Matches in UGent Biblio for { ?s ?p The phenomenon of autogenous healing of cracks in cementitious materials has already been known for many years. Cracks in old concrete structures, like Roman aqueducts or gothic churches are healed when moisture contacts with unhydrated cement clinker in the crack. Because of this, new CaCO3 crystals are formed which can be seen as white crystalline material at the crack surface. However concrete composition has changed over time and less unhydrated cement is present in current concrete structures. Nevertheless in their research, Aldea et al., also noted some self-healing behaviour while they studied the water flow through cracked concrete. A reduction in water flow was observed after some time, indicating self-healing of the cracks. However this healing effect was restricted to the healing of small cracks. Therefore, in this study, it is tried to stimulate the self healing potential of cementitious materials by varying the mix composition and cement type. Cement is a hydraulic binder that hardens in contact with water. The active component in cement is Portland clinker and for some cement types also blast furnace slag, fly ash or limistone. Clinker has strong hydraulic properties and is produced by sintering calcium carbonate and silicium-, aluminium- and iron oxide. Blast furnace slag is a residue from the steel industry and it has latent hydraulic properties. This means that the hydration reaction needs to be activated by substances such as calcium hydroxide, e.g. from clinker hydration. Fly ash is a waste product from coal combusted power stations. This is a component with pozzolanic properties which means that it binds with the lime that is formed during hydration of the clinker. Limestone however is an inert material, used to improve the concrete workability.. }
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- aggregation abstract "The phenomenon of autogenous healing of cracks in cementitious materials has already been known for many years. Cracks in old concrete structures, like Roman aqueducts or gothic churches are healed when moisture contacts with unhydrated cement clinker in the crack. Because of this, new CaCO3 crystals are formed which can be seen as white crystalline material at the crack surface. However concrete composition has changed over time and less unhydrated cement is present in current concrete structures. Nevertheless in their research, Aldea et al., also noted some self-healing behaviour while they studied the water flow through cracked concrete. A reduction in water flow was observed after some time, indicating self-healing of the cracks. However this healing effect was restricted to the healing of small cracks. Therefore, in this study, it is tried to stimulate the self healing potential of cementitious materials by varying the mix composition and cement type. Cement is a hydraulic binder that hardens in contact with water. The active component in cement is Portland clinker and for some cement types also blast furnace slag, fly ash or limistone. Clinker has strong hydraulic properties and is produced by sintering calcium carbonate and silicium-, aluminium- and iron oxide. Blast furnace slag is a residue from the steel industry and it has latent hydraulic properties. This means that the hydration reaction needs to be activated by substances such as calcium hydroxide, e.g. from clinker hydration. Fly ash is a waste product from coal combusted power stations. This is a component with pozzolanic properties which means that it binds with the lime that is formed during hydration of the clinker. Limestone however is an inert material, used to improve the concrete workability.".