The Adobe bricks we made were 12″ X 5.5″ X 3″ in dimensions. Adobe bricks are sun dried bricks we made with mud dug from a pond we excavated in between the rice fields. Since the soil was clayey, we added sand to being the clay % to less than 30%.
We added hay to the bricks for adding strength. We used admixtures such as fermented Kadukkai Jaggery mix to increasing binding strength. We used a neem-turmeric-copper sulphate mix to prevent termites and fungi to attack the mud bricks.
We made test bricks for doing compressive strength test at Francis Xavier Engineering College at Tirunelveli. And the results turned out to be impressive and surprising. The strength of the bricks were above 2.5 MPa without lime, which is impressive for sun dried Adobe bricks. But with stabilization, the strength was less than 2 MPa on average. This sounded counter intuitive. But, we decided not to stabilized the mud with lime or cement. Because the stabilizing with lime would have cost more for us.
The cost per brick has turned out to be Rs. 9. The usual environment-for-the-environment burnt bricks almost cost Rs. 5.5 (including transport). Considering the fact that the bricks we have made are double in volume of the usual bricks, we have made bricks on our own without much experience at an economical cost.
Volunteers have done 2 coats of mud and mud-lime plaster on the internal walls and 1 coat of mud plaster on the external faces of the walls.
With the south west monsoon hitting us suddenly, we weren’t prepared with protection of the bricks from the rain on time. We had covered them with tarpaulin but thy didn’t seem to be sufficient. We lost approximately 500 out of the 6500 bricks we had made to the rain. For half of the house, we are going to be building with Adobe bricks. For the other half of the house, we will be building with cob. Fingers crossed for good results 🙂 More updates in the next month.