Optimization of the Granular Mixture of Natural Rammed Earth Using Compressible Packing Model

Abstract

Rammed earth (RE) construction is an ancestral technique that allows for the building of durable and resistant constructions. RE buildings are sustainable and environment-friendly, and ensure energy optimization during the construction cycle. For these reasons, many of the following RE characteristics are studied: mechanical strength, seismic resistance, and thermal performance. However, the mix design of RE soils has been rarely studied. There is practically no scientific approach that allows for defining precise dosages of clay, silt, sand, and gravel used in RE materials. The broader aim of this article is to determine a scientific mix design method to find an optimal RE granular mixture. The compressible packing model (CPM) is applied to study the effect of every granular class on compactness and define the optimum mixture. Many tests have been conducted such as the Modified Proctor, compression test, and ultrasonic velocity pulse test to evaluate the relevance of this model. The results suggest many granular corrections for RE material that considerably enhance compactness and unconfined compressive strength (UCS). It was found that one granular correction provides a 137% increase in the initial UCS. Therefore, this approach enables the defining of which granular class is to be added or reduced to optimize the mechanical properties of RE.

Quantification and Optimization of Compaction Energy Used in Earth Construction: Case of Static and Dynamic Compaction

“…Nowadays, earth is still considered an attractive building material because of its good mechanical characteristics, its low carbon footprint, its durability, and its thermal characteristics. The mechanical properties of the used earth can be enhanced by various processes such as granular correction [1], stabilization with mineral binders [2], such as cement and lime, and chemical stabilization using geopolymers [3]. These processes allow to achieve good mechanical strength and ensure better durability by just studying the mix design of the used material [4,5].…”