Paper and Presentation by Juan Pablo Covarrubias, Carlos Binder & Victor Roco from ASCP 3rd Concrete Pavements 2015
A new methodology has been developed to design the concrete slab thickness by optimizing the slab size given the geometry of the truck axles, the design is based on an unbonded system with either granular, HMA, Stabilized or Concrete Base. The key principle of the design method is to configure the slab size so that not more than one set of wheels are on any given slab thereby minimizing the critical top tensile This solution has been used in over 100 projects in more than 6 countries, all with excellent results.
Mechanistic-based software, called OptiPave 2, has been developed to geometrically optimize the design of concrete slabs for any set of climate, traffic, layer, and material inputs. Critical tensile stresses have been calculated using finite element analysis for a variety of mechanical and thermal loading conditions and load positions. Slab cracking is determined based on the concrete fatigue and performance models utilized for the 2007 Interim AASHTO Guide and calibrated with the full-scale test sections. The design method also is able to efficiently design lower volume concrete roads that are not comprehensively covered with existing pavement design methods.
In some cases fiber reinforcement has been added to the concrete. This improves the structural capacity of the pavement, increases the fatigue resistance achieving further reduction of the thickness of the slab and simultaneously gives a better performance over its lifetime in the post-cracking stage. It also allows to control cracking settlements due to possible inhomogeneity’s of the supporting surface of the concrete slab.
An extension of the design of Ultra-Thin Concrete Pavement (U-TCP) with optimized geometry has been developed for low volume roads (up to 1,000,000 ESALS) with FRC and placed directly over the existing granular road, no base is required.
Five test sections of this UTCP system have been constructed to see the performance of 6 to 12 cm thick slabs. These tests were used to verify the behavior and calibrate OptiPave 2 ® under these extreme conditions.