Influence of the soil characteristics

There are many factors to consider in the ability of a polymer to act as a soil stabilizer for making soil bricks or blocks; the most important properties are related to the main raw material component, the soil. In a recent published study (Galan- Mann et al., 2013) different soil types stabilized with a natural polymer (alginate) were compared in relation to their mechanical behavior and to their compactness.

The materials used in these experiments were three different types of clay soils, alginate, wool, and lignin. The physical properties and Atterberg limits of the three different types of alluvial soils used in this experimental investigation are described in Table 4.1. All the soils used for this study were supplied by Scottish brick manufacturers; Errol (from the East Coast of Scotland) and Ibstock and Raeburn from Glasgow. All three soils had different colors and textures but importantly, their particle-size distributions were all within the maximum limits specified for utilization within CSEB.

Table 4.1 Physical characteristics, grain size, and Atterberg limits of the three soils

Atterberg limits define moisture content (in mass percentage) at which clays and silts pass from semisolid into plastic states and then into a liquid state. These are empirical divisions between the solid, plastic, and liquid limits of clay. Errol soil has a much higher liquid limit compared to the other soils, as can be seen in Table 4.1. The clay in each soil sample acts like cement in concrete, binding all the larger particles in the soil, whereas the silt and sand particles behave as fillers in the soil matrix in a similar manner to aggregates.

Errol soil is described as a silty clay loam and contains a significantly higher proportion of clay compared to either an Ibstock or Raeburn soil. The Ibstock soil is classified as a silt loam and the Raeburn soil is classified as a loam (Craig, 2004). With regards to their plasticity indexes, it is interesting to note the quite remarkable variation, being all of them soils currently used in the brick industry (see Table 4.1).