A lightweight concrete formulation containing Portland cement, aggregate, glass particles, water and metakaolin. At least 80% of the glass particles have a grain size of less than 2 mm. The glass particles contribute between 3% and 20% of the total weight of the concrete formulation. The metakaolin contributes between 4% and 12% of the total weight of the concrete formulation. The glass particles are preferably expanded glass particles. Also provided is a lightweight grout formulation containing Portland cement, glass particles, water and metakaolin. At least 80% of the glass particles have a grain size of less than 2 mm. The glass particles contribute between 3% and 15% of the total weight of the grout formulation. The metakaolin contributes between 7% and 15% of the total weight of the grout formulation.