Assessing the Rebound Hammer Test for Rammed Earth Material

Abstract

Rammed-earth (RE) is a construction material manufactured from the soil. The soil is compacted at its optimum water content, inside a formwork to build a monolithic wall. RE material is attracting renewed interest throughout the world thanks to its sustainable characteristics: low embodied energy, substantial thermal inertia, and natural regulator of moisture; on the other hand, the existing historic RE buildings is still numerous. This is why several research studies have been carried out recently to study different aspects of this material. However, few investigations have been carried out to explore the possibility of applying the nondestructive techniques on RE walls. This paper presents an assessment of the well-known rebound hammer test on RE walls. The calibration curves of the rebound hammer test have been established for conventional concrete where the rebound number is more than 20. For RE material with lower compressive strengths, a new calibration curve must be established. In the present study, two soils were used and different homogenized specimens with different dry densities were manufactured and tested, to plot a general calibration curve. Then, this calibration curve was applied to RE specimens; different results at different positions in an earthen layer were observed, due to the inhomogeneity of the material. The final results showed an acceptable accuracy of the calibration curve in the prediction of the compressive strength of RE material.

Mechanical Properties of Rammed Earth With Respect to Clay Mixture Composition

“…The tensile bending strength (0.35÷0.39 MPa) and the compressive strength (1.21÷1.42 MPa) were lower than many results obtained by other researchers [8,[10][11][12]29], so we compared our results with a doctoral dissertation [10]. The reason for this choice was that the dissertation used similar experimental measures, includes the same testing methods and sizes of test specimens (40×40×160 mm).…”

Rammed Earth Construction: A Proposal for a Statistical Quality Control in the Execution Process

“…This criterion is considered for determining the ultrasonic pulse velocities X-UPV and Y-UPV for those directions that are perpendicular to the compaction direction, and Z-UPV for the compaction direction. The rebound index (R) determination is another indirect non-destructive method that, only by itself or combined with ultrasound, may assess the quality of a rammed earth wall [52,53]. This technique is based on a surface hardness test that is made by means of a suitable equipment for soft materials, which is similar to the Schmidt OS-120PT pendulum hammer.…”

“…This technique is based on a surface hardness test that is made by means of a suitable equipment for soft materials, which is similar to the Schmidt OS-120PT pendulum hammer. Note from [51] that the 15 cm cubic samples (which are termed A samples from now on; see Figure 5) required at least nine The rebound index (R) determination is another indirect non-destructive method that, only by itself or combined with ultrasound, may assess the quality of a rammed earth wall [52,53]. This technique is based on a surface hardness test that is made by means of a suitable equipment for soft materials, which is similar to the Schmidt OS-120PT pendulum hammer.…”

Predicting Compressive Strength of Cement-Stabilized Rammed Earth Based on SEM Images Using Computer Vision and Deep Learning

“…Sci. 2019, 9, 5131 2 of 14 designing CSRE of sufficiently high compressive strength is difficult because this feature depends on several mixture properties and technological issues, such as a compaction method [3], density of elements [4][5][6], porosity of elements [6], particle size distribution of the soil [4,5,7], mineral composition of the soil [8], content and type of cement used as a stabilizer [6,9,10], moisture content of the soil-cement mixture during construction [4,9,[11][12][13], moisture content of element during service [11,12], exposure conditions of the construction elements [5,14], and age of the construction elements [6,15,16].…”