Investigations on the creep behaviour of unfired clay block masonry

Abstract

Unfired clay blocks offer a sustainable alternative to traditional masonry by reducing CO₂ emissions and raw material consumption. Despite these environmental benefits, detailed knowledge about their structural properties remains limited. To fill these knowledge gaps, this research focuses on the creep behaviour of unfired clay masonry by examining the creep deformation of unfired clay masonry under long-term loading. Test specimens made from various types and combinations of unfired clay blocks (Compressed Earth Blocks (CEB) and Moulded Earth Blocks (MEB)) and mortars (Earth Mortar (EM), Earth Adhesive Mortar (EAM) and Bastard Mortar with Earth adhesive (BME) were subjected to a constant compressive load for three months, during which deformations were measured. These tests are the first of their kind exploring the creep behaviour of unfired clay masonry. The results highlighted that MEB masonry has a 74-140 % higher creep deformation compared to CEB masonry (MEB-EM: 1692 µε; MEB-EAM: 1441 µε; CEB-EM: 705 µε; CEB-EAM: 830 µε), possibly due to their lower compressive strength (MEB: 4 MPa, CEB: 10 MPa). For CEB masonry, the mortar type did only influence the creep behaviour to a very limited extend, where for MEB masonry this influence was much more pronounced, with EM mortar showing 17 % higher creep deformations (1692 µε for EM compared to 1441 µε for EAM) and 203 % higher shrinkage (558 µε for EM compared to 184 µε for EAM). On the results of the tests, multiple models (Burgers, Lenczner, and Van Zijl) were fit and compared for their ability to predict the creep behaviour of unfired clay masonry. Here it was shown that the Burgers model provided the best fit if no correction for shrinkage is accounted for. If this correction is required, the Van Zijl model is the better choice.