Installation

Studies show that the failure to achieve the required noise reduction with SDA pavements is often due to the quality of the mix. In some cases, however, the installation process also plays a crucial role.

Practical experiences demonstrate that favorable weather conditions and a well-coordinated and uniform rolling process significantly increase the likelihood of successful SDA installation. For long-term good technical and acoustic durability, adequate compaction is crucial – under-compaction should be avoided at all costs. Optimal compaction levels are between 99 and 102%.

Assessment of Deviations

Deviations are assessed based on their relevance and classified accordingly. The cantonal deduction systems provide, depending on the severity, that either no further measures are necessary, a warranty performance is required, or a replacement must occur.

A client laboratory and a carefully prepared testing plan are crucial for meeting the required quality standards. The testing procedure remains fundamentally open; however, clear contractual agreements with the involved companies are essential.

Responsibilities

The responsibility for material transport lies entirely with the executing company. The rolling also falls under its responsibility, with current technical standards needing to be adhered to.

There are no specific requirements for the rolling process; however, it must be ensured that the rolling work is carried out adequately and professionally.

Requirements for the Substructure when Installing Low-Noise Pavements (LAB)

The mechanical stability of a low-noise surface layer significantly depends on the condition of the substructure:

• If the load-bearing capacity of the supporting layers is no longer given or if there are already damages, these layers must be completely or partially replaced, regardless of the planned surface layer.
• In the case of minor defects in the substructure and a projected lifespan of the LAB of 10 to 15 years, installation can still proceed, especially if a later renewal or reinforcement is planned.
• A soft substructure increases the risk of early damage to the surface layer. In this case, the substructure must be reinforced or repaired, regardless of the LAB.
  
• A hardened substructure promotes the formation of structural cracks, especially with LAB, and should therefore also be replaced.

Requirements for Load-Bearing Capacity

The installation of a LAB requires that the load-bearing capacity is ensured across the entire road width. A visual assessment should be conducted before installation. If structural damages or frost heaves are detected, additional investigations into the depth of the damage and the affected layer are necessary.

Before the installation of a LAB, it must be ensured that the causes of the existing damages have been completely resolved, so that a recurrence after installation can be excluded.

In principle, the binder layer does not necessarily have to be replaced when installing SDA pavements. However, there is an increased risk of structural cracking if depressions are expected – for example, with a high number of manholes. In such cases, the use of pavement reinforcements is recommended.

Requirements for Binder Layer

The pavement structure developed for the SDA in ASTRA and in the cantonal standards prescribes an AC 22 or AC 16 for the binder layer. In the canton of Zurich, the binder layer for the SDA is an AC EME 22, due to the higher performance requirements for this road structure (Kanton Zürich, Baudirektion, 2023)¹.

Before the surface layer is applied to the binder layer, a bitumen emulsion must first be applied. This is usually done with a machine but can also be done manually for local areas. Additionally, the edge and center joints must be sealed with sealing tapes (That, 2022).