Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

Abstract

Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs) seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials.

Hygral Behavior of Superabsorbent Polymers with Various Particle Sizes and Cross-Linking Densities

“…Since the later-age water migration from SAP to cement paste is primarily governed by the RH gradient between the SAP and cement paste [4,34], it is important to evaluate how the absorptivity varies at different RH levels. SAP samples were prepared with the same procedure utilized in the desorption test to identify the water release across different levels of RH.…”

“…It is well recognized that 1 g of SAP could absorb up to 500 g of aqueous solutions within a few minutes [1,2]. Taking advantage of such super-absorptive characteristics, SAPs have been popularly used in the hygiene, agriculture, forestry, and medical industry since the 1970s [3,4].…”

Effect of submicron admixtures on mechanical and self‐healing properties of cement‐based composites

“…On the contrary, in a SAP‐reinforced cement specimen, when a crack reaches the surface of a SAP particle, it will need more energy to propagate through the inclusion. Thus, the creation of a new crack surface is needed, which is as an energy‐consuming process, corresponding to increased flexural strength in cementitious matrices with SAP addition …”

“…In cementitious materials of early age, SAPs release water they have absorbed gradually during cement setting and hardening thus mitigating autogenous shrinkage and enhancing prolonged hydration reactions which contribute to the densification of the cement microstructure and thus to the improvement of the structure durability . SAPs have also been used in cement as additives to stimulate autogenous self‐healing/sealing behavior when cracks are introduced in concrete structures . As water penetrates the formed crack, it is absorbed by SAPs which on one hand swell filling the crack volume (self‐sealing behavior) and on the other hand stimulate further hydration reactions and calcium carbonate precipitation (self‐healing behavior) according to the mechanisms that have already been explained for autogenous self‐healing/sealing in cementitious materials earlier …”

“…Nevertheless, there are still great challenges reported in literature regarding the SAPs/cement composites: (1) the process followed for their incorporation in the concrete mix as well as the decrement in the mixture's workability, (2) the preservation of their ability to absorb and release water multiple times and specifically upon crack formation so that a self‐healing/sealing event will take place, (3) the macropore formation in the produced specimens due to the absorbing/desorbing behavior of SAPs during and after the mixing procedure which leads to the degradation of their mechanical properties, and (4) the lack of adhesion between the phases of the cement matrix/SAPs interface which could result in the development of additional defects acting as stress inducers.…”