WHEN TO WORRY ABOUT TEST RESULTS OAPA 2007 ANNUAL CONFERENCE WHEN TO WORRY ABOUT TEST RESULTS Danny Gierhart, P.E. ODOT Bituminous Engineer

ANSWER: ALWAYS! (However, you need to worry about some more than others)

What is the test designed to tell you? What are the potential ramifications of a failing test result? Are the potential ramifications minor or major? For this test, how much could the degree out of specification affect pavement performance?

Test results are often used to document the degree out of specification so that a corresponding financial penalty can be assessed. The very best use of test results is to track the ongoing quality of a project and make corrections as necessary to ensure a quality pavement.

LIQUID ASPHALT AGGREGATE HOT MIX ASPHALT

DYNAMIC SHEAR RHEOMETER (DSR) ASPHALT BINDER TEST – DYNAMIC SHEAR RHEOMETER (DSR) 1.15

DYNAMIC SHEAR RHEOMETER (DSR) ASPHALT BINDER TEST – DYNAMIC SHEAR RHEOMETER (DSR) What is the test designed to tell you? The purpose of the test is to address potential rutting due to binder stiffness. What are the potential ramifications of a failing test result? Typical failing DSR tests reveal increased rutting and/or cracking potential. from negligible up to an average of 1/4”. They can also indicate whether or not the binder has sufficient polymer.

DYNAMIC SHEAR RHEOMETER (DSR) ASPHALT BINDER TEST – DYNAMIC SHEAR RHEOMETER (DSR) Are the potential ramifications minor or major? A typical failing DSR test indicates relatively minor problems. Large deviations can indicate significant problems. How much does the degree out of spec affect pavement performance? DSR tests that are slightly low (running 0.90 to 0.99) are minor. Tests that are ½ the target indicate a lower grade of binder was sampled.

ASPHALT EMULSION TEST – SAYBOLT-FUROL VISCOSITY 1.15 77 20 - 100 22

ASPHALT EMULSION TEST – SAYBOLT-FUROL VISCOSITY What is the test designed to tell you? The purpose of the test is to show the as-delivered viscosity, or fluidity of the material. What are the potential ramifications of a failing test result? Failing tack coat results will often be on the low side, indicating a deficiency of residual asphalt. This could cause slippage between lifts. For chip seal emulsions, a low value could mean that aggregate particles will not stick well. Results on the high side may be caused by an old sample.

Slippage between lifts as a result of insufficient adhesion.

ASPHALT EMULSION TEST – SAYBOLT-FUROL VISCOSITY Are the potential ramifications minor or major? Failing viscosity tests that are an accurate indicator of low residual asphalt content can, under the right circumstances, have serious ramifications. How much does the degree out of spec affect pavement performance? Field application has a significant effect on performance. It is very difficult to establish how big the problem is based on test results alone.

RED FLAG ALERT! Emulsion test results are only as good as the sample quality. Emulsion samples are particularly susceptible to compromise. Samples obtained after the emulsion is diluted onsite. Samples obtained, but not submitted for weeks. Samples allowed to sit in sun or roll around in truck. Samples placed in a contaminated container.

ASPHALT CUTBACK TEST – KINEMATIC VISCOSITY 30 - 60 45

ASPHALT CUTBACK TEST – KINEMATIC VISCOSITY What is the test designed to tell you? This test also shows the as-delivered viscosity, or fluidity of the material. It tells the supplier about the uniformity of shipments. What are the potential ramifications of a failing test result? Low test results indicate a higher ratio of diluent to asphalt cement. The prime may not provide the moisture barrier intended. High test results indicate a lower ratio of diluent to asphalt cement.

ASPHALT CUTBACK TEST – KINEMATIC VISCOSITY Are the potential ramifications minor or major? Failing viscosity tests have a minimal effect on the quality of prime. For example, both MC-30 and MC-70 are acceptable for use as prime coat. An out-of-spec high MC-30 may meet or be low for MC-70. How much does the degree out of spec affect pavement performance? Out-of-spec on the high side should not have a major effect. Tests for MC-30 that are significantly low will likely result in an ineffective moisture barrier.

AGGREGATE TEST - GRADATION Comparison

Comparison

Comparison

AGGREGATE TEST – GRADATION (Max. Agg. Size) What is the test designed to tell you? The maximum aggregate size influences allowable pavement thickness, susceptibility to segregation, asphalt content, and volumetric requirements. What are the potential ramifications of a failing test result? A gradation on the maximum sieve size that is less than 100% indicates the presence of over-sized particles. This could result in compaction difficulties, segregation, and asphalt content problems.

AGGREGATE TEST – GRADATION (Max. Agg. Size) Are the potential ramifications minor or major? Gradations results showing less that 100% passing the maximum sieve size are rare and usually only slightly less than 100%. Potential ramifications are minimal. How much does the degree out of spec affect pavement performance? Results deviating by 10% or more indicate that a different type of HMA was sampled than expected.

Comparison

AGGREGATE TEST – GRADATION (% Passing # 200) What is the test designed to tell you? The % passing the # 200 sieve influences compaction, asphalt content, and volumetric requirements. What are the potential ramifications of a failing test result? A low % passing the # 200 may result in high air voids, permeability, and a lower AC demand. A high value may result in low air voids and VMA, a higher AC demand, and a tender mix.

Check cracking as a result of a high % passing the #200 sieve combined with a low binder content

High % passing the #200 gives the HMA a lighter appearance, indicating a lower film thickness and lower durability.

AGGREGATE TEST – GRADATION (% Passing # 200) Are the potential ramifications minor or major? High dust portions can have major ramifications on the longevity of a roadway. They are typically accompanied by lower than necessary binder contents which reduce pavement durability. How much does the degree out of spec affect pavement performance? Deviations inside the tolerance of 2% typically don’t have too much of an effect. Deviations greater than 2% should be addressed immediately.

Comparison

AGGREGATE TEST – GRADATION (% Passing # 8) What is the test designed to tell you? The % passing the # 8 sieve has a major influence on voids and permeability. What are the potential ramifications of a failing test result? A low % passing the # 8 sieve may result in a permeable mix. A high value is not as worrisome as a low value.

Low % passing the # 8 indicates a mix that is subject to permeability, which in turn can lead to stripping.

AGGREGATE TEST – GRADATION (% Passing # 8) Are the potential ramifications minor or major? A low % passing the # 8 sieve can have major ramifications on the longevity of a roadway. They are often accompanied by permeability issues which can lead to stripping. How much does the degree out of spec affect pavement performance? Gradations near the lower broad band are especially of concern when accompanied by a low % passing the # 200 sieve.

AGGREGATE TEST – SAND EQUIVALENT

AGGREGATE TEST – SAND EQUIVALENT What is the test designed to tell you? The test is intended to show the relative proportions of fine dust or clay-like material in the aggregate. What are the potential ramifications of a failing test result? A low sand equivalent result indicates a high percentage by volume of clay-like fines. These fines may cause the asphalt binder to debond from the aggregate in the presence of moisture.

Low sand equivalents indicate a high percentage of clay-like fines, which can cause a poor bond with the asphalt binder.

AGGREGATE TEST – SAND EQUIVALENT Are the potential ramifications minor or major? Although extremely rare, a failing sand equivalent test indicates a very poor aggregate quality, which can have major ramifications to the longevity of the pavement. How much does the degree out of spec affect pavement performance? Sand equivalent results do not have to be much out of spec to be a cause for concern.

HOT MIX ASPHALT TEST – TENSILE STRENGTH RATIO

HOT MIX ASPHALT TEST – TENSILE STRENGTH RATIO What is the test designed to tell you? The test is intended to show the susceptibility of the HMA to moisture damage. What are the potential ramifications of a failing test result? A failing TSR indicates the mix is inherently susceptible to stripping and raveling.

Tensile Strength Ratio AASHTO T 283 Moisture Sensitivity Prepare set of 6 specimens 6.5 to 7.5% voids Represents anticipated in-service voids Use 3 specimens as controls Remaining 3 specimens are vacuum saturated 70 to 80% Min. 16 hour freezing at 0oF 24 Hours in 140oF water bath Bring all specimens to test temperature (77oF) and determine indirect tensile strength The mix must also be checked to insure that it is not susceptible to moisture damage.

Tensile Strength Ratio AASHTO T 283 Saturating Specimens Freezing Specimens Specimens in Hot Water Bath

Moisture Sensitivity AASHTO T 283 Determine the indirect tensile strengths of both sets of 3 specimens Calculate the Tensile Strength Ratio (TSR) The tensile strength of the mix is determined both before and after conditioning. TSR = Avg. wet tensile strength Avg. dry tensile strength Minimum of 75% required for field tests

HOT MIX ASPHALT TEST – TENSILE STRENGTH RATIO Are the potential ramifications minor or major? The ramifications of a failing TSR can be severe. How much does the degree out of spec affect pavement performance? Because the test procedure is not one of the most repeatable, results down to around 70% should be confirmed by further testing. TSR results less than 65% would be just cause for immediate work stoppage to investigate and fix the problem.

HOT MIX ASPHALT TEST – ASPHALT BINDER CONTENT Result JMF Comparison

HOT MIX ASPHALT TEST – ASPHALT BINDER CONTENT What is the test designed to tell you? The test shows the percent of asphalt binder by weight of the total mix. What are the potential ramifications of a failing test result? A low binder content can lead to premature aging of the pavement, stripping, or raveling. A high binder content can lead to flushing or bleeding in the pavement.

Low binder contents can lead to raveling, stripping, and premature aging.

High binder contents can lead to flushing or bleeding.

HOT MIX ASPHALT TEST – ASPHALT BINDER CONTENT Are the potential ramifications minor or major? The ramifications would likely be different depending on the degree out of spec. Whether any of the potential pavement distresses occur also depend on other factors. How much does the degree out of spec affect pavement performance? Binder content is one of several parameters that affect each other. However, binder contents very far out of spec should be a major cause for concern.

HOT MIX ASPHALT TEST – AIR VOID CONTENT Specimen 1 Specimen 2 Average

HOT MIX ASPHALT TEST – AIR VOID CONTENT What is the test designed to tell you? The test shows the percent air voids in lab-molded specimens. This test indicates a mix property, not in-place air voids. What are the potential ramifications of a failing test result? With a low air void content, the pavement is susceptible to rutting, flushing, and bleeding. For high air void contents, the pavement is susceptible to premature aging, raveling, and stripping.

HOT MIX ASPHALT TEST – AIR VOID CONTENT Are the potential ramifications minor or major? The ramifications can be severe depending on the degree out of specification. Whether any of the potential pavement distresses occur also depend on other factors. How much does the degree out of spec affect pavement performance? All failing void contents need some type of action. Mixes that are 1% or more out of spec indicate a need for immediate shutdown for more trials.

HOT MIX ASPHALT TEST – VOIDS IN MINERAL AGGREGATE (VMA) Specimen 1 Specimen 2 Average

HOT MIX ASPHALT TEST – VOIDS IN MINERAL AGGREGATE (VMA) What is the test designed to tell you? VMA is calculated from the binder content test and lab-molded specimens. It tells about the total volume of the voids created by aggregates. What are the potential ramifications of a failing test result? Samples with low VMA do not have enough void space to provide the proper amount of binder and the proper amount of air. Low VMA, depending on the reason, could result in many distress types.

HOT MIX ASPHALT TEST – VOIDS IN MINERAL AGGREGATE (VMA) Are the potential ramifications minor or major? The ramifications can be severe depending on the degree out of specification. Whether any of the potential pavement distresses occur also depend on other factors. How much does the degree out of spec affect pavement performance? Mixes that are 1% or more out of spec indicate a need for immediate shutdown for more trials.

HOT MIX ASPHALT TEST – ROADWAY DENSITY Core 1 Core 2 Core 3

HOT MIX ASPHALT TEST – ROADWAY DENSITY What is the test designed to tell you? The test indicates the in-place density achieved by the compactive effort of the rolling operation. What are the potential ramifications of a failing test result? Low density may result in permeability, stripping, raveling, cracking, premature aging, and premature failure. High density may result in rutting, flushing, or bleeding.

HOT MIX ASPHALT TEST – ROADWAY DENSITY Are the potential ramifications minor or major? The ramifications of failure to achieve proper density are major. Proper density can in part make up for other shortcomings. Improper density can cause failure even if other parameters are good. How much does the degree out of spec affect pavement performance? Any failing density report should cause the agency to closely examine the rolling operation. The further out of spec, the shorter the anticipated pavement life.

In summary, all failing test results should be followed up on. Some test results may be received after all of the material is already in place. Some test results will be received in time for corrective action, which should be immediate. Remember that a few hours time addressing a problem may prolong the pavement life by several years.

QUESTIONS?