Abstract
This study addresses the issues of the reduced strength and increased brittleness of non-autoclaved aerated concrete by introducing an ionic modifying additive (MIA) derived from lignin-rich softwood sawdust. The additive is intended to reduce internal stresses during hydration and enhance the stability of the pore structure. Concrete samples containing 10%, 20%, and 30% additive are tested for compressive strength, wear resistance, water absorption, frost resistance, thermal conductivity, and mineral composition. Optimising the MIA content to 20% increases compressive strength by 19%, improves wear resistance by 15%, reduces water absorption by 22%, and achieves a frost resistance class of F50 versus F30 for the control sample. An X-ray diffraction analysis shows a reduction in the portlandite content from 52% to 31%, as well as increased calcite and hatrurite formation. These results confirm that the MIA optimises hydration, enhances microstructural homogeneity, and significantly extends the service life of non-autoclaved aerated concrete under cyclic freeze–thaw conditions.