Why this research is important

Historical data shows that unreinforced rubble stone masonry structures, often built with brittle mud mortar, do not perform well in earthquakes. That's why we at Smart Shelter Foundation built our schools with cement mortar and other reinforcements, including horizontal bands. All our projects successfully withstood the 2015 earthquakes in Nepal without any significant damage.

However, our extensive literature reviews reveal a critical knowledge gap: the mechanical properties of stone masonry built with cement-based mortar, essential for seismic calculations and modelling, are not well-documented. Furthermore, there are no specific international test standards for determining the mechanical properties of stone masonry, so researchers often have to adapt European (EN) and American (ASTM) standards intended for brick masonry.

What we need to do

To fill a major gap in the literature, we must determine the mechanical properties of random rubble stone masonry specimens with cement-based mortars, which are currently non-existent in scientific databases. This includes parameters for stones, mortars, and their combined action into masonry, as well as for concrete used in horizontal reinforcing bands in the walls.

The quality of construction in remote areas is often substandard due to incorrect mixing, handling, and curing of materials. We need to replicate this "low-strength" reality in lab tests to accurately determine the various strength and stiffness parameters of mortars, concrete, and masonry specimens as they are used in the field.

Most importantly, no specific international test standards currently exist for rubble stone masonry. The existing standards are meant for higher-quality mortars and concretes, and based on brick masonry panels, which are not suitable for our purpose. Our research will address this by creating the first standardized tests for key parameters like compression, tensile, and shear strength for low-strength rubble stone masonry.

Our research approach

We will test rubble stones for their compression, tensile, and absorption characteristics. We will also test various mortar types, with a focus on low-strength cement mortar (1:6 cement-to-sand ratio) as required by Indian and Nepalese regulations. This realistic field scenario will be compared against results for higher-strength mortars (1:4 ratio) and weak mud mortar.

Rubble stone masonry will be tested for compressive, tensile, and shear strength using masonry wallettes and representative wall panels. Our research will also focus on the interaction between the masonry and the horizontal concrete bands, specifically measuring friction and cohesion.

Since mechanical properties for low-strength materials are almost non-existent in the literature, our results will be a valuable contribution to international material databases.

Get involved

We invite students and experts with an interest in material testing and the development of test standards to join us.

By following our research methodologies, you can help us multiply the impact of this work by replicating and cross-checking our findings. If you're passionate about advancing seismic safety and want to join our research team or exchange knowledge, please get in touch.