Effect of superabsorbent polymers (SAP) on fresh state mortars with ground granulated blast-furnace slag (GGBS)

Although cementitious materials are the main construction materials and worldwide produced, there is still a major concern about their sustainability and durability, especially in terms of conserving resources, reducing wastes, and decreasing the environmental impacts of repair and replacement. In general, cementitious materials are very susceptible to cracking provoked by autogenous shrinkage due to their associated self-desiccation process. The problem is even more critical in concrete with blended cements, including Portland cement with ground granulated blast-furnace slag (GGBS). The current paper evaluates efficiency of superabsorbent polymers (SAP) as internal curing agents; shrinkage reduction in mortars with different levels of cement replacement by GGBS (0, 25, 50, and 75%) is presented. The study is focused on three types of SAPs with different water absorption/desorption capacities (SAP I: 10 g/g, SAP II: 25–30 g/g, and SAP III: 35 g/g in cement paste solution). Tests of consistency, density, air content of fresh mortar, setting times, and autogenous shrinkage are analysed. The results showed that mortars with SAP can significantly reduce autogenous shrinkage for any studied GGBS content in comparison with the reference mortar. The reduction of autogenous shrinkage by SAP may decrease the cracking susceptibility and hence increase the sustainability level of the material for more durable constructions

Particle size characterization of SCMs by mercury intrusion porosimetry

Mercury intrusion porosimetry (MIP) is widely used for the microstructural characterisation of porous solids. Comparatively few studies have employed the technique to characterise the size of particles within powdered samples. The present study uses the MIP technique to characterise the particle sizes of contemporary supplementary cementitious materials (SCMs), and in particular uses the technique to present particle size distributions, rather than a single mean size. Representivity of the technique for known limitations of non-spherical and porous particles are checked using the Scanning Electron Microscope. The findings indicate that the MIP affords a good approximation of particle sizes, including distributions, of spherical and non-spherical particles. The technique was also found to provide reasonable accuracy for estimating the particle sizes of highly porous particles, where distinction between inter-particle and intra-particle porosity was made