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14 pages, 3270 KiB

Open AccessArticle

Alkali-Activated Mortars for Sustainable Building Solutions: Effect of Binder Composition on Technical Performance

by Agnese Attanasio, Livio Pascali, Vito Tarantino, Wanda Arena and Alessandro Largo

Environments 2018, 5(3), 35; https://0-doi-org.brum.beds.ac.uk/10.3390/environments5030035 - 28 Feb 2018

Cited by 18 | Viewed by 5451

There is a growing interest in the construction sector in the use of sustainable binders as an alternative to ordinary Portland cement, the production of which is highly impacting on the environment, due to high carbon dioxide emissions and energy consumption. Alkali-activated binders, [...] Read more.

There is a growing interest in the construction sector in the use of sustainable binders as an alternative to ordinary Portland cement, the production of which is highly impacting on the environment, due to high carbon dioxide emissions and energy consumption. Alkali-activated binders, especially those resulting from low-cost industrial by-products, such as coal fly ash or metallurgical slag, represent a sustainable option for cement replacement, though their use is more challenging, due to some technological issues related to workability or curing conditions. This paper presents sustainable alkali-activated mortars cured in room conditions and based on metakaolin, fly ash, and furnace slag (both by-products resulting from local sources) and relevant blends, aiming at their real scale application in the building sector. The effect of binder composition—gradually adjusted taking into consideration technical and environmental aspects (use of industrial by-products in place of natural materials in the view of resources saving)—on the performance (workability, compressive strength) of different mortar formulations, is discussed in detail. Some guidelines for the design of cement-free binders are given, taking into consideration the effect of each investigated alumino-silicate component. The technical feasibility to produce the mortars with standard procedures and equipment, the curing in room conditions, the promising results achieved in terms of workability and mechanical performance (from 20.0 MPa up to 52.0 MPa), confirm the potential of such materials for practical applications (masonry mortars of class M₂₀ and M_d). The cement-free binders resulting from this study can be used as reference for the development of mortars and concrete formulations for sustainable building materials production. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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5200 KiB

Open AccessArticle

Geopolymer Composites for Potential Applications in Cultural Heritage

by Laura Ricciotti, Antonio Jacopo Molino, Valentina Roviello, Elena Chianese, Paola Cennamo and Giuseppina Roviello

Environments 2017, 4(4), 91; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4040091 - 13 Dec 2017

Cited by 40 | Viewed by 6370

Abstract

A new class of geopolymer composites, as materials alternative to traditional binders, was synthesized and its potentialities as restoration material in Cultural Heritage has been explored. This material has been prepared through a co-reticulation reaction in mild conditions of a metakaolin-based geopolymer inorganic [...] Read more.

A new class of geopolymer composites, as materials alternative to traditional binders, was synthesized and its potentialities as restoration material in Cultural Heritage has been explored. This material has been prepared through a co-reticulation reaction in mild conditions of a metakaolin-based geopolymer inorganic matrix and a commercial epoxy resin. The freshly prepared slurry displays a consistency, workability and thixotropic behavior that make it suitable to be spread on different substrates in restoration, repair and reinforcement actions, even on walls and ceilings. Applicability and compatibility tests on tuff and concrete substrates were carried out and the microstructure of the samples in correspondence of the transition zone was analyzed by means of scanning electron microscope (SEM) observations and energy dispersive spectroscopy (EDS) mapping. Our studies pointed out the formation of a continuous phase between the geopolymer composite and tuff and concrete substrates, highlighting a high compatibility of the geopolymer binder with different kinds of materials. These features indicate a large potential for applications of these materials in Cultural Heritage. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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4570 KiB

Open AccessArticle

Addition of WEEE Glass to Metakaolin-Based Geopolymeric Binder: A Cytotoxicity Study

by Michelina Catauro, Isabella Lancellotti and Cristina Leonelli

Environments 2017, 4(4), 89; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4040089 - 07 Dec 2017

Cited by 10 | Viewed by 4993

Abstract

Waste Electrical and Electronic Equipment (WEEE) types of glass, including Cathode Ray Tube (CRT) glass, are now separately collected in European Union 28 (EU28) zone. Due to the high level of Pb and Ba in their compositions, this type of waste finds its [...] Read more.

Waste Electrical and Electronic Equipment (WEEE) types of glass, including Cathode Ray Tube (CRT) glass, are now separately collected in European Union 28 (EU28) zone. Due to the high level of Pb and Ba in their compositions, this type of waste finds its way to the disposal. In the present research, a geopolymer matrix based on metakaolin is used to blend in fine powder panel and funnel glass from personal computer (PC) and television (TV) monitors. Such waste glass, which cannot be directed to glass melting furnaces, is safely incorporated into a geopolymer matrix. The consolidation of the geopolymeric matrix containing the waste glass was followed by pH and conductibility up to 28 days of curing. Scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) was used to obtain information on the microstructure of the consolidated products. Cytotoxicity tests helped the environmental evaluation of these materials. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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3888 KiB

Open AccessArticle

Porous Geopolymer Insulating Core from a Metakaolin/Biomass Ash Composite

by Annalisa Natali Murri, Valentina Medri, Elettra Papa, Luca Laghi, Claudio Mingazzini and Elena Landi

Environments 2017, 4(4), 86; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4040086 - 01 Dec 2017

Cited by 24 | Viewed by 6681

Abstract

Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers [...] Read more.

Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers in a metakaolin-based geopolymer composite to produce, by direct foaming, sustainable and lightweight boards with thermal insulating properties. The investigated materials were obtained by activating a blend of metakaolin and biomass ash in a weight ratio of 1: 1 and foamed with the addition of H₂O₂ in measure of 5 wt. %, to maximize the volume of disposed ash and ensure adequate properties to the material at the same time. The obtained geopolymer composite was characterized by microstructural, chemical-physical, mechanical and thermal analysis: the obtained results showed that biomass ash and metakaolin well integrated in the microstructure of the final porous material, which was characterized by a density of about 310 kg/m³ and a thermal conductivity of 0.073 W/mK at a mean test temperature of 30 °C, coupled with an acceptable compressive strength of about 0.6 MPa. Dilatometric and thermogravimetric analysis, performed up to 1000 °C, highlighted the thermal stability of the composite, which could be regarded as a promising material for low-cost, self-bearing thermal insulating partitions or lightweight cores for thermostructural sandwich panels. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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1414 KiB

Open AccessArticle

Mechanical Behaviour of Soil Improved by Alkali Activated Binders

by Enza Vitale, Giacomo Russo, Gianfranco Dell’Agli, Claudio Ferone and Chiara Bartolomeo

Environments 2017, 4(4), 80; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4040080 - 11 Nov 2017

Cited by 16 | Viewed by 5553

Abstract

The use of alkali activated binders to improve engineering properties of clayey soils is a novel solution, and an alternative to the widely diffused improvement based on the use of traditional binders such as lime and cement. In the paper the alkaline activation [...] Read more.

The use of alkali activated binders to improve engineering properties of clayey soils is a novel solution, and an alternative to the widely diffused improvement based on the use of traditional binders such as lime and cement. In the paper the alkaline activation of two fly ashes, by-products of coal combustion thermoelectric power plants, has been presented. These alkali activated binders have been mixed with a clayey soil for evaluating the improvement of its mechanical behaviour. One-dimensional compression tests on raw and treated samples have been performed with reference to the effects induced by type of binder, binder contents and curing time. The experimental evidences at volume scale of the treated samples have been directly linked to the chemo-physical evolution of the binders, investigated over curing time by means of X Ray Diffraction. Test results showed a high reactivity of the alkali activated binders promoting the formation of new mineralogical phases responsible for the mechanical improvement of treated soil. The efficiency of alkali activated binders soil treatment has been highlighted by comparison with mechanical performance induced by Portland cement. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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5664 KiB

Open AccessArticle

Production of Geopolymeric Mortars Containing Forest Biomass Ash as Partial Replacement of Metakaolin

by Sebastiano Candamano, Pierantonio De Luca, Patrizia Frontera and Fortunato Crea

Environments 2017, 4(4), 74; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4040074 - 15 Oct 2017

Cited by 40 | Viewed by 6116

Abstract

Geopolymers are a new class of binders based on alkali activation of natural and by-products raw materials. Their properties and eco-compatibility highly depends on the reaction system. The (Na,K)₂O-Al₂O₃-SiO₂-H₂O system shows a distinguishing [...] Read more.

Geopolymers are a new class of binders based on alkali activation of natural and by-products raw materials. Their properties and eco-compatibility highly depends on the reaction system. The (Na,K)₂O-Al₂O₃-SiO₂-H₂O system shows a distinguishing pseudo-zeolitic network structure, but reaction requires a high amount of activators. The aim of this work is to investigate how the use of forest biomass ash (FBA), as partial replacement material in the production of metakaolin (MK) based geopolymeric mortar, and affect its properties. FBA is a by-product of the combustion process of forest biomass in thermal power plants. Mortars with a FBA content of 0%, 10%, 20%, and 30% wt have been tested for workability, flexural, and compressive strength. Capillary absorption, micro-morphological features, thermal, and shrinkage behavior have been investigated. The addition of FBA allowed for a decrease in the use of alkaline activator up to 20%, while preserving the characteristic broad hump centered at approximately 28° 2θ Mechanical properties of the geopolymeric mortars decrease proportionally with metakaolin replacement, even if a compression strength of more than 35 MPa is still obtained with a FBA content of 30% wt. After thermal cycles of up to 700 °C, all of the mortars still retain their cohesiveness, with an overall loss of mechanical strength of about 80% of the initial value that can be attributed to the formation of microcracks as a consequence of the network strain and distortion due to dehydration and shrinkage. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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3198 KiB

Open AccessArticle

Calcium Sulfoaluminate, Geopolymeric, and Cementitious Mortars for Structural Applications

by Alessandra Mobili, Alberto Belli, Chiara Giosuè, Antonio Telesca, Milena Marroccoli and Francesca Tittarelli

Environments 2017, 4(3), 64; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4030064 - 16 Sep 2017

Cited by 24 | Viewed by 6026

Abstract

This paper deals with the study of calcium sulfoaluminate (CSA) and geopolymeric (GEO) binders as alternatives to ordinary Portland cement (OPC) for the production of more environmentally-friendly construction materials. For this reason, three types of mortar with the same mechanical strength class (R3 [...] Read more.

This paper deals with the study of calcium sulfoaluminate (CSA) and geopolymeric (GEO) binders as alternatives to ordinary Portland cement (OPC) for the production of more environmentally-friendly construction materials. For this reason, three types of mortar with the same mechanical strength class (R3 ≥ 25 MPa, according to EN 1504-3) were tested and compared; they were based on CSA cement, an alkaline activated coal fly ash, and OPC. Firstly, binder pastes were prepared and their hydration was studied by means of X-ray diffraction (XRD) and differential thermal-thermogravimetric (DT-TG) analyses. Afterwards, mortars were compared in terms of workability, dynamic modulus of elasticity, adhesion to red clay bricks, free and restrained drying shrinkage, water vapor permeability, capillary water absorption, and resistance to sulfate attack. DT-TG and XRD analyses evidenced the main reactive phases of the investigated binders involved in the hydration reactions. Moreover, the sulfoaluminate mortar showed the smallest free shrinkage and the highest restrained shrinkage, mainly due to its high dynamic modulus of elasticity. The pore size distribution of geopolymeric mortar was responsible for the lowest capillary water absorption at short times and for the highest permeability to water vapor and the greatest resistance to sulfate attack. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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2610 KiB

Open AccessArticle

Geopolymerization Ability of Natural and Secondary Raw Materials by Solubility Test in Alkaline Media

by Barbara Liguori, Ilaria Capasso, Marco De Pertis, Claudio Ferone and Raffaele Cioffi

Environments 2017, 4(3), 56; https://0-doi-org.brum.beds.ac.uk/10.3390/environments4030056 - 11 Aug 2017

Cited by 13 | Viewed by 5121

Abstract

The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a [...] Read more.

The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a method to test the ability of a material to react in alkaline media, different aluminosilicate sources have been selected: a mineral resource (a zeolitized tuff), an industrial by product (silt from washing process of construction and demolition wastes), a heat treated clay sediment and a calcined clay (metakaolin). Two test methods, static and dynamic, have been applied to evaluate the attitude of a silicoaluminate precursor to give a geopolymerization reaction. In particular, a fixed amount of precursor was put into contact with a alkaline solution under continuous stirring or in static conditions at 60 °C for fixed times. The dynamic test method seems to be more suitable, since it is faster and requires lower amounts of reactants (solution). Moreover, the dynamic test provides a reactivity sequence (ordered from the more to the less reactive precursor) metakaolin > treated clay sediment > zeolitized tuff ≈ silt both for Si and Al release, which is coherent with the performances of geopolymers obtained by using the above precursors. Full article

(This article belongs to the Special Issue Environmentally Friendly Geopolymer Composites)

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