The invention relates to a method for grinding an inorganic solid from the series cement clinker, pozzolan and/or raw material for cement production, where a grinding additive is added before or during grinding, and the grinding additive, based on the dry mass, comprises 6% to 80% by weight of caprolactam and 1.5% to 30% by weight of aminocaproic acid, where, based in each case on the dry mass, 0.002% to 2% by weight of the grinding additive is used, based on the total solid. Further claimed are a grinding additive and the use thereof for increasing the compressive strength of the cured product produced therewith.