The engineering of our infrastructure is ever changing. Line sections are being downsized or abandoned and re-routed. Flowable fill is an economical and reliable solution when faced with these issues. We have seen various flowable fill mixes in each county and town we have worked on, but the most common flowable fill has yields with a compressive strength of 125 psi at 28 days. Flowable fill with flyash is probably the most popular in the industry, but due to larger restrictions from the Government, we have seen a lot fewer companies offer the material. Instead, the industry is turning to foam balls or plastic balls to keep the concrete flowable.

First we will build bulkheads of brick at each end of the pipe, with a 2-inch diameter fill and vent line to pump the concrete mix into. Once the concrete is shown to come out of the vent line we know the entire line section is fully abandoned. At this point the abandonment or pipe diameter reduction is complete.

The only difference one may see when installing a smaller diameter pipe is that the flowable fill must be guided in a way so that it does not affect the invert of the pipe. It’s best to center the pipe in the line section prior to pumping with flowable fill; Or, filling the new smaller diameter line section with water prior to the flowable fill process. Filling it with water will keep the line section weighed down as the flowable fill pumping process is performed.

The amount of bulkheads usually has a large impact on the amount of flowable fill that may be pumped in one day.