Mar 31

Maintenance Tips for Gunite/Dry-mix Equipment

A little planning and precaution always goes a long way in the success of a project and the life of your equipment.

For any given job, a gunite contractor and its crew will have, as a very minimum, to operate and maintain a gunite machine, a material nozzle and hose, water hose, air compressor and an air hose.

Lubrication is an essential part of maintenance

A good part of maintenance on new and used machines will involve regularly oiling various part of your equipment and replacing certain parts over time. That’s just the reality of operating heavy equipment! Another good thing to remember is that every part of the machine that touches material flowing through it will wear out the fastest. So let’s see what some of these are.

If you have a bowl-type gunite machine, you will eventually have to replace the wear plate, the wear pad and material outlet. But before you get to that point, you will need to oil the pockets of the bowl after having cleaned it first after each job so that you don’t get material accumulation. If you have a steel bowl, you will need to use a hammer and something like a chisel to dislodge dried leftover material. If you have a steel/poly bowl, flip it on its belly and pound it  all over using a rubber mallet then chip any small pieces left, after every job.

Over time, the wear plate will also start to degrade. How can you tell?  Grooves will be showing up on the plate and/or in the pocket surfaces which can affect the rotation of the plate. When this happens, you should have a company resurface the plate.

Another part that will also show sign of deterioration is the wear pad due to its contact with the material. Don’t wait to replace it because it will cause faster wearing out of the wear plate if left damaged. It will also affect the quality of the air flow into the system.

DON’T: Tighten the hold clamp to try to extend the life of the wear!
DO:  Replace the wear pad as soon as it shows signs of slight deterioration.

There is also a piece of felt that protects the wear plate from the bottom of the hopper that should be lubricated until it becomes flexible and seal. No need to take anything apart to reach the felt, just use the holes in the hopper to do the lubricating. Having well oiled seals will prevent dust from escaping and create a safer work environment for your crew.

DON’T: Ignore an accumulation of dust next to your gunite machine. This is a sign that something is not working properly and needs to be checked.
DO: Replace the felt piece with a new one.

What about the air motor? The air lines comes with a filter and lubricator. Without the filter, the air that goes into the motor wouldn’t be clean and the lubricator puts a small amount of oil into the air. Both are required for the motor to function properly. As with all filters, you will need to check it to see whether or not they need to be replaced. Make sure to regularly inspect and adjust the oil level of the air lubricator.

Most gunite machines are connected to a gear box which will also need to be oiled. Some models come with an exhaust chamber that needs to be emptied out on a daily basis. The idea is to remove anything that could end up in the hopper base and could prevent rotation in the feed bowl.

DON’T: ever reach inside the hopper with your hands or arms while the air line is connected because the agitator could be moving.

DO: Connect an extra exhaust hose to the machine to bring down even more the level of dust on the job site.


What about hose accessories and nozzle maintenance?
The one more important piece to take care of in a nozzle is the water ring, usually made of brass or aluminum. You must inspect the tiny holes in the ring before starting any job and make sure there is nothing clogging them from a previous job. When cleaning the holes is no longer possible it is time to replace the ring.

DO: coat the water ring with some oil for extra protection
DON’T: ever drill holes in the water ring if the original holes are no longer working.

To eliminate any potential defects which cannot be seen by visual examination or in order to determine certain characteristics of the hose while it is under internal pressure, we suggest you conduct non-Destructive Hose Pressure Tests

Airplaco PG25 Gunite Machine

If you are looking for a  great gunite machine for your next job, give us a call at 503-281-2105 and we can help you find a perfect fit.

Mar 07

Best Concrete Pumps for Building a Gunite Pool

Luxury pools

Since we are experiencing one of the worse winter in decades in most of the US, we thought we would talk about swimming pools! Native Americans do rain dances during droughts, we will invoke milder weather through visions of gorgeous swimming pools!

In terms of types of swimming pools, gunite pools are, by far, one of the most popular types of pools built in the US. One of the reasons is that they are super durable and can be built in any shape or size. To build a gunite pool there are basically 9 steps you must follow, they are:

  1. Obtain permits
  2. Design layout
  3. Excavate
  4. Put plumbing in place
  5. Assemble & lay the steel framework
  6. Spray the concrete shell
  7. Apply finish coat
  8. Lay Tile/coping stone
  9. Place decking and pool finish

Since they are many other good articles that cover steps 1 through 4 and 8-9, we will focus on the gunite process itself. Once the framework grid has been assembled and laid (using 3/8 inch steel rebars), you are now ready to spray a thick coating of gunite (a mixture of cement, sand and water), around the reinforcing rods that are usually spaced 10 inches apart and secured by wire. The concrete sprayer machine combines the dry mix with water just before spraying.

After the shell is applied, a crew will smooth out the surface using trowels and let it sit for about a week before adding a finish coat because the surface will be rough and uncomfortable to the touch. At this point, some companies wet down the shell once or twice a day for a week to help the curing process. There are many types of finish like tile, fiberglass but plaster is one of the most popular ones (a mixture of marble sand and cement), and concrete paint is another good option.

Now that we are a little clearer on the overall process what are some of the best concrete pumps for the job? We recommend the following:

The Mayco LS-400 Concrete Pump

Mayco LS400






The Olin 545-65 

Olin 565 Concrete Pump







The Reed B50 HP 

A Reed B50 ready to ship








The Schwing BPA 450-500

Schwing BPA-500 concrete pump








The Putzmeister TK40-50

Putzmeister TK40








So, why these pumps?
First, they are all medium size pumps, so they can easily being towed behind a pickup truck carrying all the needed hoses and accessories.

Second, these models are not only easy and quick to setup, they also have a low hose pulsation, meaning the hose doesn’t vibrate or shake very much and greater safety for the crew.

In terms of power, they can output 7-15 yards per hour, so you will have more than you need.  Another important advantage these four models offer is the ability to pump long distances, no matter how far your ready mix truck happens to be parked on the street. You get perfect mobility which is always a plus for this type of job.

Still have questions? Don’t be shy! Just call Dick Hibbard at United Equipment Sales at (503)283-2105. He can help you solve problems,  find the perfect machine for your next job! Or visit: for more details.

Jan 30

United Equipment Sales Expands Its Operations!

Moving into a new home is considered to be a life event, but when you move 40 years of business, a warehouse and its entire inventory, it takes a move to an entire new level! So when we decided to move to a new and larger facility, we knew that it would temporarily disrupt our business so we chose a quieter period. We ended up not only expanding our working space, but also upgrading some of our office equipment, software that was in serious need of upgrade. More space means more machines, more business, more custom repair which have kept us busy, busy, busy!  And that’s a good thing!

So, we have put together a short video tour of our new 13,000 sq ft facility. You’ll get to meet Dick Hibbard, a.k.a. Mr. Concrete Pump! See our certified mechanics take concrete pumps in dire need of TLC and bring them back to life!

Our PARTS SHOP has everything you need!

Parts Shop

Clamps, couplings, reducers, gaskets, nozzles, elbows, adapters, welded groove ends, hoses of all sizes and much more…


Rich runs the repair Shop






Talk to Rich in our Repair Services if your pumps or hoses need to be repaired or have some custom work done.

Our staff is here to serve you and your business.

Meet The Team!

Our company mascot and official greeter couldn’t make it for the group photo, so here she is in her command post:


 If you are in the area, come by and visit us, we would love to see you!
Or call us at: (503)283-2105


Jan 04

Minimize Rebounding in Shotcrete

Shotcrete, a.k.a gunite, is a wet mix technique that produces a high velocity cone-shaped spray pattern via pneumatic mechanism onto a horizontal or vertical surface. Increase the air from the shotcrete nozzle to increase the velocity and the compaction of the particles and produce a denser concrete. Shotcrete uses either aggregates or mortar.

When to use shotcrete?
When you need to apply concrete vertically but do not want to deal with formwork and poured in concrete. Shotcrete works best for covering or repairing curved surfaces like swimming pools, bridges, tunnels, dams, slope reinforcement…

Strength of Shotcrete
Shotcrete uses a wet mix so the water/concrete ratio is very important and controlled by the nozzle man. It needs to be low (under 0.5) to obtain a denser and water-resistant mix.  This will also help reduce shrinkage and lower permeability in the finished product.

What is rebound?
One of the problems with shotcrete is the loss of material from concrete ricochets off the target surface due to the high velocity of the spray. This causes having to use more concrete, longer application times etc. The result can be vastly different when it comes to the properties of the in-placed concrete mix. If you use steel fibers as a distribution solution, the problem is even more problematic than with aggregates. According to Austin and Robins (1995), aggregates rebound is about 20-30% whereas with steel fibers, rebounding can reach 35-78% (Morgan et al., 1987; Banthia et al., 1992) with dry-mix shotcrete. With such high rebound, compaction is reduced and the concrete strength ends up greatly compromised.  The rebound of non-adhering material during a gunite operation (using a dry process) is greater than during a shotcrete job (wet process) because gunite requires a much larger air compressor. On a gunite job, the rebound material can be reused, whereas, on a shotcrete job, the non-adhering material is wasted. Removing it is time consuming, slows progress and can be costly. So choosing the right technique for the job is essential.

Thick or thin applications?
It turns out that the percentage of loss is affected by the thickness of the layer sprayed. In other words, the thinner the layer of shotcrete, the larger the percentage loss. The highest amount of rebound happens in the first spray on concrete. With subsequent coats, rebound diminishes. Another factor affecting the rate of rebound is aggregate density. A lower density will result in lower rebound rate.

Some solutions
Some polymer additives (Etonis) or modified starches can improve the adhesion and flow properties of concrete and reduce crack formation.

What pump is best for your job?
 If you are not sure what concrete pump is best for your next job, call Dick Hibbard at (503) 283-2105. With over 40 years experience in all things concrete, no question is too simple or too complex for him!

Some great pumps he recommends are:

Schwing WP 1000 concrete pump

A Schwing Wp-1000X






A Reed B-50 or C50Hp

Reed B50 and C50HP concrete pumps







Check all the great deals he has on Mayco, Schwing, Olin, Reed and Putzmeister used shotcrete pumps on United Equipment Sale’s website:
If you you need a gunite machine, check our site for our latest great deals.

Reference material
Parametric Studies on Fiber Rebound in Dry-Mix Shotcrete
The American Shotcrete Association
Polymer modification of shotcrete