Page 68 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

after 20 cycles of wetting and drying and expansion adequate wet strength, but may expand on
due to saturation (which will be discussed later) for saturation and shrink on drying. Expansion and
2 cement percentages of 5 percent and 10 percent. shrinkage due to saturation and drying can cause
The following observations can be made from the shrinkage cracks in the masonry wall, ultimately
results of the table. leading to peeling off of the plaster.

(i) The percentage weight loss is more for 5 Dimensional stability of the soil-cement block can
percent cement stabilised cubes compared be easily estimated by measuring the expansion
to 10 percent cement stabilised cubes, due to saturation. The test involves in measuring
irrespective of soil type and composition. The the length of the cured, well dried soil-cement
percentage weight loss varies between 1.60 cube before and after saturation. The length of
percent and 63.5 percent for 5 cement cubes the dried cube is recorded at three different places
and between 0.4 percent and 30.20 percent for (marked with a paint) and then soaked in water for
10 percent cement cubes. 48 hours. The cube is wiped clean after removing
from water. Now the length of the wet cube is again
(ii) The percentage weight loss decreases with recorded at three marked places. The difference

increase in sand content (decrease in clay between the corresponding two measurements
content) of the soil for both the cement will give expansion due to saturation. This test was
percentages, irrespective of the soil type. conducted on soil-cement cubes prepared using 6
For example in case of BC soil with 5 percent different soils and their reconstituted variants as
cement, there is a 7 fold reduction in described in the earlier section. The results of the
percentage weight loss when the sand content expansion test are given in Table 3. The following
of the soil is changed from 35.7 percent to 78.6 points are clear from the results given in the table.
percent.
(i) Expansion due to saturation is greater in
(iii) The percentage weight loss is more for the case of soil-cement cubes with 5 percent
soil cement cubes using soils containing cement compared to those with 10 percent
montmorillonite clay mineral. Generally all cement, irrespective of the soil type. This can
natural soils with high clay content perform be attributed to better stabilisation of clayey
badly against wetting and drying. material when the cement percentage is
greater. The magnitude of the expansion due

EXPANSION DUE TO SATURATION to saturation varies between 0.03 percent and
2.90 percent for 5 percent cement cubes and
Any building block used for masonry construction between 0.01 percent and 1.05 percent for 10
should possess good dimensional stability. Soil- percent cement cubes.
cement blocks of poor quality have a tendency
to expand on saturation and shrink on drying.
This problem is accentuated if the soil used for (ii) Expansion due to saturation is greater for
soil-cement blocks contains a high proportion soils containing expansive clay minerals such
of clay (say more than 25 percent). This is due as montmorillonite. The magnitude of the
to inadequate stabilisation of clayey material. expansion due to saturation decreases with
Sometimes, the soil-cement blocks may possess an increase in sand content of the soil for both
the cement percentages irrespective of the soil

The Indian Concrete Journal | November 2018 69