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George Reed

09 Nov

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Cold Weather Paving

November 9, 2016 | By | No Comments

This article is from a Technical Bulletin prepared by Flexible Pavements of Ohio

Introduction

The issue of placing hot mix asphalt (HMA) in cold weather comes up every fall, winter and springs.  Projects get delayed and damp.  Specifications generally set weather and temperature limits beyond which paving is to be stopped.  But jobs often need to be completed in spite of the specification limits.  Everyone starts to wonder whether they should continue to pave.  The question is, “Will HMA pavement placed in cold weather perform adequately?”

An industry survey conducted and analyzed by a group of researchers at Auburn University revealed the prevalence of cold weather paving.  The responses showed that in the north-central region of the country up to five percent of all projects get placed outside the normal paving season of April to November, and many of these jobs are placed in adverse weather conditions.

The challenge of cold weather HMA paving is to achieve adequate compaction. There is a consensus that if adequate density is obtained the pavement will perform as expected.  Thin courses and surface courses are at the greatest risk for low density and poor performance when placed in cold weather.  Intermediate and base courses greater than two inches thick generally can be constructed with little change in normal procedures.

Time for Compaction

Cold weather compaction depends upon having enough time and enough rollers to obtain adequate density while the temperature of the HMA mix being placed is still within the compaction temperature range, approximately 275 – 175 degrees Fahrenheit.  What factors affect the time it takes for the HMA to cool below 175◦F?  All weather factors affect this time – air temperature, wind speed and the presence or absence of sunlight.  The type and temperature of the surface on which the HMA is to be placed is a factor also.  But the two most important factors are the temperature of the mix and the thickness of the course being placed.  It is generally accepted that if conditions do not permit 10 minutes of time for compaction, adequate density probably cannot be achieved.

It is easy to determine this time for any set of conditions.  Dickson and Corlew published cooling curves in 1910 showing the time available for compaction for any given set of ambient and mix conditions.  Determining the available time became even easier with the development of the PaveCooI software by the Minnesota DOT.  (PaveCool can be downloaded from www.mrr.dot.state.mn.us/research/mnroad_project/restools/cooltool.asp)

Let’s look at an example.

Conditions

30◦F air and base temperature

5 mph wind

Clear and dry

Mid-Afternoon

Mid December

Columbus, Ohio

Binder grade, PG 64-22

Single course being placed on an existing asphalt concrete surface.

At a mix temperature of 275◦F and a course thickness of 1.25 inches, the time available for compaction is 7 minutes, too short to realistically achieve density.  If the mix temperature is raised to 325◦F and all other factors are the same, the time available for compaction is 12 minutes.  Now you have a chance of getting the mat compacted before it cools.  If the mix temperature is held at 275◦F but the course thickness is increased to 2 inches, the time available for compaction is 17 minutes.

The other challenge in cold weather construction is economics.  Cold weather construction will cost more.

Plant Production

Mix temperature is one of the most influential factors on time available for compaction, so an obvious solution is to produce hotter mix.  How much can the mix temperature be raised without causing damage and what is the cost?

Binder suppliers normally recommend a mixing temperature based on viscosity tests.  The NAPA publication on cold weather compaction suggests that it is probably safe to mix at a temperature 18◦F above the recommended temperature.  However, mixing above that temperature level risks excessively aging the binder or placing too thin a coating on the aggregates.  Raising the mix temperature takes extra fuel and lowers the production capacity of the plant.  An examination of the plant production tables in the Hot-Mix Asphalt Paving handbook indicates that raising the mixing temperature 25◦F can reduce the production capacity of the plant by 15 percent or more.

Likewise, increased aggregate moisture contents reduce the production capacity even more dramatically.  Given the combination of need for a higher mix discharge temperature and the presence of colder aggregates with higher moisture contents, it is easy to see that the plant production rate may be cut in half in cold weather.  Stated otherwise, twice as much fuel may be required to produce mix in cold weather.

Hauling and Temperature Segregation

The next challenge is to get the mix into the paver with as much retained heat as possible.  The first thought is to tightly tarp truck bets.  Research has shown, however, that tarping of loads has little effect on the average temperature of the load for normal haul times.  So why bother?  This raises the topic of temperature segregation.  Temperature segregation is the presence of masses of mix in the mat with temperature differentials that prevent uniform compaction.  When a load is transported in cold weather without a tarp, the cold crust that forms on the load may be placed by the paver creating a cold spot in the mat that cannot be adequately compacted.  There is little consensus as to how important this phenomenon is.  Some believe this may be an important issue in the performance of pavements, and as a result there has been recent proliferation in equipment for re-mixing material as it is fed to the paver.  Other point out that we didn’t know about this effect until the advent of the thermal imaging camera – if it wasn’t a problem before, is it now?

Until this is issue is resolved, the recommendation is to tightly tarp the loads, at least for longer hauls, and prevent exposure to precipitation.  If tarps are used, they should tightly cover the load and seal over the sides of the truck bed.  Loose, flapping tarps may actually increase the heat loss.  Tarping loads for short hauls will not save much heat and may take precious time.  Tarping loads for longer hauls will not significantly raise the temperature at which the mix is delivered to the paver, but may result in a more uniform temperature mix, thereby minimizing the effect of temperature segregation.

The basic objective in cold weather paving is to keep the total time from mixing to compaction as short as possible.  Haul trucks should not be kept waiting to unload into the paver.  Minimize the handling and exposure of the HMA.  Windrow paving and transfer devises that extend the time and further expose the HMA to the environment should probably be avoided.  Move the material as a mass directly from the haul truck into the hopper of the paver.

Placement

If the HMA course is to be placed on an aggregate base, the base must be solidly compacted at or below optimum moisture and not frozen.  Frozen or excess moisture rapidly saps the heat out of HMA and may contribute to soft spots in the base.  If being placed over and existing paved surface, the surface must be dry and the tack coat material must be set.  How do you get that slow-setting emulsion tack coat to break and dry in cold, damp weather?  If obtainable, you could use rapid-curing liquid asphalt for tack.  Instances have been reported where contractors have used racetrack jet-dryers or infrared heaters to dry the surface before placement of the HMA.

Areas that require handwork or feather of the mix can probably not be placed rapidly enough to permit adequate compaction.  Work of this type should be avoided during cold weather or be considered as a temporary solution.  Construction of transverse joints must be accomplished with good technique, starting off with the screed at the joint and on starting block so that time is minimized and the need for handwork is eliminated.  Paver speed should be regulated to allow the rollers to complete compaction within the time and temperature constraints.

Compaction

Understanding that compaction is directly related to the mix temperature, it is necessary to maintain a high mix temperature during production, transportation and placement of the HMA.  The main thing to remember in cold weather paving is that the Tim Available for Compaction (TAC) is dramatically reduced.

Specifications and Quality Assurance

Is it worth the extra cost and effort to place HMA in cold weather?  Ultimately, only the person paying the bill can answer that question.  Research at Washington State has indicated that even a few percentage points less density results in double-digit percentage losses in durability (pavement life).  So if you are the owner, it probably makes sense to invest the extra cost to get adequate density if you absolutely have to have the work completed in cold weather.

How do you handle the extra cost and payment for this extra effort?  The usual way is by change order, but scarce, suitable working days can be lost while such things are negotiated and processed.  If an owner anticipates that such a situation might occur on his project, it may be worthwhile to set up an alternate bid item for the extra cost of cold weather paving in order to establish in advance a price for the extra work needed to adequately place and compact HMA in cold weather.  Issues such as changes to course thickness and mix type would have to be addressed and some quality assurance or acceptance measures might have to be altered.  If the project were to be a density acceptance project then the effectiveness of the contractor’s compaction procedures would be revealed by the acceptance cores.  If density measurements are not available, then some other measure for verifying the effectiveness of the contractor’s placement and compaction procedures would have to be established in the specifications.  The owner may require the placing of a control or test strip to ensure minimum acceptable density results from the contractor’s proposed procedures.

Conclusion

Hot mix asphalt paving can be successfully accomplished in cold weather without compromising the performance of the pavement.  The mix must be compacted while it is still in the compaction temperature range.  Adequate time for compaction can be obtained by:

  • Increasing mix temperature
  • Increasing the layer thickness
  • Minimizing the time/length of haul
  • Working the rollers as close to the paver as possible
  • Using more and/or higher-capacity rollers

05 Aug

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Gone Fishin’

August 5, 2016 | By | No Comments

The GRI crew left from Berkeley Marina on July 16th and booked a fishing trip with http://berkeleycharterboats.com/. We chartered a total of three boats, one for salmon and two for bottom fishing (Rock Fish, Ling Cod and Cabazone). There were about 48 George Reed Inc. employees. As you can see from the photos, a good time was had by all!

10 Jun

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New GRI team member Keith Jones

June 10, 2016 | By | No Comments

It is our pleasure to announce that Keith Jones has joined our organization in the role of Private Works Manager. Keith has been in the construction industry for 20 years. He attended Chico State where he earned a bachelor’s degree in Construction Management.

After graduation he started his career with DSS as an estimator, and moved to the field as a superintendent.  He also spent time at Teichert Construction as an estimator and project manager.  He comes to us most recently from Goodfellow Top Grade Construction, where he spent the last 3 years as an Senior Estimator bidding private works projects. Keith is very excited to join the team and help expand George Reeds private works market.

Outside of work Keith enjoys spending time with his wife Kristy, and his two son’s Kole and Kayson.  The boys are very active in Baseball, Rugby & Soccer and therefore the family spends a lot of time at the boys sporting events. In their free time they like getting out on the lake.

Keith will be located at our George Reed Office and can be reached on his cell phone at 209-321-1503 or his desk phone at 209-557-3129.

Please join in welcoming Keith to our team.

23 May

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Jr. Navy Seals Honored

May 23, 2016 | By | No Comments

Friday night we opened the Reed Carseum to the Stanislaus Junior Navy Seal Annual Dinner honoring an amazing group of kids who recently competed in the 2016 Navy Seals Trident Challenge at the Naval Seal Base in Coronado, CA. Led by mentor Buddy Wesson, our Companies and the Norma and Wendell Reed Family Foundation been annually supporting this endeavor for the many years.

18 Mar

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Grissom makes decade mark at George Reed

March 18, 2016 | By | No Comments

Congratulations to Naiome Grissom for 10 years of service with George Reed. Naiome came to George Reed in March of 2006 as a Contract Administrator for our then Lodi Construction Division. She transferred to our Modesto Office in 2008 where she is currently the Office Manager for the Contract Administration Department. Thank you Naiome for your many years of service!

11 Mar

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2016 Season Prep: Construction Foreman Training

March 11, 2016 | By | No Comments

In gearing up for another busy season, George Reed recently had a Construction Foreman Training session conducted by HCSS. The Program is an Estimating / Job Costing Program. The training covered topics such as Heavy Bid, Heavy Job, Dispatch and Equipment 360.

09 Feb

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Drivers awarded for 50 years of service!

February 9, 2016 | By | One Comment

Randy Questo (Tuolumne Transit Mix) and Brad Burton (Calaveras Transit Mix) were awarded plaques for years of service to GR’s concrete supplier division.

It might come as a surprise to some that George Reed has a concrete (supplier) division!
Both drivers have given the company 25+ great years of dedicated service and are very well thought of in the Calaveras/Tuolumne County construction community.

07 Jan

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Fisicaro joins the George Reed team

January 7, 2016 | By | No Comments

It is our pleasure to announce that Amy Fisicaro has joined our organization in the role of Certified Payroll/Insurance Clerk.

Amy has grown up in Oakdale where she graduated in 2008 from Oakdale High School. She worked in the grocery business for 5 years and attended Paul Mitchell in Modesto where she received her cosmetology license in 2012. Amy is eager to start a new career path and gain experience in the construction business.

She is excited to be part of our team and looks forward to meeting and working with all of you. She will be located in our Modesto Construction office and can be reached at Extension 3120.

Please join us in welcoming Amy to our team.

21 Dec

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Christmas at George Reed

December 21, 2015 | By | No Comments

George Reed Inc recently had their annual Administrative Luncheon. The staff was treated to a holiday feast prepared by Vice President / General Manager Ed Berlier. He was assisted by his wife Cathi, Naiome Grissom, Kathleen Williams, CT Tuthill and Clayton Terry. Thank you to Adam Hanson for blessing the food and leading us in giving thanks. An ugly sweater contest was held which was won by Ruben Trillo. There was also a raffle with each employee receiving a gift. A special thank you to Helen Quintana and Jennifer Beals-Torres for directing  the raffle. The grand prize 55” TV was won by David Cox. A great time was had by all.

We at George Reed Inc would like to thank all of our customers, friends and families for a successful year and wish you all a very Merry Christmas and the Happiest of New Years!

11 Dec

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Josh Hinchey joins George Reed

December 11, 2015 | By | No Comments

It is my pleasure to announce that Josh Hinchey has joined our organization in the role of Sales Manager.

Josh has been a sales representative selling construction materials in the central valley for nearly 14 years. He graduated from the University of Redland where he earned a bachelor’s degree in Business Administration and played football.

After graduation he returned to his home town of Modesto and started his career with RMC Pacific Material. Shortly thereafter he married his wife Tasha. Together they have three daughters, Jisselle 10, Sophia 9 and Isla 6.

He comes to us most recently from Granite Construction where he spent the last two years responsible for two asphalt plants and two aggregate plants. Josh has a long record of building lasting relationships with key accounts in his territory and doing so with integrity, honesty and professionalism.

Outside of work Josh enjoys spending time with family and friends. He also plays golf, basketball, does home improvement and has chauffeur duty for his daughter’s sports activities.

Josh will be located at our Munn & Perkins office and can be reached on his cell phone at 209-247-5257 or his desk phone at 209-557-3011

Please welcome Josh to the team.

Bitnami