TxDOT Approves Special Specification 3224

Print this Article | Send to Colleague

Item 341, which is the most frequently used specification for laying asphalt pavements on TxDOT projects, has been the subject of many changes and improvements over the past few years. This week, it was announced that a new special specification received approval. This special specification, which is listed as SS 3224, will be used in lieu of Item 341 on all future projects. This is the culmination of months of work led by Dale Rand and staff at the Flexible Pavement Branch of TxDOT's Construction Division.

Special Specification 3224 was written to merge Item 341 and Special Provision 341-024. In addition, SS 3224 addresses numerous deficiencies in testing, reporting and sample custody that were brought to light by the 2008 FHWA stewardship assessment review and inspections by the Office of Inspector General (OIG) in review of numerous "stimulus" projects constructed in 2009 & 2010. There were also a number of other changes that were incorporated into the SS 3224 based on documented recommendations from TxDOT districts and industry representatives. The Flexible Pavements Branch of CST began documenting these recommendations in 2004 when the Standard Specification Item 341 was implemented. It should be noted that SS 3224 also contains various incentives for Contractors to use the Pave-IR system.

Many thanks are in order to TxDOT employees, along with members of TxAPA, TxAPA's Specification Committee and members of the AGC that reviewed several draft versions of this special specification and made recommendations to Dale in support of this work. The cumulative efforts of everyone involved produced a special specification will enhance the viability and quality of HMA in Texas.

TxDOT is now in the process of writing very similar special specifications to replace all other HMA mixes (Items 340,342,344,346).

This fall, TxAPA and TxDOT will hold a series of seminars across the state that will further explain the latest changes. Information regarding the location and dates of these seminars should be available by mid-to-late summer of 2011.

The following is a brief description (and commentary) of major changes.

1. Allows "intermediate" aggregate as well as coarse and fine aggregate.
   
2. Adds wording that the engineer may test during production to insure 50 percent of #4 aggregate comes from a class A source. Applies only when contractor blends aggregates to meet class A requirement.
   
3. Stipulates that engineer will perform Micro-Deval abrasion test during production. Test data is used to estimate the MgSO4 soundness loss.
   
4. Changed RAS gradation from a minimum of 90 percent passing to a minimum of 95 percent passing the 3/8 sieve.
   
5. Adds wording that addresses the possible consequences if a contractor fails to comply with a specification requirement to suspend production or placement.
   
6. Stipulates to use TxDOT provided software for reporting.
   
7. Addresses mixes that are too stiff. Essentially requires more asphalt. Also allows the contractor some latitude.
   
8. Addresses concerns of paving at low (particularly daytime) temps.
   
9. No longer allows waiving the thermal profile. It is required for every sublot and documentation is required at the end of each lot.
   
10. Addresses the contractor using the PAVE-IR for specification compliance and stipulates reporting requirements.
    
11. Under "material transfer devices" allows the PAVE-IR to be used in lieu of a specified MTD.
    
12. Under "hauling equipment" adds additional requirements when end dumps are allowed.
    
13. Addresses potential damage caused by screed heaters being left on during long paver stops.
    
14. Allows Lot 1 to be larger than 1,000 tons.
    
15. Allows small quantity clause to be used when mutually agreed, even if production does not meet default definition of small quantity production.
    
16. Stipulates when the contractor will obtain samples for informational Cantabro & Overlay testing. We are trying to establish a database for future specification consideration.
    
17. Addresses the consequences of VMA being out of specification. This is important to prevent dry mixes because we do not have minimum asphalt binder requirements.
    
18. Specifically defines what is and is not considered "miscellaneous" and what is subject to air void testing.
    
19. Requires engineer to witness coring operations. Requires onsite trimming of cores. Allows for trimming at an alternate location. Stipulates engineer will maintain custody of core or use CST protocol to provide a secure means and process that protects the integrity of the cores during transport.
    
20. Segregation (density profiles) are required for every sublot. Waiving the density profile is no longer an option. They are required for every sublot and documentation is required at the end of each lot similar to the segregation profile. Note: FHWA stewardship assessment showed that density and thermal profiles were not being performed as needed and not documented. There were essentially no reported failures, yet plenty of evidence that both thermal and physical segregation occur frequently.
    
21. Similar to thermal profiles and density profiles, joint density evaluations are required on every sublot and documentation is required at the end of each lot.
    
22. Recovered asphalt dynamic shear Rheometer (DSR) is not required when the Pave-IR system is used for specification compliance since the PAVE-IR provides a continuous profile of the mix temperature.
    
23. To receive bonus, contractor is required to comply with specification requirements to report results for required tests.
    
24. Table 16 – when target density is 96.5 or 97.0, pay adjustments are the same but we do not allow continued production if the lab density exceeds target by ±1.0%. Flushing & rutting are concerns when the lab density gets too high.
    
25. The engineer may allow failing placement Sublots to be left in place without payment in lieu of removal and replacement. Makes placement similar to production.