Mechanical Activation of Construction and Demolition Waste in Order to Improve Its Pozzolanic Reactivity

Mucsi, Gábor; Papné, Nóra Halyag; Ulsen, Carina; Figueiredo, Paula Oliveira; Kristály, Ferenc

doi:10.1021/acssuschemeng.0c05838

Cited by 22 publications

(28 citation statements)

References 58 publications

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“…Some peaks derived from the ceramic compounds present in C&DW, such as albite (A, NaAlSi 3 O 8 , PDFcard 090466) and muscovite mica (M, MgAlSi 4 O 10 (OH) 2 , PDFcard 210993). The presence of these crystalline compounds was similar to the C&DW studied by other authors [ 19 , 20 ].…”

Section: Resultssupporting

confidence: 89%

“…The main oxides present in waste were CaO (23.41%) and SiO 2 (38.41%). These percentages were similar not only the C&DW investigated by Mucsi et al [ 19 ] with CaO (21.1%) and SiO 2 (38.7%), but also to the waste used by Robayo–Salazar et al [ 12 ] with CaO (21.2%) and SiO 2 (47.6%). Regarding the composition of the BFS, this residue had a lower percentage in CaO and slightly higher percentage in SiO 2 .…”

Section: Resultssupporting

confidence: 85%

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Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement

et al. 2022

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Large amounts of waste are derived not only from construction processes, but also the demolition of existing buildings. Such waste occupies large volumes in landfills, which makes its final disposal difficult and expensive. Reusing this waste type is generally limited to being employed as filler material or recycled aggregate in concrete, which limits its valorisation. The present work proposes reusing construction and demolition waste to manufacture alkali-activated cement to improve its sustainability and recovery. Construction and demolition waste (C&DW) from a demolition waste collection plant in Valencia (Spain) was physically and chemically characterised. This residue contained large fractions of concrete, mortar, bricks, and other ceramic materials. X-ray fluorescence (XRF) analysis showed that its chemical composition was mainly CaO, SiO2 and Al2O3. X-ray diffraction (XRD) analysis revealed that it presented some crystalline products, and quartz (SiO2) and calcite (CaCO3) were the main components. Blends of C&DW and blast furnace slag (BFS) were alkali-activated with mixtures of sodium hydroxide and sodium silicate. The corresponding pastes were characterised by techniques such as thermogravimetry and scanning electron microscopy (SEM). The alkali-activated mortars were prepared, and the resulting mortars’ compressive strength was determined, which was as high as 58 MPa with the 50% C&DW-50% BFS mixture. This work concluded that it is possible to make new sustainable binders by the alkali activation of C&DW-BFS without using Portland cement.

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Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 85%

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement

et al. 2022

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“…Q 0 means the isolated silicon−oxygen tetrahedron; Q 1 represents the silicon−oxygen tetrahedron of the silicate dimer or the end of the silicate chain; Q 2 represents the middle tetrahedron in the silicate chain; and Q 2 (1Al) represents the paired sites with an aluminate tetrahedron coordination. The spectrum lines of the 27 Al NMR spectrum are composed of numerous signals of Al [4] in the C-S-H gel, Al [6] in AFt, the hydrotalcite-like phase, and TAH. Moreover, I 0 (Q 0 ) and I(Q 0 ) are the relative intensities of Q 0 species in the unhydrated and hydrated paste, respectively.…”

Section: ■ Experiments and Simulationmentioning

confidence: 99%

“…3 The addition of slag powder can significantly reduce the use of cement, reduce emissions of CO 2 , and protect the ecological environment, achieving sustainable development in marine and inland areas. 4,5 The partial substitution of slag powder improves the interface interaction between concrete components and enhances the fluidity and workability of composite cement materials. 6 Especially, the compressive and waterproof properties and the resistance to chlorine, sulfate, and acid of concrete materials can be considerably improved by adding slag powder.…”

Section: ■ Introductionmentioning

confidence: 99%

Temperature Effect of Hydration and Microstructure of Tricalcium Silicate–Slag Powder Hydrated Composites: An Experimental and Molecular Dynamics Investigation

Hou

Yang

et al. 2021

ACS Sustainable Chem. Eng.

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Slag powder is an effective and promising alternative to cementitious materials for improving the microstructure of cement composites due to its high environmental and economic benefits. The hydration products of cement–slag powder composites have a typical C-A-S-H gel structure. Especially, the hydration temperature significantly impacts the microscopic characteristics of C-A-S-H crystals, which directly determines the efficiency of the slag powder in modifying cementitious materials. In this paper, the microscopic characteristics of tricalcium silicate (C3S)–slag powder hydrated composites at 20, 50, and 80 °C were investigated, while the molecular structure and mechanical properties of C-A-S-H gels at different temperatures were simulated based on molecular dynamics. The results illustrate that the hydration degree of the C3S–slag powder composites is immensely improved with the increased temperature, while the MCL and Al[4]/Si values of the C-A-S-H gels are both increased. Meanwhile, the conversions of dissociative Al[6] to Al[4] and Al[5] in the C-A-S-H structure are promoted at high temperatures. Furthermore, the elevated temperatures cannot affect the “sandwich-like” microstructure of the C-A-S-H gel but are conducive to the polymerization of the aluminosilicate chains and the increasing proportion of Al[4] in the C-A-S-H crystal. Importantly, an increasing temperature leads to a C-A-S-H structure that has higher tensile ductility. This paper reveals the mechanism by which the environmental temperature affects the microstructure of C-A-S-H crystals and provides insights into the research and design of sustainable and environmentally friendly cement–mineral admixture composites with superior durability.

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“…Furthermore, there are other methods to increase the reactivity of clays described in the literature, such as mechanical activation. Mechanical activation significantly changes the structure of clay, increasing the specific surface area, and decreasing the particle size, for example from 13.89 m 2 /g to 21.1 m 2 /g and 35.7 m 2 /g, milling the clay for 4 and 8 h, respectively [ 11 ], and improving the compressive strength of paste due to the higher reactivity, also reaching 53 MP [ 12 ]. In this work the thermal treatment of clays was the subject of study.…”

Section: Introductionmentioning

confidence: 99%

Mine Clay Washing Residues as a Source for Alkali-Activated Binders

Sgarlata

Formia²,

Siligardi

et al. 2021

Materials

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The aim of this paper is to promote the use of mine clay washing residues for the preparation of alkali activated materials (AAMs). In particular, the influence of the calcination temperature of the clayey by-product on the geopolymerization process was investigated in terms of chemical stability and durability in water. The halloysitic clay, a mining by-product, has been used after calcination and mixed with an alkaline solution to form alkali activated binders. Attention was focused on the influence of the clay’s calcination treatment (450–500–600 °C) on the geopolymers’ microstructure of samples, remaining in the lower limit indicated by the literature for kaolinite or illite calcination. The mixtures of clay and alkali activators (NaOH 8M and Na-silicate) were cured at room temperature for 28 days. The influence of solid to liquid ratio in the mix formulation was also tested in terms of chemical stability measuring the pH and the ionic conductivity of the eluate after 24-h immersion time in water. The results reported values of ionic conductivity higher for samples made with untreated clay or with low temperature of calcination (≥756 mS/m) compared with values of samples made with calcined clay (292 mS/m). This result suggests that without a proper calcination of the as-received clay it was not possible to obtain 25 °C-consolidated AAMs with good chemical stability and dense microstructure. The measures of integrity test, pH, and ionic conductivity in water confirmed that the best sample is made with calcined clay at 600 °C, being similar (53% higher ionic conductivity of the eluate) or equal (integrity test and pH) to values recorded for the metakaolin-based geopolymer considered the reference material. These results were reflected in term of reticulation and morphology of samples through the analysis with scanning electron microscope (SEM) and X-ray diffraction (XRD), which show a dense and homogeneous microstructure predominantly amorphous with minor amounts of quartz, halloysite, and illite crystalline phases. Special attention was dedicated to this by-product to promote its use, given that kaolinite (and metakaolin), as primary mineral product, has a strong impact on the environment. The results obtained led us to consider this halloysite clay very interesting as an aluminosilicate precursor, and extensively deepening its properties and reactivity for the alkaline activation. In fact, the heart of this work is to study the possibility of reusing this by-product of an industrial process to obtain more sustainable high-performance binders.

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Mechanical Activation of Construction and Demolition Waste in Order to Improve Its Pozzolanic Reactivity

Cited by 22 publications

References 58 publications

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement

Temperature Effect of Hydration and Microstructure of Tricalcium Silicate–Slag Powder Hydrated Composites: An Experimental and Molecular Dynamics Investigation

Mine Clay Washing Residues as a Source for Alkali-Activated Binders

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