Abstract
The article presents the results of an experimental investigation into the effect of modifying additives on the workability and setting times of a concrete mix used in the production of a two-component wall block. The block structure consists of an external façade layer and an internal structural–thermal insulation layer, which requires precise control of the rheological and technological parameters of the concrete mix during sequential casting. Lignin and soapstock, which are by-products of the wood-processing and fat-processing industries, were used as modifying components. The experimental program included the determination of concrete mix flowability and cement paste setting times at various additive dosages. The results showed that the incorporation of lignin and soapstock increased the workability of the concrete mix compared to the reference composition: the maximum increase in flowability reached up to 6.4% for lignin and up to 9.5% for soapstock. Their combined application produced a pronounced synergistic effect, resulting in an increase in workability of up to 16% in linear terms and up to 35% in terms of spread area, as well as a reduction in data dispersion. The setting time tests revealed opposite effects of the additives: lignin contributed to a reduction in both initial and final setting times, whereas soapstock, due to its hydrophobic properties, led to their extension. The obtained results can be used to optimize the technological regulations for manufacturing two-component wall blocks and to improve the quality and stability of the final products.