Experimental evaluation of the optimum lime content and strength development of lime-stabilized rammed earth

The increasing resource consumption, waste generation, and carbon footprint in the construction sector has drawn the attention of builders and researchers to alternative sustainable construction techniques and materials, such as rammed earth (RE). The mechanical behavior of RE is often enhanced through the use of diverse additives; although cement is probably the most common one, lime stabilization provides some important advantages, representing a more efficient and environmentally friendly solution with a long tradition in the improvement of the mechanical and hydraulic behavior of earthen materials. However, there are still several aspects regarding the effect of lime stabilization in RE mechanical properties that have not been thoroughly evaluated. In this regard, the present study analyze two of the main parameters concerning lime-stabilized rammed earth (LSRE), which are essential to ensure the correct use of this technique: the optimum lime content and the curing time. Several RE specimens with different lime contents, from 0 to 18% by weight, were manufactured and subjected to unconfined compression tests in order to obtain and compare their uniaxial compressive strength (UCS) and elastic modulus. An optimum lime content equal to 12% was obtained. Then, more LSRE samples with 12% lime were manufactured and tested at increasing curing times during 100 days to evaluate the development of their strength and stiffness. The results showed a logarithmic growth of both the UCS and the elastic modulus, with the majority of the strength (over 80%) developed during the first 30 days. In addition, non-destructive ultrasonic pulse velocity tests were carried out on the samples, proving to be a useful tool for predicting the mechanical properties of the material without damaging the specimens.