a temperature gradient in the concrete 20 Weiss

21 Workability Owner should not really care, but Too wet = edge slump Too dry = poor consolidation & air loss Good indicator of uniformity and consistency Need a measure of the response to vibration 21

22 Workability Kelly ball test Developed in the 1950s in US Standardized in California DOT test Comparable to slump test 1.1 to 2.0 times the Kelly ball reading 22

23 Workability Vibrating Kelly Ball Test AASHTO TP129 Measure initial slump (initial penetration) Start vibrator for 36 seconds at 8000 vpm Record depth every 6 seconds Repeat Plot on root time Calculate slope = VKelly Index 23

24 Workability VKelly Index 24

25 Workability Effect of the aggregate system 25

26 Workability Box Test A simple test that examines: Response to vibration Filling ability of the grout (avoid internal voids) Ability of the concrete to hold an edge Ley

27 Workability The edges of the box are then removed and inspected for honey combing and edge slump

28 QC QC reassures contractor that the mix will get there Unit weight Calorimetry Maturity Strength development Air void stability 28

29 QC Calorimetry Tells us about the chemistry of the system (uniformity and compatibility) 29

30 QC Maturity Sensors in the pavement determine in-place maturity and thereby strength for opening 30

31 QC Foam drainage Air void systems can change with working/pumping Depends on system chemistry 31

32 What Else? Intelligent Compaction What about the ride? When should I saw? Finding the flaws Sensor technologies 32

33 Construction Foundations intelligent compaction 33 White

34 Construction Real time smoothness Allows contractor to learn and control critical activities 34

35 Field Investigation Base on time-of-flight of light (LIDAR) 35

36 Field Investigation LIDAR output 36

37 When to Saw? Ultrasonic P-wave velocity Measure speed of a compression wave through a sample Governed by dynamic modulus of elasticity, Poisson s ratio, and density (Biot s theory) 37

38 When to Saw? Lab data 38

39 When to Saw? Field data Early entry saw 39

40 When to Saw? Field data Conventional saw 40

41 Finding the Steel Sensors MIT Scan-2 MIT Scan-T2 41

42 Finding Flaws GPR Scan MIRA 42

43 Whew Use the right test for the right purpose at the right time It can keep us out of trouble 43