Notched mini round determinate panel test to calculate tensile strength and fracture energy of fibre reinforced Cement-Stabilised Rammed Earth

The use of natural fibres (like hemp or bamboo) to improve the mechanical performances of rammed earth structures is not new in construction practice in many parts of the world. However, little scientific investigation has been carried out so far to better understand the real improvement obtained by the addition of fibres. In a recent publication [1], the feasibility of notched mini Round Determinate Panels (mRDP) has been investigated with the aim of deriving a procedure to estimate the intrinsic material properties of Fibre Reinforced Shotcrete (FRS). It was found that it was possible to recover the tensile strength and the fracture energy of the material using an inverse analysis of the experimental data and the well-known Olesen constitutive model [2]. In this paper, the use of the notched mini round determinate panel test to characterise the post-cracking performances of Cement Stabilised Rammed Earth (CSRE) was investigated. For quality control issues, in this study the soil mix consisted of crushed limestone stabilised with 8% cement by soil mass and compacted at its optimum water content (11%). Three specimens were made of CSRE alone and three samples were made of fibre-reinforced CSRE. The fibres used in this experimental campaign were unbundled synthetic copolymer fibres, 54 mm long and 0.3 mm thick. This paper discusses the applicability of a laboratory test conceived for concrete samples to rammed earth specimens. It also presents the comparison between the performances of CSRE materials with and without fibres.