Abstract

Lightweight cellular concrete (LCC) is a mixture of cement, water and foam, with a density less than 50 pcf. This material is being used increasingly often in a variety of construction applications due to its self-leveling, self-compacting, and self-consolidating properties. LCC may be used as a backfill or structural fill in areas where traditional granular backfill might normally be used. This material may be especially advantageous in areas where the underlying soil may not support the weight of a raised earth embankment. Testing on the behavior of LCC when used as backfill behind retaining walls is relatively limited. The effects of surcharge on the development of active pressure material are unknown. Two large-scale active pressure tests were conducted in the structures laboratory of Brigham Young University. Each test was performed within a 10-ft x 10-ft x 12-ft box that was filled with four lifts of LCC. Hydraulic jacks mounted to a steel reaction frame provided a surcharge load to the LCC surface. In the first test, the LCC was confined on three sides by the reaction frame, while the fourth side was confined by a reinforced concrete cantilever (RCC) wall. Both vertical and horizontal pressures and deflections were measured to determine the effect of the surcharge load on the development of active pressure behind the wall. In the second test, the LCC was confined on three sides and exposed on the fourth. Surcharge was applied to this sample in a similar fashion until the LCC reached ultimate failure. Vertical pressures and displacements, along with horizontal displacements, were measured in this test. Sample cylinders of LCC were cast at the time the test box was filled. These samples were tested periodically to determine the material strength and density. It was observed that the LCC backfill developed active pressure most similarly to a granular soil with a friction angle of 34º and a cohesion between 700 and 1600 psf. The RCC wall was seen to add vertical bearing capacity to the LCC, as well as prevent the catastrophic and brittle failure seen in the free-face test. It was also observed that an induced shear plane in the material dramatically decreased the total bearing capacity when compared to a uniformly loaded specimen with no induced shear plane. The results of this study were compared with design parameters given in previous research, and new design suggestions are presented herein.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2021-06-16

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd11739

Keywords

active pressure, backfill, cellular concrete, surcharge

Language

english

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