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TECHNICAL PAPER COLLECTOR’S EDITION

type. The degree of change in expansion due It has also been found from the field observations
to sand addition varies with the composition of that these limits are quite satisfactory from the
a soil. For instance there is a 13 fold decrease in point of view of durability aspects.
the expansion value for BC soil with 5 percent
cement when the sand content of the soil is Some of the soils (like ML and SH soils) do
changed from 35.7 percent to 78.6 percent not show strength improvement with sand
(clay reduces from 36 percent to 12 percent). addition. However, these soils show much better

durability characteristics with increased sand
percentage. This shows that the presence of sand
is critical to provide overall strength and durability
characteristics in stabilised soil blocks.

CONCLUSIONS
Effect of soil composition/grading on the strength
and durability characteristics of soil-cement blocks
has been discussed. The following conclusions can
be summarised from the results.

(i) Soil composition/grading has a significant
influence on the strength and durability
Fig 6 Weight loss versus expansion characteristics of soil-cement blocks. The sand
content of any soil can be easily increased by
The tests on expansion due to saturation and
mixing additional quantities of sand. Increase
alternate wetting and drying, have clearly
in sand content leads to a proportionate
demonstrated the importance of sandy soils decrease in clay fraction of the soil.
for soil-cement block production. Values of
percentage weight loss have been plotted against (ii) The wet compressive strength of soil-cement
percentage expansion (in log scale) for all the blocks increases with increase in sand content
cases in Fig 6. The best fit line is an exponential of the soil for soils containing expansive clay
curve. The equation of the exponential curve is minerals such as montmorillonite. Whereas
Y=e(0.426+3.14X), where Y is the percentage weight for soil cement blocks using soils containing
loss and X is the percentage expansion due to predominantly non-expansive clay minerals
saturation. This is the best fit line with a coefficient such as kaolinite, increase in sand content leads
of correlation of 0.79. It is clear from this figure that to a marginal variation in wet compressive
the percentage weight loss is almost constant at strength.
2 percent up to an expansion value of about 0.15 (iii) Alternate wetting and drying test and the test
percent. When the expansion is more than 0.15 of expansion due to saturation could be used
percent the percentage weight loss increases very as indicators of the durability characteristics of
rapidly. These results indicate the upper limits soil cement blocks. Soil-cement blocks using
for expansion due to saturation and percentage sandy soils possess good dimensional stability
weight loss could be fixed at 0.15 percent and 2.0 and better performance when subjected to
percent respectively. alternate wetting and drying cycles.

70 The Indian Concrete Journal | November 2018