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How pavements are affected by traffic and weather
Published in Maxwell Lay, John Metcalf, Kieran Sharp, Paving Our Ways, 2020
Maxwell Lay, Metcalf John, Sharp Kieran
A pavement meeting these requirements has three basic components. There is a surfacing which directly carries and services the traffic and protects the remainder of the pavement from the weather. The vertical location of the surface is governed by the required alignment of the road. Next, there is a basecourse (or roadbase) which provides the strength and stiffness needed to carry the traffic wheel loads for the intended life of the pavement. It may incorporate the surfacing function. It will commonly be constructed from imported material and may be comprised of a number of horizontal layers. The basecourse sits on a prepared surface known as the grade or formation level. The underlying material below the grade surface is called the subgrade. It is also sometimes called the subsoil or road foundation, but in this book, we will use subgrade.
Asphalt Equipment
Published in John E. Schaufelberger, Giovanni C. Migliaccio, Construction Equipment Management, 2019
John E. Schaufelberger, Giovanni C. Migliaccio
Asphalt pavement structures are constructed in layers, as illustrated in Figure 22.1, to improve the load-carrying capacity of natural soils. They distribute wheel loads over a cone-shaped area under the wheel to reduce the induced loading of the subgrade. The composition and thickness of each layer are selected to support the design load. The compacted subgrade may be imported material or natural material stabilized with cement or lime. The base course or layer generally is well-graded granular material. The asphalt pavement provides a wearing surface and waterproofs the structure to prevent surface water infiltration and subsequent weakening of the subgrade. The asphalt pavement also carries the design load and distributes it so it can be carried by the base material.
Flooding effect on granular road base material with clay subgrade
Published in Eyad Masad, Amit Bhasin, Tom Scarpas, Ilaria Menapace, Anupam Kumar, Advances in Materials and Pavement Performance Prediction, 2018
Road Pavement structures are constructed to support loads generated by traffic vehicles and to dissipate them safely to the underlying existing subgrade. The main structural failure mechanism considered in flexible pavement are rutting and fatigue cracking. Rutting is related to permanent deformation and is caused by an accumulation of irrecoverable strains in the various pavement layers. The deformation of subbase/base course plays vital role in the rutting failure of pavement. Hence, road construction technologies are rapidly advancing with time to meet the optimum structural requirement with low investment. In Australia, 80% of the total road network, that constitutes low or medium volume roads, have thin asphalt layer overlying on an unbound granular base layer on subgrade (Chakrabatri, 2002). High quality aggregates, which include crushed stone, sand, gravel or other durable materials of mineral origin, are not always available and/or cost effective for the construction of road base of flexible pavement. Hence, locally available low quality aggregates stabilized lightly with some cementitious binders such as cement-flyash mix are often used as an alternative.
Ground penetrating radar (GPR) applications in concrete pavements
Published in International Journal of Pavement Engineering, 2022
Alireza Joshaghani, Mehran Shokrabadi
The base course layer is an important layer in pavement structure that is made of unbound aggregates. Researchers have studied the relationship between dielectric properties of base materials, moisture content, and stability properties (Saarenketo and Scullion 1996). Moisture susceptibility was tested with a dynamic cone penetration (DCP) test, tube suction, and dynamic triaxial tests. Results have shown that using dielectric constant values, which represents free water in materials and the water content between aggregates, is a better method to characterise the mechanical and volume-related properties of the base course than the moisture content (Saarenketo and Scullion 2000). Lin et al. tried to provide a practical and reliable method to improve the soil condition under rigid pavements in a damaged airport runway (Lin et al. 2021). A ground-penetrating radar (GPR) and a falling weight deflectometer (FWD) were used to verify its effectiveness. Every aggregate has a particular relationship between dielectric value and moisture content due to the void concentrations. Higher dielectric constant values (>16) are suitable indicators for detecting potential defects in the layer (Saarenketo, van Deusen et al. 2000). Ranges of quality control for the unstabilized base are listed in Table 4.
Stabilisation of expansive soils subjected to moisture fluctuations in unsealed road pavements
Published in International Journal of Pavement Engineering, 2022
Jaspreet Pooni, Dilan Robert, Filippo Giustozzi, Sujeeva Setunge, Srikanth Venkatesan
Pavement structures of sealed or unsealed roads are identical as they support the same traffic load over a given subgrade. The spray seal adds no structural strength but rather improves vehicle traction and reduces moisture penetration. However, unsealed roads are typically designed for a 10 year design period and with low standards when compared to sealed roads due to limited funding and its coverage in the road network (Giummarra 2009). Unsealed roads commonly consist of a basecourse over the subgrade (Figure 1). The basecourse provides the pavement strength and additionally functions as the wearing course. The higher plasticity of a basecourse that acts additionally as a wearing course makes the pavement more susceptible to moisture damage. These roads are typically designed using an empirical design method that includes the below design procedures (Austroads 2009). Determination of subgrade strength at equilibrium moisture content.Determination of design traffic in equivalent standard axles (ESA).Determination of pavement base thickness from design chart.
Development of an artificial neural network (ANN)-based model to predict permanent deformation of base course containing reclaimed asphalt pavement (RAP)
Published in Road Materials and Pavement Design, 2021
Saad Ullah, Burak F. Tanyu, Binte Zainab
PD test has become an acceptable testing tool to investigate the response of base course material for the design of pavement structures. Existing literature reports that the vertical compressive strains in the base course can cause up to 70% of the rutting of the pavement surface (Korkiala-Tanttu et al., 2003; Little, 1993; Pidwerbesky, 1996). Therefore, a reliable constitutive model, to predict the response of the base course material under repeated load triaxial test, must be developed. During a repeated load triaxial test, the specimen undergoes three distinct stages of PD under set loading conditions regardless of the material type (NCHRP 1-37A, 2004). The first stage is called the primary stage characterised by high strain rate and is generally termed as post compaction deformations associated with volumetric changes, the second stage is characterised by relatively small and constant strain rate associated with volumetric changes and finally the tertiary stage which occurs as a result of shear failure under no volumetric change condition (see Figure 1).