Quality assurance for rehabilitation of lateral connection with mortar in lined pipes
Towards the end of the 1980s the robotic rehabilitation of lateral connections had not reached a satisfactory level. The well-known spatula technique using resin and the hat profile technique proved not to be effective for all situations and even today still show a variety of weaknesses. With the development of the injection technique using cement based mortar, the sewer rehabilitation market entered a new era.
Whether it is a small area of damage, serious leakage, or where water inrush has actually disconnected the lateral from the main pipe, the system can still be used. In all situations high quality results are delivered with a long life of more than 50 years. However, the standard achieved is not only the result of the material and the rehabilitation system used, but is also strongly influenced by the skill of the operator of the cutter.
In order that a rehabilitation system could be developed and continually improved, it was essential to find a special type of mortar which would be waterproof, corrosion resistant and able to be processed through long and relatively thin hoses.
At that point, Hächler AG Umwelttechnik and Hermes Technologie Germany began to take the first steps towards developing a mortar and a robot that would work in combination to rehabilitate lateral connections in all situations and conditions. After many years of feedback from many users and a long series of field-tests, the combination of mortar and robot was ready to meet the market’s requirements.
Today the rehabilitation market can call on a hi-tech cement-based mortar: ERGELIT Kanaltec. The mortar demonstrates a very high adhesive strength on wet surfaces and has a bond-strength 3 times great than that of tiling adhesives. Today the robotic support technique in combination with ERGELIT-Kanaltec is used to deal with all common symptoms of damage. The system combination is able to permanently rehabilitate poorly connected laterals and keep them watertight for more than 50 years. Furthermore, this rehabilitation system can cope with any angular offsets. At last, a hi-tech robotic system with cement based injection mortar can easily ensure high quality rehabilitation in lined pipes.
ERGELIT-Kanaltec is an environmentally friendly product and it is compliant with EN 1504. Because of its material composition, the mortar can be used in all groundwater protection zones and even in its raw state it releases no pollutant substances into the environment. This has been investigated and proved by the leaching test carried out by the Hygiene Institute. In addition, the DIBT has also tested the ERGELIT-Kanaltec cF mortar for any pollutant substances, and confirmed that none were found. The DIBT approval certificate was issued many years ago, and because it is waterproof and corrosion resistant the mortar can be used in all domestic wastewater pipes.
The mortar’s compressive and flexural strength values exceed by far these values for the existing pipe and therefore the bond between the mortar and the pipework is much stronger than either the main pipe or the lateral connection. The tensile strength on concrete or vitrified clay pipes is impressive and on liners is most satisfactory. Also, the shear strength is outstanding. Therefore, a rehabilitated lateral connection repaired with ERGELIT-Kanaltec creates a good anchorage for the liner. However, realistically great tensile strength is not required, because the mortar is injected into the voids to create a form-locking system. Like a cork in a wine bottle, the mortar penetrates and grips all cavities, cracks and gaps.
Due to its viscosity the mortar is able to flow into the gaps between the liner and original pipe and seals the connection area permanently. The mortar is shrinkage free. It has also been subjected very successfully to the Hamburg flushing test. 50 cleaning runs were carried out at 130 bars containing granulate and 50 runs without, to test functionality. The result was that the rehabilitated connection only showed slight cosmetic damage. After the test, impermeability was tested according to EN 1610, and it can be said that in principle the connection can withstand a 100 years of mechanical stress.
As stated earlier, the mortar can be pumped long distances and can be processed in almost all temperatures, but in temperatures of -5°c special measures have to be taken.
During recent years thousands of lateral connections of all types and in all conditions have been rehabilitated. Today the suppliers can provide an impressive list of references. The mortar and its specifications are also described in GSTT information sheet Nr. 18. The water/cement ratio is very flexible. The mortar is very fine and its perfect grain size distribution is the basis for its impressive impermeability and its ability to cling to the tiniest cracks and holes. At present, there is no other system on the market that can ensure that the pipe voids are back-filled efficiently. Even in the worst cases such as where the lateral pipe or main pipe bedding is destroyed, the mortar will re-instate its functionally. Last but not least, the combination of the mortar and robot has no problem coping with even heavy ingress of water. At last the transport of the mortar is easy and processing places no danger at all. DWA M143-16.
Operators are in general well trained to deliver top quality work. However, often the preparatory work is not spelled out specifically in the tender, which will eventually result in it being accorded little importance. In fact, the milling work should be documented carefully with pictures and videos, which should then be approved by a project manager before the injection process begins. In order to ensure a high quality rehabilitation of the lateral connection it is absolutely crucial that the preparatory work is not pushed out of the picture. The system that is used to rehabilitate defects within the sewer network is only as good as the preparation that is carried out.
Robot and cutting tools
It is very important to use high performance robots and cutting tools. The operator is the person responsible for ensuring successful rehabilitation of the lateral connection. Therefore, it is very important that the operator is given the right robot and milling tools to work with. The simple reason being, the operator does the same job day in, day out, and therefore might get annoyed and frustrated by having a weak robot that is not capable of performing efficiently and fast. In addition, a hydraulic powered robot ensures that it is easy to mill the necessary groove, in which the mortar is to stick subsequently.
Lateral cutting tool Giant
If the milling work is carried out correctly, as successful repair will be the result.
Liner fixed points
The liner is usually installed with a small gap between the original pipe and liner. The structural inspection of the liner according to DWA M 143-2 also takes this gap into account. The gap leads to the problem of groundwater pressure around the lateral connection. Therefore it is important that enough mortar is injected between the gap of the liner and original pipe. This is assured by the EL 300/600, as the mortar is forced behind the liner and penetrates into every small crack, holding the liner firmly in place. The liner will be fixed to the pipe as if by bolts every 10 metres and can therefore absorb greater movements and temperature changes.
Contractor and contracting body are both equally responsible for maintaining a certain standard and quality of work. It has been shown which materials are available and that they are approved according to DIN 19573. Preparatory work should be done with care, as this is the key to every job in order to ensure a long lasting high quality result. In addition, it has been demonstrated that the system is also perfect for laterals in lined pipes and is ideal for creating a good fixed point.
We all have to work economically, but a cheap solution is a more expensive solution.
DIN EN 206-1 (July 2001), Concrete - Part 1: Specification, performance, proiduction and conformity.
DIN EN 1504-3 Products and systems for the protection and repair of concrete structures - Definitions, requirements, quality control and evaluation of conformity - Part 3: Structural and non-structural repair
CEN/TR 15697 Cement - Performance testing for sulphate resistance – Report on the latest technology (2008)
DIN 19573 Mortars for new build and rehabilitation in wastewater systems outside buildings – Draft version(October 2012)
DIN EN 15885 (March 2011) Classification and characteristics of techniques for renovation and repair of drains and sewers.
DIN En 1504 (December 2005) Products and systems for the protection and repair of concrete structures - Definitions, requirements, quality control and evaluation of conformity
DIN 1045-2 (August 2008) Concrete, reinforced and pre-stressed concrete structures - Part 2: Concrete - Specification, properties, production and conformity - Application rules for DIN EN 206-1 (Foreign Standard)
DWA-M 168 (June 2010) Corrosion in wastewater facilities and sewage pipes
DWA-M143-2 Rehabilitation of drain and sewer systems outside buildings: Part 2 Visual inspection
DWA-M143-3 Rehabilitation of drain and sewer systems outside buildings: Part 3 - Relining procedures in wastewater pipes and conduits
DWA-M 143-16 Rehabilitation of drain and sewer systems outside buildings: Part 16 – Robotic procedures for repairing wastewater pipes and conduits
DWA-M 149-3 Condition classification and evaluation of wastewater sustems outside buildings: Part 3 - Classification and assessment of condition
GSTT Information Nº 18 (2004) Specifications for mortars for wastewater pipes and local drainage systems
Indirect dischargers Regulation Part II Austria July 1998
RiLi-SIB Guidelines for the repair and protection of concrete sections