Concrete carriageways are intentionally designed with a low slump value, typically around 30mm. This specification is crucial for optimizing the pavement’s performance and longevity, as it directly endures the impact of traffic loads.
Freshly placed concrete is prone to segregation, a phenomenon where the cement paste separates from the aggregates, potentially leading to bleeding. The workability of concrete, which is directly related to its slump, significantly affects its resistance to segregation. Higher slump values often correlate with increased bleeding, resulting in a weak and porous laitance layer forming on the pavement surface, while the aggregates settle at the bottom.
Conversely, a low-slump concrete minimizes bleeding, ensuring a denser and stronger surface layer with enhanced abrasion resistance. This superior surface quality is pivotal for withstanding the constant wear and tear of traffic, ultimately extending the lifespan of the pavement.
Furthermore, low-slump concrete proves advantageous when constructing concrete pavements using slipform pavers. Its lower water content helps the concrete maintain its compacted shape as the paver moves away, preventing surface deformation and guaranteeing a smooth and even finish. Conversely, high-slump concrete tends to slump and deform at the edges, compromising the pavement’s overall quality.
In conclusion, the deliberate specification of low slump concrete for carriageways is a multifaceted approach. It not only maximizes surface strength and abrasion resistance but also facilitates efficient slipform paving. This holistic strategy ensures the creation of durable and long-lasting pavements that can effectively endure heavy traffic loads.