“Old Wooden Bridge” Bridge to No Name Key from Big Pine Key, Florida

Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory by Mike Jackson for Mario Paredes

Sponsors American Association of State Highway and Transportation Officials (AASHTO); Technology Implementation Group (TIG); Florida Department of Transportation; TRB Committee AFN30 – Durability of Concrete.

Participants California Department of Transportation; Colorado Department of Transportation; Federal Highway Administration; Florida Department of Transportation; Florida Atlantic University; Grupo Carmelo, Puerto Rico; Indiana Department of Transportation; McGill University;

Participants (Continued) Nebraska Department of Transportation; New York Department of Transportation; Puerto Rico Highways and Transportation Authority; Purdue University; Titan America –Tarmac; The University of North Florida; and Virginia Department of Transportation.

Round-Robin Testing Program ASTM Designation C802, “Standard Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials.” AASHTO Designation: TP95-11, “Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration 2.”

Round-Robin Testing Program Fourteen (14) different laboratories; Twelve (12) different concrete mixtures; Wide range of constituent materials; and Two (2) different commercial SR meters: CNS Farnell Ltd. Proceq SA.

Concrete Mix Constituents

Mix w/cm ratios ranged from ; Ten of the12 mixes contained fly ash; One mix contained no granular admixtures; One mix contained 25% slag; One mix contained 10% meta-kaolin; and Two mixes contained 4% - 6% silica fume.

Test Samples Hardened 4-in. diameter by 8-in. long cylindrical concrete specimens were tested; Test specimens were fabricated by 12 of the participating labs, and shipped to all participants for SR testing; SR was measured in accordance with AASHTO Designation: TP95-11 after 28, 56, and 91 days of standard laboratory curing.

Sample Packaging After 2 weeks of curing in lime saturated water, specimens were wrapped and sealed to avoid loss of moisture during shipping.

Sample Shipping The specimens were then carefully packaged for 2 nd Day shipping to avoid damage and/or drying during shipping.

Surface Resistivity Testing SR was then measured after 28, 56, and 91 days of standard laboratory curing.

Example SR Test Results Surface Resistivity (SR) Readings (Kohm-cm) Sample #0°90°180°270°0°90°180°270°Average CTA CTA CTA Set Average Curing Condition Correction (x 1.1 lime tank or 1.0 for moist room) 1.1 Penetrability Based on Test Chloride Ion Penetration TypeMODERATE Air Temperature of testing room (°F) 67 Water Temperature of lime bath (°F) 72 Curing history specific to your lab once you received the specimens Any abnormalities, comments, and/or notes.

Mean SR at 28 Days Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

Std. Dev. at 28 Days Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

Mandel’s k-statistic at 28 Days

Mandel’s k-statistic at 56 Days

Mandel’s k-statistic at 91 Days

Mandel’s h-statistic at 28 Days

Mandel’s h-statistic at 56 Days

Mandel’s h-statistic at 91 Days

Precision Calculations at 28 Days Note: Lab #7 Data Removed Based on Mandel’s h-statistic.

Precision Estimates at 28, 56, and 91 Days Lab Cured Age (Days) Variance (Kohm-cm) 2 Standard Deviation (Kohm-cm) Precision (d2s) (Kohm-cm) Repeatable, (within lab) s r 2 Reproducible (between lab) s R 2 Repeatable (within lab) s r Reproducible (between lab) s R Repeatable (within lab) r Reproducible (between lab) R

Precision Statements Lab Cured Concrete Age (Days) COV (1s%)Precision (d2s%) Repeatability (within lab) COV (s r ) (%) Reproducibility (between lab) COV (s R ) (%) Repeatability (within lab) r % Reproducibility (between lab) R %

Proposed Precision Statements Single-Operator Precision – The results of two properly conducted tests by the same operator on concrete samples from the same batch and of the same diameter should not differ by more than 12.1% of their average. Multilaboratory Precision – The results of two properly conducted tests in different laboratories on the same material should not differ by more than 32.5% of their average. Bias - This procedure has no measurable bias.

Equipment Equivalence

Paper Published in the Journal of ASTM International, Paper ID #JAI , “Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory.”