Structural behavior of rectangular cement-stabilized rammed earth column under compression Deb Dulal Tripura Research Scholar, Department of Civil Engineering, Indian Institute of Technology Guwahati, India. Konjengbam Darunkumar Singh Associate Professor, Department of Civil Engineering, Indian Institute of Technology Guwahati, India. Abstract: The paper presents a novel experimental investigation, comprising material tests and column tests, focusing on the effect of concentric axial loading and slenderness on the capacity reduction factors of cement stabilized rammed earth (CSRE) columns of rectangular (R) cross sections. The study also attempted to calculate the ultimate compressive strength of columns using the tangent modulus theory. The experimental results compare quite favorably with published codal provisions. There is a reduction in strength as the slenderness ratio (effective height to thickness ratio) increases from about 2 to 10. At higher slenderness ratios, there was a close agreement between the experimental value and value predicted by tangent modulus theory on ultimate strength. Author keywords: Stabilized soil; Rammed earth; Compressive strength; Prism, Wallette; Column. 1 Introduction Rammed earth is a construction technique and in the recent past it has gain much popularity as a sustainable building technology in various parts of the world. In this technique, the temporary formwork is filled with a 10 to 12 cm moist earth (stabilized or unstabilized) layer followed by ramming and then a new 10 to 12 cm layers are added and rammed in progressive layers. The formwork is removed and placed at a higher level until the desired height is reached. Soil, sand, gravel and stabilizers (cement, lime etc.) are the major constituents for both stabilized and unstabilized rammed earth construction. A significant number of magnificent rammed earth buildings are to be found in southern India, particularly in Bangalore. Due to limited structural design regulations for earth buildings, rules developed for masonry construction are generally followed. At present, the most well known structural design standard for earth building has been developed in New Zealand (NZS: 4297, 4298, 4299 - 1998), India (IS: 13827-1998), Australia (Standards Australia 2002), the United States (ASTM: E2392/E2392M-10 -2010) and Zimbabwe (SAZS:724-2001) [1-7]. Over the past 50 - 60 years, structural design guidance for simple earth buildings has also been published in various parts of the world, some of them are Australia (Middleton 1987), the United States (Tibbets 2001), Germany (Minke 2000) and the United Kingdom (Walker et al. 2005) [8-11]. Apart from the afore mentioned standards and guidelines, some extensive study has also been carried out on structural behavior of rammed earth columns and walls. Maniatidis and Walker [12] studied the structural capacity of unstabilized rammed earth columns of square cross section focusing on the effect of load eccentricity and slenderness, determined the capacity reduction factors in combined axial compression, and bending. The study states that the variation between theoretical and experimental results of column failure load for high load eccentricities is attributed to suppressed cracking, ignored in the simple analysis, due to the inherent material tensile strength and confinement. There was a significant variation in material performance between small-scale 100 mm diameter cylinders and full-scale prisms and columns using the same material. The reduction in compressive strength and stiffness of the full-scale specimens is attributed to variation in material grading inclusion of aggregates greater than 20 mm, subsequent crushing of the higher aggregate content during compaction, and variation in compactive effort. The study also presented that the load carrying capacity of the axially loaded columns increases with increasing slenderness ratio, which is a contradictory result. Reddy and Kumar [13] investigated the strength and structural behavior of story-high CSRE walls under compression, assessed its ultimate crushing strength considering slenderness effects, and reported that the CSRE wall strength decreases steadily as the slenderness ratio increases and there is a close agreement between the experimental value and the value predicted by tangent modulus theory for the height - to - thickness ratio of 19.74. From the detailed literature review it is observed that there is still a lacking in systematic studies on structural behavior of rammed earth columns and walls. Hence, there is a need to study the strength and behavior of columns and walls for better understanding of structural behavior and design principles.