Diagonal Tension Testing of Interlocking Compressed Earth Block Panels

Abstract

This thesis examines the use of diagonal tension (shear) testing to determine factors affecting shear strength of Interlocking Compressed Earth Block (ICEB) panels. This work expands on the current information available about strength properties of ICEB assemblies, which are dry-stacked, as opposed to having mortared beds. Variables such as block strength, grout strength and grouting pattern can influence the results of these types of tests and are examined in this investigation.To study variables affecting diagonal shear strength, 9 panels were tested, consisting of blocks produced by a manual block press. Strength testing was adopted from common ASTM standards to determine constituent material properties. A modified version of ASTM E519 test procedure is used to perform diagonal tension testing. Imaging analysis, using a high resolution camera, was run simultaneously during testing to capture displacement histories of select panels.It was determined that both block and grout strength significantly affect the shear strength of ICEB panels. Additionally, vertical grouting and block type also have a strong influence. Imaging analysis results confirm that the dominant failure mode in ICEB panels is bed joint sliding both pre and post peak load, with noticeable displacements at head joint locations on a few panels. Lastly, diagonal cracking along the block face was noticeable on several panels following peak load. Further testing remains to determine other factors affecting shear strength, namely, the application of normal pre-compression loads to the panel.

In-Plane Shear Wall Performance as Affected by Compressed Earth Block Shape

“…This artificially increases the block's strength compared to the completely unconfined failure that would take place in a full-scale stack of blocks. It also causes a characteristic conical failure visible in Figure 3.19 that has been widely observed by past research, including Bland (2011) and Pringle (2016). These testing artifacts can be overcome with prism tests.…”

“…Previous research (Bland, 2011) has indicated that directly applying existing code-based masonry design equations dramatically over-predicts the in-plane shear capacity of interlocking compressed earth block walls. The research in this thesis continues prior work examining the in-plane lateral capacity of full-scale walls (Bland, 2011;Stirling, 2011) as well as research on factors specifically affecting shear capacity (Pringle, 2016).…”

“…All Rhino blocks used mix proportions developed by Pringle (2016) using equal stock weights of sand and Las Tablas soil with 9% Portland cement as a percentage of 31 dry ingredients. All sand was passed through a #4 sieve before batching to remove large particles.…”

“…The soil/sand proportions were selected by Pringle as a balance between block strength (which decreases with increased soil content) and cohesion immediately after pressing (which increases with soil content and is necessary for conveying blocks from the press to the curing rack). A spreadsheet designed by Pringle calculated the amount of water required to reach optimal water content, determined by a series of Proctor compaction tests outlined in Pringle (2016). This same spreadsheet also determined the approximate amount of ingredients required for an individual block based on the finished block's expected volume.…”

“…Rhino blocks were half blocks. Not only does this reduce the additional resources and effort required to make the total number of blocks, but Pringle (2016) also concluded that tests of half blocks were more consistent than comparable tests of full blocks. No V-Lock half blocks were available for testing, so all V-Lock tests were performed on full blocks.…”