In order to optimize the grain size composition of Portland cement with the addition of silica fume and to activate the hardening process of composite cement the method for surface modification in high-voltage electric field is proposed. The electrical agglomeration setup to produce modified composite cement has been designed. An observation of a cross-section of a cement particle by scanning electron microscopy and an analysis of the element distribution on the surface of modified composite cement particles are shown. According to the test results, cement pastes based on the modified composite cement possess the 28-day compressive strength of up to 89.3MPa, a 37% increase over the reference.