A new method and apparatus for evaluation of the K-slump of concrete

This paper introduces a new digital model of the K-slump tester. For the new tester (patent pending), it is theoretically shown that an inverse linear relationship exists between the K-slump of freshly mixed concrete or mortar and the yield stress τ 0 in the Bingham model. The validity of this relation was investigated experimentally. Tests were conducted on cement pastes, mortar, and fresh concrete mixtures using a Hobart food mixer and the new tester. Power consumed by the mixer at three different speeds was measured along with the K-slumps for fresh concrete mixtures. The results give excellent agreement with the theoretically derived relationship. Hence, the K-slump of concrete was shown to be related to the yield stress τ 0 by the equation K = K max − (constant × τ 0 ), where K max is the maximum K-slump. To determine the precision of the new tester, an interoperator reliability test program was carried out in accordance with ASTM designation C 802. The results indicate that the new apparatus is accurate and reliable in evaluating the K-slump of fresh concrete. Key words: cement paste, concrete, consistency, flow, flowability, fresh concrete, K-slump, mortar, slump, rheology, workability.