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Glass with different chemical compositions, deriving from separate collection, has been used as fine aggregate to formulate cementitious mortars, substituting natural sand. Glass coming from cathode-ray tube monitors, fluorescent lamps, and crystal glass (from production of home décor items) along with glass deriving from soda-lime glass containers, which has been taken as a reference, have been investigated. Glass solubility has been determined in alkaline environment similar to the one inside the cementitious composite. Alkali silica reaction has been tested on glass modified cement mortar in different accelerated conditions. Mortar samples containing glass with chemical composition different with respect to soda-lime glass are subjected to alkali silica reaction. This behaviour is largely dependent on the ratio among modifier and stabilizer oxides in the glass. The same ratio affects glass solubility and consequently composition of expanding gels when alkali silica reactions take place. [ABSTRACT FROM AUTHOR]

Alkali activation of fly ash can be considered as one of the more promising alternative systems to traditional hydraulic binders, particularly if the process can be carried out at room temperature. With the aim of finding the best solution chemistry for room temperature activation, two types of fly ash have been activated using Na 2 O/SiO 2 molar ratio ranging from 0.12 to 0.20. It was found that the behaviour of the resultant geopolymer and mortars in the fresh and hardened state is more influenced by the type of fly ash, in particular by their fineness and mineralogical composition, than by the increasing proportion of sodium silicate solution in the mix. [ABSTRACT FROM AUTHOR]

Abstract: The effects of bulk composition and microstructure on strengthening mechanisms and fracture resistance were investigated for metakaolin based geopolymers. Crack initiation and propagation under mechanical and environmental stresses were correlated to pore size distribution and bulk composition. Based on IR spectra and porosity analysis, it was observed that capillary pores and the nature of alkali-aluminosilicate hydrated named polysialates (H–M–A–S) determine cracks initiation site in the Al-rich geopolymer samples with low Si/Al molar ratio (range 1.23–1.5). These samples exhibited low flexural strength, Young modulus and Impact toughness as well as delayed failure under environmental stresses. Increasing the Si/Al molar ratio (range 1.79–2.42) improved the flexural strength and Impact toughness. Formation of more polymerized H–M–A–S phases contributed to strengthening the matrices and hinder axial cracks; consequence of toughening mechanisms developed by the coarsening on molecular scale of H–M–A–S. [Copyright &y& Elsevier]

Graphical abstract Highlights • Fly ash was successfully alkali activated at room temperature. • The use of expanded perlite and H 2 O 2 allowed obtaining lightweight mortars. • Numerical simulations predicted a satisfactory fire behaviour. • Alkali activated lightweight mortars were able to outperform cement-based ones. Abstract Alkali activated lightweight mortars, obtained by room temperature activation of coal fly ash, were studied as passive fire protection systems for steel elements. Physical, mechanical and thermal properties were investigated as a function of the compositional Si/Al molar ratio and of the amount of lightweight aggregate and foaming agent. Experimental findings were used as input data to assess their fire resistance by finite volume simulations. Results pointed out that the optimized alkali activated lightweight mortars are able to outperform alternative commercial cement-based mortars, thus representing a promising technology. [ABSTRACT FROM AUTHOR]

Air- and formulated lime mortars with pulverized brick waste were synthesized with addition of two organic waste-based additives: spent cooking oil and albumen. The addition of spent oil in the mortar induced significant hydrophobic effects, but decreased permeability values and setting kinetics. Parallel additions of oil and albumen in lime mortars significantly increased their hydrophobicity and superficial durability without retarding their setting time thanks to role of fatty acids and unfolded proteins under alkaline conditions. The parallel valorization showed high potentials in synthesis of restorative mortars design with low environmental impact and high respect to the feature of historic mortars. [ABSTRACT FROM AUTHOR]

The suitability of new lime mortars for restorative rendering applications was investigated. Air-, formulated- and hydraulic-lime mortars were synthesized with inclusion of two different types of spent sunflower cooking oils and, when necessary, brick waste powder as pozzolanic addition. The results of spent cooking oils addition in the mortars exhibited promising hydrophobic effects, such as sorptivity reduction up to 60 times and improvement of superficial durability. Addition of high-oleic acid cooking oil in 13 wt% in the formulated and hydraulic lime mortars significantly increased their hydrophobicity without worsening their mechanical strengths. All the investigated mortars exhibited appropriate indexes as restorative materials. [ABSTRACT FROM AUTHOR]

This work investigates the effects of the structure, the bulk chemical composition and amount of the aluminosilicate fines on the strength development, pore refinement, water permeability, moisture control capacity and the microstructure of inorganic polymer concretes (IPC). The amorphous fines, one from pumice and another from recycled glass, presented sponge-like microstructure with tortuous pore network that maintained the presence of fine capillary pores while semi-crystalline feldspar sludge, the third type of fine aggregates used for this study, showed more dense and compact microstructure that explain the higher strength enhancement. Both amorphous and semicrystalline fines contributed to decrease the porosity, improve the strength and microstructure. However, based on the moisture control capacity and the durability indicators, the fine aggregate derived from semicrystalline feldspar was found to be more appropriate and efficient for the development of IPC at short time scale of curing. Pumice fine aggregate was found to be effective only with a long term curing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reclaimed asphalt pavement (RAP) was tested as aggregate replacement for concrete. • Five types of RAP sourced by different Italian collection sites were characterized. • RAP shows irregular porous surface due to bitumen covering the natural aggregate. • RAP shows hydrophobic behavior. • RAP exhibits dimensional stability and frost resistance. A study about the performances of reclaimed asphalt pavement (RAP) sourced from 5 different Italian collection sites is presented to evaluate RAP as aggregate for concrete. Several RAP properties were investigated: physical properties (particles size distribution, water absorption, porosity, wettability), microstructure by microscopy, dimensional stability (drying shrinkage of mortar and concrete with 100% of RAP as aggregates) and durability assessment by freezing-thawing cycles. Several differences between RAP and natural aggregates used for concrete were highlighted. The use of RAP as recycled aggregate for concrete is a promising route, but a complete characterization is needed to ensure concrete performance and durability. [ABSTRACT FROM AUTHOR]