Physico–mechanical and durability performances of compressed earth blocks incorporating quackgrass straw: An alternative to fired clay

In developing countries such as Benin, the use of clay soils to produce fired clay bricks can be confronted with the problems of availability of the energy required for firing. The present study assesses the possibility to use these clay resources to produce compressed earth blocks (CEB) as alternative to fired clay. CEBs were produced by physically stabilizing a highly clayey soil with 0/5 granite dust, followed by chemical stabilization with 8wt% cement and the incorporation of 0 to 1.5wt% quackgrass straw. This resulted in dimensional stability of CEB, despite a slight swelling of 16.33 mm/m upon immersion observed only on CEB containing 1 and 1.5wt% straw. The coefficients of resistance to abrasion are well improved above the standardized minimum threshold of 2cm2/g, i.e. 29.7 to 7.72cm2/g for straw contents of 0 to 1.5%. Moreover, the maximum erosion depth of the CEB of 32.6mm/h, is well below the limit of 120mm/h, despite using a water pressure 10 times higher than the standard pressure of 50kPa. These results testify to the durability of stabilized CEB. However, the dry and wet compressive strength decreased from 5.1 to 2.84MPa and from 3 to 1.02MPa, respectively, with the straw content of 0 to 1%. This does not hinder the use of these CEB for sustainable building construction, as the values of their compressive strength in dry and wet conditions were respectively above the required values of 2MPa and 1MPa.