Concrete is widely used in construction, but its production generates significant carbon dioxide emissions due to the use of cement. Cement is produced through the calcination of limestone, which releases large amounts of carbon dioxide. Reducing these emissions is crucial for Sweden’s net-zero targets, and one approach is climate-improved concrete. This involves replacing a portion of cement by industrial by-products like slag or fly ash, reducing the carbon footprint. In this chapter, a comprehensive literature review explored the effects of such materials on various concrete properties, including the compressive strength, tensile strength, modulus of elasticity, carbonation depth, creep, workability, and drying shrinkage. Findings revealed both positive and negative impacts, depending on the type and amount of the substitute used. Fly ash and slag improved the strength but could negatively affect the modulus of elasticity, shrinkage, and workability at higher volumes. Recycled aggregates, while environmentally sustainable, generally reduced performance unless combined with materials like fly ash or slag. Moderate replacement levels are recommended to balance environmental benefits with the concrete performance, as higher substitution rates often degrade properties like strength and durability. This chapter emphasizes the need for careful selection and proportioning of alternative materials to optimize climate-improved concrete.