Acid-Activated Olivine Cement Filler

The invention relates to a relates to an acid activated mixture comprising: an acid activated magnesium-iron solid solution silicate filler; cementitious material; and carbon dioxide (CO2); wherein the magnesium-iron solid solution silicate filler has at most 7% free water, and wherein the magnesium-iron solid solution silicate filler is between 4% and 55% by weight of cementitious material. The invention further relates to a method for producing an acid activated cement slurry comprising the steps: making a slurry comprising a non-acid activated or acid activated magnesium-iron solid solution silicate filler, water, and cementitious material; adding carbon dioxide (CO2) to the slurry; and optionally adding an acid to the slurry; wherein the magnesium-iron solid solution silicate filler is between 4% and 55% by weight of cementitious material. The invention also relates to a process for making an acid activated structure, an acid activated cement slurry obtainable by the method, use of the acid-activated cement slurry for making an acid activated structure, aspect, and an acid activated structure obtainable by the process.