چكيده به لاتين
Concrete transition zone, which is a highly porous space in the cement paste adjacent to the aggregate surfaces causes reductions in compressive and flexural strengths of the concrete and results in structural degradations by increasing its permeability against sulfates and chlorides. For this reasons, researches are trying to reduce the negative consequences of transition zone. In this work, the effect of using Portland cement clinker as aggregate on the microstructure of transition zone in both normal concrete (NC) and reactive powder concrete (RPC) has been studied. Replacement of aggregate with Portland cement clinker in NC and RPC resulted in the development of new concretes, named Reactive-Aggregate Concrete (RAC) and Reactive-Powder & Aggregate Concrete (RPAC), respectively, exhibiting improved properties. Microstructural studies with scanning electron microscope confirmed that this technique greatly improves or eliminates the transition zone and effectively increases the compressive and flexural strengths of the concrete by creating chemical bonding between cement paste and aggregate. This technique also results in significant reductions open pore volume, the amount of water adsorption, and chlorine penetration depth in concrete. According to the results, replacement of aggregate with Portland cement clinker resulted in 143% increase in 3-day compressive strength in NC and 75% decrease in Chlorine penetration depth in RPC.
