It is 1991 and I work for a true pioneer of the industry, Ed Meidling. Even in the days of hand rodding, he spends his afternoons on a Master triple trowel burnishing pours of size comparable to 2015. Testing prototype equipment and a passion for seeking new technologies has led us to the Issaquah School District whitetopping project.
The school district has a problem. Their 3-acre asphalt parking lot servicing the administrative offices and elementary school has been failing. The first bid for asphalt repair and reconstruction came in 30% over budget. Jon Delony, a PCA regional engineer and with the Northwest Concrete Promotion Group, and Bruce Chattin, director of the Washington Aggregates and Concrete Association, call me to discuss a whitetopping alternative. In 1991 in our region, whitetopping is in its infancy.
The site directly abuts a stream with a nearby fish hatchery, has only a few catch basins for stormwater collection, and the parking lot is on the verge of total failure. With Jeff Davis from local ready-mix supplier Cadman Sand & Gravel, we develop a proposal for a new alternative: whitetopping the existing asphalt. Heavy and repetitive bus traffic and service vehicles with restrictive traffic lanes offer an opportunity for a concrete solution that will provide both immediate cost benefits and life-cycle returns on investment.
The rebid attracts two asphalt bids and two whitetopping options. We are second bidder, at $14,000 higher than the low asphalt bid. However, Meidling offers a three-year unconditional warranty versus the specified one-year warranty and, confident in our design, assures the client of a 20- to 30-year service life with minimal maintenance. The 30% budget gap from the first bid round is closed to less than 5% and we are ultimately awarded the project.
Unbonded overlay
Significant issues regarding stormwater run-off require that the existing and extremely limited three catch basins remain undisturbed. Further, some pavement areas designated as complete failures require point repairs before installing the overlay. We choose to go with an unbonded overlay due to the severe alligator cracking and potholes and begin with a thin sand level-up course. (Frankly, looking back, our concrete sections were conservative despite being first-cost competitive and also assuring an extended life-cycle benefit.)
A few wide-bay pours are done with a conventional truss screed but the bulk of the pavement is struck off with a Bunyan roller screed, then a state-of-the-art technology. Fairly precise grade control is a prerequisite to moving heavy rainfall across minimally sloped grades over long distances to the three catch basins. Ultimately, there are no birdbaths nor any grinding required. Joints are cut with Soff-Cut early-entry saws and left unsealed.
We are fortunate that the existing grades abutting curb and sidewalk allowed some latitude in final finish elevations. At the elementary school busloading area, we overlay a limited area of sidewalk for transition to the school entry path.
The local concrete industry supports the pilot project and shoots a construction video entitled “The Flexible Solution” for future use in regional promotion (see the video at the end of this article). We also use the opportunity to host design professionals in order to promote whitetopping on future projects.
Still performing well
Flash forward to 2015. I revisited the project recently. Twenty four years later, the lot is still in use and except for a few utility cuts, some patches for unrelated work, and a small full-depth concrete expansion outside the limits of our project, the overlay is performing well. The lot exhibits no signs of degradation, potential failure, or even required maintenance. My fellow concrete contractors will appreciate that during initial construction over the 3 acres, we had one 5-foot-long random crack. As days often go in this industry, this crack was in the superintendent’s designated parking space. We epoxy-injected that crack and today it looks the same as it did 24 years ago.
Whitetopping was and is a competitive and viable alternative to asphalt, even though the American Concrete Pavement Association doesn’t even use the term whitetopping anymore, opting for simply calling it an overlay, either bonded or unbonded. Over the years, technology advances in both mix design and construction techniques have allowed for successful ultra-thin overlays that provide life-cycle benefits far beyond the initial cost.
Finding suitable overlay candidates
Unfortunately in our region, many of the initial construction sections are inadequate to begin with and the cure is often a cycle of repetitive thin-asphalt overlays that satisfy and maximize street bond investments while minimizing the performance of the pavement involved. As such, it is difficult for us to find suitable candidates for overlays. The concrete industry in our area has made significant inroads in marketing and constructing full-depth concrete pavement, particularly in intersections or heavily travelled main arterials. Yet there is still a major market opportunity for overlays in both the public and private sector throughout the country.
Many of my colleagues have similar stories to tell and, as an industry, we need to dust off some of these examples and pursue the opportunities. With shrinking city and county budgets and resources, we need to recognize that repetitive thin asphalt overlays with minimal life-cycles are not an effective solution. Now more than ever, life-cycles are valid, especially in a time when our infrastructure dollars allow no maintenance and minimal first cost funding. Whitetopping is still “the flexible solution” and as an industry, we need to deliver the message.
Pete Reed is a concrete consultant in the Pacific Northwest U.S.
The Flexible Solution
Bruce Chattin took the only surviving copy of the original 1991 video on VHS tape to Mike Lorrain at Quantum Productions. Using color correction to adjust the video and EQ techniques for the audio, he converted to a 16x9 aspect ratio in MP4 format. Despite all that, the colors are still variable, but the process and the pride of the local concrete industry shines through.
