The quality of concrete products made of semi-dry concrete significantly depends on the compaction (porosity) achieved. The latter already differs within a concrete batch owing to varying filling levels in separate mold parts. In the last decades, the semi-dry concrete grades used contained ever more moisture in order to obtain a better compaction and more complete hydration of the cements. Unfortunately, this increases the stickiness and enhances variations in the filling level, causing above all visually annoying differences in the edge pattern as well as the drying behavior and efflorescence behavior, apart from varying strengths. Consequently, a uniform filling of all mold parts by a free-flowing semi-dry concrete is the prerequisite for the manufacture of high-quality paving blocks, masonry units and curbstones.
The „flowability“ test method, especially developed by Sika for the issue of „uniform mold filling behavior“, enables a systematic examination of the influencing factors in respect of concrete technology. Tests of numerous admixture raw materials coming into question resulted in the innovative admixture technology. The admixture is available under the name of SikaPaver HC-218 and was already presented in the BFT 07/2019 edition. Link: www.bft-international.com/en/artikel/bft_Filling_and_compaction_aid_for_concrete_products_developed_3388211.html