Alkali-activated materials (AAMs), as eco-friendly alternatives to Portland cement (PC), have attracted increasing attention of researchers and users in the past decades. Despite the eco-friendly nature of AAMs, doubts about these materials as an essential ingredient of concrete exist, regarding, for example, their volume stability. One possible volume change concerns autogenous shrinkage. Autogenous shrinkage is the self-created volume reduction of materials due to chemical reactions without the need for substance or heat exchange with the environment. If the autogenous shrinkage of a binder material is too large, cracking might happen, which will seriously impair the durability of concrete. The aim of this chapter is to provide a state-of-the-art review on the autogenous shrinkage of AAMs. The different characteristics and mechanisms of autogenous shrinkage of different AAMs are reported. Corresponding shrinkage-mitigating strategies are summarized. Existing models to simulate and predict the autogenous shrinkage of AAMs are reviewed. Remarks are then given on testing methods of autogenous shrinkage, which link back to the determination of the magnitude of autogenous shrinkage of AAMs. Connections between autogenous shrinkage and other deformations such as drying shrinkage, thermal deformation and creep are also discussed. Research gaps and outlook on future research in this field are given in the end.

In this paper, fresh (setting and rheology) and hardened properties (strength and shrinkage) of one-part alkali-activated slag (AAS) with and without rice straw ash (RSA) are comprehensively investigated. The reaction kinetics and microstructure of the mixtures are characterized by a series of experimental techniques. The results reveal that RSA plays dual roles in AAS, as a precursor (though not fully reactive) and an internal curing agent. The reactive K and Si in RSA participate in the formation of C-(A)-S-H gel and the alkaline groups dissolved from the ash facilitate the hydrolysis of slag. Besides, the porous RSA absorbs liquid in the first day and releases it afterwards, thus providing internal curing to the matrix. The consistency index of the paste becomes higher with the incorporation of RSA. Both autogenous and drying shrinkage of AAS, which are considered as two problematic issues for this material, are mitigated by RSA.

One-part alkali-activated slag (AAS) as a binder material has a promising application in the construction industry. The properties of one-part AAS incorporating agricultural wastes have been seldom studied. In this paper, the fresh and hardened properties of one-part AAS with the addition of rice straw powder (RSP) were investigated. The reaction rate in the acceleration period of AAS is reduced by RSP. The compressive strength of the mixture decreases with the introduction of RSP, while the flexural strength increases. The porosity of the hardened mixtures becomes lower when RSP was incorporated. N-(C)-A-S-H gel was detected in the system when 4.2% RSP was present. The RSP reduces the early-age autogenous shrinkage of AAS by providing internal curing to the matrix, but its effect on long-term drying shrinkage is limited.