Each layer of pavement consists of soil filled from original soil and above it a SubGrade layer, namely the selected material which will be used as the base layer for runway, taxiway and apron pavement. Above that there is a Sub Base layer, which is a grandual layer of choice that is smaller than SubGrade, then Base Coarse is the layer that determines the pavement before the final layer or RIGID or FLEXIBLE top layer. In this article we will discuss a little about Base Coarse for RIGID PAVEMENT.

A. Base Coarse Function for RIGID Pavement

Reducing Bonding Stress from concrete slabs.

2. Reduces deflection at joints and cracked parts of concrete slabs.

3. Protects SubGrade against excessive Moisture (Water Content) and Vertical Strain.

4. Improve the Drainage layer function.

5. Provide a stable work floor during implementation.

6. Obtain surface flatness before casting the concrete slab.

B. 4 types of Base Coarse for RIGID Pavement.

1. CTB – Cement Treated Base

2. ATB – Asphalt Treated base

3. LCB – Lean Concrete Base

4. Grandual Base

C. In the state of Indiana, CTB, ATB and LCB are not used, because apart from being expensive, they also do not provide a very strong BONDED (adhesion) between the Coarse Base surface and the Concrete Slab. In Indonesia, Highway RIGID Pavement lays a plastic sheet over the LCB and under the concrete slab, so that the FRICTION is 0 (zero), and there is no BONDED between the LCB and the concrete slab.

D. In Indiana, Granular Base (Aggregate Base or densely graded crushed stone) is more often used as Base Coarse, because apart from being cheaper, it also provides a very strong bond between the surface of the Base Coarse and the Concrete Slab. As a result, the FRICTION between the Coarse Base surface and the concrete slab is also stronger, and the effect of CURING (the convex nature of the concrete slab during the day and concave at night) becomes smaller.

E. Concrete Slab Work, cement use in Indonesia is almost 2 times more than in the USA, to achieve the same strength. The reason is, in the USA requires gradation and cleanliness of Flexural Strength (fs) while in other countries they still use Compressive Strength (fc) and this is not a problem.

Note

1. In Indonesia, recently CTB has been widely used as Base Coarse for FLEXIBLE Pavement Runways, because they never thought that the price was expensive, and did not pay attention to the bonded/interface Shear Strength between the Base Coarse surface and the HMA Surface Coarse. It’s best to understand the correct Basic Theory.

2. Technical specifications for Airside Pavement layers in Indonesia are regulated in KP 14 of 2021