Statewide Implementation of the SPG Specification for Chip Seal Binders in Service TxDOT Implementation Project 5-6616 Darren Hazlett, Jerry Peterson Amy Epps Martin, Edith Arambula Tom Freeman, Jon Epps Shi Chang, Juan Carvajal Munoz Summer 2015

MOTIVATION & OBJECTIVE Improve chip seal binder spec & selection performance-related tests @ temperatures that cover entire in service range for specific climate consider aging during critical 1st year reduce variability in grades possibly adjust due to traffic Implement SPG in TX in 4 year, staged effort (this is the second year) Replace Seal Coat Binder Selection Table & Item 300 specified properties in service

TxDOT Specification Evolution Binder Specifications for Hot Mix Asphalt

Classification of Asphalt Binders - HMA Stiffness -20 C 25C 60C 135C Low pavement temp Avg High Construction Long-term aging Short-term aging Original Temperature Penetration 1962 historical development TxDOT HMA binder specifications from 1962 used only penetration of original and short-term aged binder.

Classification of Asphalt Binders - HMA Stiffness -20 C 25C 60C 135C X Low pavement temp Avg High Construction Long-term aging Short-term aging Original Temperature Viscosity 1972 X historical development In 1972 TxDOT moved to viscosity graded specifications for HMA binders. This was an improvement in that additional temperature regimes that were more related to the temperature the pavement sees were included. Tests at 25C were penetration. Tests at 60C and 135C were viscosity tests. 60C is a temperature that more related to pavement temperature and 135C is application temperature (pumping into the HMA plant).

Classification of Asphalt Binders - HMA Stiffness -20 C 25C 60C 135C Low pavement temp Avg High Construction Long-term aging Short-term aging Original Temperature 3. Performance 1997 (SHRP Superpave) historical development In 1997 TxDOT implemented the Performance Grade Binder Specification for all HMA binders. This was developed as part of the $50M Strategic Highway Research Program from 1989 to 1993. It addresses testing at temperatures and aging states where a pavement would be susceptible to rutting, fatigue, and thermal cracking. Additionally, application temperatures are also addressed. Original, Short-Term aged, and Long-Term aged binders are tested. Rutting occurs usually soon after placement when the binder is in it softest (least stiff) state. Consequently, original and rolling-thin-film-oven aged binder (simulating HMA plant aging) is tested. Fatigue and Thermal Cracking occur later in the pavement live, consequently testing is performed on Pressure-Aging Vessel aged binder (simulating long-term aging in the pavement). This represents a significant improvement in binder requirements over previous specifications.

TxDOT Specification Evolution Binder Specifications for Hot Applied Chip Seals

Classification of Asphalt Binders – AC Chip Seal Stiffness -20 C 25C 60C 135C Low pavement temp Avg High Construction Short-term aging Original Temperature Penetration 1962 historical development Hot applied chip seal binders have followed a similar path as HMA binders did historically. 1962 Specifications were only penetration based and only tested at 25C. Not realistic for pavement performance.

Classification of Asphalt Binders – AC Chip Seal Stiffness -20 C 25C 60C 135C X Low pavement temp Avg High Construction Short-term aging Original Temperature Viscosity (1972) X historical development 1972 saw the same improvements for hot applied chip seal binders as HMA binders. TxDOT moved to the viscosity grading system. It was better than the penetration system, but still not related to the range of high pavement temperatures we see and there was no low temperature testing at all. TxDOT is still stuck in the 1970s for the most part for hot applied chip seal binders. Some polymer modified binders have some additional tests, mainly to show there is polymer in the product. We have a very few newer binders that have a few PG-type tests in their spec.

TxDOT Specification Evolution Asphalt Emulsion Specifications for Chip Seals

Classification of Asphalt Binders – Chip Seal Emulsions Stiffness -20 C 25C 60C 135C Low pavement temp Avg High Construction Original Temperature 1 classification systems 1. Penetration 1962 (-) historical development TxDOT emulsion specifications have pretty well stayed stuck in the 1960s. Unmodified emulsions only have penetration requirements. Some newer materials (polymer modified for the most part) have some viscosity requirements and tests that indicate the presence of polymer. We could use much improvement in specs for emulsions.

DEVELOPMENT OF SPG TxDOT Research Project 0-1710 (45 field sections) NCHRP Research Project 14-17 (3 field sections) SPG spec for chip seal binders in service Method B for emulsion residue recovery + shear strain sweep with new threshold X m-value MSCR not added SPG specification part of system to be used with design guidelines quality control procedures construction techniques TxDOT started looking at performance-based chip seal binder specifications about 15 years ago. The object was to bring the specifications for these binders into the 21st century. Use the tests developed for the PG binder specification for HMA binders and apply them to chip seals in a logical way. TxDOT will have spent $1.3M in this effort over several research projects.  

RECOMMENDED SPG Original Binder with AASHTO PP 72-11 Method B Performance Grade SPG 64 SPG 67 SPG 70 -13 -16 -19 -22 -25 -28 -31 Average 7-day Maximum Surface Pavement Design Temperature, °C <64 <67 <70 Minimum Surface Pavement Design Temperature, °C >-13 >-16 >-19 >-22 >-25 >-28 >-31 Original Binder Dynamic Shear, AASHTO TP5 G*/Sinδ Minimum: 0.65 kPa Test Temperature @10 rad/s, °C 64 67 70 Shear Strain Sweep % strain @ 0.8Gi*, Minimum: 17.5 (25) Test Temperature @10 rad/s linear loading from 1-50% strain, 1 sec delay time with measurement of 20-30 increments, °C 25 Pressure Aging Vessel (PAV) Residue (AASHTO PP1) PAV Aging Temperature, °C 100 Creep Stiffness, AASHTO T 313/ASTM D6648 S, Maximum: 500 MPa Test Temperature @ 8s, °C Gi*, Maximum: 2.5 MPa Test Temperature @10 rad/s linear loading at 1% strain and 1 sec delay time, °C Overall format – looks similar to PG spec. The idea is that we want to prevent loss of aggregate when the chip seal is first placed. This means we need to look at how stiff the binder is originally (we want the binder to be stiff enough to hold the aggregate so as not to be dislodged by traffic) . Since chip seal binders do not go through an HMA plant, there is no need to simulate HMA plant mixing with requirements on RTFO aging binder, so this is not included. We do see loss of aggregate after long-term aging (usually at the first winter). This means we need to look at long-term aging simulation (PAV – just like PG binders) and stiffness at low temperature (we don’t want it to be too stiff).

SPG Climate-Based Requirements Using weather stations and practical considerations we have developed 5 SPG climate-based zones. At the last AGC Seal Coat Committee meeting, AGC indicated they support the SPG specification and would like to see at least 2 projects in each of the climate zones for the 2016 seal coat season.

TxDOT 5-6616 Summary AC10 AC10-2TR AC20-5TR AC15P AC20XP A-R Type II 61-13 64-16 67-16 x2 61-19 67-19 76-19 x2 73-19 x2 73-19 67-22 x3 73-22 x3 70-22 x3 67-22 73-25 70-25 67-25 79-25 70-28 x2 70-31 76-? Across the top are the conventional grade samples we took and in the cells is the SPG grade those samples met. What you should get from this is that we took multiple samples from projects across the state and graded them with SPG. The samples did not meet a consistent grade. The SPG spec will allow TxDOT to get a more uniform material with properties specific to the project’s specific climate and adjustments for traffic or pavement structure. Suppliers will have to pay more attention to the binders they provide us, as we will be asking for a specific “cut” of what we had been getting. As an example, if I asked for an SPG 73-19, I could get material from those suppliers that in the past gave me AC-20-5TR, AC-20XP, and AC15P. We see that they could meet the our specification, but not all their product would meet. They have shown they have the capability of meeting what we wanted.

WORK PLAN Determine SPG Grades & Monitor Performance near construction & @ 1-year (including embedment depth) 2013 - 30 binders & 26 sections 2014 - ~25 sections & Plan Note 2015 - ~20 sections in > 2 districts 2016 - ~15 districts statewide Increasing use and effort leading up to full implementation in 2017.

WORK PLAN Review SPG for possible modifications Consider 3°C vs 6°C increments, single maximum surface temperature, & traffic effects Further explore exclusive use of DSR w/predicted low temperature property & LAS for intermediate temperature Add high temperature property & threshold to ensure modification = d < 80 @ continuous TH for UTI > 89 Verify thresholds Our ramp up of use for SPG will allow us to modify the specification to add or remove parts that, while we thought they made sense when we first built the spec, may not add to the value of the spec and should be removed. Also, we have already added a requirement for phase angle for any binder with a useful temperature interval (UTI – the difference between the high and low spec temperatures) to insure that these grades have elastic properties (contain elastic polymers).

Effects of SPG Specification Select Binders based on Climate Modify Climate Grade based on traffic or other considerations. Can set hot applied versus emulsion (both would have to meet the same binder or emulsion residue properties). Can restrict to only hot applied or only emulsion. You can start with the base climate grade (using the map) and then modify that grade to address traffic conditions, pavement structure, or other considerations. You could choose to only allow hot applied SPG binders. (Ex: Provide SPG 73-19. Notice that this would be a polymer modified binder as it would have a phase angle requirement with a UTI of 92) You could choose to only allow emulsified SPG binders. (Ex: Provide CRS-2-SPG 73-19. Same residue as above hot applied binder, but in an emulsified form) You could allow either hot applied or emulsified as long as they have the same SPG base. (Ex: Provide SPG 73-19 or CSR-2-SGP 73-19)

Effects of SPG Specification Every material will meet some grade. SPG is a tighter spec and we will get less variability. Current higher performing binders will still be higher performing binders – we will have a way to say they are higher performing. Tiered System “as we know it” goes away for a better system based on performance. We should get more uniform materials, and therefore more uniform performance. We can ask for higher performing binders, and get them. Also, the tiered system where we have to select multiple binders that we think could give us more or less equivalent performance goes away. Select an SPG for what roads you want them on and multiple suppliers can compete to provide you with a performance-based chip seal binder (hot and/or emulsion). The SPG system brings chip seal binder specifications into the 21st century. (You also don’t have to put up with vendors visits lobbying you to use their specific product. If they meet, we will accept.)

Effects of SPG Specification Economic Payoff If by using the SPG for all chip seals: 1) to insure the asphalt materials will perform in the climate, traffic, and structural conditions they are placed in, and 2) we get only one extra year of life from only 20% of the chip seals we place each year; We could save $9 million each year. Economic Payoff If by using the SPG for all chip seals: 1) to insure the asphalt materials will perform in the climate, traffic, and structural conditions they are placed in, and 2) we get only one extra year of life from only 20% of the chip seals we place each year; We could save $9 million each year.

THANK YOU