Concrete cracks due to its low tensile strength. The presence of cracks endangers the durability as they generate a pathway for harmful particles dissolved in fluids and gases. Without a proper treatment, maintenance costs will increase. Self-healing can prevail in small cracks due to precipitation of calcium carbonate and further hydration. Therefore, the use of microfibres is proposed to control the crack width and thus to promote the self-healing efficiency. In the current research, crack sealing is also enhanced by the application of superabsorbent polymers. When cracking occurs, superabsorbent polymers are exposed to the humid environment and swell. This swelling reaction seals the crack from intruding potentially harmful substances. Mortar mixtures with microfibres and with and without superabsorbent polymers were investigated on their crack sealing and healing efficiency. Regain in mechanical properties upon crack healing was investigated by the performance of four-point-bending tests, and the sealing capacity of the superabsorbent polymer particles was measured through a decrease in water permeability. In an environment with a relative humidity of more than 60%, only samples with superabsorbent polymers showed healing. Introducing 1 m% of superabsorbent polymer gives the best results, considering no reduction of the mechanical properties in comparison to the reference, and the superior self-sealing capacity.
h i g h l i g h t sHydrogel was used as the bacterial carrier in concrete for self-healing cracks. Hydrogel acts as water reservoirs for continuous crack healing (autogenic-, biogenic-). Carbonate precipitating bacteria can precipitate CaCO 3 in/on hydrogel. Crack of a width 0.5 mm can be completely healed in the specimens with bio-hydrogels embedded. Bacterial based self-healing is a potential solution for sustainable development of concrete.
h i g h l i g h t sSuperabsorbent polymers cause a densification of the cementitious matrix. Additional water counteracts densification and leads to the same capillary porosity. Care needs to be taken when using high amounts of SAPs in cementitious materials. Superabsorbent polymers affect the microstructure and strength properties.
Fly ash and blast-furnace slag containing binders are frequently used in the construction industry and it is important to know the extent of autogenous shrinkage and its (ideal) mitigation by superabsorbent polymers in these systems as a function of their age. In this paper, the autogenous shrinkage was determined by manual and automated shrinkage measurements. Autogenous shrinkage was reduced in cement pastes with the supplementary cementitious materials versus Portland cement pastes. At later ages, the rate of autogenous shrinkage is higher due to the pozzolanic activity. Internal curing by means of superabsorbent polymers is successful, independent of this long term higher rate of shrinkage in mixtures with supplementary cementitious materials.
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