Compression stress-strain curve of rammed earth: Measuring and modelling
Ahmed Koutous, E. Hilali
Abstract
This research article is about a study on the mechanical behavior of rammed earth under compression stress. The main purpose is to establish a simple stress-strain model for rammed earth. The tested rammed earthen materials are made of various local materials with different grain-size curves and grain shapes. Some of them are stabilized using cement and lime, or reinforced using barley straw and date palm fibers. The compression tests , the results of which are reported and analyzed in this article, were conducted in a monotonic manner on the produced cylindrical specimens at their almost dry state. For each compression test, the stress-strain curve is established, then the main mechanical characteristics are determined. These characteristics are the compressive strength , the initial tangent modulus , and the peak strain corresponding to the maximum compressive stress . Also, the secant modulus, defined as the ratio of the compressive strength to the peak strain, is calculated. Results show that, for all the tested materials, stabilized or not, the stress-strain relationships observed can be modeled as quadratic polynomial. On the basis of this stress-strain model, the stress limit of the linear mechanical behavior of rammed earth was established. This stress limit, stated as a percentage of the compressive strength , depends on the ratio of the secant modulus to the initial tangent modulus, which themselves depend on the component materials used to manufacture the specimens.