Water resistance of clay materials

Abstract

In this bachelor thesis the aim is to improve water resistance of clay materials by using different additives while retaining or enhancing the other mechanical properties of the clay. Casein, starch and tannin were chosen based on papers that suggested that they might have a positive effect on the water resistance of clay and also because they are eco-friendly. Three different percentages (related to the clay mass) of each additive were tested to study their effect on the properties of clay materials. Sand was also used in each mix to reduce the shrinkage of clay samples. For the highest percentage of every additive, two additional mixture were tested, one with additional dispersant and another one with dispersant and coagulant. That's why five dif- ferent mixture for every additive were tested.

Several tests were conducted according the stages of clay materials. In the fresh state, the slump test was performed, and the density of fresh paste were measured. During the drying process, the weight loss of the samples was determined. The dried samples were used to find out the mechanical strength and the water resistance.

The best results were achieved with the use of tannin which made the samples lighter, gave them a higher mechanical strength and performed better in the water resistance test. Casein improved the mechanical strength and reduced the weight loss. It failed in the water resistance test. Starch did not interact with the clay; it hardly changed its properties.

In general, the dispersant and the dispersant in combination with the MgO increased the work- ability. For the density there is no clear tendency. For all combinations both mix designs de- creased the weight loss of the samples except for the samples with Casein. How the mechanical strength was affected does not have a clear tendency. The dispersant had a positive effect on the water resistance, while the samples with MgO and dispersant were generally worse than the ones with just dispersant.

The best mix out of all of them was T5D.