Guide for Conducting Forensic Investigations of Highway Pavements (2013) / Chapter Skim
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Pages 43-59
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43 This chapter covers destructive field testing and laboratory testing of samples and specimens removed from the pavement being investigated. Investigation arrangements, detailed visual assessments, coring, test pits, and laboratory tests are discussed.
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44 For the safety of work crews and road users, always keep sufficient space between the core rig and the centerline when coring in the wheelpath closest to traffic. Do not take cores between the centerline/lane delineator and the wheelpath unless both lanes are in the closure.
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45 – Follow agency practice and standards for location references in a linear reference system (chainage, post-mile, station)
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46 • AASHTO T 225, Diamond core drilling for site investigation • ASTM D2488, Description and identification of soils (visualmanual procedure) • ASTM D4083, Description of frozen soils (visual-manual procedure)
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47 If there is a time constraint on the closure, consider the following: • Immediately number all cores and mark them in terms of orientation to traffic direction (typically an arrow marked on the surface of the core with a waterproof marker)
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48 – Document key observations on the form for later reference when logging the cores off-site. – Pack the cores in an air tight plastic canister and place the canisters in a crate to prevent damage during transport.
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49 • If required in the test plan, measure and record the total thickness of the core as well as the thickness of each layer on the core to the nearest ± ¹⁄¹0 in.
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50 suggested criteria (additional/other criteria may be appropriate depending on the issue being investigated)
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51 • Note and describe evidence of leveling or correction courses in asphalt concrete pavements and interlayers in concrete pavements and between concrete and the base. • Note and describe other distresses and/or observations and the potential implications such as material degradation or segregation, pumping of fines from lower layers, erosion of the surface of stabilized base layers due to pumping, and drainage deficiencies.
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52 four holes on the slab, place eyebolts in them and epoxy the bolts into place. Once the epoxy has set, use a small hydraulic lift arm or other available equipment to lift the joint out of the pavement and onto a truck for transport to the laboratory.
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53 • Mottling, which usually indicates fluctuating moisture contents. • A layer of loose material on top of a stabilized layer, which could indicate that carbonation of cemented layers has occurred, or inappropriate curing, re-mixing and/or final compaction techniques were followed on cementitious or asphalt stabilized layers.
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54 – Take a 10 lb (5.0 kg) sample for laboratory moisture determination from each layer stockpile.
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55 manner and all observations carefully noted to ensure that data is useful for subsequent interpretation and analysis. Capture all relevant and potentially relevant information on a form, or series of forms (example Forms #20 through #23 in Appendix C)
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56 or combine Zones 2, 3, and 4 into one zone and divide the test pit face into three zones as follows: – Zone 1: Edge of test pit (shoulder) to outside edge of outer wheelpath – Zone 2: Area under and between the wheelpaths – Zone 3: Outside edge of inner wheelpath to edge of test pit (inside lane edge)
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57 – Obvious differences between the pavement design and as-built records (e.g., thicker or thinner layers [Figure 7.20b]
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58 – Spray areas of suspected carbonation with a dilute hydrochloric acid (HCl) solution to check for the presence of cement and the degree of reaction (fizzing)
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59 In addition to standard tests, specialists on the investigation team may request/undertake specialized testing to fully understand the issues being investigated. Examples include: • X-ray diffraction and surface energy measurements to assess aggregate chemistry and its effects on bonding of asphalt and cement and hydration products of portland and other hydraulic cements.
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