Pullout resistance of geogrid and steel reinforcement embedded in lightweight cellular concrete backfill

Abstract

Lightweight Cellular Concrete (LCC) has been increasingly used as backfill material for retaining walls, ground improvement, and pavements due to its low self-weight, quick installation, and high compressive strength as compared with soils. This paper presents a series of pullout tests performed in the laboratory to investigate the pullout resistance of geogrid (extensible reinforcement) and steel strip (inextensible reinforcement) embedded in LCC. Pullout displacements and pullout forces were monitored using displacement transducers (DT) and a load cell during the pullout process. This study investigated the effects of age, normal stress, fly ash, the presence of a cold joint, and re-pullout on the pullout resistance and calculated the pullout resistance factors F* for geogrid and steel strip embedded in LCC. Test results show that for the geogrid embedded in LCC, the maximum pullout force increased as the normal stress increased. For the steel strip embedded in LCC, the maximum pullout force was independent of the normal stress and increased as the age and the cement to fly ash ratio increased. Test results also show that the presence of a cold joint did not reduce the pullout resistance, while the re-pullout test had lower pullout resistance compared to the original pullout test for the same specimen. The pullout resistance factors F* for steel strips were greater than those for geogrids and these factors decreased as the normal stress increased.