Embodied energy in cement stabilised rammed earth walls

Rammed earth walls are low carbon emission and energy efficient alternatives to load bearing walls. Large numbers of rammed earth buildings have been constructed in the recent past across the globe. This paper is focused on embodied energy in cement stabilised rammed earth (CSRE) walls. Influence of soil grading, density and cement content on compaction energy input has been monitored. A comparison between energy content of cement and energy in transportation of materials, with that of the actual energy input during rammed earth compaction in the actual field conditions and the laboratory has been made. Major conclusions of the investigations are (a) compaction energy increases with increase in clay fraction of the soil mix and it is sensitive to density of the CSRE wall, (b) compaction energy varies between 0.033 MJ/m(3) and 0.36 MJ/m(3) for the range of densities and cement contents attempted, (c) energy expenditure in the compaction process is negligible when compared to energy content of the cement and (d) total embodied energy in CSRE walls increases linearly with the increase in cement content and is in the range of 0.4-0.5 GJ/m(3) for cement content in the rage of 6-8%. (C) 2009 Elsevier B.V. All rights reserved

Structural Behavior of Story-High Cement-Stabilized Rammed-Earth Walls under Compression

A rammed-earth wall is a monolithic construction made by compacting processed soil in progressive layers in a rigid formwork. There is a growing interest in using this low-embodied-carbon building material in buildings. The paper investigates the strength and structural behavior of story-high cement-stabilized rammed-earth (CSRE) walls, reviews literature on the strength of CSRE, and discusses results of the compressive strength of CSRE prisms, wallettes, and story-high walls. The strength of the story-high wall was compared with the strength of wallettes and prisms. There is a nearly 30% reduction in strength as the height-to-thickness ratio increases from about 5 to 20. The ultimate compressive strength of CSRE walls predicted using the tangent modulus theory is in close agreement with the experimental values. The shear failures noticed in the story-high walls resemble the shear failures of short-height prism and wallette specimens. The paper ends with a discussion of structural design and characteristic compressive strength of CSRE walls. DOI: 10.1061/(ASCE)MT.1943-5533.0000155. (C) 2011 American Society of Civil Engineers

Cement stabilised rammed earth. Part B: compressive strength and stress-strain characteristics

Strength and behaviour of cement stabilised rammed earth (CSRE) is a scantily explored area. The present study is focused on the strength and elastic properties of CSRE. Characteristics of CSRE are influenced by soil composition, density of rammed earth, cement and moisture content. The study is focused on examining (a) role of clay content of the soil on strength of CSRE and arriving at optimum clay fraction of the soil mix, (b) influence of moisture content, cement content and density on strength and (c) stress-strain relationships and elastic properties for CSRE. Major conclusions are (a) there is considerable difference between dry and wet compressive strength of CSRE and the wet to dry strength ratio depends upon the clay fraction of soil mix and cement content, (b) optimum clay fraction yielding maximum compressive strength for CSRE is about 16%, (c) strength of CSRE is highly sensitive to density and for a 20% increase in density the strength increases by 300-500% and (d) in dry state the ultimate strain at failure for CSRE is as high as 1.5%, which is unusual for brittle materials

Role of clay content and moisture on characteristics of cement stabilised rammed earth

Rammed earth is an energy efficient and low carbon emission alternative for load bearing walls. This paper attempts to examine the influence of clay content and moisture content on the compressive strength of cement stabilised rammed earth (CSRE) through experimental investigations. Compressive strength of CSRE prisms was monitored both in dry and wet (saturated) conditions. Major conclusions of the study are:(a) Optimum clay content for maximum compressive strength is about 16%, (b) the strength of CSRE is sensitive to the moisture content at the time of testing, (c) Strength in saturated condition is less than half of the dry strength and (d) Water absorption (saturated water content) increases as the clay content of the soil mix increases and it is in the range of 12 to 16% for the CRSE prisms with 8% cement

Cement stabilised rammed earth. Part A: compaction characteristics and physical properties of compacted cement stabilised soils

Rammed earth is used for load bearing walls of buildings and there is growing interest in this low carbon building material. This paper is focused on understanding the compaction characteristics and physical properties of compacted cement stabilised soil mixtures and cement stabilised rammed earth (CSRE). This experimental study addresses (a) influence of soil composition, cement content, time lag on compaction characteristics of stabilised soils and CSRE and (b) effect of moulding water content and density on compressive strength and water absorption of compacted cement stabilised soil mixes. Salient conclusions of the study are (a) compaction characteristics of soils are not affected by the addition of cement, (b) there is 50% fall in strength of CSRE for 10 h time lag, (c) compressive strength of compacted cement stabilised soil increases with increase in density irrespective of moulding moisture content and cement content, and (d) compressive strength increases with the increase in moulding water content and compaction of CSRE on the wet side of OMC is beneficial in terms of strength

Double fetus-in-fetu: CT scan diagnosis in an adult

A fetus-in-fetu (FIF) is an uncommon developmental abnormality characterized by a reasonably well-formed but aborted fetus that is seen in the form of an encapsulated, pedunculated vertebrate tumor in the patient's abdomen. We report an interesting case of a double FIF in a 20-year-old man, who presented with acute abdominal pain and a lump. CT scan of the abdomen revealed two ill-formed fetuses-in-fetu, which were seen as a 15-cm complex, encapsulated mass in the lower retroperitoneum; there was also free fluid in the abdomen. The diagnosis of a ruptured twin FIF was made. Complete surgical excision of the lesion was performed and the diagnosis was confirmed histopathologically. To the best of our knowledge, the CT scan findings of a ruptured double FIF in an adult have not been previously documented

In vivo morphometry of menisci of the knee in South Indians: A preliminary study

Background: Since the in vivo morphometric data on the menisci of the knee joint of Indian subjects are scarce, we hereby studied the width and thickness of the menisci using Magnetic Resonance Imaging (MRI) to establish standard dimensions of the normal medial and lateral meniscus as an aid to orthopaedic surgery. Methods: Eighty menisci from 40 knee joints were analysed in each of three regions, the anterior horn, the mid body and the posterior horn. The thickness and width of the menisci were measured in sagittal and coronal T1-weighted and T2-weighted MRI images and analysed statistically. Results: The mean thickness of medial meniscus at the anterior horn, mid body, and posterior horn were 6.3 ± 1.1 mm, 5.2 ± 1.3 mm, and 6.9 ± 1.1 mm, respectively. The respective values for the lateral meniscus were 4.8 ± 0.7 mm, 6.4 ± 1.1 mm, and 7.0 ± 0.9 mm. The mean width of medial meniscus at the anterior horn, mid body, and posterior horn were 10.5 ± 1.2 mm, 7.8 ± 1 mm and 13.9 ± 0.9 mm, respectively. The widths of lateral meniscus at the same regions were 11.8 ± 1.4 mm, 8.6 ± 1.2 mm, and 12.0 ± 0.9 mm, respectively. The lateral meniscus was significantly wider than medial at the anterior horn and mid body (p = 0.00). In contrast, the posterior horn of medial meniscus was significantly wider than lateral meniscus. Both menisci were significantly wider at their posterior horn, followed by the anterior horn and were significantly narrower at their mid body. Conclusion: The present study provides new information on the meniscal thickness and width in South Indians that can be used in planning of orthopaedic and arthroscopic surgeries of the knee joint. However, the study needs to be analyzed with a large sample size for the better interpretation