Stage grouting is not about pumping a predetermined amount of grout into a hole. Such an approach would result in the grout pushing away from the wall, which is not the desired outcome. The goal is to keep the grout close to the wall, as the purpose of this process is waterproofing, not soil modification or permeation grouting.
The stage grouting process begins with a cup test to determine when the grout starts to react and turn into foam. Typically 45 seconds to a minute is a good time but adjust as necessary for field conditions. At this point, it is recommended to pump a small amount of grout, perhaps a third or even a quarter of the planned total, into the hole. After that initial amount begins to react, another burst of grout is pumped in, and the process is repeated. The aim here is to slowly build a foam mass on the backside of the wall. This foam mass, once formed, will hold the new grout against the wall, allowing it to travel vertically or horizontally. This is the desired outcome, as it facilitates communication between the ports or holes drilled into the wall.
Stage grouting is a crucial technique in curtain grouting. Many issues arise when too much material is used without significant impact. Stage grouting allows for careful monitoring and slow, methodical application, ensuring that the grout is effectively used and serves its purpose. If, after several stages of grouting, no progress is observed, it may be necessary to move to another area. This could indicate an anomaly or unidentified voids. The key takeaway here is that the right answer is never to pump more grout when in doubt. The process should be slow, methodical, and thoughtful to ensure impact.
With technical expertise and reliability, the methodical approach of stage grouting emphasizes the importance of patience and careful monitoring in achieving optimal results. Remember, when it comes to grouting, the goal is not to use more material, but to use the material more effectively. Go slow, be methodical, think about it, and make sure you're having an impact.