Expanded clay is the only lightweight aggregate certified for geotechnical uses, and is CE marked as compliant with EN 15732. This European Standard defines the required characteristics and properties of the product, together with the procedures for testing, marking and labelling it for civil engineering uses.
Laterlite Expanded Clay is available in a wide range of granulometric sizes. The most suitable sizes for geotechnical use are 3/8, 8/20 and 0/30. Specific granulometric sizes can be prepared to meet particular requirements.
Thanks to its high percentage of voids, the density of Laterlite Expanded Clay is considerably lower than that of traditional aggregates (in the case of granule size 8/20, up to more than 6 times lower).
The loadings imposed by expanded clay embankments are assessed in Section X
Angle of internal friction
The angle of friction of unbounded expanded clay is obtained from triaxial tests by varying the lateral confining pressure of the aggregate and its degree of compaction (fig. X).
For design purposes, with a confining pressure of 200 kPa (which is typical of the most important geotechnical applications), a value of approximately 40° can be assumed.
Trend of the angle of friction as a function of the confining pressure and the degree of compaction.
Surface stiffness of embankments– plate loading tests
The surface stiffness of expanded clay embankments is determined by plate load testing. The stiffness values obtainable will depend on the technical solution chosen, the granulometry of the expanded clay, and the degree of compaction.
The various methods for constructing an embankment are described in detail in Section X. In general these include a finishing layer to distribute the loading.
The graph shows the trend of the modulus of deformation Md as a function of the relative density, for an 80 cm thick layer of 0-30mm expanded clay finished with 20 cm of granular mix.
If necessary, an asymptotic value of Md??200 Kg/cm2 can be considered for design purposes, which corresponds to a degree of compaction of the aggregate that is easy to attain using ordinary ground-compacting machinery (plate vibrators, compaction rollers).
Values for the modulus of deformation Md as a function of the compaction of individual layers and different granulometries of Laterlite Expanded Clay are available by request.
Trend of the modulus of deformation Md (measured on the first load for a 30 cm plate load test
for variable vertical strain values between 150 and 250 kPa) as a function of the relative density.
Water absorption and drainage
Laterlite Expanded Clay is an inert, vitrified, dimensionally stable material whose volume remains unchanged in contact with water.
When the inter-granular voids (i.e. the voids between the granules, which interconnect with one another) are immersed in water they immediately become saturated; the intra-granular pores (the voids within each granule) only fill more slowly with water by capillary action, and some of them will never become saturated.
The excellent drainage capacity of expanded clay is due to this network of inter-granular pores, whilst the water absorption is due to the intra-granular pores.
In accordance with European Standard EN 13055-2 (par. 4.8), the coefficient of water absorption of expanded clay is determined by immersing a dry sample in water for 24 hours. Comparison of its weight before and after the test (of the drained material) gives the quantity of water that has been absorbed by the granules (this will vary, depending on the granulometry).
For design purposes, the coefficient of water absorption of Laterlite Expanded Clay can be conservatively considered as always less than 25% by weight.
Laterlite Expanded Clay is also available in the special Laterlite Plus dry hydrophobic variant, which maintains its extremely low coefficient of water absorption over time.
Expanded clay can be delivered:
A mix of different denominations and sizes can be supplied by request.
in big bags
By request Laterlite Expanded Clay can be delivered in big bags of approximate capacity 1 – 1.5 – 2 – 3 m3.
Laterlite Expanded Clay is delivered in easy-to-handle 50-litre polythene bags on non-returnable wooden pallets (20 bags/m3).