Compression stress-strain curve of rammed earth: Measuring and modelling

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. Resultsshow 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.