Cementitious material offers proven durability and scalability but lacks dielectric and magnetic loss capabilities, limiting its ability to absorb or shield electromagnetic (EM) waves. Traditional EM absorption systems employ a metal backplane based on transmission line theory, which conflicts with architectural applications. To address this, a multilayer carbon fiber (CF) cement system optimized for absorption-dominated electromagnetic interference (EMI) shielding without secondary reflection was proposed. Chopped CF of three lengths was incorporated into cement matrices with varying loadings to build an EM parameter database. EM parameters and layer thicknesses were optimized using genetic algorithms, achieving a three-layer composite with over 90 % absorptivity across the entire X-band. Increasing fiber length and content enhanced complex permittivity and conductivity via percolated conductive networks. Single-layer samples exhibited high reflectivity over 50 %, confirming reflection-dominant behavior. In contrast, the optimized multilayer structure achieved average reflectivity below 0.1 and EMI shielding effectiveness (SE) from 37.8 to 62.3 dB in simulation, with experimental reflectivity of 0.25 and SE between 28.3 and 62.2 dB. Impedance analysis revealed a descending gradient across layers, enabling progressive EM wave penetration and internal dissipation. Microwave attenuation constants confirmed EM energy loss within each layer, contributing synergistically to overall performance. This absorption-dominant design eliminates the need for metallic reflectors and overcomes the functional and architectural limitations of conventional EMI shielding, demonstrating that engineered CF cement composites offer an effective, scalable, and construction-compatible solution for EM protection.