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19 pages, 7923 KiB

Open AccessArticle

Combined Influence of Low-Grade Metakaolins and Natural Zeolite on Compressive Strength and Heavy Metal Adsorption of Geopolymers

by Alcina Johnson Sudagar, Slávka Andrejkovičová, Fernando Rocha, Carla Patinha, Maria R. Soares, Ana Luísa Velosa and Eduardo Ferreira da Silva

Minerals 2021, 11(5), 486; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050486 - 01 May 2021

Cited by 7 | Viewed by 2534

Abstract

Metakaolins (MKs) prepared from low-grade kaolins located in the Alvarães (A) and Barqueiros (B) regions of Portugal were used as the aluminosilicate source to compare their effect on the compressive strength and heavy metal adsorption of geopolymers. Natural zeolite, an inexpensive, efficient adsorbent, [...] Read more.

Metakaolins (MKs) prepared from low-grade kaolins located in the Alvarães (A) and Barqueiros (B) regions of Portugal were used as the aluminosilicate source to compare their effect on the compressive strength and heavy metal adsorption of geopolymers. Natural zeolite, an inexpensive, efficient adsorbent, was used as an additive in formulations to enhance geopolymers’ adsorption capacities and reduce MK utilization’s environmental footprint. Geopolymers were synthesized with the replacement of MK by zeolite up to 75 wt.% (A25, B25—25% MK 75% zeolite; A50, B50—50% MK 50% zeolite; A75, B75—75% MK 25% zeolite; A100, B100—100% MK). The molar ratios of SiO₂/Al₂O₃ and Na₂O/Al₂O₃ were kept at 1 to reduce the sodium silicate and sodium hydroxide environmental impact. Geopolymers’ crystallography was identified using X-ray diffraction analysis. The surface morphology was observed by scanning electron microscopy to understand the effect of zeolite incorporation. Chemical analysis using X-ray fluorescence spectroscopy and energy dispersive X-ray spectroscopy yielded information about the geopolymers’ Si/Al ratio. Compressive strength values of geopolymers obtained after 1, 14, and 28 days of curing indicate high strengths of geopolymers with 100% MK (A100—15.4 MPa; B100—32.46 MPa). Therefore, zeolite did not aid in the improvement of the compressive strength of both MK-based geopolymers. The heavy metal (Cd²⁺, Cr³⁺, Cu²⁺, Pb²⁺, and Zn²⁺) adsorption tests exhibit relatively higher adsorption capacities of Barqueiros MK-based geopolymers for all the heavy metals except Cd²⁺. Moreover, zeolite positively influenced divalent cations’ adsorption on the geopolymers produced from Barqueiros MK as B75 exhibits the highest adsorption capacities, but such an influence is not observed for Alvarães MK-based geopolymers. The general trend of adsorption of the heavy metals of both MK-based geopolymers is Pb²⁺ > Cd²⁺ > Cu²⁺ > Zn²⁺ > Cr³⁺ when fitted by the Langmuir isotherm adsorption model. The MK and zeolite characteristics influence geopolymers’ structure, strength, and adsorption capacities. Full article

(This article belongs to the Special Issue Role of the Clay Minerals in Construction and Building Materials)

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20 pages, 1815 KiB

Open AccessArticle

Design of Concrete Made with Recycled Brick Waste and Its Environmental Performance

by Ivan Janotka, Pavel Martauz and Michal Bačuvčík

Minerals 2021, 11(5), 463; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050463 - 28 Apr 2021

Cited by 3 | Viewed by 2355

Abstract

In addition to the known uses of natural clays, less publication attention has been paid to clays returned to the production process. Industrially recovered natural clays such as bricks, tiles, sanitary ceramics, ceramic roofing tiles, etc., are applicable in building materials based on [...] Read more.

In addition to the known uses of natural clays, less publication attention has been paid to clays returned to the production process. Industrially recovered natural clays such as bricks, tiles, sanitary ceramics, ceramic roofing tiles, etc., are applicable in building materials based on concrete as an artificial recycled aggregate or as a pozzolanic type II addition. In this way, the building products with higher added value are obtained from the originally landfilled waste. This paper details the research process of introducing concrete with recycled brick waste (RBW) up to the application output. The emphasis is placed on using a RBW brash as a partial replacement for natural aggregates and evaluating an RBW powder as a type II addition for use in concrete. A set of the results for an RBW is reported by the following: (a) an artificial RBW fine aggregate meets the required standardized parameters for use in industrially made concrete, (b) a RBW powder is suitable for use in concrete as industrially made type II addition TERRAMENT showing the same pozzolanic reactivity as a well-known and broadly used pozzolan-fly ash, and (c) such an RBW as aggregate and as powder are, therefore, suitable for the production of industrially made TRITECH Eco-designed ready-mixed concrete. Full article

(This article belongs to the Special Issue Role of the Clay Minerals in Construction and Building Materials)

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Review

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22 pages, 2376 KiB

Open AccessReview

Using Calcined Marls as Non-Common Supplementary Cementitious Materials—A Critical Review

by Abdelmoujib Bahhou, Yassine Taha, Yassine El Khessaimi, Rachid Hakkou, Arezki Tagnit-Hamou and Mostafa Benzaazoua

Minerals 2021, 11(5), 517; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050517 - 14 May 2021

Cited by 11 | Viewed by 4517

Abstract

This review summarizes the major research and scientific findings on the relevance of using calcined marl as supplementary cementitious material in developing eco-friendly cement for the next generation. Incorporation of calcined marl into cement can result in changes in the properties of these [...] Read more.

This review summarizes the major research and scientific findings on the relevance of using calcined marl as supplementary cementitious material in developing eco-friendly cement for the next generation. Incorporation of calcined marl into cement can result in changes in the properties of these binders, and thus compatibility with other additions could be potential challenging, particularly at higher replacement ratios. From the reviewed literature, a detailed investigation on the characterization of calcined marls, activation methods, influencing parameters, along with studies on the hydration and microstructure was discussed, the overall objective aimed at coming up with the optimal physical and chemical parameters to generate highly reactive marl. Full article

(This article belongs to the Special Issue Role of the Clay Minerals in Construction and Building Materials)

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