Mexico is the cradle of great ancient civilizations that promoted earth-based architecture (cob, mud-brick, structure fills). Nowadays, such earth-based materials are widely investigated to understand their composition, mechanical properties and its resistance to aging. The present study evaluates the effect of composition on flexural and impact properties as well as water absorption capabilities. Soil was used from pre-Columbian site of la Joya, in Mexico, to manufacture experimental mud-bricks emulating the ancient technique using cut grass and asphalt emulsions. It was found that mechanical stabilization and material cohesion are in function of the additive's nature. Flexural and impact strengths of samples were examined and results were correlated to damage mechanisms by using acoustic emission technique exhibiting the onset, propagation and fracture. Mechanical properties were found to be higher in samples with synthetic additives, compared to control samples.