Permanent Sealing for the Water Bearing Cracks or Moving Joints in Concrete Structures

The construction industry has come across situations when the concrete structure has developed cracks and water has seeped inside. Also there are situations when the same crack starts behaving as a moving / dynamic crack by relieving the internal stress in the structure. Some times the Construction joints / cold joints also start leaking due to the movement of the structure due to development of some stresses. Now it becomes challenging to stop the leakage, as the waterproofing system employed has to resist not only the water pressure from the negative side (Exit side of water) but also the flexibility required for absorbing the stresses due to the dynamic nature of the crack / joint.

Koster KB-PUR® Injection System is a unique method introduced from Chowgule Koster (India) Construction Chemicals Pvt.Ltd.

The system is initiated with the injection of the KB PUR® IN I a two component water activated PU-Injection Foam into the crack, which stops the ingress of water and immediately thereafter is followed by injecting the KBPUR® IN II which is a flexible 2 Component polyurethane – Injection Resin which not only seals off the water but also remains permanently flexible.

The KB-PUR® IN I is water activated hydrophobic MDI based polyurethane foam. The system only reacts when it comes in contact with water, expands and converts into stiff closed cell, waterproof polyurethane foam. KB-PUR® IN I is free of solvents and fillers; it is resistant to hydrolysis and is suitable for use in drinking water areas (KTW-Test). KB-PUR® IN I consists of a resin and a special catalyst, supplied separately, to allow on-site adjustments of gel.

The KB-PUR® IN II is a solvent and filler free, low viscosity, 2 component, elastic polyurethane injection resin for sealing of dynamic / moving cracks. The KBPUR® IN II is permanently elastic and is designed to withstand continuous contraction and expansion. With flexible resin, the crack is converted into an equivalent of an expansion joint and movement can thus continue without leakage or damage to the structure.

Application Procedure

Mark and drill the holes on either side of the Crack / Joints in staggering manner and at a distance of 30 cm c/c on each side and at 45 degree angle, clean the hole and fix the packers and tighten it.

For dry joints KB-PUR® IN IIPU resin can directly be injected. But if the water is oozing out, then KB-PUR® IN I is injected first to stop the water by foaming.

Add the KB-PUR® IN I component A and B and mix thoroughly with a slow speed mixer until a homogeneous mixture is obtained (avoid mixing humid air into the resin). Inject the material with conventional single component pumps at high or low pressure.Always start at the bottom and continue upwards, if in doubt, go back and inject the same packer once again.

As soon as the KB-PUR® IN I comes in contact with water, it reacts and forms foam having 30 times volume expansion. Water will be replaced by the rigid closed cell foam and can no longer pass through the crack.

Mix both the component of KB-PUR® IN II and inject through another pump into the same port injected with KB-PUR® IN I. KB-PUR® IN II will replace the Foam and occupy the entire depth of the crack.

Case Study

In a classic example of Box Push Tunnel Sub - Way constructed at Virar Railway station below the busiest Western Railways, the Butt joint between the pre - cast tunnels started leaking and the problem Was aggravated due to the vibrations from the traffic. The joints were treated Vertically, Horizontally and Overhead by Koster KB-Pur® Injection System.

The joints were treated under water pressure with the KB-PUR® IN I - foam forming material and then with KB-PUR® IN II- flexible PU Resin.

Similar treatment was also adopted for the Moving Joints of large basements, settling joints of Thickener at steel plants, Cooling Towers of Power Plant etc.