Answer: The main tests are workability, slump and air content of the mixture. Workability is comprehensively expressed by cohesion, water retention and fluidity.
(1) Cohesion - observe with eyes. When measuring slump, the specimen collapses to the surroundings, which means good cohesion. The specimen collapses to one side or part of the stone leaks out. The surface is not sticky to mortar, which means poor cohesion.
(2) Water retention - after the concrete mixture is put into the slump cone and compacted, there is a little slurry or no mortar at the bottom of the cone, which means good water retention. If the concrete mixture is poured on the iron plate and water or cement slurry precipitates on the surface, it means poor water retention (i.e. segregation).
(3) Fluidity - after the mixture is piled up, it immediately flows to the surroundings, which means good fluidity. Otherwise, it means poor fluidity.
