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  • Author: Carmen Răcănel x
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Abstract

The benefits of WMA technologies include reduced fuel usage and emissions in support of sustainable development, improved field compaction, which can facilitate longer haul distances and cool weather pavement, and better working conditions. Since this is a relatively new technology, it is necessary to determine the behavior and the performances of this type of asphalt mixture depending on additive percent.

These technologies tend to reduce the viscosity of the asphalt and provide for the complete coating of aggregates at lower temperatures. WMA is produced at temperatures 20 to 30°C lower than typical hot-mix asphalt (HMA).

The paper presents the results obtained in the Road Laboratory of Technical University of Civil Engineering Bucharest on an asphalt mixture with fibers (MASF16) prepared according to the “warm mix” technology with chemical additive. Different percent of additive are used in laboratory to draw up the “master curves” of asphalt mixture obtained by 4PB-PR stiffness modulus results.

Abstract

“Warm Mix Asphalt” (WMA) is a technology developed to obtain an asphalt mixture at lower temperatures. The method has significant benefits for the economic and environmental area.

As known, “warm mix asphalt” uses additives in bitumen having the purpose to reduce the viscosity in order to decrease the mixing and compaction temperatures.

Hot mix asphalt used in the airport area, especially the area of taxiway and the apron must satisfy beside usual requirements for roads, some requirements related to fuel resistance and de-icing agents according to European norms.

Does warm mix asphalt for airport use meet the requirements according to European norms? This is the question from this paper which aims to determine the characteristics of asphalt mixtures for airports BBA16 when using or not using an additive, considering a series of laboratory tests: cyclic triaxial compression test, fatigue test, stiffness modulus test and resistances to fuels test.

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.

Abstract

As a result of the economic crisis of 2009-2010, the road traffic on the national road network, for the period 2011-2014, decreased considerably. Thus, the evolution coefficients, for the period 2020-2025, registered a trend of decrease in road traffic.

Based on the analysis of the results of the automatic traffic records, it was found that the average daily average traffic increased by about 4.7% in 2016 compared to 2015 (the year of the last general circulation census) and is in continuous growth, one of the reasons being removal of car registration tax. In 2015, for the development of evolution coefficients and the rates of evolution of traffic on the national road network, the linear regression method was used which took into account both the evolution of road traffic reported in 1995, 2000, 2005 and 2010, as well as the evolution of road traffic on the traffic counters network for the period 2010-2015.

The paper analyzes aspects of the efficiency of the method used until the present and the need to develop coefficients and rates of evolution based on more complex methods, based on several economic and social indicators, including the projected evolution of GDP.

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.

Rezumat

Mixturile asfaltice sunt materiale compozite realizate din amestecuri de agregate naturale sau artificiale, filer și bitum, avȃnd la baza dozaje bine stabilite și o tehnologie adecvata astfel încȃt să rezulte un material rutier cât mai durabil posibil.

În urma studiilor efectuate pe plan internațional cât și pe plan național, s-a demostrat că se pot înlocui cu succes agregatele naturale cu zguri siderurgice sau de oțelărie, care prin prelucrare și sortare la dimensiuni necesare sunt cele mai adecvate din punct de vedere al proprietăților fizico-mecanice.

Mixturile asfaltice ecologice obținute prin înlocuirea agregatelor minerale cu zguri siderurgice vor intra în alcătuirea structurii rutiere, începand cu studiul pentru un strat de bază. Pentru evaluarea performanțelor mixturilor asfaltice în care agregatele naturale sunt înlocuite cu agregate artificiale, se va studia o mixtură asfaltică pentrul stratul de bază respectiv AB 31.5 pentru care se vor face încercări pentru trei rețete de mixturi asfaltice: mixtura asfaltică cu agregate minerale de carieră, mixtura asfaltică în care agregatele minerale vor fi înlocuite în proporție de 50 % cu zguri siderurgice și o mixtură asfaltică care va conține zguri siderurgice în proporție de 100%.

Încercările de laborator se vor face în cadrul Laboratorului de Drumuri din cadrul Facultății de Căi Ferate, Drumuri și Poduri, Universitatea Tehnică de Construcții București; rezultatele obținute vor fi detaliate sub forma de tabele și grafice, concluziile urmând a face aprecieri asupra performanțelor mixturilor asfaltice ecologice. Astfel, se vor stabili performanțele mixturilor asfaltice ecologice comparativ cu calitățile mixturilor asfaltice clasice, folosind următoarele încercări: determinarea densității aparente, a volumului de goluri, caracteristicilor Marshall și a modulului de rigiditate.