Types of Compaction Equipment and Their Applications

 

Choosing the Right Compactor for You

Use this guide as your starting point when discussing equipment purchases with a White Cap associate. Then review the detailed info in this article to build-up your knowledge base.

Terms You Need to Know

Here are a few terms that you need to be familiar with when considering purchasing compaction equipment.
 

Frequency is the speed that an eccentric shaft rotates or the plate jumps. Each compactor operates at an optimum frequency to supply the maximum force. Frequency is expressed in vibrations per minute (vpm) for plates and blows per minute (bpm) for rammers. 

Amplitude is the maximum movement of a vibrating body from its axis in one direction. Double amplitude is the maximum distance a vibrating body moves in both directions from its axis. The apparent amplitude varies for each machine under different jobsite conditions. The apparent amplitude increases as the material becomes denser and compact. 

Lift height is the depth of the soil layer, and it’s an important factor that affects machine performance and compaction cost. Vibratory and rammer-type equipment compacts soil in the same direction: from top to bottom and bottom to top.
 
As the machine hits the soil, the impact travels to the hard surface below, and then returns upward. This sets all particles in motion and compaction takes place. 

As the soil becomes compacted, the impact has a shorter distance to travel. More force returns to the machine, making it lift off the ground higher in its stroke cycle. If the lift is too deep, the machine will take longer to compact the soil, and a layer within the lift will not be compacted. 

Soil can also be over-compacted if the compactor makes too many passes. A pass is the machine going across a lift in one direction. Over-compaction is like constantly hitting concrete with a sledgehammer. Cracks will eventually appear, reducing density. This is a waste of man-hours and adds unnecessary wear to the machine.

Compaction Specifications

Here’s a topic that is rarely covered, but we would be amiss if we didn’t touch on it.

Contractors are usually given parameters for a project’s compaction specifications in one of two ways.

1.  Method specifications is an outdated version of detailed instructions and may include information such as:

 

2.  End-result specifications are the final compaction requirements detailed by engineers. These give contractors more flexibility and independence in determining the best, most economical way to fulfill the project’s specs.
This is most likely the type of specs you’ll receive because end-result specifications also allow you to use the latest technology.

Equipment Types

Rammers

Soils: Great choice for cohesive and semi-cohesive soils

Compaction: Impact, vibration, and kneading

Rammers deliver a high impact force (high amplitude). The frequency range is 450 to 800 blows per minute (bpm) on most rammers.

Some rammers with the highest bpm are classified as vibratory impact rammers and can also be used on granular and mixed soils.

Rammers are inclined at a forward angle to allow forward travel as the machine jumps.

Rammers cover three types of compaction:

1. Impact
2. Vibration
3. Kneading

An efficient rammer should provide:

• High impact power which allows the ramming shoe to come off the ground 2”–3”.
• Good balance making it easy to guide and good shock isolation to reduce operator fatigue.
• Durability to withstand the high stresses created in the rammer.
• Easy maintenance
• Dependability

Features to Look for When Choosing a Rammer:

Considerations when purchasing:

 

• Engine: Choose gas or diesel with a large piston set with two sets of springs. Some manufacturers are also offering battery-powered rammers, plates, and backpacks as an eco-friendly alternative with zero-emissions. Battery power is ideal for indoor applications and jobsites with noise and/or emission guidelines.
  
  Be wary of imported knockoffs and rammers with modified or recycled brand name engines that are intended for plate compactors and air compressors. Check with a White Cap sales rep about this year’s best-performing models.
  
  
• Bellows: This crucial part gives the rammer and its internal spring the ability to jump around at 700 beats per minute! Located below the gearbox, but above the rammer shoe, be sure to choose a rammer made with high-quality polyurethane and a strong spring.
  
  Avoid recycled and off-brand name bellows that may last less than 20 hours. Replacing a bellow can take up to four hours and cost over $400.    

• Fuel system: This influences your rammer’s longevity. You’ll want a diaphragm carburetor which adequately supplies fuel steadily to the rammer, no matter how tough the impacts and vibrations are. Also, choose a 3-in-1 fuel system which makes starting and stopping easy; just twist a knob and pull the recoil starter. Try to avoid rammers with a bull float carburetor; they gum up and jump sporadically.
  
  
• Parts availability: Knowing that parts are easily and quickly available means that you can keep your jobsite running smoothly and efficiently with minimal downtime.
  
  
• Price: This is always a consideration when buying anything, and high-quality tools are no exception. High-quality, well-made rammers that will last for years and handle the rough wear they’re designed for are going to cost more than rammers with recycled parts, knock-offs, and cheap imports. White Cap sales reps are trained on all name brand rammers that White Cap stocks and can help you select a rammer in your price range for your applications.
  
  Quality vs. force is a key consideration. Is the hardest hitting machine always the best? Usually not, and here’s why. Each jobsite has different requirements; there is no one-size-fits-all compaction equipment. Soil conditions and compaction specifications don’t always require the toughest, roughest, hardest-hitting machine. In fact, it is possible to over-compact the soil. Understanding the type of projects that you are usually awarded, the conditions, soil types, sizes, and compaction specifications will help you determine what kind of compaction equipment is needed.

 

Forward Vibratory Plates

 

Soils: Granular soils (sand and gravel), mixes of granular and cohesive soil, and asphalt mixes (hot and cold).  
 

Compaction: Vibration 

Applications: Road construction (drainage pipe systems, drainage collectors, culverts and curbing, pipe bedding and areas around services, e.g. drainage dewatering pipes),
and critical areas around surface water collectors which are susceptible to later settlements. 

This is the second most common piece of compaction equipment, and it’s also known as a “vibe plate.” It’s the least expensive compactor and can be easily loaded into a truck by two or three people. 

Engines: Choose either a gasoline- or diesel-powered engine. The engines drive one or two eccentric weights operating at a high speed to develop compaction force. Vibrations are created, causing the plates to move in a forward motion. The engine and handle are isolated from the vibrations, and they should be relatively steady. This is a benefit as it reduces operator fatigue. The heavier the plates, the more compaction force is generated. 

Frequency range is usually 2500 vpm to 6000 vpm. 

Asphalt plates have a water tank and sprinkler system to prevent asphalt from sticking to the bottom of the baseplate. 

 

Reversible Vibrator Plates

This compactor is considered to be the most versatile compactor. With the touch of a finger, an operator can throttle the reversible plate to move forward, positioning the compactor over areas that need more passes. 

Soils: Semi-cohesive 

Compaction: Forward or reverse travel vibration. Change of direction occurs instantaneously at full shaft speed without having to bring the plate to a full stop or put it in a neutral position. Reversible plates may be stopped and can maintain its force for “spot” compaction. 

Applications: Retaining walls, trenches, tight spaces, and deep compaction 

Smaller plates (100 - 400 lb.) are suitable for peripheral areas, cable trenches, sand bed compaction, sub-grade surfaces, and asphalt patchwork, but their main application is trench work and confined areas. Larger plates (over 700 lb.) offer high performance compaction for major surface compaction jobs and trench work. 

The plate design features two pairs of reversible eccentrics in the exciter housing. These plates are fully steerable at the touch of a finger despite being heavier than forward vibratory plate units. Their weight delivers a heavier compaction force. 

Cable or infrared remote control is available on some steerable plates. This feature offers added safety as the operator can stand outside or on top of a trench while the unit works inside the trench. This safety feature may save costly trench shoring in many places. 

A wide variety of plates are available ranging from 100 lb. to over 36,000 lb. making it possible to work on a wide size range of jobs. An experienced White Cap associate who is specially trained on compaction equipment can help you select the right plates and the right equipment.

 

Rollers (Walk-Behind and Ride-On Rollers)

Walk-behind — Popular for many years, these smooth drum machines are smaller than ride-on rollers, but bigger than reversible plate compactors. Dual steel drums are mounted on a rigid frame and powered by gasoline or diesel engines with manual steering.

Frequency is about 4,000 vpm. Amplitudes range from .018 to .020. Vibration is provided by eccentric shafts placed in the drums or mounted on the frame.

Ride-on — Configured as static steel-wheel rollers, ride-ons use tandem vibratory rollers with drum widths of 30” up to 110;” the most common being 48.” 

The ride-on roller is used for more industrial applications or large land areas for soil compaction. 

A wide variety of sizes are available, but the smallest still weighs one ton. 

Single-drum machines feature a single vibrating drum with pneumatic drive wheels. The drum is available as smooth for sub-base or rock fill or padded for soil compaction. Additionally, a ride-on version of the pad foot trench roller is available for very high productivity in confined areas, with either manual or remote-control operation.

Hand Tamper

As basic as a hammer, this simple tool is inexpensive and only requires some sweat equity to compact soil for small home projects such as walkways, small shed foundations, and mailbox posts.

Tips for Proper Compaction

Now that you have a better idea of the best compaction equipment for your applications, here are some tips and steps to make your soil compaction projects more productive. 

Retaining walls: This application needs to be heavily compacted so loose soil will not slide or cause the walls to break apart. Use a rammer or heavy-duty plate compactor. 

Roads and patchwork: Use a vibratory roller or plate compactor. 

Building foundations, sidewalks, and trench work: Compact with a jumping jack or tamping rammer. 

Always test your soil to make sure the soil is not too wet nor too dry but just right to be compacted. Here’s an easy test: grab a handful of soil, and squeeze it in your hand. If it doesn’t break apart and remains in one clump, then it’s ready for compaction. 

The most important step in construction is to have an experienced operator compact the soil.

White Cap can help you make smart choices by aligning the numerous compaction equipment options and jobsite conditions with our experienced sales associates. We’re here to help you!