If the soil shrinks more than 60mm, or it is more than 30% clay, then lime or a combination
of lime and OPC may be the best choice of stabiliser. The amount of lime needed increases as
the clay content of the soil increases. The best way to find out how much lime is needed is to
make blocks with different amounts of lime (everything else being the same) and have them
tested for strength.
As a rough guide the table on page 10 can be used to get lime quantities for a first test.
Linear shrinkage of a high silt/clay soil
Linear shrinkage of a sandy soil
Percentage of clay in the soil
30
40
50
60
70
80
90
3 (approx 1:32), 5 and 7
4 (1:24), 6 and 7
5 (1:19), 7 and 9
6 (approx 1: 16), 8 and 10
7 (approx 1: 13) and 9
8 (1:11.5) and 10
10 (1:9)
NOTE: All percentages and ratios are given by mass, which we can call weight. For example:
1 part cement to 16 parts soil, or 6.25%, means that a 50 kg bag of cement would be used
8