Durability of concrete

Improving the durability of concrete by mitigating autogenous shrinkage and healing of cracks

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To improve concrete’s durability, innovation in concrete technology is necessary. Ultra-high performance concrete (UHPC), characterized by a very low water-to-cement ratio together with a high amount of fine-sized powders, is one of pathways leading to an increase in durability and mechanical properties. Due to the low water-to-cement ratio, these systems are prone to autogenous shrinkage and cracking. A solution to decrease the risk of cracking is by internal curing, provided by the addition of superabsorbent polymers (SAPs) to the cementitious matrix. These SAPs have the ability to absorb large amounts of water, which are released upon further hydration of the cement particles. Moreover, their addition promotes self-sealing and –healing of the material upon cracking, as water is available for further hydration and reaction products are precipitated inside the cracks. However, a drawback can be seen upon the use of these polymers, as they initiate pores and decrease the compressive strength. For this reason, nanoclays are added to the mixture. Due to their small volume compared to a large surface area, they act as a highly reactive filler increasing both strength and durability.


Long lasting reinforced concrete for energy infrastructures under severe operating conditions LORCENIS

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The main goal of the LORCENIS project is to develop long lasting reinforced concrete for energy infrastructures with a lifetime extended up to a 100% under extreme operating conditions. At the Ghent University, the main focus lies on the development and testing of superabsorbent polymers (SAPs) for internal curing, self-sealing and self-healing of concrete. Due to the combined effect of mitigating shrinkage at the one hand and the sealing and healing of possible cracks at the other hand, the durability of the concrete is enhanced. Different in house synthesized SAPs will be tested in concrete under severe conditions, see picture, both at lab scale and in real scale prototypes.
Long lasting reinforced concrete for energy infrastructures under severe operating conditions LORCENIS

 

Durability of concrete in marine environments

(Mathias Maes, for more info: )

Marine constructions are exposed to very aggressive substances since sea water consists mainly of chlorides and sulphates. Chlorides affect durability by initiating corrosion of the reinforcement steel and sulphates affect durability by deteriorating the concrete itself. Former research mostly focused on the individual attack mechanisms, although multi-ion transport of chlorides and sulphates changes the attack mechanisms since both ions bind with the aluminate minerals in cement. In case of chloride attack, binding is beneficial since less free chlorides remain to reach the reinforcement, but in case of sulphate attack, binding means formation of expansive reaction products. In this research, the reciprocal influence is investigated and the obtained results will be used to refine service life prediction models

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Marine structure exposed to sea water

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Chloride penetration: visualization by 0.1 M AgNO3 – profile grinder – titration equipement – chloride profiles