Soil-Structure Interaction of Steel Fiber Reinforced Concrete Slab Strips on a Geogrid Reinforced Subgrade

Performance of slabs on grade is governed mainly by the mutual coupled performance of the slab stiffness and the subgrade support. The use of reinforcement geogrids to increase the stiffness and structural capacity of the subgrade support can be potentially advantageous, but is currently poorly understood, especially under frequent transient loading conditions. The objective of this experimental study is to investigate the beneficial use of geogrids as a reinforcing material in a loose subgrade. This paper presents the results of large scale laboratory tests on slab strips (300 mm wide × 150 mm thick × 2,500 mm long) supported on a reinforced subgrade. The slab strips contained either steel fibers or were reinforced with welded wire fabric (WWF), and are compared with earlier tests on an unreinforced subgrade. All slab strips were tested under a central point load and were restrained from uplift at the ends. Both monotonic and cyclic loads are considered. The geogrid increases the bottom surface cracking load of the slab strip, does not affect the top surface cracking load, and increases the ultimate load carrying capacity. The use of steel fiber reinforced concrete (SFRC) was successful in providing post-cracking strength to maintain slab integrity when compared to the WWF reinforced slab strip used in this investigation. A simplified analysis of beams on grade is carried out for the elastic and post-cracking regions, and predicted values for the SFRC slab strip under monotonic load are compared to the measured load-deformation response. The comparison indicates that the theoretical response underestimates the capacity of the SFRC slab strip.