Internal Curing Mechanisms in Cementitious Materials

Internal curing refers to the incorporation of internal water reservoirs within cementitious mixtures to sustain hydration, mitigate early-age self-desiccation and control autogenous shrinkage. By embedding materials such as superabsorbent polymers, pre-wetted lightweight aggregates or hydrogel particles, water is gradually released as cement hydration consumes mixing water. This controlled release preserves internal relative humidity, refines pore structure and reduces capillary tension, leading to lower cracking risk and improved long-term durability. Beyond shrinkage control, internal curing enhances mechanical performance, promotes further hydration in under-hydrated zones and can stimulate autogenous healing of microcracks. Applications span high-performance concrete, ultra-high-performance systems and alkali-activated binders, with global significance in reducing repair costs, extending service life and lowering the carbon footprint of built infrastructure.

Research from Nature Portfolio

Recent studies have employed nuclear magnetic resonance to visualise and quantify water exchange between superabsorbent polymers and cementitious matrices. One investigation mapped the kinetics of water release from swollen polymer networks, revealing a two-stage desorption process that maintains internal humidity during the acceleration phase of hydration. This work confirmed that polymer typology and crosslink density dictate release rate and thereby influence early-age autogenous shrinkage. Another study quantified autogenous healing by measuring further hydration around cracks in polymer-modified cement pastes. The findings demonstrated that even brief daily moisture contact triggers up to 40% additional hydration compared with unmodified systems, while retained moisture within polymer inclusions sustains healing under high-humidity conditions. Together, these advances offer quantitative insight into the interplay between internal curing agents and microstructural evolution.

Internal Curing Mechanisms in Cementitious Materials publication trend

The graph below shows the total number of articles in internal curing mechanisms in cementitious materials across all publications each year (not limited to Nature Index journals).

Technical terms

Internal curing: Controlled release of water within a cementitious matrix to sustain hydration and reduce shrinkage.

Superabsorbent polymer (SAP): High-capacity water-absorbing particles that serve as internal water reservoirs during cement hydration.

Autogenous shrinkage: Volume reduction in cementitious materials caused by self-desiccation during hydration without external moisture exchange.

Self-desiccation: Internal drying resulting from chemical water consumption during cement hydration leading to reduced internal relative humidity.

Lightweight aggregate (LWA): Porous aggregates pre-saturated with water to act as internal curing reservoirs in concrete.

Alkali-activated materials: Cementitious systems activated by alkaline solutions, often requiring internal curing to control early-age deformation.

References

1. The water kinetics of superabsorbent polymers during cement hydration and internal curing visualized and studied by NMR. Scientific Reports (2017).
2. Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?. Materials (2017).
3. Internal curing of alkali-activated fly ash-slag pastes using superabsorbent polymer. Cement and Concrete Research (2019).
4. Application of super absorbent polymers (SAP) in concrete construction—update of RILEM state-of-the-art report. Materials and Structures (2021).
5. Autogenous Healing in Cementitious Materials with Superabsorbent Polymers Quantified by Means of NMR. Scientific Reports (2020).