Cement in concrete, the second most used entity after water in the world today, is the fourth largest source of anthropogenic carbon emission. Thus, cement is called a carbon-positive binding material. Ferrock is a carbon-negative material created from the reaction of waste steel dust and silica-based mineral admixture with carbon dioxide from the surrounding atmosphere. Chemically it is an iron carbonate matrix that is very stable under severe exposure. In the present study, the two types of Ferrock specimens made with various solids compositions of 1) iron powder (10–20%), iron dust powder (40–60%) and cement (50%) and 2) iron powder (10–20%), iron dust powder (40–60%), cement (20–30%), and fly ash (20–30%) for water-cement ratio of 0.61. Similarly, a cement mortar reference specimen is made with cement and Indian standard sand for a water-cement ratio of 0.37. Iron dust powder used for the study as fine aggregate replacement has a similar gradation as that of sand. After the valuation of optimum content for the combination of iron dust, cement, fly ash, and water–solid ratio, the concrete cube’s solid ratio for Ferrock concrete is arrived at based on the workability requirements of the mixture and can be easily altered by using a superplasticizer. For the developed Ferrock concretes, strength properties such as compressive, and split tensile are evaluated to compare with the corresponding properties of OPC-based concrete made for similar proportions.