Datorită degradării în timp a îmbrăcăminților rutiere, trebuiesc adoptate măsuri pentru reabilitarea acestora cu costuri cât mai mici. Una din soluțiile des utilizate îl reprezintă așternerea covoarelor asfaltice peste cele degradate. Problema principală care apare în cazul acestei soluții este transmiterea fisurilor din stratul existent în covorul de protecție (fisurare reflectivă).
Adoptarea soluției optime în cazul straturilor asfaltice de protecție, din punct de vedere al comportării la fisurare, scade considerabil costurile de întreținere/reabilitare a structurii rutiere existente. De aceea sunt necesare studii experimentale efectuate în laborator, care presupune costuri mici, dar și o perioadă mai scurtă de timp față de sectoarele experimentale.
În cadrul încercărilor de laborator efectuate, s-a urmărit și măsurat parametrii fisurării: deschiderea și lungimea fisurii în mixtură, deschiderea fisurii betonului, deformația probei și numărul de cicluri. Interpretarea acestor parametri, prin stabilirea unor legi de evoluție a acestora, ne poate oferi o imagine a modului în care fisura se transmite din betonul de ciment prefisurat în stratul de protecție și apoi se propagă pe întreaga grosime a acestuia.
Se poate astfel stabili care este rețeta de mixtură asfaltică care se comportă cel mai bine la acest tip de fisurare, evitându-se astfel adoptarea unei soluții neadecvate care atrage după sine costuri ridicate de întreținere.
Maintaining the conditions for optimum exploitation of road networks is one of the primary activities of their administrators.
The basic elements for establishing the decision-making act, are obtained by the correct evaluation, from the technical and financial point of view, of what is necessary for the normal unfolding, without interruptions, and in complete safety, of the car traffic.
In the evaluation process, the managers must have at their disposal sufficient information, regarding the technical status of the road network from the administration, when and where it is appropriate to intervene and what maintenance and repairs operations should be performed.
Only in this way, road managers will be able to adopt the appropriate strategy so that the investment reaches the highest rate of return and of course falls within the limits of the allocated funds.
This paper presents A.D.T.S. (Automatic Determination of the Technical Status) application, designed using the Microsoft Access program. The application allows the determination of the technical status of the roads, storage, retrieval, updating and verification of information regarding the technical status of the roads. The information is kept in a road reference table, as a storage model in data banks, which can be used by public road administrators in their work, regarding the scheduling of works and justifying the need to finance road intervention works.
The implementation of road infrastructure projects often results in delays due to objective causes, with repercussions on the final execution deadline and with value implications. The use of critical path method for planning and the executin windows, will result in better time process management and optimization delays.
In Romania, with time, settlements located along the main roads have developed and transformed into linear towns, with significant local and connection traffic, important administrative, economic, commercial and touristic activities concentrated in the central area, as well as pedestrian traffic of over 200 pedestrians per hour in the main pedestrian crossings on the route.
The object of the present study is made by a series of junctions situated on National Road 1 in Busteni town, on a dangerous road sector. For this study, traffic measurements, simulations and suggestions for improving the existing situation were made.
Based on the simulated traffic flows, there were performed capacity analysis with PTV Vissim and Traficware Synchro softwares, and were developed appropriate planning solutions for the intersections, resulting in tables with extracted performance indicators based on micro simulation of the traffic values. Also planning solutions for horizontal design and proposals for traffic lights were made for junctions that can not operate under priority traffic on one direction or which are presenting traffic safety risk.
Based on the traffic data, it was taken in consideration the necessity to make planning proposals and to develop design solutions immediately applicable, with minimum intervention.
Solutions will refer to the geometric planning of the intersections, but with new plans and timings for traffic lights, including proposals for new equipment; regulating the traffic flow: development/ refurbishment of intersections and pedestrian crossings; optimization of routing programs in order to achieve a higher level of service and more efficient traffic control indicators; segregation of pedestrian movements by vehicles traffic, implementation of physical devices to lock / channel the traffic.
The paper follows the potential practice of fiber reinforced concrete (FRC) as a solution for airport`s runway pavements, in order to increase the bearing strength, resulting in decreasing the height of the concrete layer that is currently used.
Experimentally, the study focuses on the properties of fiber reinforced Portland cement concrete using 3 different percentages (0.5%, 1% and 1.5% of the concrete volume) and 4 different types of fiber (for 1% percentage – hooked steel fiber 50 mm length, hooked steel fiber 30 mm length, crimped steel fiber 30 mm length and polypropylene fiber 50 mm lenght), using as reference a plain concrete with 5 MPa flexural strength.
More exactly, the study presents the change in compressive and flexural strength, shrinkage, thermal expansion factor, elastic modulus and Poisson`s ratio over fiber type and dosage.
For the highest performance concrete (7 MPa flexural strength), it has been made a study using two methods for rigid airport pavements design (general method and optimized method), and one method for evaluation of bearing strength (ACN – PCN method), which is compared to a plain 5 MPa concrete. Furthermore, the decrease in the slab`s thickness proportionally to the growth of the flexural strength is emphasized by evaluating the slab`s height for a high performance 9 MPa concrete using both design methods.
In this paper will be presented the influence of high temperatures on asphalt street pavement in terms of the influence of temperature on permanent deformations and thus the technical condition of the streets, comparable to the effects induced on extra-urban roads.
Environmental factors are one of the mayn factors being assaulted in operation and road structures are very important in terms of the influence they can have on the state road transport technical infrastructure.
Will be presented differences between urban road structures (streets) and extra-urban (road) both in terms of construction, the demands of traffic and environmental conditions to which they are subject.
Road structures extra-urban and urban areas are required differently in terms of the environmental conditions of the location ambient different thereof, that is, when the streets they are inside localities and the built environment significantly affect road infrastructure, unlike in the case of roads where they are located just outside the settlements, reducing the effect of air currents accumulation pavement surface temperature.
To demonstrate the influence of high temperatures on the pavement were conducted laboratory tests on asphalt mixtures in order to demonstrate the occurrence of reduction of physical characteristics, with adverse implications on the performance of applications similar to traffic.
This paper evaluates the possibility of using artificial aggregates from blast furnace slag, considered industrial waste, which can replace, in a certain dosage, the natural aggregates in the composition of an AB 22,4 asphalt mixture. Furthermore, it is presented the possibility to replace the usual filler with powders from industrial wastes such as the desulphurization waste, generated by the combustion of the energetic coal.
Laboratory studies and researches are carried out according to prescribed techniques. For this purpose, for the evaluation of the performance of the asphalt mixture recipes will be evaluated by static and dynamic tests as described in AND 605: 2016.
The results of this study show the possibility of using asphalt mixtures with different dosages of industrial wastes in composition.
The results obtained from the laboratory tests have shown that materials from industrial waste can be used in the design of asphalt mixtures with the purpose of replacing natural materials, used in certain dosages, which demonstrates good behavior in interaction with the usual bituminous binder.
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.
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.