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Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C3S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C3S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures. [ABSTRACT FROM AUTHOR]

As an internal curing substance for cementitious materials, superabsorbent polymer (SAP) is emerging as the most potential solution. Nanomaterials and their composites have wide applications in concrete mainly as crack sealants and viscosity modifiers. Silane, as a coupling agent, is utilized in cementitious materials for its effective particle dispersion and adhesion characteristics. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetry (TGA) analysis, and Scanning electron microscopy (SEM) are utilized to characterize the microstructures and phase compositions of nanoalumina, (3-aminopropyl) triethoxysilane (APTES) and polyacrylamide (PAM) SAP. The impacts of silane-functionalized nanoalumina combined polyacrylamide SAP in cementitious materials are carefully investigated in this work. Compared with plain SAP, the application of silane-functionalized SAP was found to exhibit increased compressive strength, flexural strength and split tensile strength of concrete. The chemical durability properties of cement mortar, rheological and mechanical properties of concrete under self-curing and water curing with cement replaced by the prepared composites at 0.1, 0.2, 0.3, 0.4 and 0.5% by weight of cement are studied experimentally. Results revealed that silane-functionalized nanoalumina modified SAP has good water holding capacity than those with individual SAPs contributing to the advancement of internal curing materials in concrete buildings. The weight loss measurements reveal that lower weight loss is observed for the concrete containing SAP/APTES/nanoalumina in chloride, acidic and sulphate media. This work contributes to the advancement in material technologies for the prevention of building fractures. [ABSTRACT FROM AUTHOR]

An attempt was made to drift nanoalumina particles into concrete pores through electrokinetic treatment. An external electric current (current density = 3 A/m 2 ) was applied for 3 and 15 days in reinforced concrete blocks toward steel reinforcement and microstructural characterizations (i.e. morphology observation and porosity analysis) were performed on concrete fragments of different depth from exposure surface. The morphology observation evidenced transport of nanoalumina from the exposure surface even reaching the rebar-concrete interface (up to 25–30 mm, in 15 days treatment). The porosity analysis of treated samples revealed that reduction of porosity of rebar interface was more pronounced as compared to the exposure surface and the treatment for 15 days was more beneficial for porosity refinement than treatment for 3 days. Effects of the electrokinetic NA treatment on strength of rebar-concrete interface were evaluated through pull-out test. The results showed that by increasing current density, bond strength of rebar-concrete interface increased. [ABSTRACT FROM AUTHOR]

Carbon nanoplatelet and nanoalumina reinforced PEEK nanocomposites were fabricated by twin-screw extrusion followed by injection molding. The effect of the filler loading on mechanical properties, morphology, dielectric strength, and thermal stability of the composites has been analyzed. The mechanical properties were found to increase with nanoplatelet content up to 1% loading (optimum filler content) and after that, due to agglomeration of filler, slight decrease in properties were observed. For alumina-filled systems mechanical properties increased with increasing filler content due to the well-dispersed fillers in the composites. The modulus and toughness of alumina-filled composites were higher than platelet-filled composites. [ABSTRACT FROM AUTHOR]