SAP Rut-free Asphalt Pavement Technology (Super Anti-rutting Pavement) is a new-generation high-strength asphalt mixture developed based on polymer polyolefin and inorganic modification principles. Adopting composite modification by increasing asphalt viscosity and aggregate friction resistance, it greatly improves the bearing capacity of asphalt pavements. The rut depth can be controlled within 1.5 cm during a 3–5 year maintenance cycle. This technology addresses rutting-prone sections such as ultra-heavy load sections, intersections, expressway ramps and long steep longitudinal slopes, so as to achieve the goal of rut-free high-strength asphalt pavement.
The construction technology of SAP rut-free modified asphalt mixture is basically consistent with the conventional process. During production, the SAP rut-free modifier is added externally into the mixing drum according to the conventional mix proportion of asphalt mixture. The typical dosage is 1.0% by mass of asphalt mixture. Appropriately extend the mixing time to achieve full and uniform blending; no other special requirements are needed. Paving and compaction shall be performed on site by conventional methods. Traffic can be opened when the pavement temperature drops below 50℃ (water spraying is allowed for cooling), and no curing is required.
For asphalt surface structure design at heavy-load intersections, a two-layer modified asphalt SAP rut-free pavement structure is recommended:
| Course | Description |
|---|---|
| Surface Course | 4 cm SAP-modified SUP13/AC-13 (SAP dosage: 1%) |
| Intermediate (Lower) Course | 6–8 cm SAP-modified SUP/AC-20(25) (SAP dosage: 1%) |
| Subsurface Course or Base Course | — |
(1) Material Requirements for SAP Polymer Stabilized Rut-free Modifier
Table 1 Technical Requirements of SAP Modifier
| Index | Unit | Technical Requirement | Test Method |
|---|---|---|---|
| Appearance | — | Black, uniform granules | JT/T 860.1 |
| Mass of Single Particle | g | ≤0.05 | JT/T 860.1 |
| Melt Index (190℃, 2.16kg) | g/10min | ≤5 | GB/T 3682.1 |
| Density | g/cm³ | ≥1.2 | GB/T 1033.1 |
| Tensile Strength | MPa | ≥30 | GB/T 1040.1 |
| Flexural Strength | MPa | ≥25 | GB/T 9341 |
(2) Technical Requirements for Asphalt Mixture
Table 2 Technical Indicators of SAP Modified Asphalt Mixture
| Item | Unit | Technical Requirement | Test Method |
|---|---|---|---|
| Air Void VV | % | 3~6 | T 0705 |
| Marshall Stability MS | kN | ≥15 | T 0709 |
| Dynamic Stability (60℃) | times/mm | ≥20000 | T 0719 |
| Dynamic Stability (70℃) | times/mm | ≥10000 | T 0719 |
| Residual Stability of Immersed Marshall Test | % | ≥85 | T 0709 |
| Tensile Strength Ratio after Freeze-thaw Splitting | % | ≥80 | T 0729 |
| Ultimate Failure Strain (-10℃) | με | ≥2000 | T 0715 |
At present, as specified in national standards for the rut dynamic stability of asphalt mixtures, the value shall be no less than 800 times/mm for ordinary asphalt mixtures and no less than 3000 times/mm for modified asphalt mixtures. The rut dynamic stability of asphalt mixtures with SAP rut-free modifier can exceed 20000 times/mm, while maintaining the ultimate failure strain of no less than 2000 με.
