The base course is the load-distributing foundation of many traffic and utility surfaces—from roads and paths to industrial areas, hall floors, and foundation slabs. It forms the connection between the subgrade and the surface course, ensures load-bearing capacity, drainage, and frost resistance, and significantly influences the service life of the entire pavement structure. In deconstruction and adaptation measures, the base course plays a central role: it is often to be preserved, locally strengthened, or selectively removed in an orderly manner. From a tooling and process perspective, concrete pulverizers as well as hydraulic rock and concrete splitters are particularly relevant, as they work with low vibration and under control in concrete demolition and special demolition, gutting works and cutting, and in rock excavation and tunnel construction, thereby protecting adjacent layers—especially the base course.
Definition: What is a base course
A base course is a layer of mineral construction materials (unbound or hydraulically bound) placed between the subgrade or formation level and the surface or wearing course. Its main tasks are load distribution from traffic or use, limiting deformations and settlements, water drainage, and frost protection. Depending on the construction task, the base course may be executed as an unbound base course (UGT), as a frost protection layer with a load-bearing function, or as a hydraulically bound base course (HGT). In paving and slab construction, the bedding layer lies above the base course; in asphalt and concrete road construction, binder/wearing courses or concrete slabs rest on the base course.
Structural variants and functions of the base course
Base courses are designed and constructed so that they transmit actions from use and the environment to the subgrade without overloading its bearing capacity. Unbound variants consist of well-graded aggregates with defined particle size distribution and sufficient permeability. Hydraulically bound base courses use binders (e.g., cement) to increase shear strength and stiffness. In both cases, degree of compaction, flatness, and uniform layer thickness are decisive. Typical layer thicknesses—depending on traffic load, subgrade, and climatic conditions—range from a few centimeters in light path construction to several decimeters in heavy-duty or industrial surfaces. In deconstruction or remodeling measures, the base course is often preserved when the upper concrete or asphalt layer is removed using low-vibration methods (e.g., with concrete pulverizers or stone and concrete splitters).
Structure of the pavement and functional relationships
The pavement structure usually consists of the subgrade/formation, possibly a frost protection layer or subgrade improvement, the base course, and the surface or wearing course. The base course is the structural link: it ensures homogeneous load transfer and protects the subgrade from moisture ingress and frost heave.
Load transfer and limitation of deformations
Through sufficient stiffness and shear strength, the base course distributes traffic loads over an area. Parameters such as deformation modulus (for example from a load plate test) and state of compaction describe performance. Well-graded aggregates and professional compaction are decisive here.
Water balance and frost resistance
A capillary-breaking, permeable structure limits water accumulation and frost damage. The aggregate gradation and fines content govern infiltration, while layer thickness and arrangement contribute to protection against frost heave.
Materials and types of construction
The choice of material depends on use, subgrade, and environmental requirements. The following types are common:
- Unbound base courses (UGT): Crushed rock or gravel blends with defined gradation, high compactability, and sufficient permeability. Common applications: paths, paved surfaces, driveways, and industrial areas.
- Hydraulically bound base courses (HGT): Mixes stabilized with binders for higher stiffness and reduced permanent deformations, for example beneath concrete slabs or in heavily loaded areas.
- Recycled construction materials (RC): Processed, quality-assured aggregates from deconstruction materials can be used as a sustainable alternative where suitable and meeting requirements.
Design, quality, and verification
The dimensioning of a base course is based on the imposed loads and the bearing capacity of the subgrade. Typical test parameters are degree of compaction (for example in accordance with Proctor methods), deformation modulus, and particle size distribution. Proven practices include staged placement in defined lifts, accompanying compaction controls, and flatness and thickness measurements. Requirements are derived from recognized rules of practice and project-specific specifications.
Construction and compaction
Uniform placement conditions, correct placement moisture, and coordinated compaction equipment are crucial for a durable, load-bearing base course. Placement is carried out in layers using suitable rollers or vibratory equipment. Particular care must be taken at edges and interfaces—especially with paving and slab surfaces—so that load transfer is not impaired by edge weakening.
Base course in deconstruction: preserve, strengthen, selectively remove
In concrete demolition and special demolition, base and surface layers are often separated selectively. The goal is to preserve the base course or improve it in a targeted way. Low-vibration methods reduce the risk of settlement or segregation in the base course. Tools that work in a controlled manner, with high clamping force, and without impact energy—such as concrete pulverizers and stone and concrete splitters—are particularly suitable; the required power is provided by appropriate mobile hydraulic power units.
Selective deconstruction of concrete slabs and foundations
When removing concrete slabs, hall floors, or foundations, a step-by-step approach can protect the base course:
- Expose joints or cuts and locate embedded items to avoid imbalances.
- Crush or split the concrete in a controlled manner, for example section by section with concrete pulverizers or stone and concrete splitters.
- Separate reinforcement and inserts, for example with Multi Cutters or Steel Shears, without disturbing the base course.
- Remove material, clean the base course, and check for flatness, compaction, and moisture.
This approach reduces vibrations and lowers the risk of fines being tamped into the pore structure of the base course.
Work in existing structures and sensitive environments
In remodeling within urban areas, above utilities, or at interfaces with existing structures, low vibration and dust emissions are important. The controlled biting off of edges with concrete pulverizers and the targeted splitting of components with stone and concrete splitters help protect the base course and adjacent components. This is also relevant in special operations, for example when working inside buildings, on bridges, or in areas with operation-sensitive infrastructure.
Base courses in rock excavation and tunnel construction
In rock demolition and tunnel construction, temporary and permanent driving and working areas are built with load-bearing, free-draining layers. Rock wedge splitters and stone and concrete splitters are used to release rock in a controlled manner and create an even, load-bearing sub-base. The resulting layers must conduct water reliably and accommodate varying loads. Homogeneous gradation and layer-by-layer placement are decisive for durability.
Base course in paving and path construction
Under paving and slab coverings, the base course ensures stable support and drainage. During redesigns—such as the reconstruction of courtyard or traffic areas—it is often economically and technically sensible to preserve the base course when the upper concrete layer is removed selectively. Tools such as concrete pulverizers enable edge-precise work without tearing up the base course. The base course is then profiled, possibly re-compacted, and prepared for the new use.
Repair and rehabilitation
Typical damage patterns include ruts, settlements, softening when wet, or pumping of fines. Causes often lie in insufficient compaction, unsuitable gradation, inadequate drainage, or overloading. Rehabilitation approaches range from partial removal and replacement of material, through profiling and compaction, to binder stabilization. Selective deconstruction with concrete pulverizers and controlled material recovery from existing structures support an orderly rehabilitation.
Sustainability and resource conservation
Preserving intact base courses reduces material and transport requirements. Qualified recycling of deconstruction materials can supplement the supply of aggregates. Methods with low vibration and dust emissions improve the environmental footprint and working conditions—an aspect that is particularly important in inner-city projects and in special demolition.
Occupational safety and general notes
When working on base courses, stability, traffic management, dust and noise protection, and the safe handling of hydraulic tools must be observed. Tests for bearing capacity and compaction should be carried out at appropriate intervals. The recognized rules of practice and project-specific requirements are authoritative. Legal and normative requirements must always be checked on a case-by-case basis and may vary depending on the project.