Bus Parking Lot Finds Stability through Full-Depth Reclamation with Cement

Spotsylvania County, located halfway between Richmond, Va. and Washington, DC, is considered in the top 100 of fastest growing counties in the nation. Since the year 2000 the population has increased by 33 percent.

Due to this tremendous growth, a transportation facility was constructed with a 45,000 square yard bus parking lot to accommodate the entire fleet for the county schools. The 140-bus fleet would make two trips in and two trips out per day for the 200-day school year. This equates to more than 100,000 bus passes.

Within six months of completion of the parking lot, the pavement began to experience severe deterioration and within a year 35 percent of the surface was distressed with rutting and cracking.

Rehabilitation was necessary to restore the lot to its expected structural capacity. Removal and replacement of the aggregate base would have been extremely expensive, and with bearing capacity an issue, the use of an asphalt overlay would not solve the pavement base and subbase problems. The perfect solution was full-depth reclamation (FDR) with cement since it would restore bearing capacity to the parking lot and provide a cost-effective, durable base.

FDR is also an environmentally friendly repair option because it uses in-situ materials, and thereby the process conserves natural resources and energy. Portland cement was the obvious stabilizer choice for the varying thickness and changing nature of underlying materials due to its ability to adequately stabilize clay-rich (cohesive) and granular (unbound) materials. More on the Spotsylvania County parking lot.

Full-Depth Reclamation with Cement Recycles Failed Asphalt Pavements
Thursday, October 15, 2009, 10:00 – 11:00 AM CDT

Cost savings and environmental benefits result from use of existing pavement materials, reduced hauling associated with removing old materials and placing new materials, and from the longer expected life of a pavement with a cement-stabilized base.

This one-hour webinar (PDH credit available) will discuss applications, benefits, design, construction, testing, performance, and sustainability aspects of FDR as it relates to recycling failed flexible pavements. The cost is $60 ($30 for PCA members; government officials; students and educators). More information and purchase.

For concrete pavements, how does the new MEPDG differ from the 1993 AASHTO Guide?

A new approach to pavement design promises a more realistic comparison of construction materials and acknowledges concrete's benefits such as durability. Called the Mechanistic-Empirical Pavement Design Guide, or MEPDG, the proposed guide will replace the current 1993 AASHTO Guide for the Design of Pavement Structures, which is based on data collected from road tests conducted in the 1950s.

To address the limitations of the 1993 Guide, the National Cooperative Highway Research Program is developing the new design procedure based on mechanistic principles. Mechanistic design uses a model to calculate the effects of traffic loading, paving materials, design features, and other variables.

View or download a free two-page pdf summarizing MEPDG.

Known for its innovation in concrete pavements, Iowa took another leap forward with the recent completion of two stringless slipform concrete overlay projects. Stringless technology, as the name implies, replaces the traditional stringline with an electronic tracking process that controls the horizontal and vertical operation of the slipform paver. The process eliminates the installation and maintenance of stringlines and can decrease surveying and increase smoothness.

Earlier this year a 9.5 mile-long, two-lane concrete overlay project was completed on route V18 in Poweshiek County near Brooklyn. Building on its success, a second project is currently under construction on US-65 in Worth County near Mason City. It consists of a 10.5 mile, 32-feet wide, 5-inches thick unbonded overlay.

Stringless technology holds special potential for increasing the application of concrete overlays. Along with advancements in streamlined profiling of the existing pavement, it could significantly decrease the amount of surveying that is required prior to placing a concrete overlay. Iowa, and other states, have seen a dramatic increase recently in demand for concrete overlays due to spiking asphalt prices. More on stringless technology.

The National Concrete Pavement Technology Center offers a Guide to Concrete Overlays which provides the key elements of the six major types of concrete overlays along with specifics on materials, typical sections, and important construction elements.

Design and Construction of Roller-Compacted Concrete Pavements
Thursday, December 10, 2009, 10:00 – 11:00 AM CDT

A roller-compacted concrete (RCC) pavement takes its name from the construction method used to build it. It's placed with conventional or high-density asphalt paving equipment, then compacted with rollers. RCC is used when strength, speed of construction, and economy are primary needs. It is commonly used at port, intermodal, and military facilities; parking, storage, and staging areas; streets and intersections; highway shoulders; and low-speed roads. It can also be used in a composite system as a base material.

This webinar will discuss RCC applications, benefits, mix design, construction, testing, and performance. The cost is $60 ($30 for PCA members; government officials; students and educators). More information and purchase.

Recent Changes to ASTM Cement Specifications C150, C595 and C1157

ASTM International Committee C01 has recently approved changes to ASTM C150, Standard Specification for Portland Cement, ASTM C595, Standard Specification for Blended Cements, and ASTM C1157, Standard Performance Specification for Hydraulic Cement.

Modifications to ASTM C150 include a new Type II(MH) cement, provisions for use of up to 5% inorganic processing additions, revision to sulfate content requirements, and fineness requirements. The 2009 update to ASTM C595 includes a specific designation for a ternary blended cement—that is, one with two supplementary cementitious materials (SCMs)—Type IT. The revision to ASTM C1157 makes Type HE strength requirements equivalent to ASTM C150 Type III portland cement. More on the 2009 revisions to the standards.

A special one-hour webinar on the recent changes will be offered on Tuesday, October 13, 2009. More information on the webinar.

Sustainable Development Leadership Award Winners Announced

The Portland Cement Association (PCA) is pleased to announce the winners of its second annual Sustainable Leadership Awards. The awards honor individuals who have enacted policies or completed projects exemplifying creativity and best practices in using concrete and cement-based products for sustainable applications. Learn more about the awards and winners.

Get Free Registration to World of Concrete 2010

PCA offers free registration to the exhibits at the World of Concrete held in Las Vegas, February 2-5, 2010. You can also get a discount on seminars held February 1-5 by signing up here.

Complete listing of conferences and training.

New Directories Help Locate Local Contractors

PCA has compiled directories of contractors who construct soil-cement and roller-compacted concrete pavements. Click on the appropriate link to find a contractor who does work in your area.

If you are a contractor and would like to be included in the directory, please contact Wayne Adaska.