Reseach Adobe Bricks
Based on the results from the first soil test, several mixes are tested. In a first series of tests the shrinkage and strength is tested. Also, the number of cracks is visually observed and compared. Adobes are not water resistant, they therefore have to be plastered.
Firstly, different amounts of sand are added to the sieved soil (which will also be referred to as just ‘clay’, since it has a high clay content). From these different mixtures, the optimal clay-sand ratio is obtained.
Secondly, different additives are tested. Both straw and manure (donkey poo in this case) are added. Animal products like blood, urine, manure, casein and animal glue have been used through the centuries to stabilise loam. If manure is used, it should be allowed to stand for one to four days in order to allow fermentation; the stabilisation effect is then considerably enhanced due to the ion exchange between the clay minerals and the manure.
Straw is usually added to reduce shrinkage and increase thermal insulation.