Asphalt Repair Specifications — Materials, Mix Designs, and Construction Standards
The specification governing your asphalt repair determines whether the patch lasts 7 years or fails in one winter. Here is what we specify and why it matters for commercial properties.
Hot-Mix Asphalt Material Specification
We use UDOT-approved Superpave mix designs for all commercial asphalt repairs in Utah. The Superpave system (Superior Performing Asphalt Pavements) selects aggregate gradation and binder grade based on traffic loading and local climate. For commercial parking lots in the Salt Lake Valley, we specify SP-12.5mm (formerly UDOT Type SP) surface mix with a PG 64-28 performance-grade binder. The PG 64-28 binder is formulated to perform at a high temperature of 64°C (sufficient for Utah summer surface temps) and a low temperature of -28°C (exceeding typical Wasatch Front winter minimums of around -15°C). For primary drive aisles with heavy truck traffic, we step up to SP-19mm base mix under the surface course for improved load distribution. All hot-mix is sourced from a UDOT-certified plant with current mix design documentation on file.
Repair Depth and Lift Specifications
Patch depth is determined by failure mode, not surface appearance. Full-depth patches require excavation to solid, uncontaminated base—typically 6 to 8 inches for standard commercial parking lot conditions with a stable granular sub-base. Each lift of hot-mix asphalt must not exceed 3 inches (compacted) to achieve proper density through the lift depth with a standard vibratory roller or plate compactor. A 6-inch full-depth patch is placed in two 3-inch lifts. The bottom lift (binder course) uses the same SP-12.5mm mix as the surface; in high-traffic drive aisles the bottom lift uses SP-19mm for stability. Each lift is compacted to a minimum of 92 percent of maximum theoretical density per ASTM D2041 Rice density measurement, or 95 percent of Standard Proctor (ASTM D698) density. Compaction is verified by nuclear gauge or core sampling on large repair projects.
Tack Coat Specification
Tack coat is applied to all vertical saw-cut walls and the sub-base surface before placing hot-mix. We use CSS-1h (cationic slow-setting) emulsified asphalt at a residual rate of 0.05 to 0.10 gallons per square yard on vertical walls and 0.03 to 0.06 gallons per square yard on the sub-base. Tack coat must break (emulsion water evaporates, leaving the residual asphalt binder) before hot-mix placement—typically 20 to 40 minutes at 70°F ambient. Applying hot-mix over unbroken tack coat (still milky gray in appearance) creates a slip plane that causes delamination. Visual confirmation of break (brown/black color return) is part of our quality control checklist before hot-mix placement.
Sub-Base Compaction and Moisture Requirements
Sub-base under a full-depth asphalt repair must be compacted to 95 percent of Standard Proctor density (ASTM D698) before asphalt placement. For repairs in water-impacted areas (potholes from drainage failure, utility cut zones), any soft, saturated, or contaminated base material is removed and replaced with Class 6 crushed aggregate compacted in lifts. Adding hot-mix over wet, soft, or uncompacted base is the single most common cause of premature patch failure—the patch will rut and develop alligator cracking within one to two seasons as the base consolidates under load. We probe sub-base material manually and with a compaction test device before placing any asphalt to confirm adequate density. Repairs will not proceed over unsuitable sub-base without owner notification and scope adjustment.
Recent Asphalt Repairs Projects
Common Questions
- What is the difference between Superpave and Marshall mix design?
- Marshall mix design (ASTM D1559) is the older method, selecting mixes based on stability and flow in a lab at fixed temperature. Superpave (AASHTO M 323) designs mixes based on actual traffic loading and climate data, selecting aggregate gradation and binder performance grade for the specific application. UDOT has required Superpave for all state highway projects since the late 1990s. Both methods produce suitable commercial parking lot mixes, but Superpave is the current standard for specified work and produces demonstrably better performance in high-temperature rutting resistance.
- Does the mix design affect how fast the patch cools and opens to traffic?
- Mix design has less effect on cooling time than lift thickness and ambient temperature. A 3-inch lift at 70°F ambient typically reaches traffic-safe surface temperature (below 120°F) in 45 to 75 minutes. A 3-inch lift at 45°F ambient cools in 20 to 30 minutes. Thicker lifts hold heat longer. We manage cooling time expectations at the time of installation and will not accept traffic on a hot patch.
- Can you provide mill design documentation for our property records?
- Yes. We retain and can provide plant tickets (hot-mix weight and temperature records at the plant), delivery tickets (weight and temperature at delivery), and compaction records for any project requiring documentation. For large projects or projects with specified material documentation requirements, we confirm documentation scope during the pre-construction meeting.
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