Last edited 27 Nov 2018


The term 'slaking' refers to a process in which earth materials such as aggregates disintegrate into smaller sizes when exposed to moisture or immersed in water. It can be used to refer to natural geologic formations or land modifications such as may be necessary for construction works.

Slaking tends to occur when large soil aggregates are not strong enough to withstand stresses that are incurred by rapid water uptake. These internal stresses are the result of the differential swelling of clay particles, air that is trapped and escapes in soil pores, and the rapid release of heat during the wetting process, as well as the mechanical action of moving water.

The stability of soil aggregates, their resistance to erosion, and how well the soil can maintain its structure when rapidly wetted are all indicated by the process of slaking. If slaking is minimal, it is an indication that the soil contains organic matter that helps to bind soil particles and microaggregates into larger and more stable aggregates.

Slaking can be caused or exacerbated by:

  • Tillage methods that disturb the soil and accelerate the decomposition of organic matter.
  • The burning or removal of crop residues.
  • The use of pesticides that are harmful to soil organisms.

The term slaking can also refer to an exothermic reaction initiated by sprinkling water on hot-mixed mortars. For more information see: Hot-mixed mortars.

It can also refer to lime blow out in clay bricks, plasters and renders.

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