Rammed Earth with Straw Fibers and Earth Mortar: Mix Design and Mechanical Characteristics Determination

Maria Francesca Sabbà,Dora Foti,Mariateresa Tesoro,Cecilia Falcicchio

doi:10.3390/fib9050030

Abstract

Raw earth is one of the oldest building materials, which is suitable for various uses: from the construction of load-bearing walls to use for plasters and finishes. The presence of straw fibers can give different behavior to this material. The present paper illustrates preliminary sensory and qualitative analyses, and subsequent laboratory tests that allow the characterization of the raw earth material with straw fibers for rammed earth constructions through mechanized compaction and the identification of a compatible earth mortar. The raw material considered in this study is mainly clayey; for this reason, a mix design usable with the pisé (or clay) technique has been developed. Cylindrical samples have been made through a press and subject to unconfined compression and indirect tensile tests. The results of the tests showed consistent tensile and compressive strength values in the context of earth materials. At the same time, a study for the realization of a mortar with the same base soil was carried out considering four mixtures, in order to investigate the best compromise between workability, shrinkage and compressive strengths. The purpose of the study was to investigate the mechanical characteristics of the local material through preliminary and laboratory tests, to classify it according to the Unified Soil Classification System (USCS) and to verify its suitability for a possible use in the construction field.

Highlights

Raw earth is one of the most utilized materials in the world, as well as having been used by most ancient civilizations
Young’s modulus it was necessary to consider the value soil S3 through the following relations: of the maximum peak between 5 and 30%, through linear regression, since the literature σc − σt data were calculated under such φconditions
The results summarized specimen and Ft is the maximum force applied

Summary

Introduction

Raw earth is one of the most utilized materials in the world, as well as having been used by most ancient civilizations. Raw earth buildings were among the first capable of guaranteeing the building’s protection from the outside and durability, constituting the first forms of urban settlement. By means of some archaeological excavations carried out in Italy and in the rest of the world, today it is possible to argue that the origin of the constructions made of raw earth dates back to about 6000 B.C. The most ancient examples are the mosque of Djienne in the Republic of Mali, the granaries of the temple of Ramesses in Egypt, the monastery of Tabo in India [1].

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