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Ştefan Marian Lazăr and Carmen Răcănel

Abstract

The judicious pavement design is the key factor in achieving the longest service life and the lowest maintenance and rehabilitation costs. It is based on the consideration of the phenomena in which the pavement structures are subjected to exploitation and the limitation of their destructive effects.

The aim of this study is to verify the possibility of implementing in the flexible pavement structures design practice of another design criterion based on limiting the bituminous mixtures creep phenomenon and that to be called: The criterion of admissible octahedral shear stresses in the bituminous layers.

Estimation of octahedral shear stresses is done with a calculation model based on finite element method, and hereafter referred to as 2D ASFEM (2D Axi-Symmetric Finite Element Model). The paper presents the results obtained by modeling several specific calculation assumptions for the behaviour of flexible pavement structures in service.

The study underlines the fact that the Octahedral Shear Stresses Ratio (OSSR) can be an additional design criterion to be taken into account when designing flexible pavement structures alongside other established criteria.

Open access

Ştefan Marian Lazăr and Elena Diaconu

Abstract

This paper aims to establish the interface conditions influence on the flexible pavement structures life. The methodology consists in using the interface constitutive model available in the Alizé calculation program to calculate the stresses and strains in the flexible pavement structures.

The design criteria related to limiting fatigue cracking of asphalt layers and permanent deformations at the subgrade level from the road bed are used to estimate the flexible pavement structures lifetime.

When calculating the critical stresses and strains, most mechanical design methods of the flexible pavement structures considers that the road layers at interfaces are perfect bonded or total unbonded.

Proper modeling of the interface binding condition is an important aspect in understanding the real behaviour of in-service flexible pavement structures.

Open access

Carmen Răcănel, Mihai Dicu, Ştefan Marian Lazăr and Adrian Burlacu

Abstract

Asphalt mixtures are mixtures of mineral aggregates, filler, bitumen and eventually additives in proportions determined by recipe designed in the laboratory. Asphalt mixtures used as base course are bituminous concrete.

The natural aggregates are granular materials of mineral origin that come from natural or artificial crushing of the rocks. In our country there are the various rocks: eruptive or magmatic rocks, metamorphic rocks, sedimentary rocks.

To the category of sedimentary rocks belong limestone. Sedimentary rocks are characterized by relatively high porosity and a pronounced stratification, which causes mechanical resistance to be low and vary by direction of load. Due to the structure less dense and weaker mechanical resistance, the limestone are used less in heavy traffic pavement structures.

This paper presents an asphalt mixture recipe for the base layer developed in the Laboratory of Roads from Technical University of Civil Engineering Bucharest (TUCEB), using limestone aggregates extracted from Hoghiz Quarry. The paper contains laboratory test results to determine the recipe and laboratory findings leading to the schedule of product.