## 1 Introduction  
Cementitious materials have been widely used over the years in the construction sector due to the cement abundance, its low cost and excellent durability [1; 2]. In 2017 the global cement production came up to 4.1 billion tones. China and India which currently represent two of the most rapidly growing countries worldwide produced 57% and 7% of the global cement production in that year, while 6% of the same production is attributed to Europe [3]. It is estimated that the cement production will double in the decades to come [2; 4]. Nevertheless, cement is prone to cracking as a result of both inherent material properties such as low tensile strength and application related factors such as tension inducement during the infrastructure service life thus compromising its integrity and durability [1; 5; 6; 7]. Aggressive environment conditions (i.e., wide ambient temperature fluctuation, rich presence of ions, pH levels etc.) combined with external loading favor crack propagation often leading to the formation of an interconnected crack network that allows corrosive factors to penetrate the structure and assault the reinforcement thus leading to its deterioration. This raises huge safety issues and makes maintenance and repair high priority concerns [6; 7; 8]. Even though autogenous crack self-healing in cementitious materials has been known for centuries, its effectiveness highly depends on numerous factors, namely the crack width and age, water abundance upon the crack formation, environment conditions such as pH and presence of ions etc. [6; 9; 10; 11]. Conventional retrofitting/repair methods applied up to now mainly consist of textile reinforced mortar/concrete (TRM/TRC), the textiles used mainly being based on carbon, glass and aramid fibers, polymer crack injection and polymer modified concrete [1; 9; 10]. These methods have proven to be effective but in several cases, the cost is prohibitive and/or these methods are difficult or even impossible to apply because of the location of the damaged spot on the infrastructure [6; 9]. As a result, internal curing promoting methods have gained a lot interest in the last two decades [1; 9]. These methods focus on (i) maintaining continuous water provision and thus continuous cement hydration and (ii) restraining cement self-desiccation [1]. Over the years, the incorporation of several internal curing agents in cementitious materials such as Light Weight Aggregates (LWA) [1; 2; 5; 9; 12; 13], Superabsorbent Polymers (SAPs) [9; 10; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26], Rice Husk Ash (RHA) [1; 5; 27], bottom ash [1; 5; 28], fly ash [1; 2; 5; 9; 13; 29], enospheres [1; 5; 30], crushed returned concrete fine aggregates (CCA) [1; 13] and wood fibers [1; 13] has been tested. In this application field, SAPs seem to have very promising results and gain more research interest [10]. The SAPs are 3-D polymer networks that due to their hydrophilic nature absorb huge amounts of water (even thousands of times their own dry weight), while due to the network crosslinking they retain their structure and are not dissolved [1; 14; 15; 19; 22; 24; 31]. It is confirmed that their total water absorption level is inversely dependent on environment related factors such as the presence of ions and pH values [10; 18; 22; 24]. Due to their properties, SAPs are used in a vast variety of applications such as hygienic products, agriculture, drug delivery systems, sealing, pharmaceuticals, biomedical applications, tissue engineering, biosensors and the construction field [32]. In the construction field, attention has been drawn to different strategies to obtain coatings with debonding properties [33]. One of these strategies is to incorporate SAPs into an intermediate primer layer between the substrate and the top coatings.