Introduction of Roller
Most construction sites require an anchored ground to perform. One of the principal common kinds of compaction equipment is the road roller. Rollers are a sort of construction plant utilized for compacting stuff like soil, gravel, sand, road surfaces, etc.
The material is compacted by vibration, impact loading, kneading, & direct pressure. There is a sundry separate range of rollers that work best for diverse styles of compaction.
Types of Rollers:
Different types of rollers are as follows.
- Cylindrical Rollers.
- Grid Rollers.
- Pneumatic Tyred Rollers.
- Smooth Wheeled or Static Rollers.
- Single Drum Rollers.
- Double Drum Rollers.
- Vibratory Rollers.
#1. Cylindrical Rollers:
It generally estimates around 1 m in diameter and 1.5 m long & generated ground pressure is around 7kg/cm2.
#2. Grid Rollers:
They encompass a network of grid-like steel bars which can even be ballasted with concrete blocks or steel adjuncts. These sorts of rollers are generally towed or pulled behind a tractor at speeds amidst 5 & 24 km/h
The grid design churns out a high contact pressure with bijou kneading venture on compaction job. They are most fitted on well-graded, boorish soils, disintegrated rocks, and for subgrade and sub-base road constructions.
#3. Pneumatic Tyred Rollers:
Pneumatic rollers are colossal, ride-on roller with series of rubber tires at the front or at the occiput part. The rubber tyre supplies 80% coverage area & invariable pressure disseminated throughout the breadth of the tires.
They are typically utilized for highways, streets, dams and might aid to shine a project, but additionally are extraordinary for cold-laid bituminous veneers & veneers of loose soil.
The pneumatic roller has the ductility to exercise contact pressure ranges from 500 – 700 Kpa or 7k g/cm2. The weight of the roller is 6-10 tonnes which are surged to 25 tonnes by ballasting.
The utmost bulk is acquired by 8 passes & the optimum speed of the roller retains somewhere between 6-24 km/h.
Sheepsfoot rollers are occasionally called padfoot or tamping rollers. They have innumerable rectangular-shaped lugs or “feet.” They’re adept in compacting soil & silty clay during a construction job.
The sheepsfoot drum’s weight might be surged by ballasting (with water, damp sand, or mounting steel sections). The area of each & every portion can range from 30 to 80 cm2. About 10-20 passes are required to provide thorough coverage.
Coverage Area is about 8-12 % because of boots on drums. Contact Pressure ranges from 1200-7000 Kpa. The soupiness of compacting layer is about 5 cm extra the length of every foot.
The factors that govern the quantity of compaction of soil are given subsequently:-
- The aggregate weight of the roller.
- Area of every lug.
- No of feet or lugs in touch with the ground.
- Total no of lugs per drum.
- Paramount pressure exercised on the soil when a foot is vertical.
- The density of the blended soil should be about 1.48 kg/cm3.
- Pressure on the feet maybe 4 to 7 kg/cm2 for light rollers and up to 25-70 kg/cm2 for brobdingnagian rollers.
#5. Smooth Wheeled or Static Rollers:
There are 2 kinds of smooth wheeled rollers: single & double drum roller. They are again noted as static rollers. Smooth wheel roller and vibratory rollers are basically alike.
Both have identical features. There’s just one point of distinction, i.e., vibratory equipment. Smooth wheel roller has no vibrator attached and is best suited to rolling of fragile aggregates and in compacting asphalt pavements.
#5.1. Double Drum or Tandem Roller:
The tandem, or double drum roller, has one steel drum at the front and another at the rear. As soon as the two drums move, the roller moves.
These rollers are adept in compacting silty or sandy or flat soil with gradual surfaces like asphalt but are not nominated for any distinctive job.
According to the number of wheels on the rear, it is of subsequent two types:
- Tandem rollers (having one wheel at the rear and one wheel in front)
- Three-wheeled rollers (having two wheels at the rear and one in front)
The weight of the tandem roller varies from 2 to 8 tonnes, and the two-wheeled roller ranges from 8 to 10 tonnes.
#5.2. Single Drum or Three-wheeled Roller:
They possess a steel drum at the front & 2 special wheels at the rear. Single drum rollers can toil at tighter spaces due to their bijou size. They are adept at creating foundations for buildings and paving highways or sidewalks.
The ground coverage is 100%. The pondage of the roller is surged by filling the within space of the drum with water or wet sand. This process is named ballasting. The ground pressure exercised by tandem rollers is about 10 to 17 kg/cm2.
The optimum working speed has been found to be 3 to 6 km/h, and about eight passes are ample for compacting 20 cm layer. Smooth wheel rollers are most fitted for blending stone soling, gravel, sand, hardcore, ballast & surface dressings. The paramount grade a road roller can climb is 1 in 5.
#6. Vibratory Rollers:
Vibratory rollers are nearly indistinguishable from smoothing wheel rollers aside from one major distinction: i.e., the vibrating component. Since soil, asphalt, and concrete have natural bare spaces, they will cause a vandalization to the structure of the building.
Employing a vibratory roller retains the building’s structural integrity. This style of the roller is usually fitted with 1 or 2 smooth surfaced steel wheels 0.9 m to 1.5 m in diameter and 1.2 m to 1.8 m wide.
Self-propelled vibratory rollers are now obtainable pounding from 4 to 6 tonnes. Vibrations are generally generated by the swiveling of an eccentric crankshaft present within it.
Vibratory rollers are utilized for compacting granular base courses. It’s frequently utilized for asphaltic concrete jobs. They have higher outputs and improved performance juxtaposed to other rollers but also generally come at a lofty cost.
Advantages of Roller Compacted Concrete:
The sturdiness of Roller compacted concrete pavements eliminates some ordinary issues. Pros of using Roller Compacted Concrete are:
- Brisk placement.
- Shorter haul distance.
- Small construction crew.
- Can resistance lofty temperatures.
- Heat isn’t evolved during the dehydrating of concrete.
- In this roller-compacted concrete rebar isn’t required.
- Roller compacted concrete requires the minutest nurture.
- Roller compacted concrete requires minimal maintenance.
- Roller compacted concrete is resistant to shoving & pushing.
- Roller compacted concrete brings forth substantial durability.
- Will not be affected by oil spills, fuels, and/or hydraulic juices.
- It may be used as a roadway after only 24 hours of being placed.
- This roller compacted concrete is gobbling less time for construction.
- This roller compacted concrete is cost-effective and brisk construction.
- Roller compacted concrete doesn’t buckle under ponderous concentric loads.
- Also, it reduces cement consumption as lissom concrete blends are also used.
- Also, it reduces cement consumption as concrete blends are routinely utilized.
- The cost of formwork is diminished or eradicated due to the layer placement method.
- There is not any concern about the discharge of lofty heat during the drying of concrete.
- Roller compacted concrete has a plain surface, and no pits & holes are contemporary in it.
- Roller compacted concrete surface is smooth & plain and there are also no potholes present.
- Roller compacted concrete doesn’t crumble under ponderous concentric loads i.e., can withstand massive loads.
- Transportation costs, placement, and compaction of concrete are minimized, as a result, the concrete is handled by dump vehicles, sprinkled by the bulldozers, and squeezed by vibration rollers.
Also, Read: Core Cutter Method | What is Compaction of Soil
Disadvantages of Roller Compacted Concrete:
Cons of using Roller compacted concrete are:
- Reveling of cracks.
- Adept workers are required.
- Smoothness is onerous to attain.
- Dams constructed or renovated with roller-compacted concrete may undergo water leakage.
- In roller compacted concrete dams, the drainage gallery often surges construction time and additionally surges costs.
- Although it’s accustomed to design RCC dams efficiently, in comparison to other dams because of the low-cost option, there are situations which will make RCC costlier.
- Situations where Roller Compacted Concrete might not be germane is when aggregate material isn’t considerably accessible, the foundation rock is of abysmal quality, or where foundation conditions can result in imprudent differential settlement.
Advantages of Road Roller:
The subsequent advantages of road roller are:
- They are secure.
- The road rollers are brawny.
- To engender a finish that’s easy to the eyes and effortlessly works out, the road rollers are utilized.
- The vehicles are effortless to utilize and to handle everything the project demands, the road roller is befitting.
Disadvantages of Road Roller:
The disadvantages of Road Roller are as follows.
- Cost is lofty.
- Noise is illustrious.