The present work aims to investigate the influence of clay nanoparticles (CNP) on the mechanical, physical and microstructure cement pastes composites. The cement paste composites were formulated by adding 20-60 mass % fly ash (FA), fine blast furnace slag (FBFS) and/or 6 mass % clay nanoparticles. The physico-chemical properties of the cement paste composites (CPC) were improved by the substitution of 6 % CNP in instead of OPC (ordinary Portland cement) in the consistence of the superplasticiser (SP). The physico-mechanical properties and hydration characteristics were investigated by the determination of the setting times (STs), the consistency (W/C, %), the free lime (FL), the combined water (Wn), the gel/ space ratio (X), the total porosity (TP), the compressive strength (CS) and the bulk density (BD). The compressive strength values of the cement-CNP hybrid were higher than those of the cement paste composites without CNP. The STs of CPC-pastes containing CNP were accelerated. The CNP showed synergetic effect with the FA and FBFS to enhance the performance of pozzolanic reaction to form supplementary CSH, CAH and CASH, these phases are responsible for bridging, producing a rigid closed compact structure; hence the compressive strength, gel/space ratio, bulk density and chemically combined water increased, whereas the porosity decreased.