Feasibility for the Recovery of Excavated Soils in Compressed Earth Blocks as a Sustainable Building Material

Abstract: Soil is continuously excavated for development activities in urban and rural areas and
treated as waste. This study investigates the characteristics of urban soils excavated from earthworks
of buildings in the Brittany region of France for their perspective reuse in earthen construction
materials to valorize soil waste and provide a sustainable building material locally. Excavated soil
from earthwork activities was taken from the Brittany region of France from three different locations.
Soil suitability for compressed earth blocks was investigated based on their granulometry, consistency
limits, and mineralogy. Finally, compressed earth blocks with dimensions of 4 4 16 cm3 were
manufactured with different formulations and compacted dynamically. Flexural and compressive
strength tests were performed on bricks to observe their mechanical behavior. Grain size analysis
of soil samples shows that the percentage of clay in the landfill stockpile of excavated soils varies
between 13% and 16%, while at some local sites, the percentage of clay goes up to 57%. The grain
size of soils varies from the recommended zone. The plasticity of soil samples ranges from 17.3%
to 20.4%. The plasticity index and clay content of the soil show that these soils are inactive clays
with a lesser possibility of swelling and shrinkage. Mineralogical analysis of soil shows the absence
of water-sensitive clay minerals, while quartz, kaolinite, and illite are major minerals present in
soils. Linear shrinkage in bricks ranges from 0.6% to 2.2% and is considerably higher for clayey soils.
Mechanical testing of earth bricks shows that the compressive strength of earth blocks ranges from
0.92 MPa to 2.22 MPa while the flexural strength ranges from 0.25 to 0.74 MPa. A mixture of sandy
and clayey soils shows good strength due to improved granulometry. Earth bricks with soils from
some stockpiles, excavation sites, and soil mixture show compressive strength higher than 1 MPa,
which is recommended strength by international standards, and offer the opportunity to produce
sustainable building materials locally.