SINGLE DRUM ROLLERS WITH SMOOTH DRUM

BOMAG ROLLERS AND THEIR DESIGNED CAPABILITY:

LIGHT ARTICULATED TANDEM ROLLER-These machines are generally designed with double drum vibration and double drum drive and normally work with one frequency. The machines range from 3 to 4.5 t with sufficient power to be used behind a paver with in put of 500 to 800m2 per hour on surface courses or300 to 400m2 per hour on base courses, depending on the asphalt mixture. They are therefore specially recommended for this type of application. A part from this there is another type of application for these small self-propelled tandem rollers, which are available in different designs and successfully used.

HEAVY TANDEM ROLLERS

Heavy tandem rollers with operating weights between 6 and 12t are used for the compaction of asphalt surface course, asphalt binder courses, asphalt base course and unbound base courses. They normally work with two amplitudes or two frequencies for an optimal compaction of different lift heights. Heavy tandem rollers are equipped with vibration automatic, a system which switches the vibration off when stopping the machine or when changing the travel direction, thereby avoiding transverse depression and unevenness in the asphalt course. Heavy tandem rollers are available with spit and non-split drums. Split drums reduce the risk of shoving and cracking when compacting in tight curves. Depending on the design one must differentiate between tandem rollers with articulated steering and pivot steering, which enable different modes of steering

COMBANATION ROLLERS:

The combination roller is a combination of pneumatic-tired roller and vibratory roller. The combination combines the advantages of the vibrating drum with the benefits of rubber tires, which have a kneading effect and seal the asphalt surface. One axle of the combination rollers consists of a smooth drum, the other axle carries smooth rubber tires. These rollers are also powered by air cooled diesel engines which drive the hydrostatic travel and vibration system. The rubber tires are driven in pairs by two hydraulic motors, ensuring adaption of the rolling speed differential when driving around curves. Single lever control, hydrostatic power steering as well as vibration automatic ensuring simple and safe operation of large combination rollers.

SINGLE DRUM ROLLERS WITH SMOOTH DRUM

Single drum rollers are self-propelled combination with a front drum and rear tires. The roller types are specially designed for soil combination, where high tractive power and grad ability required besides excellent compaction work. Front frame with drum and rear frame are connected by a central oscillating articulated joint. The rear frame carries diesel engine, drive elements and operator`s stand. The infinitely controllable travel system works hydrostatically via the rear wheel single drum rollers are normally equipped with drum drive. Depending on soil or rock material single drum rollers are used with pad foot drum

BOMAG COMPACTOR AND BASIC PRINCIPLES OF VIBRATORY COMPACTION:

BOMAG COMPACTOR AND BASIC PRINCIPLES OF VIBRATORY COMPACTION:

The BOMAG compactor has been approved as the best compactor in compaction technology for earthwork, highway and transportation engineering. It has performed well in soil, rock and asphalt compaction though compaction technology concentrates on enhancing the performance capacity of machines, on user friendly and environmentally compatible designs with extending the functional structure range of application. Electronic measuring and compaction technology as well as micro-processor controls. These machines integrated system enable an almost automatic control of compaction work and an optimisation use of equipment as well as a surface covering assurance of compaction quality. Better quality work is ensured for production with consideration of measuring and testing unit and use of the machine parameters for process control of projects .A development leap in control automation of vibratory rollers has been in fact achieved by the possibility to combine data of compaction quality and management. Further developments aim at the possibility to localise the roller position exactly via a position system suitable for practical application and to specify control and record the number of roller passes. The great present and future challenges of engineering technology prefer BOMAG to the current technology. Intended sequential volume special subjects and special application for BOMAG compaction technology are planned. This includes subjects such as the compaction of unbounded and hydraulically bonded base course and soil-binder mixes in highway and transportation engineering, the compaction of recycling materials, industrial wastes and household refuse, the compaction of cable and pipeline trenches ,backfill and embankments, as well the compaction sanitary landfill and mineral sealing. Quality assurance of work can be achieved by measuring, testing and good system recording. With the rotating eccentric masses mounted on or several drive shafts depending on system, BOMAG is designed for vibratory compaction to generate uniform, stable rotary vibrations. These vibration are transferred to the substrate through contact areas such as special pad feet, plates, roller drum either flat or liner. They act as dynamic forces in a spatially distributed manner with pressure and vibration increasing the physical-mechanical characteristics. Compaction of any ground should be taken under high consideration to avoid over compaction and poor test. The direct vibration systems from BOMAG unify the advantages of rotary and oscillatory vibrators. With the newly developed directed vibration systems rollers a long striven goal of development and important technological leap was achieved. 

ASPHALT LAYING AND INFLUENCE FACTORS:

In laboratory simulation as well as during the laying of asphalt the compaction process is influenced by a number of factors, which interact integrally in a very complicated manner and can only be examined separately in the analysis. Both the mixture components as well as the compaction temperatures belong to the factors with highest influence and leaflet on compaction of asphalt.

COMPACTION OF MIXTURE:

By experience, mixture  components and mineral aggregates in particular have the most significant influence on the compaction resistance. The mechanical properties of the mineral aggregates influence the compatibility in such a way, that ,due to their lower inherent friction and interlocking resistance, round particle mixture are easier to compact than mixtures consisting of crushed particle. Sand particle and chipping fractions thereby have the strongest effect, whereby the compaction resistance mainly rises with the increasing proportion of crushed sand or a  high content of chippings.

               With a decreasing coarse particle fraction bigger than 2mm the so-called mortar components(binder, sand, filler) gain a higher influence with mixture types composed according to the asphalt concrete principle, whereas the compaction resistance does not increase to such an extent when increasing the coarse particle content. Mixtures with a very high proportion of chippings( stone mastic asphalt and drainage asphalt) are also mainly influenced by the mortar content.

               The influence of the filler with its stabilising effect on the compatibility of the mixture is only of minor significance, but is effective in the entirety of the mortar components, whereby the compaction resistance of the mixture decreases with increasing mortar content. The  compaction resistance is highly influenced by the binder content, however, the grade of binder is only of minor significance. The sliding resistance on the binder film on the particle surfaces, which enhances the compaction of the mixture.

INFLUENCE OF THE TEMPERATURE TO ASPHALT:

The highly temperature dependent properties of the bituminous binder in turn result in a significant influence of the temperature on the compaction characteristics of the mixture. The temperature of the mixture is very sensitive influential factor, which has an effect in combination with the mixture composition and temperature dependent variable viscosity of the binder. With increasing compaction resistance the mixture specific critical compaction temperature rises to a  level, where an  effective compaction temperature must therefore not drop below a critical limiting value. The required minimum temperature is considerably higher than for easily compactible material. The critical temperature limits must be carefully evaluated by suitability tests and monitored during the laying and compaction of the asphalt by measurements

Under aspects of compaction practice the temperature shall be as permissible at beginning of compaction work, since this is of advantage for compaction effect. The top temperature limit is specified because the fact that the mixture must remain stable under the influence of the roller and that an effective particle redistribution and reduction of air voids occurs during compaction must be accomplished without any shoving or lateral displacement of mixure. Depending on the grade of binder the normal temperature when tipping the mixture into paver is 150-180c, the compaction temperature range approx..130-170c. In temperature range between 90-100c compaction must be finished, because a futher drop in temperature will result in an excessive increase of the binder viscosity, making compaction work almost effective.

ASPHALT FOR SPECIAL CONSTRUCTION METHODS:

VIBRO ASPHALT(ROLLED POURED MASTIC ASPHALT)

The mixture consists of approx.60% chipping,10% filler, equal proportion of crushed and natural sand as well as approx.6.4% binder B45. It is mixed at a temperature of approx.230c and transported with insulated special trucks. During laying with a paver the mixture is liquefied and compacted by vibration and chippings are subsequently spread over this poured mastic asphalt like surface and rolled in.

DRAINAGE ASPHALT(POROUS ASPHALT)

The mixture for drainage asphalt surface courses is combined of a high quantity of chippings with a highly resistant binder and mortar. It is then applied as a surface course on a dense substrate or an additional waterproofing layer. This type of asphalt is characterised by a higher content of air voids which enhances the drainage between the surface of  the carriageway and the vehicle tires.It also  changes the thermal conductivity and low temperature performance.

COLD LAYING IN THIN LAYERS:

Cold mixer asphalt consisting of mineral aggregates 0/3 to 0/8mm, water, polymer modified cationic bitumen emulsion and additives is mixed and placed with a laying weight of 10 to 30 kg/m cube (dry mass), using special self-propelled mixing and paving equipment. The necessary bonding between the layers requires an absolutely clean substrate.

HOT LAYING IN THIN LAYERS:

Hot placed thin layers consist of asphalt concrete, stone mastic asphalt or gussasphalt and are applied with a laying weight of 30 to 50 kg/m cube, depending on load and condition of substrate

ASPHALT VENEER COATS:

Asphalt veneer coats are placed on surface courses in order to seal these surface or enhance their grip.They are applied as so-called surface treatment or in form thin layers by cold laying. This treatment is applied as protection against moisture, mainly on low volume traffic areas(construction classes iv to vi), as well as for sidewalks and yards, but not as an independent surface course.

               For the surface treatment the substrate or the previously spread chipping are sprayed with bituminous binder agent and subsequently gritted once or twice with raw or coated chippings. Cold placed thin layers are mixtures consisting of mineral aggregates(high-grade chippings,high-grade crushed sand and reclaimed filler), polymer modified cationic bitumen emulsion, additives and water.

ASPHALT PAVEMENTS IN HIGHWAY AND TRANSPORTATION ENGINEERING:

Asphalt technology is used for pavements of high ways and urban roads, for junctions and interchanges, for bus and rail tracks, for multi-purpose traffic lanes, hard shoulders and median strips, cycle paths and footways, for traffic lanes in service areas etc.

               Pavements of traffic areas are built in form of asphalt surface courses, binder course and base courses to ensure high durability against stresses caused by traffic and weathering. The typical structure of asphalt pavement and their functional properties dipper according to design. The design and execution of highway and transportation areas is based on engineering requirements concerning load bearing capacity, stiffness against permanent deformation, frost resistance and evenness and the required profile of the pavement. Besides the pavement the highway construction also comprises the subgrade and the sub base influenced by static and dynamic traffic loads.

               This multi-layer system is stressed by load, time and temperature dependent shearing and bending forces and deformed in dependence of the stiffness of effective layers. The carriageway pavement must be designed and built for safe riding traffic under any load condition, whereby its stability shall not be at risk at any time. This design goal demands a constructive interaction of all effective layers and a low and uniform level of deformation. According to this principle the layers must have load distributing properties complying with the different possible types of loads and be able to mutually compensate overloads. These performance requirements depend on the stiffness of system, which in turn is depending on the strength and deformation characteristics of layers as well as the layer thicknesses including the thickness ratio of successive layers. This principle of the constructive interaction is met when the stiffness properties of the individual layers are adapted to each other in way that the system stiffness increases from the bottom upwards according to the course of stresses. The stiffness of the system changes because of permanent mechanical load applied by traffic in combination with local condition or seasonal climatic cycle. Particularly critical condition may arise during winter, when frost related non-uniform heaves occur or the stiffness of the sub-layers drops during thawing intervals. During summer, when warping stresses develop and the stiffness of the visco-elastoplastic deformable asphalt layers is reduced by high temperatures.

ASPHALT FOR SURFACING AND GENERAL REQUIREMENTS:

The required composition of asphalt for surface courses and binder courses depends substantially on type of traffic load and the construction class. Specifies normal aggregate sizes for asphalt binder courses and surfaces courses, as well as for various types of mixtures, depending on traffic load.

               The permissible laying thickness for the relatively thin surface courses depends mainly on the particle size of the mixer independently from the standardised thickness according to the design. The stability of asphalt surfacing (asphalt binder courses and surface courses) made of rolled asphalt can be improved by favourable adjustment of the proportions of chippings and crushed sand as well as the use of high-grade aggregates with higher proportion of crushed surfaces, whereas the durability can be enhanced by a perfect adaptation of the binder content to the air void content.

               Hard binder or low binder contents, as may be considered for high traffic loads, contribute to the potential of crakking.The stability and durability of gussasphalt depends to great extent on the interaction between binder and filler and their homogeneous distribution in chipping/sand particle skeleton. For the polishing resistance of high-grade chippings in surface courses and spreading of chippings. The deformation resistance of asphalt surface courses is substantially influenced by the temperature of the mixture and, during laying, by its cooling and reheating. During mixing and laying certain maximum and minimum temperatures must therefore be complied with dependence of binder grade and type of mixture.

NATURAL ASPHALT AND MODIFIED ASPHALT:

NATURAL ASPHALT-Natural asphalt is added to gussasphalt, stone mastic asphalt and mortar enriched asphalt concrete among others, e.g. as natural Trinidad-asphalt. These additives can enhances the stability of surface course or binder course and have a positive effect on processing and compaction.

ELASTOMERE MODIFIED ASPHALT:

The mechanical and elastic properties of rolled asphalts can be modified by adding caoutchouc or rubber. This improvement is particularly related to elasticity, adhesion strength, ageing resistance against water and weather influences as well as fatigue resistance.

POLYMER MODIFIED ASPHALT:

The use of polymer modified bitumen or the addition of polymers enhance the adhesive properties, the stability and elasticity and, when increasing the binder content, even the ageing resistance and durability against the influence of water and weather.

 

WHEEL EXCAVATOR:
It machine which is used to excavate tunnel, drainage and slope cutting.