Reinforcing the Past, Building the Future: Enhancing Adobe Masonry with Traditional Binders and Modern Techniques

Adobe construction is the traditional building method that uses adobe bricks, a natural building material made from a mixture of sand, clay, water, and often an organic material such as straw or dung. These ingredients are mixed together, formed into bricks using molds, and then dried in the sun. Adobe bricks are known for their thermal mass, which helps regulate indoor temperatures, keeping buildings cooler in the day and warmer at night. It is characterized by its eco-friendly materials and ability to sustain indoor air humidity and temperature, plays a crucial role in accommodating populations in less developed countries and preserving historical and vernacular landmarks. However, the vulnerability of earth constructions to seismic action, environmental erosion, and human activities necessitates effective retrofitting methods to ensure safety and longevity.

The research team from Sichuan University, led by Professor Yao Zhang and Professor Lingzhi Xie, conducted on a comprehensive study to address the challenges faced by adobe masonry structures, which are prevalent in less developed regions and carry significant historical and cultural value. Recognizing the vulnerability of these structures to environmental and seismic stresses, the researchers focused on retrofitting techniques that could enhance the resilience and load-bearing capabilities of adobe masonry, particularly through the application of coating mortar. The research work is now published in ACS Omega.

The researchers investigated four distinct retrofitting methods, each targeting different factors that influence the bonding effectiveness. Firstly, targeting the factors of surface roughness where they increased the roughness of the adobe surface to improve physical bonding. Secondly, shear dowel depth where they utilized shear dowels to provide mechanical interlocking and improve the structural connection between the mortar and adobe. Thirdly, wire mesh size and in this they incorporated wire mesh to distribute stresses more evenly and provide additional support to the mortar layer. Fourthly, sticky rice pulp Binder where they employed a traditional chinese binder made from sticky rice pulp to enhance chemical bonding between the mortar and adobe. The researchers conducted a series of experimental tests on adobe masonry Wallettes, fabricated using traditional methods and materials, to assess the effectiveness of each retrofitting strategy under compressive and lateral loads. The experiments were designed to simulate the conditions and challenges faced by actual adobe structures, ensuring the relevance and applicability of the findings.

The team designed an experimental setup which included the fabrication of adobe masonry Wallettes using traditional methods, with the incorporation of local materials and techniques to ensure authenticity and relevance to real-world applications. The use of sticky rice pulp as a binder is particularly noteworthy, as it leverages historical construction practices with proven longevity and sustainability. The single shear tests conducted to assess the effectiveness of SRP surface treatment in enhancing bonding between adobe and mortar highlight the innovative approach of integrating traditional materials with modern engineering practices.

The authors found that the application of mortar coatings combined with the four retrofitting methods resulted in substantial improvements in both compressive and lateral load-carrying capacities of the adobe masonry Wallettes. Notably, the maximum improvements observed were 177% for compressive capacity and 743% for lateral capacity. They also found a relationship between bonding strength and load-carrying capacities. While increased bonding strength had a negative impact on compressive load-carrying capacity, it positively affected the lateral load-carrying capacity. This highlights the importance of balancing bonding characteristics to optimize structural performance under different load conditions. Among the factors investigated, shear dowel depth emerged as having the most significant impact on both compressive and lateral load situations, underscoring the critical role of mechanical interlocking in retrofitting strategies. The use of sticky rice pulp as a binder proved effective in enhancing the bonding behavior between adobe and mortar, demonstrating the potential of integrating traditional materials with modern engineering practices for sustainable and culturally sensitive retrofitting solutions.

In conclusion, the new study by Sichuan University scientists provided innovative and effective retrofitting methods for adobe masonry structures. The integration of traditional materials like sticky rice pulp with modern engineering practices not only enhances the structural performance of adobe constructions but also preserves their historical and cultural significance. This study paves the way for further research and development in sustainable construction practices, with a focus on leveraging local materials and traditional techniques to address contemporary engineering challenges.