Advantages with Conjet hydrodemolition method

The conventional way to remove damaged concrete using percussive tools is an extremely bad method: it is very time consuming; it damages the reinforcement steel and the aggregate; and it causes cracking in the underlying, sound concrete. What is more, it demands a great deal of extra work such as cleaning the reinforcement steel of concrete residue. Worst of all, a lot of sound concrete has to be removed in order to ensure that you get to the bottom of the rot.

No New Damage
With the Conjet method, you remove all damaged concrete at great speed -only the damaged concrete. And you do this without causing any new damage. Conjet was the first equipment of its kind to be approved by the National Road Administrations of Sweden and Norway as early as 1985. Since that time, Conjet has further increased its leadership in waterjet technology.

The photograph was taken through a microscope. The "white" crack is going from the surface through the cement paste and aggregate down into the concrete structure. This white line shows newly made micro-crack caused by percussive tools during so-called renovation.

A concrete surface removed using Conjet shows neither micro-cracks nor damage to aggregate. After pouring new concrete, a high level of quality is obtained.

Furthermore, the Conjet System is ideal for sensitive environments in which low noise- and vibration levels are stipulated.

Selective removal
Our method is called selective hydrodemolition. Some who sells hydrodemolition equipment claims that this is what they offer. But it is not always the case. A concentrated water jet of sufficiently high pressure can, by means of external brute force, easily cut holes in completely sound concrete, a technique known as water-milling, but determining the penetration depth has nothing to do with selectivity. This is a fact you should know about.

What distinguishes Conjet and true selective hydrodemolition from other methods is that Conjet applies minimal external force to the material. Conjet works on the basis of a crucial balance between water pressure and flow, jet movement and the angle of attack. In this way it forces water into the concrete, where it builds up an internal hydraulic pressure that lifts up the material, leaving the sound concrete fully intact. The reinforcement steel is left clean and free of rust and concrete residue.

Surface for perfect bonding

Damage spreads through concrete in a very irregular way. This means that, when the damaged concrete is removed, the surface should be left uneven and irregular. Not only does this roughness give a perfect interface for effective bonding, it shows that time and money has not been wasted removing sound concrete

This means that there is a clearly visible difference between a surface selectively hydro demolished by Conjet, and one which has been demolished using external brute force (water-milling). The rugged, uneven surface left by Conjet is a sign of quality. In other words, true selective concrete removal, to the right depth and quality level, should leave the surface looking ugly!

When hydrodemolition methods that employ external brute force are used instead of Conjet, the end result does not necessarily have to be worse. The big difference is that, with the other method, a great deal more concrete has to be removed in order to be sure that you get to the bottom of the rot. Apart from the extra man- and machine hours needed to do this, the costs of subsequent cleaning and site clearance rise proportionately.

Conjet, the Market Leader
There are of course occasions where true selectivity is not required. Sometimes, you might want to aggressively remove the material to a predetermined depth, or even to cut straight through it. On such occasions, you will be pleased to learn that Conjet is equally good at this kind of work.

By means of a minor pump modification and the selection of a more primitive program, you can turn your Conjet robot into an apparatus that is at least as efficient at raw demolition as all the others.

Conjet is the market leader, with more experience in hydrodemolition than any other supplier. All the component solutions that put Conjet head-and-shoulders above the competition are unique. They are the result of intensive and continuous product development.

Ease of use, accuracy of cut, and a proven record of quality and reliability have all contributed to the success of Conjet hydrodemolition equipment.

Summary of advantages with the Conjet method:

• One man, continuous operation.
• Selective removal to a preset "quality depth".
• Up to 50% better bonding on rough surfaces.
• Causes no vibrations or micro-cracks.
• 25-50 times faster than jackhammers.
• Removes concrete under rebars.
• Removes rust from rebars.

Safety and Quality
Safety is essential in all Conjet System's. Utmost care must be taken of water pressure over 1000 bar (14500 psi). Within the Conjet System's circuits and computer programs, safety features are built in. Even so safety equipment should be used, laws, regulations and instructions should be observed.

To ensure the best result and proper handling of the customers investment our service engineer will train and transfer the necessary know how to operators and local service men. This starting up training program can be held on or off site, depending on the customer's wish. In accordance with the high quality ambition of Conjet all equipment delivered from the Conjet factory has been thoroughly and individually tested. A signed test certificate is issued and supplied with the equipment. The supplied equipment conforms with the EU-machine directive and is marked in accordance. A full documentation package, spare part list, operating instruction and service instruction are supplied with the equipment. On request we can also issue an on site spare part proposal.

If you want to know more about the Hydrodemolition technique, read

Hydrodemolition for Bridge Repair
(Reprint from Nordisk Betong no. 2-3:1988).