Details of Minutes

Mar 09, 2000: MC² Meeting - Kansas City, MO

1. Gary Whited (MC² Chmn) opened the meeting and summarized the status of the MC² Initiative for Cement Acceptance Procedures:

Manufacturers are responsible for base testing Acceptance across State lines is the goal The initiative is fully endorsed by MC² Now looking for States to pilot use of the multi-State acceptance procedure (WI and MI will begin use of the procedure as written.

2. Paul Tennis (PCA) summarized the status of the Opening to Traffic Model or Guide Specification initiative:

Looked at the 10 states in the midwest and their criteria for opening concrete pavement to traffic; 6 states use flexural strength specs and 4 use compressive strength. The mean flexural strength is 485 and the mean compressive strength is 4250. Nationally 18 States use flexural strength, 22 use compressive strength and 2 States use both. The national mean for flexural strength is 470 and the mean for compressive strength is 4000. There is also possible use of ACI 318 for consideration. A draft document will be sent to the task group at the end of March and to the MC² at the end of May. The draft will also cover the maturity meter option. A second draft document will be provided at the next MC² meeting.

Some questions for consideration and discussion as research is completed: 1. Go beyond the status quo with the model/guide? 2. Use SP201 support data and work done by CTL (not final yet)? 3. Push the envelope? 4. Look at HiperPave use and lower the opening strength allowance?

Question raised about how much would be gained in lowering the opening strength criteria? Responses included benefits for A+B bid projects (MI) and staging of construction. 6-7 hour difference in opening can be critical.

3. Jim Groves (IA) summarized the status of the "Quality Concrete" project (old Demonstration Project 119):

The task group is to develop a proposal for delivery to the States this summer and have indication of support and sources by the next MC² meeting. The module to be addressed is the training for troubleshooting on the job sites. Plant operation and mix design is now covered or under development, but full coverage is needed for project application. Basic training for the work crew before beginning work is the goal. Provide cause and effect based on specification compliance or non-compliance. The possibility of a videotape will be looked into. Task Group membership consideration: Jim Groves Victoria Peters Doug Schwartz Tom Keith Youlanda Bellew Jim Parry John Staton Dan DeGraaf Tom Bryan John Wojakowski George Woolstrum Bryan Pfeifer James Mack

4. Tom Keith (MO) reported that the dowell bar basket report would be done this summer.

5. Tom Bryan (FHWA-MRC) had no new information on the NTPEP admixture work.

6. Angel Correa (FHWA-ERC) made a presentation on a National Overview of CPR The full report is to be available next year. Two technical reports will be available by the end of this year on 1) diamond grinding, and 2) full depth patches.

7. Bryan Pfeifer (IL) reported on the results of a statewide review on patching techniques:

Currently the required flexural strength for opening to traffic is 650 on new pavements, 550 on four lane facilities and 450 on local roads. Several changes and adjustments were tried in different districts. Consideration will be given to new flexural strength requirements for opening to traffic, that may be in the range of 150 for two lane local roads and 300 for four lane roads. Patch designs will likely be modified: For overlays use smaller dowells Use less steel overlap in CRCP Use dowells in CRCP patching Consideration is being given to identifying the patching techniques and required strengths according to the end product. Relative importance of durability and strength changes with the character of the end use product. For curing, the use of insulated blankets was disallowed when the temperature is >85F0.

8. Chuck Luedders (KS) gave a presentation on the Kansas I-70 Dowell Retrofit 1994.

KS is anticipating a lot of retrofit dowell projects on the pavements constructed in the 1980s where skewed joints were used. About 20 projects anticipated in the next 3-4 years. Use a wax base curing compound coating on the dowells, do the sawing well ahead of the refit work, and note that the mesh in the pavement has to be cut which is labor intensive. Form-boards in the joints were eliminated in the summer when the pavement was in compression. Used a rapid set wet bond and dry bond backfill material in the sawed slots. Note: Be careful of the water content and drop in w/c for all of the proprietary materials. Use of aggregate extenders will lower the mix strength of the proprietary mixes, but in practice 5,000 psi was achieved in one day. Be careful not to hit the dowell bar when vibrating in the slot as this will misalign the bar and result in the slab being torn up in future. It was recommended to overfill the slot with the backfill material (finish about 1/8" high) and then diamond grind. Grout that isnt properly consolidated will scale off under traffic. It was found to be cheaper to saw each side of the slot and jack hammer out the material. Extra blade use is expensive and large quantities of grout are generated by the water cooling when grinding is used. All retrofit bars need to be put at the mid-depth of the slab. Use of 1 ½" diameter dowels is recommended. Joint resealing was found to be about 25% of the cost, so now looking at something other than silicone sealer. Few failures were noted in bonding between the slot backfill grout and the existing pavement.

9. Gary Rhinehart of Iowa Erosion Control, Inc. gave a presentation on the "Contractor Perspective on Concrete Pavement Patching":

Public Perception How often are we repairing the same road? Is there a specification being used for performance and for ride quality? Repair is only as good as the product on each end of the repair. A minimum 6' panel repair full lane width is recommended. Include a smoothness specification in the contract. Iowa requires smoothness criteria on patches >50'. This will get a better quality of bidder on the work proposed. Consider traffic control and efficiency of the repair work in preparing the contract plans and requirements. Full depth repair should be packaged in contracts at no less than 5000 square yards quantity. Complete rehabilitation is preferred as far as efficiency and resultant performance is concerned.

10. James Mack of ACPA gave a presentation on a Diamond Grinding Study conducted by PCA and overseen by ACPA and IGGA.

The diamond grinding is done using 150-160 blades per 4' spindle. 177 different ground sections were looked at in various States. From the information obtained from the owners, grinding has a service life around 11.8 years in wet environments and 20 years in dry environments. The survival analysis showed expected life of grinding before any other work would be required, as shown below: 50% Reliability 13.5 yrs or 12.5 x 106 ESALs 90% Reliability 9.5 yrs or 6.0 x 106 ESALs

Grinding is appropriate once the faulting reaches 0.15". Where there are dowels to be retrofitted, do the dowel retrofit first (three in each wheel path) and then grind. According to a Wisconsin Study, there was 16-17% reduction in accidents attributed to freezing weather and a 40% reduction in wet weather accidents after grinding. The mean texture of the pavement decreases in depth with age. Can get 10-12 year life out of the new macro-texture, although there is a little less life in wet-freeze climates. In the wet-freeze climate the macro-texture life reduction can be addressed by provision of transverse grooving, particularly when dealing with a soft aggregate (1/4" depth cut). A typical concrete pavement can be ground 3 times without compromising fatigue life, whether doweled or not doweled. There is a quick initial redevelopment of faulting that occurs withing the first 2 x 106 ESALs after grinding, however the rate of faulting then decreases. If there is poor material, diamond grinding wont help.

Discussion: Were soft limestones looked at in the study? Yes, with soft limestones you would increase the spacing of the blades on the spindle, then there would be little difference compared to hard aggregate. The final report should be placed on the PCA web site in the near future, www.portcement.org

11. The State representatives provided their reports concerning pavement patching/repair.

12. Cliff McDonald of 3M Company gave a presentation on "What Fiber Can Do For You to Meet Concrete Goals?"

Fiber reinforcing should be approached the same way as conventional reinforcing steel, that is, "What do you want to do or prevent?" The difference is a matter of scale and mixture considerations. What are the Issues? Keep micro cracks from becoming macro cracks. Considerations due to fiber reinforcing Surface area of the fibers will require modification of the mix design The aspect ratio (D/L - depth to length)of the fiber can affect mixing Orientation and distribution of the fibers in the mix to create a homogenous mix Tensile strength is really a materials behavior question Elongation/Elasticity is a materials behavior question Configuration is a materials behavior and design question In looking at the hardened mix characteristics, the time frame of consideration is the "post crack formation environment" When looking into use of fiber reinforcing, consider the entire cradle to grave cycle. Mix design Mixing Placing Finishing Curing Service conditions Repair Removal Recycling When looking into the use of fiber reinforcing, look at the entire cost of the project with and without the fibers

13. Frances McNeal, Master Builders, Inc., gave a presentation of National Concrete Research Directions. Handout provided.

14. New Business Discussion: Fall Meeting Theme New urban and reconstruction work in Des Moines, IA Indiana high profile projects using performance related specifications CTL site Build the theme around the site activity

Discussion: How can we increase attendance at the MC² meetings? Move the spring meeting to April time frame Coordinate with the western and southeastern groups developing Provide a web site list server to improve communications directly Extend our membership beyond the midwest Involve the Mississippi Valley Association AASHTO Region Talk to and coordinate with AASHTO task forces on concrete Everyone bring a friend to the meetings.

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