In order to exploit to the full the insulating and lightness characteristics of granular Laterlite Expanded Clay, the material should be laid loose and simply levelled to the thickness desired (with slight falls if required). If the top surface is not to be walkable it can be left as it is. If it is to be accessible or walkable or if a surface
finish, such as an impermeable layer or paving, is to be applied, it must be covered with a layer of another material (various types of panel, a screed, a non-structural or structural floor slab, or plant growth soil), incorporating separation layers if required.
N.B. the space to be filled with Laterlite Expanded Clay must be adequately contained at the sides, particularly if the layers are thick and if the material is to serve as backfill.
Surface bonding with cement slurry
The topmost granules of a layer of loose Laterlite Expanded Clay can be fixed with a cement slurry to make the surface easy to walk on for completing the job (by adding a top slab, a screed, etc.).
The cement slurry (a mixture of cement and water) should be spread over the surface of the loose Laterlite Expanded Clay after it has been levelled. By varying the proportions of water and cement (w/c), the slurry can be made more on less fluid and will penetrate to a greater or lesser depth into the layer of expanded
clay. The suggested approximate w/c ratio is 0.8 (equivalent to 1 no. 25 kg bag of cement + 20 litres of water).
If the top surface is to be accessible/walkable, or if a top finish is to be applied (such as an impermeable layer or paving), an appropriate levelling or top screed will be required.
Binding with cement
Permeable concrete (no fines)
Laterlite Expanded Clay binds easily with cement to give a lightweight insulating permeable concrete with better mechanical strength as compared to the loose product. These concrete mixes can be prepared using ordinary batchers or mixers.
Typical formulation per m3:
Preparation in a concrete mixer:
Pre-humidify the granules by emptying 3 bags of expanded clay (150 litres) into the mixer along with 10 litres of water. Then add 1 bag of cement (25 kg) and 5 more litres of water. Mix for approx. 3 minutes.
No sand should be included in the mix. The dosages of cement should not be increased as this would increase the weight of the mix and reduce its insulating characteristics.
Due to the open-pore structure of a porous concrete of this type,it cannot take reinforcement. If the final surface is to be accessible or walkable or if a top finish is to be applied (such as an impermeable layer or paving) a screed will be required.
other types of binder, such as hydraulic lime and resins, can also be used with Laterlite Expanded Clay. In some situations it may be necessary to use the hydrophobic version of Laterlite Plus. For further information, consult Technical Support.
LAYING WATERPROOFING AND PAVING:
If paving or waterproofing is to be laid on top of loose Laterlite Expanded Clay whose surface has been consolidated with slurry or that has been bound with cement, a top screed is required to level the surface and distribute the loading. This screed can be made using one of the Latermix range of pre-mixed screeds, or a traditional sand/cement mix. It can vary in thickness from 3 cm if it is to take an impermeable membrane to 5 cm if a residential type of floor finish is to be applied.