Multi-technique characterization of a fine fraction of CDW and assessment of reactivity in a CDW/lime system

This study analysed the fine particle (<5 mm) waste generated during siliceous or calcareous (depending on the composition of the original aggregate) concrete waste crushing. In the absence of industrial applications, such waste is amassed in open-air stockpiles on construction and demolition wastes (CDW) management plant grounds. The aim pursued was to find an outlet for that material in the cement industry. The starting waste, sourced from six Spanish management facilities, was characterised for its chemical and mineralogical composition, physical properties and pozzolanicity. The mineralogical phases in the CDW/lime system and their variations during the pozzolanic reaction were likewise identified. The findings showed that the fine waste consisted primarily in quartz, calcite, micas and feldspars, with smaller fractions of kaolinite and cement anhydrous phases. No portland cement hydration phases were identified. All six types analysed exhibited medium to low pozzolanicity, with the highest values recorded for the siliceous waste. Ettringite, C–S–H gels and calcium aluminate hydrates (C4AH13, C4AcH12) were identified during the pozzolanic reaction in CDW/lime system. Therefore, this type of waste can be reused as supplementary cementitious material with low-medium pozzolanic activityThis research was funded by Spain’s Ministry of Science, Innovation and Universities under National Project RTI2018-097074-B-C21, the EU’s ERDF, the Spanish National Research Agency (AEI), the Spanish Construction and Demolition Waste Recycling Association (RCDA), Sika (Madrid, Spain) and the Spanish Institute of Cement and its Applications (IECA

Reactivity of Binary Construction and DemolitionWaste Mix as Supplementary Cementitious Materials

Calcareous and siliceous CDW wastes from concrete and glass wastes when mixed in binary mixtures has been analyzed in this study. Fine CDW fractions (<5 mm) of different sorts are selected: siliceous waste (HsT), calcareous waste (HcG) and laminated glass waste. The binary mixtures HsT/glass and HcG/glass at mix-proportions of 1:1, 2:1 and 1:2, respectively, are analyzed with a range of characterization techniques (XRD, TG/DTA, SEM-EDX, NMR, FT-IR) in the pure pozzolan/lime system over a reaction time of 90 days. The results showed that the incorporation of highly reactive recycled glass modified the pozzolanic reaction of the binary mixtures with respect to each particular concrete waste (of low activity). The principal mineralogical phases of the reaction were calcite and C¿S¿H gel, the latter modifying the C/S and A/S ratios as a function of either the silica or the lime-based concrete waste and the glass content of the mixtures. A higher degr

THERMAL AND CHEMICAL TREATMENTS FOR REMOVAL OF ALKALI OXIDES OF ELEPHANT GRASS ASHES

Elephant grass ash (EGA) was produced at 700 °C, with two different treatments: hot water (EGAhw) or acid solution (EGAas). The efficiency of the treatments at removing the potassium oxide was evaluated with the aim of using the EGA as a pozzolanic mineral addition for cement-based composites. Characterizations were carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), pozzolanic activity by electric conductivity and application of the kinetic-diffusive model. The analysis evidenced that the chemical treatment was more efficient for removing potassium oxide. The pozzolanic activity test and the kinetic parameters for the EGAas indicated that this ash is suitable for cement-based composites

Reactivity of binary construction and demolition waste mix as supplementary cementitious materials

Calcareous and siliceous CDW wastes from concrete and glass wastes when mixed in binary mixtures has been analyzed in this study. Fine CDW fractions (<5 mm) of different sorts are selected: siliceous waste (HsT), calcareous waste (HcG) and laminated glass waste. The binary mixtures HsT/glass and HcG/glass at mix-proportions of 1:1, 2:1 and 1:2, respectively, are analyzed with a range of characterization techniques (XRD, TG/DTA, SEM-EDX, NMR, FT-IR) in the pure pozzolan/lime system over a reaction time of 90 days. The results showed that the incorporation of highly reactive recycled glass modified the pozzolanic reaction of the binary mixtures with respect to each particular concrete waste (of low activity). The principal mineralogical phases of the reaction were calcite and C–S–H gel, the latter modifying the C/S and A/S ratios as a function of either the silica or the lime-based concrete waste and the glass content of the mixtures. A higher degree of polymerization, morphology, and sodium content of C-H-S gel formed when glass was added.Peer ReviewedPostprint (published version

Quantitative Comparison of Binary Mix of Agro-Industrial Pozzolanic Additions for Elaborating Ternary Cements: Kinetic Parameters

In this research work, the quantitative characterization of a binary blend comprised of two pozzolans (sugar cane straw (SCSA)¿sugar cane bagasse ashes (SCBA), bamboo leaf ash (BLAsh)¿SCBA and paper sludge (PS)¿fly ash (FA)) taking into account the calculated values of the kinetic parameters of the reaction in the pozzolan/calcium hydroxide system is shown. The paper shows the most significant and important results obtained by the authors in the quantitative assess-ment (calculation of kinetic parameters) of the pozzolanic reaction of different mixtures of poz-zolanic materials that are residues from agriculture or industrial processes. This allows a direct and rigorous comparison of the pozzolanic activity of the binary combinations of materials. The values of the kinetic parameters (reaction rate constant or activation free energy) constitute a very precise quantitative index of the pozzolanic activity of the binary combinations of materials, which is very useful for its employment in the elaboration of ternary cements. This paper shows that the binary blends 1SCBA60Blash40, 1SCBA50Blash50, 1SCBA70Blash30 have a very high pozzolanic reactivity followed by PSLSFA, 2SCBA50SCSA50, PSISFA and SCWI.The authors thank FAPESP (Brazil) (process 2011/12691-2) and CNPq (Brazil) (401704/2013- 0 and 306386/2013-5) for the financial support to carry out and to conclude this research work. Also, the authors would like to thank the FAPESP (process n. 2011/16842-5) and the CSIC-FAPESP program (i-Link+2013, project ref: i-link0675, 2013/50790-8) for their financial support and the Framework Agreement of Collaboration between IETcc/CSIC (Spain) and FZEA/USP (Brazil) (ref: BDC 20195707 ACAM 2019040029)