Ready-Mixed Foamed Cellular Concrete as Engineered Backfill Material

Abstract

Backfill materials can be excavated soils, granular materials, or cementitious flowable materials. Depending on the application, backfill materials require specific properties such as workability for placement, resistant to settlement, minimum strength, and durability. Backfill materials must distribute loads to reduce vertical and lateral pressures on adjacent or underlying infrastructure components as well as existing materials. Historically, backfill materials are susceptible to poor quality control, high material heterogeneity and segregation, erosion, and sometimes excessive strength. Foamed cellular concrete (FCC) offers an alternative engineered material that can achieve a specified density and compressive strength while still providing superior placement efficiency and durability relative to traditional backfill materials. The density of FCC ranges from 300 to 1800 kg/m$^3$ and is achieved by the incorporating a high volume but stable air system inside the cementitious paste. Likewise, the compressive strength of FCC can be tailored from 10 to 130 kg/cm$^2$. FCC can be batched using traditional ready-mix equipment and only requires cement, water, and a foaming agent. Admixtures are beneficial to improve workability and paste stability properties while maintaining a reasonable cost. Other benefits of FCC for backfill applications are self-compacting and self-leveling, lightweight for reducing overburden, pumpability, erosion resistant, and thermal insulating, which makes it attractive for utility and drainage trenches, void filling, support layer for pavement patching, and for filling abandoned conduits.