Through our Infrastructure department, Gunite carry out the injection waterproofing and leak sealing of a variety of sub-terrain structures utilising polyurethane injection resin techniques that react with water to form a highly elastic, hydrophobic seal against water ingress. The resin reacts quickly with water and expands to produce an open-cell, rigid foam that is ideal for stemming water ingress at defects in concrete structures and both steel and secant piled walls.
There are numerous types of polyurethane in the marketplace all with unique characteristics, some are large cell and fast foaming to stop what we term as gushers and particularly large volumes of water ingress. In this instance the material needs to be fast reactive so not to get washed out with the high volume of water.
We also have a variety of closed cell slow reactive and highly flexible resins to inject fine cracks within reinforced concrete structures that are susceptible to heavy loads and or ground movement, in ground reservoirs or box culverts for instance.
All our resin injection technicians are directly employed highly trained and competent in specialist resin injection. Many of our directly employed technicians have high risk confined space entry certification, clean water, and dirty water cards for working within water utilities.
Gunite also utilise and install Poly acrylic resins for waterproofing of arches, bridges, and culverts. The acrylic gel resin can be applied to the outer face of a variety of structures to form a seamless waterproofing membrane and because of its low viscosity allows it to easily fall into the soil and concrete interface forming a highly flexible waterproofing membrane. This type of system is non-expansive and ideal for waterproofing ground slabs or stone bridges, retaining walls and or brick tunnels and culverts.
For the processing of reaction resins, the injection packers are equipped as standard with a high-pressure (HP) round head nipple with sealing cone. The opening pressure is approx. 15 – 20 bar, i. e. at this pressure the ball valve opens and the flow of the polyurethane resin into the structure begins.
Another possibility is to inject in the low-pressure process with an opening pressure of approx. 2 – 3 bar using the low-pressure (LP) nipple. As an alternative, the pan head nipple can be used, for which a sliding coupling is required on the machine side. The nipple with shut-off slide is a variant in which there is no opening pressure to overcome and thus the injection resin can flow unhindered. The use of high- or low-pressure processes depends on the requirements and complexity of the project.
