Inspectors did have some experience with lime stabilization but the higher cost of the process reduced miles of work. The lime stabilization process also required a longer construction time and a detailed traffic control plan.

A third option, overlaying the streets with hot mix asphalt concrete (HMAC), also offered the advantage of inspection experience but also provided the most expensive option. Placing the overlay required repairing the failed base, thus extending construction time. The asphalt would also need periodic seal coats and future overlays.

Rehabilitating the failed pavements with cement seemed to offer the most economical solution for the longest life. The existing base materials and asphalt mat could be reused, eliminating the cost of hauling in new base material.

The project was specified in accordance with Texas Department of Transportation (TxDOT) Specification Item 275, "Portland Cement Treated Materials (Road Mixed)." Standard compaction requirements were used. The typical section consisted of treating 6 in. of existing material with 3 percent cement (by weight of dry material), a prime coat, a one-course surface treatment, and a 1-in. HMAC surface. A concrete valley and curb and gutter at the intersections completed the project.

King-Isles Construction Inc. and its subcontractor, LM Asphalt Maintenance, both out of Corpus Christi, achieved the recycling process in one day. Crews scarified and pulverized the existing roadbed to proper gradation. Processed material was required to pass the 2-in. sieve before being pre-wetted and shaped to the lines and grades of the typical section. After workers spread portland cement over a designated area and mixed it thoroughly with the pulverized materials, water was added to reach optimum moisture.

Crews compacted and graded the mixture to finish grade. The surface was then cured with water spray for three days prior to applying the chip seal and the HMAC surfacing. The process allowed the city to avoid excavating, removing and discarding the old pavements and allowed crews to use the salvaged material.

Ultimately, the completed $258,787 project returned 2.077 mi. of city streets to a high level of serviceability, said Rios, which translated to $124,597 per mi. or $3.53 per sq. yd. for the entire recycling and surfacing process.

Note: Jeff Hawk edited this article originally submitted by Daniel 0. Rios, a transportation engineer for S&B Infrastructure Ltd., McAllen. A registered engineer in Texas, Rios spent ten years in TxDOT's Corpus Christi District in various positions.