Page 19 - CSEB Report

Study on Compressed Stabilized Earth Blocks

7. Conclusion

From the study of soil samples and the CSEB bricks, the following conclusion were drawn.

1. All the soil samples collected from three sites were Sandy silt of low plasticity and
was not suitable for Bricks making due to very low clay content. However, upon mix-
ing with more percentage of cement as recommended in the international papers, the
soil got stabilized. Many research works found out that soil with plasticity below 15%
is most suitable for cement stabilization[10]

2. Many soil is suitable for construction of CSEB after removing the top soil and organic
matter. The best proportion of the soil for CSEB is Gravel-15%, Sand-50%, Silt-15%
and Clay-20% [1]. And the soil containing more clay percentage should be stabilized
using lime.

3. The highest compressive strength of 6.5N/sq.m was obtained with 9% cement stabili-
zation for sample 3 and the strength is equivalent to the second class red-bricks. The
sample 3 test results was the most relevant amongst three sample as it’s results totally
agreed/ benchmarked by the studies carried out in [1].

4. The test results of set 2 and set 3 of the sample 1 and the sample 2 also agreed to
the [1] but set 1 of both the samples, containing highest cement content fails to corre-
spond to [1], this need further studies for verification.

5. For very small project, the labours motion dominate the CO2 emission but with in-
crease in project size, despite adding low percentage of cement, CO2 emission
would be dominated by cement content.

6. CSEB consumed less than (10 to 15) % of in put energy as used to manufacture simi-
lar red bricks. [1][10]

7. The manufacturing cost of 1 cubic meter of CSEB at site boils down to Nu. 2470 and
to purchase and transport 1cubic meter of red bricks to site, (assumed site Thimphu)
cost around Nu 7085. Thus, importing red-bricks from India cost almost triple times
the cost of CSEB manufacture at site.

8. Therefore, CSEB bricks have economic potential as well as ecological benefit. More-
over, the most attractive quality of the bricks is that it promote healthy and comforta-
ble room environment. Considering the economic viability, these bricks have more fu-
ture for the construction of low to medium cost housing construction which contribute to
sustainable development.

18 Engineering Adaptation and Risk Reduction Division (EARRD), DES, MOWHS