Mixing of the bedding mortar

Frequently, on construction sites bedding mortar and drain concrete are being mixed and processed too dry. The term “earth-moist texture” is not unambiguously defined. This is due, inter alia, to the fact that there is no construction-site suitable method (e.g. in comparison with the spread value for rigid to flowable texture) to clearly detect/define earth-moist texture. But the correct addition of water is important for the processing properties like e.g. compactability and for the obtaining the required properties of the set mortar like compressive and adhesive tensile strength.

We therefore recommend as a simple and practicable test the so-called snow ball test. This is done by forming a snow-ball like clod in the hand. The “snow ball” must not decompose when opening the hand, otherwise the mortar/concrete is to dry. A slight adhesion of binding-agent paste should remain on the hand. The “snow ball” should show a slight gloss on its surface because of a binding-agent/water film, see the figure at the very bottom of the page. During the processing time the bedding mortar resp. the drain concrete must be protected against desiccation, see Technical Bulletins..

Snow ball

Decomposed “snow ball” due to too dry texture.

Snow ball

“snow ball” at optimal earth-moist texture.

Snow ball

“Binding-agent/water film on the surface of the “snow ball” at optimal texture.