Page 67 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

of compacted soil-cement cylindrical specimen soil-cement cubes after 21 days curing under wet
subjected to 12 cycles of wetting and drying. Each burlap were dried in air inside the laboratory for
cycle involves soaking the soil-cement specimen 30 days. The cubes were then dried in an oven at
o
in water, drying in oven and then scratching with 50 C to constant weight. After removing from the
a wire brush. This test was developed to simulate oven they were cooled to room temperature and
the weathering of soil-cement road bases. Limit the weight was recorded to 1.0 gm accuracy. This
for weight loss mentioned in the ASTM test has weight is termed as initial dry weight of the cube.
been modified by several authorities according The cube is now partially immersed in water to a
to the nature and type of buildings and climatic depth of 10mm for 30 minutes allowing only a part
conditions (Fitzmaurice, 1958). Lunt (1980) reports of the cube to absorb water. Then the cube is kept
that may authorities consider that the ASTM test is for drying in the sunlight for a day. Thus the cube is
too severe a test for evaluating durability of soil- partially wetted and partially dried. This constitutes
cement blocks. one cycle of wetting and drying. The test is
repeated for 20 times and finally the cube again
o
Spray erosion test has also been used to evaluate dried in an oven at 50 C to constant weight. The
the durability of soil-cement blocks. The test weight is recorded and designated as final weight.
consists of exposing one face of a soil-cement The difference between the initial dry weight and
block to a jet of water spray, at constant pressure, the final dry weight is expressed as a percentage of
for a definite period. Then the exposed face of initial dry weight. This is designated as percentage
the block is examined for erosion and pitting. weight loss after 20 cycles of alternate wetting and
This test is not standardised and the parameters drying.
such as type of water jet, the pressure, duration of
test etc. vary in different investigations (IS:1725, Partial wetting and drying of cubes simulate to
1982, Middleton, 1987 and Reddy and Jagadish, some extent the wetting and drying taking place
1987). Reddy and Jagadish (1987) have attempted in a wall when exposed to rain and sunlight, where
to correlate laboratory erosion results to the field only external wall surface absorbs moisture. Also
erosion values by defining a term called “erosion partial wetting and drying can cause differential
ratio”. shrinkage initiating cracks in the soil-cement
blocks, ultimately damaging the edges and comers
The ASTM weathering test is too severe a test for of the blocks.
the soil-cement blocks and the spray erosion test
is difficult to standardise in order to correlate RESULTS AND DISCUSSION
with varying climatic conditions. Hence a simple Fig 5 shows a typical weathering pattern after 20
wetting and drying test has been evolved here for cycles of alternate wetting and drying. Figure shows
assessing the durability of soil-cement blocks. soil-cement cubes with 5 percent cement using SH
soil. The cube to the right is without weathering,
TEST PROGRAMME whereas the one to the left has undergone 20 cycles
Soil-cement cubes were prepared using the soils of weathering leading to severe damage to the
BG, BC, SH, ML, MBC, SBC and their reconstituted edges and comers. Results of tests conducted on
variants. The cubes are prepared using two cement soil-cement cubes using 6 types of soils and their
percentages of 5 and 10 percent by weight in the reconstituted variants are given in Table 3. The
manner described in earlier sections. Pressed table gives details of soil composition, weight loss

68 The Indian Concrete Journal | November 2018