This work is the result of the first collaborative investigation between the National Laboratory for Building and Public Works in Haiti, the Ecole Polytechnique Fédérale de Lausanne and the Swiss Agency for Development and Cooperation on the construction practices with concrete. We have set up the first practical method combining material science to socio-economics to quantify and analyze the actual practices with concrete in the field. We have collected and analyzed real concrete samples randomly selected in ordinary environment in the urban area of Port-au-Prince and recorded qualitative data on the local concrete practices. The results of the first field study are promising for both cement and concrete research and sustainable development of the construction. Approximately 30% of the concretes combine good strength and remarkably low CO₂ impact, indeed lower than concrete made in developed countries. This suggests that there is a tremendous potential to make robust and low CO₂ concrete around the world in no standardized conditions. Besides this promising perspective, the analysis of actual concretes showed that the most common wrong practice was the excessive use of water in the concrete mix. Nevertheless, these concretes with extreme (w/c) ratio revealed new insights on the cement hydration mechanisms