Abstract

The basic mixture of lightweight cellular concrete (LCC) consists of cement, water, and a stable foaming agent. It is generally classified as having a density of less than 50 pounds per cubic foot (pcf), which is less than both traditional concrete and backfill materials. LCC has gained popularity in construction due to its lightweight, self-leveling, and ease of production and placement. These characteristics have made LCC a popular lightweight backfill material for mechanically stabilized earth (MSE) walls. However, there has been relatively little research on the large-scale behavior of LCC as a MSE backfill. Therefore, large-scale test results defining failure mechanisms and the strength criteria of reinforced LCC are extremely valuable. In this study, a three walled test box (10 ft wide x 12 ft long x 10 ft high) was constructed to contain the LCC. Two 5 ft tall x 10 ft wide MSE wall segments were poured and cured, before being placed as the fourth wall of the test box. The test box was built with a steel reaction frame to reduce lateral deflections during testing of the LCC that was not in the direction of the MSE wall, thus creating a two-dimensional or pseudo "plane strain" geometry. The box was filled with four lifts of Class II LCC 2.5 feet thick with ribbed-strip reinforcements at the center of each lift. After the LCC was cured, two static load tests were performed by applying surcharge to the surface of the LCC using six hydraulic jacks. The static load tests compared the LCC behavior of an MSE wall in comparison with unreinforced LCC without MSE wall panels. Multiple forms of instrumentation were used to understand the behavior of the LCC during surcharge loading. The instrumentation also helped to characterize the strength criteria for LCC based on failure in the large-scale and laboratory testing. This was done to determine the failure mechanism for the MSE wall retaining system with ribbed-strip reinforced LCC backfill. Data was gathered primarily through lateral wall pressures, lateral wall deflections, and forces induced on the ribbed-strip reinforcements. The test results show that an MSE wall with LCC backfill can withstand significant surcharge loading with limited axial and lateral deformations. However, failure occurred at surcharge pressures of about 60% of the unconfined compressive strength. The use of a retaining system significantly increased the failure loads and produced a more ductile failure mode than Class II LCC with a free-face. The active pressures observed are similar to a granular material with a friction angle (ϕ) of 34°, Ka=0.28, and a cohesion of 700 to 1600 psf for Class II LCC. Likewise, failure of the free-face occurred at a value predicted by Rankine theory with ϕ = 34° and c = 1600 psf.

Degree

College and Department

Ira A. Fulton College of Engineering

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