1. What is hydrodemolition?
BY JOHN MACLACHLAN

2. What is hydrodemolition?
Hydrodemolition uses high pressure water jets to remove deteriorating concrete from structures like bridges and roads.
It is used the world over by those in the civil and environmental engineering industries.
It is regularly used during the development of vital everyday structures such as roads, buildings and bridges

3. Types of hydrodemolition
There are two types of hydrodemolition; handheld and robotic.
Handheld hydrodemolition:
Consists of an operator and a machine
Similar to power washing but on a much bigger scale
Can be very physical
Better for smaller scale jobs that can be completed in a matter of hours
Robotic hydrodemolition:
Consists of a robotic machine
Focuses on cracks in concrete, blasting affected concrete away
Most effective method, used regularly on road surfaces
Operators only required for setting up and monitoring
Systematic and ensures concrete is removed efficiently

4. Why is it so important?
The main component of the reinforcement structures of things like car parks, bridges and roads is steel, which tends to corrode over time.
This corrosion has a knock-on effect on the concrete which surrounds the steel, resulting in cracks and eruptions in these vital structures.
If these problems were left unattended they would have a huge effect on our daily lives.
Hydrodemolition is used to safely remove the concrete which surrounds the steel so that it can be repaired without having to demolish then entire structure, thus minimising any disruption to our everyday lives.

5. The process of hydrodemolition
Hydrodemolition was first introduced in the 1970’s with the main intention of restoring and refining structures without damaging them.
The process selectively removes deteriorated concrete from the surface of a structure without harming any other part of it.
It leaves only the good concrete intact.
This is achieved by attaching a highly pressurised head to a machine which projects powerful jets of water.
The water removes any diminishing concrete.

6. Historical methods of concrete removal
Prior to the introduction of hydrodemolition, contractors used methods such as Jackhammering and Rotomills.
Such methods had big disadvantages:
They removed sound concrete as well as bad concrete
They caused residual damage to the remaining structure as a result of the strong vibrations they produced.
Remaining concrete often became cracked as a result of these processes.
They created large quantities of dust and noise.
In an attempt to avoid these negative outcomes, hydrodemolition was created.

7. Advantages of hydrodemolition
Unlike historical methods, hydrodemolition produces minimal noise and dust as the water jets act as a deterrent.
Hydrodemolition is a much safer, greener method of demolition because of this.
The use of water jets also means there are no potentially dangerous or damaging mechanical vibrations.
Hydrodemolition does not impair the remaining structure or ‘good’ concrete.
It also leaves an optimal surface for the efficient bonding of any new material to the existing structure.