Stable Flow, a Caltrans-approved and ASTM C260-certified product, not only provides a superior, noncollapsing, flowable fill, but also reduces labor, time, and material expenses. It allows for pours in a single lift up to 4 ft. deep in a single day. It achieves a 20 to 30 pcf density and 100 to 130 psi 28-day strength. Cellular Concrete Technologies. 877-828-1954.