Guide for Conducting Forensic Investigations of Highway Pavements (2013)

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39 This chapter covers finalizing the investigation plan if a deci- sion was made to continue with the study to gather more infor- mation to address the issues being investigated. 6.1 Finalizing the Investigation Plan If a decision to continue the study was made, the investiga- tion coordinator prepares a final investigation plan based on the findings of the earlier work. This plan includes: • The initial investigation plan. • Additional visual assessment requirements including: – Specific areas on road and adjacent to road (e.g., drainage, slope stability, etc.) to examine. • Additional non-destructive testing details if required, including (example Form #13 in Appendix C): – Types of test (e.g., GPR, FWD, profilometer, skid tester, noise measurements, dowel bar locater, permeability, density, stiffness, load transfer, etc.). – A revised non-destructive testing plan (see Section 4.4). • Destructive testing details including (example Form #14 in Appendix C): – Types of test. The need for and type of testing will depend on the issues being investigated and the results of initial non-destructive testing, but will usually include cores; sampling of materials from individual layers for laboratory testing (from drilling, Shelby tube or test pit); DCP tests; and/or a test pit/trench if a visual assessment of layers is required. The plan should specify if dry cores or dry test pit/trench saw cuts (i.e., air cooled for moisture-related investigations) are required. – Test plans. Numbers of tests, test locations (including a drawing with precise locations), and protocols that should be followed. It is extremely important to sample from multiple locations of varying performance (i.e., distressed and non-distressed [control] areas). 77 Core requirements: laboratory testing typically requires 4 in. (100 mm) or 6 in. (150 mm) diameter cores. Visual inspections typically require a larger core (6 in. [150 mm] or 12 in. [300 mm] in diameter) to obtain the largest surface area to identify potential problems. Cores removed only for observation purposes can be replaced in the road after evaluation. Suggested num- bers of cores required for various laboratory tests asso- ciated with forensic investigations are summarized in Table 6.1. 77 Test pit/trench requirements (e.g., location [includ- ing a drawing with precise locations], dimensions, inpit testing requirements, a checklist of expected and potentially unexpected factors to look out for, etc.). • Sampling requirements, including location of samples, conditions under which samples should be taken, quantity of samples, packaging and storing of samples, and location where samples should be delivered. • Laboratory testing requirements, including test methods and number of tests. Examples of laboratory tests associ- ated with forensic investigations are provided in Table 6.2, Table 6.3, and Table 6.4 for asphalt, concrete, and unbound materials, respectively. – Routine laboratory tests to check conformance with material specifications or that materials have rapidly degraded/weathered to the point that deleterious miner- als are present (e.g., Atterberg limits, gradations, aggre- gate durability, asphalt content/voids/specific gravity, concrete strength [compressive or split tensile]). – Specialized laboratory tests to assess performance (e.g., resilient/complex modulus, asphalt and soils repeated load permanent deformation tests, asphalt fatigue tests [flexur- al beam, direct tension, reflective cracking], asphalt wheel- tracking tests, concrete coefficient of thermal expansion, chemical analyses, microscope analyses, CT scans, etc.). • Logistical arrangements (e.g., road closures, notifications, team and equipment availability, etc.). C h a p t e r 6 Final Investigation Plan

40 Table 6.1. Example number of cores required for various laboratory tests. Test Thickness of Material of Interest Number of Cores Per Test Core Type in. mm 4 in. (100 mm) 6 in. (150 mm) Standard tests As per test method Grading (ignition oven) 2 4 50 100 3 2 2 1 Asphalt binder grade (binder extracted from cores)1 2 4 50 100 1 1 1 1 Theoretical Maximum Density 2 4 50 100 3 2 2 1 Permeability/clogging 2 4 50 100 2 2 2 2 Surface texture 2 4 50 100 2 2 2 2 Other specialty tests (e.g., CT scan, impedance, x-ray diffraction) Dependent on test method 1 Number of cores depends on binder content; shown are suggested number of cores for 5% binder by mass of mix and bulk density of the asphalt of 18.4 lb/gal. (2.2 kg/liter). Table 6.2. Examples of laboratory testing requirements for asphalt pavement investigations. Issue Possible Contributing Factors Example Types of Laboratory Testing1 Exceptional performance Design, construction, and/or materials - Any combination of tests below depending on the specific issue being investigated Rutting Poor compaction Asphalt densification Asphalt shearing Moisture damage Incorrect binder grade Incorrect gradation Incorrect binder content Inappropriate or not followed mix design Base, subbase or subgrade failure - Surface layer - Unbound/bound layer Air-void content, wheel track test, binder content, binder type (modifier presence, PG-grading, classification tests, contaminants), aggregate grading and properties, tensile strength retained, stability, repeated load triaxial (flow number) repeated load shear, triaxial or shear frequency sweep, resilient modulus, extracted binder frequency sweep, Hamburg Wheel Track Test (moisture sensitivity) California Bearing Ratio, resilient modulus, R-Value, unconfined compressive strength, indirect tensile strength, gradation, Atterberg limits Alligator cracking Poor compaction Moisture damage Excessive aging Layer debonding Incorrect binder grade Incorrect binder content Incorrect gradation Inappropriate or not followed mix design Base, subbase or subgrade failure - Surface layer - Unbound/bound layer Air-void content, flexural fatigue, direct tension fatigue, binder content, binder type (modifier presence, PG- grading, classification tests, contaminants), aggregate grading and properties, triaxial, direct tension or flexural frequency sweep, resilient modulus, tensile strength retained, Hamburg wheel tracking test (moisture sensitivity), Texas Overlay test California Bearing Ratio, resilient modulus, R-Value, unconfined compressive strength, indirect tensile strength, gradation, Atterberg limits Transverse cracking Incorrect binder grade Excessive aging Reflection cracking Poor compaction Frost/moisture damage in unbound layer Shrinkage in stabilized base - Surface layer - Unbound/bound layer Air-void content, binder content, binder type (modifier presence, PG-grading, classification tests, contaminants), aggregate grading and properties, triaxial, direct tension or flexural frequency sweep, Texas Overlay test Stabilizer content, California Bearing Ratio, resilient modulus, R-Value, unconfined compressive strength, indirect tensile strength, gradation, Atterberg limits Longitudinal cracking Poor compaction at joints Excessive stabilizer in recycling overlaps Desiccated subgrade - Surface layer - Unbound/bound layer Air-void content at longitudinal joints Stabilizer content, unconfined compressive strength, indirect tensile strength, Atterberg limits Block cracking Excessive aging of binder Shrinkage in stabilized base - Surface layer - Unbound/bound layer Air-void content, binder content, binder type (modifier presence, PG-grading, classification tests, contaminants) Shrinkage, stabilizer content, unconfined compressive strength, indirect tensile strength, expansion/contraction tests under soaking/drying

41 Issue Possible Contributing Factors Example Types of Laboratory Testing Exceptional performance1 Design, construction, and/or materials - Any combination of tests below depending on specific issue being investigated Corner cracking (JPCP, JRCP) Low PCC strength Load transfer (joint or edge) - PCC: Compressive strength, splitting tensile strength, chloride content of concrete near dowel/tie bar - Dowel: Dowel/tie bar coating type D-cracking1 Susceptible aggregate Poor drainage - PCC: Aggregate analysis (sedimentary with high fine pore content), freeze-thaw Longitudinal cracking1 Low PCC strength High coefficient of thermal expansion (CTE) Warping or curling stresses (high CTE) Poor load transfer to tied shoulder - PCC: Compressive strength, splitting tensile strength, CTE, chloride content of concrete near dowel/tie bar Transverse cracking (JPCP) Low PCC strength High CTE Tied shoulder load transfer - PCC: Compressive strength, splitting tensile strength, CTE, chloride content of concrete near dowel/tie bar - Dowel: Dowel/tie bar coating type Map cracking1 Alkali-silica reaction (ASR) - ASR tests Faulting (JPCP, JRCP) Load transfer (dowel corrosion, looseness, misplacement, incorrect size) Erosion/pumping - Dowel bar coating type Dowel bar retrofit failure (JPCP) Low grout strength Poor bonding of grout to slab Dowel bar corrosion - PCC: Chloride content of concrete near dowel/tie bar - Grout: Grout strength, compressive strength, splitting tensile strength, Grout/PCC bond strength - Dowel: Dowel/tie bar coating type Spalling1 Poor finishing Weak aggregate Frost - PCC: Aggregate petrography Joint failure/separation (JPCP, JRCP) Dowel bar failure/seizure - PCC: Chloride content of concrete near dowel Punchouts (CRCP) (See longitudinal cracking for preceding mechanism) Low PCC strength Steel reinforcement corrosion - PCC: Compressive strength, splitting tensile strength, CTE, chloride content of concrete near rebar Excessive noise1 Poor texture from construction or grinding/grooving. Faulting, wide joint openings, spalled joints Chain or studded tire damage - PCC: Laboratory texture tests Skid resistance1 Poor surface texture from construction, grinding, grooving Polished aggregate, loss of texture - PCC: Laboratory texture tests, aggregate classification, polishing tests 1 All types of PCC pavement. Table 6.3. Examples of laboratory testing requirements for concrete pavement investigations. Table 6.2. (Continued). Ride quality/ roughness Raveling (durability) Incorrect binder content Incorrect gradation Inappropriate or not followed mix design - Surface layer - Unbound/bound layer Durability (Cantabro test), aggregate gradation and properties, air-void content, binder content, binder type (modifier presence, PG-grading, classification tests, contaminants), bond strength Stabilizer content, Atterberg limits Failure/potholes Base, subbase or subgrade failure Moisture damage Delamination - Surface layer - Unbound/bound layer Air-void content, Hamburg Wheel Track, tensile strength retained, bond strength California Bearing Ratio, Atterberg limits Excessive noise Mix design Raveling Cracking Clogging of porous surface Chain or studded tire damage - Surface layer Durability (Cantabro test), permeability Skid resistance Polished aggregate Flushing/bleeding - Surface layer Polished stone value, binder content 1 Tests may be performed on samples taken from the pavement in the field, and on field or plant samples saved from construction, or on both for comparison. Issue Possible Contributing Factors Example Types of Laboratory Testing1

42 Issue Possible Contributing Factors Example Types of Laboratory Testing Exceptional performance Design Construction Materials - Any combination of tests below depending on specific issue Rutting Base, subbase or subgrade failure Moisture damage Carbonation of stabilized layers Incorrect stabilizer contents Construction deficiencies - Bound: Stabilizer content, density, unconfined compressive strength, wet/dry durability, triaxial shear, resilient modulus - Unbound: California Bearing Ratio (CBR), triaxial shear, resilient modulus, classification tests (gradation, Atterberg limits) Alligator Cracking Base, subbase or subgrade failure - Unbound: Resilient modulus, CBR, classification (gradation, Atterberg limits) Transverse, longitudinal, block, and/or random cracks in asphalt surfaced pavement High stabilizer contents in base Soil/stabilizer expansive reaction Excessive stabilizer in recycling overlaps Expansive soils - Bound: Cement content - Unbound: Classification (gradation and Atterberg limit tests), CBR, swelling tests Early age transverse, longitudinal, block, and/or random in JPCP; Longitudinal cracks in CRCP and JRCP High stabilizer contents in base - Bound: Cement content Ride quality/roughness Soil/stabilizer expansive reaction Expansive soils - Bound: Cement content - Unbound: Classification (gradation and Atterberg limit tests), CBR, swelling tests, sulfate content Failure/potholes Base, subbase or subgrade failure - Unbound: Classification (gradation and Atterberg limit tests), CBR Salt damage to surfacing High salt contents in compaction water or base materials Conductivity and pH, soluble salt content Table 6.4. Examples of laboratory testing requirements for base and subgrade materials investigations. • Schedule, including dates and times for each resource and activity. • General data requirements (e.g., traffic, weather, other environmental, etc.). • Checklists and forms. • Data analysis, including protocols. • Report requirements, including how the results will be interpreted and used to address the reasons why the inves- tigation was undertaken. • Report review procedures (e.g., who will review the report). • Updated cost estimate. An example final investigation test plan is provided in Appendix C (example Form #15). 6.2 Approval of the Final Investigation Plan and Record of Decision The forensic investigation coordinator obtains approval (and if necessary, funding) for the final investigation plan from the investigation director and adds a record of decision to proceed in the project file.