Development of alkali-activated foamed materials combining both mining waste mud and expanded granulated cork

In Portugal, the significant amount of mine waste mud from tungsten mining operations has led to growing concerns about their ecological and environmental impacts such as the occupation of large areas of land, generation of powder and the contamination of surface and underground water. Furthermore, natural by-products in general, and natural cork particles in particular, have been used to manufacture new materials which not only provide good thermal insulation but also have a limited impact on the environment and a lower cost. Alkali-activated foamed materials have been introduced in the field of alkali-activated materials which have been produced from different raw and waste materials. It has been proposed as a new idea that involves the production of lightweight materials, thus combining the performance and the benefits of energy-saving (Carbon footprint) with the reduction of the cradle-to-gate emission obtained. Besides, in order to reduce the density of the alkali-activated materials holes or lightweight aggregates can be added for such purposes. Therefore, in this research, novel alkali-activated lightweight foamed materials (AALFM) from a combination of tungsten mine waste mud (TWM), waste glass (WG), and metakaolin (Mk) using alkali activators solution of Sodium Silicate (SS) and Sodium Hydroxide (SH) was developed and combined with natural expanded granulated cork (EGC) using aluminium powder (Al) as a foaming agent. The objective of this study is to develop a new alkali-activated foamed tungsten-based binder/mortar and to characterize the cork waste composite made from this binder/mortar and natural granulated aggregates (EG-Cork). Cork, which is the exterior bark of Quercus suber L., a natural, organic, and lightweight plant tissue with a high dimensional stability substance. Physical properties of tungsten-based alkali-activated binder/mortar such as bulk density, thermal conductivity and pore sizes distribution were provided. The formulations of the alkali-activated binders are based on a combination of tungsten waste mud (TWM), waste glass (WG), and metakaolin (Mk). The mechanical and thermal properties of alkali-activated foamed materials produced were then tested. The research work includes three main phases. The first part shows the feasibility to produce new improved lightweight foamed alkali-activated materials using Panasqueira tungsten waste mud (TWM) as major raw material incorporating expanded granulated cork (EGC). During this preliminary study, a series of mixes containing mining waste mud, milled waste glass, metakaolin and Ordinary Portland Cement, in different proportions, were prepared. The influence on porosity, density, and compressive strength of incorporating granulated expanded cork at different percentages was first studied with potential applications in artistic, architectural, and historical heritage restoration. The second part investigates the influence of different precursors’ particle sizes on the physical and mechanical properties, such as density, porosity, expansion volume, and pore size by image analysis. The design and development of tungsten-based alkali-activated foams (AAFs) were studied systematically. Moreover, the manufactured AAFs with enhanced compressive strength from non-calcined tungsten waste mud (raw material) by changing the precursor particle sizes showed results of the same level or even higher as other research results obtained with fly ash and MK. The third part of the research investigates the effect of the incorporation of expanded granulated cork (EGC) to produce alkali-activated lightweight foamed materials (AALFM) with thermal properties. The findings indicate that experimental research on different combinations of raw materials particularly tungsten mining waste mud (TMWM) contribute to the development of alkali-activated materials (AAMs) and alkali-activated foamed materials (AAFMs). These new improved materials can be used as building materials with enhanced properties such as compressive strength, density, thermal conductivity, and fire resistance. This doctoral research contributes to a sustainable development by promoting the complete recycling and use of mining wastes as construction materials.Em Portugal, a quantidade significativa de lamas residuais provenientes das operações de mineração de tungsténio, tem gerado preocupações crescentes relativamente aos impactos ecológicos e ambientais, tais como, ocupação de grandes áreas de terreno, libertação de poeiras, e a contaminação de águas superficiais e subterrâneas. Nesta pesquisa, um novo material espumoso leve obtido por ativação alcalina (AALFM) de lamas residuais da mina de tungsténio (TWM) foi desenvolvido, utilizando pó de alumínio (Al) como agente de formação de espuma e, ainda, combinado com cortiça granulada expandida natural (EGC). O trabalho de pesquisa comtemplou três fases principais. A primeira parte demonstra a viabilidade de produção de novos materiais expandidos ativados alcalinamente utilizando lamas residuais das minas de tungsténio da Panasqueira (TWM) como principal matéria-prima e, incorporando cortiça granulada expandida (EGC), com aplicações potenciais na restauração de património artístico, arquitetónico e histórico. Neste estudo preliminar, foram preparados conjuntos de misturas, contendo lamas residuais, resíduo de vidro moído, metacaulino e cimento Portland, em diferentes proporções. Em primeiro lugar, foi estudada a influência na porosidade, densidade e resistência à compressão da incorporação de cortiça expandida granulada em diferentes percentagens. A segunda parte investiga o projeto e o desenvolvimento de ligantes /argamassas espumosas ativadas alcalinamente com lamas das minas de tungsténio, utilizando três tamanhos de partícula de diferentes. As propriedades físicas e mecânicas, densidade, porosidade, volume de expansão e tamanho dos poros, foram estudados de forma sistemática. Além disso, foi também estudado o aprimoramento da resistência à compressão de espumas ativadas alcalinamente (AAFs), alterando os tamanhos das partículas precursoras. A terceira parte da investigação investiga o efeito da incorporação da cortiça granulada expandida (EGC) na produção de espumas leves ativadas alcalinamente (AALFM) nas suas propriedades térmicas. Os materiais espumosos ativados alcalinamente inserem-se no campo dos materiais obtidos por ativação alcalina, os quais têm sido produzidos a partir de diferentes matérias-primas e resíduos. Foi proposto como uma ideia nova que envolve a produção de materiais leves, combinando assim o desempenho e os benefícios da poupança de energia (pegada de carbono) com a redução da emissão “cradle-to-gate” obtida. Além disso, a fim de reduzir a densidade dos materiais ativados alcalinamente, podem ser adicionados orifícios ou agregados leves para esse fim. Os resultados dos estudos experimentais permitem desenvolver diferentes tipos de materiais, utilizando resíduos de minas como matéria-prima. Este novo material produzido pode ser usado como materiais de construção com propriedades aprimoradas, como resistência à compressão, densidade, condutividade térmica e resistência ao fogo. Esta investigação de doutoramento contribui para o desenvolvimento sustentável, promovendo a reciclagem completa e a utilização de resíduos de mineração como materiais de construção.This doctoral research work was conducted at the University of Beira Interior (UBI) and partially financed by the following grants: A Doctoral Incentive Grant (BID) – Santander-Totta/UBI research grants ‘‘Bolsa BID/ICI-FE/Santander Universidade – UBI/2017”; Portuguese national funds through FCT – Foundation for Science and Technology, IP, within the research unit C-MADE, Centre of Materials and Building Technologies (CIVE-Central Covilhã-4082), University of Beira Interior, Portugal and the European Commission Horizon2020, MARIE Skłodowska-CURIE Actions, Research, and Innovation Staff Exchange (RISE), - “REMINE- Reuse of Mining Waste into Innovative Geopolymeric-based Structural Panels, Precast, Ready Mixes and in-situ Applications”, project no. 645696, Coordinator: University of Beira Interior (PT), comprising three months secondments abroad at the company ALSITEK Limited (Ltd), Peterborough, United Kingdom (UK)

Novel Sustainable Structural Materials By Using Benign Waste Materials

We propose a Green Cement Paradigm (GCPa) for fabricating environmentally friendly cementitious materials. By using GCPa, we report for the first time, the usage of Class C Fly Ash as a sole source of cementitous phase without any activation by alkali. During this study, Class C Fly Ash, and its composites with sand were fabricated at different compaction stresses by maintaining a low w/c (w-water, c-cement) ratio of 0.17-0.24 in the compacts. The porosity and the number of days for curing played a significant role in the evolution of compressive strength. The experimental results indicate that the curing for 28 days is the optimum time required for strength development. For example, the Class C Fly Ash samples cold pressed at ~86 MPa and cured for 28 days showed a compressive strength of ~29.5 MPa. The effect of additional Ca(OH)2, high temperature curing and carbonation on the compressive strength development of the class C FA samples is reported. SEM, EDS, TGA/DSC and XRD investigations were employed to explain the obtained results. The possibility of fabricating lignin based polymer composites was investigated. The mechanical properties of the composites were reported in terms of yield strength and flexural strength

Recent advances in Geopolymer technology. A potential eco-friendly solution in the construction materials industry. A review

In the last ten years, the Portland cement industry has received wide criticism due to its related high embodied energy and carbon dioxide footprint. Recently, numerous “clean” strategies and solutions were developed. Among these, geopolymer technology is gaining growing interest as a functional way to design more eco-friendly construction materials and for waste management issues suffered by various industries. Previous research has highlighted the attractive engineering properties of geopolymeric materials, especially in terms of mechanical properties and durability, resulting in even higher performance than ordinary concrete. This review provides a comprehensive analysis of current state-of-the-art and implementations on geopolymer concrete materials, investigating how the key process factors (such as raw materials, synthesis regime, alkali concentration, water dosage, and reinforcement fillers) affect the rheological, microstructural, durability, and mechanical properties. Finally, the paper elucidates some noteworthy aspects for future research development: innovative geopolymer-based formulations (including alkali-activated blends for additive manufacturing and thermo-acoustic insulating cellular compounds), concrete applications successfully scaled in the civil-architectural fields, and the perspective directions of geopolymer technology in terms of commercialization and large-scale diffusion

Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials

This paper assesses the feasibility of two industrial wastes, fly ash (FA) and rice husk ash (RHA), as raw materials for the production of geopolymeric pastes. Three typologies of samples were thus produced: (i) halloysite activated with potassium hydroxide and nanosilica, used as the reference sample (HL-S); (ii) halloysite activated with rice husk ash dissolved into KOH solution (HL-R); (iii) FA activated with the alkaline solution realized with the rice husk ash (FA-R). Dense and porous samples were produced and characterized in terms of mechanical properties and environmental impact. The flexural and compressive strength of HL-R reached about 9 and 43 MPa, respectively. On the contrary, the compressive strength of FA-R is significantly lower than the HL-R one, in spite of a comparable flexural strength being reached. However, when porous samples are concerned, FA-R shows comparable or even higher strength than HL-R. Thus, the current results show that RHA is a valuable alternative to silica nanopowder to prepare the activator solution, to be used either with calcined clay and fly ash feedstock materials. Finally, a preliminary evaluation of the global warming potential (GWP) was performed for the three investigated formulations. With the mix containing FA and RHA-based silica solution, a reduction of about 90% of GWP was achieved with respect to the values obtained for the reference formulatio

Production of geopolymers from diatomaceous earth for wastewater treatment

Mestrado de dupla diplomação com a Université Libre de TunisGeopolymers (GPs) are inorganic binders created by adding an alkaline solution (e.g., NaOH) to silicates, such as furnace slags, fly ashes or clays, to dissolve Si and Al that polymerizes and precipitates to form an inorganic binder material while hardening. GP properties are similar to ordinary Portland cement, since it presents high compressive strength or low shrinkage, but they are particularly notable for a high resistance to acid and fire. For this reason, GP has been widely studied in its application in civil engineering. However, GPs presents other interesting properties that make it an excellent material to be used as adsorbent. The aim of this study is to investigate the suitability of commercial diatomaceous earth as a cheaper alternative to kaolin and to determine the necessary preparation steps required to produce effective geopolymer adsorbent materials. Geopolymerization is a multi-parameter system strongly influenced by the degree of activation, Si:Al ratio, amount of 5-fold coordinated Al and curing mode. Bearing this in mind, different formulations to yield geopolymeric solid samples were examined. Important parameters for the production, such as temperature, time, and heating rate are determined and discussed. Additionally, geopolymers were assessed in the removal of gallic acid and phenol, used as model pollutants, from aqueous solutions by adsorption. The results presented in this thesis indicate that commercial diatomaceous earth is a suitable raw material for geopolymer production. Proxies used to evaluate the optimal conditions for making geopolymers are determined including the Si/Al ratio as a key relationship that determines its ultimate hardness and curing mode as key factor that controls the geopolymerization process.Os geopolímeros (GPs) são ligantes inorgânicos criados pela adição de uma solução alcalina (por exemplo NaOH) aos silicatos, tais como escórias do forno, cinzas volantes ou argilas, para dissolver o Si e o Al que polimeriza e precipita para formar um material aglutinante inorgânico enquanto endurece. As propriedades do GP são semelhantes ao cimento Portland comum no que diz respeito à sua alta resistência à compressão ou baixa retracção, mas são particularmente notáveis para uma alta resistência ao ácido e ao fogo. Além disso, os geopolímeros podem ser utilizados como adsorventes de poluentes da água. As matérias-primas mais comuns utilizadas na produção de GPs são argilas de caulino. Assim, o objectivo deste estudo é investigar a adequação da terra de diatomáceas comerciais como uma alternativa mais barata ao caulino e determinar as etapas de preparação necessárias para produzir materiais adsorventes de geopolímeros eficazes. Foram examinadas diferentes formulações para produzir amostras sólidas geopoliméricas. Foram determinados e discutidos parâmetros importantes para a produção, tais como temperatura, tempo, e taxa de aquecimento. A geopolimerização é um sistema multi-parâmetros fortemente influenciado pelo grau de activação, razão Si:Al, quantidade de Al coordenada em 5 vezes e modo de cura. Os resultados apresentados nesta tese indicam que a terra diatomácea comercial é uma matéria prima adequada para a produção de geopolímeros. Os proxies utilizados para avaliar as condições óptimas para a produção de geopolímeros são determinados incluindo a relação Si/Al como uma relação chave que determina a sua dureza final e o modo de cura como factor chave que controla o processo de geopolimerização

Structural and electrical properties of geopolymer materials based on different precursors (kaolin, bentonite and diatomite)

Geopolymers (GP) were successfully synthesized from metabentonite (MB), metadiatomite (MD) and metakaolinite (MK). Characterization of their phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. A SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel, and it is significantly different from the micrographs of the other two geopolymer samples, GPMB and GPMK. A considerable amount of unreacted particles, as well as the presence of pores in the geopolymer matrix of GPMK and GPMD, indicate an incomplete reaction in the system. Aluminosilicate inorganic polymers, geopolymers, are quasi solid electrolytes which possess a high electrical conductivity at room temperature in relation to materials of similar chemical composi-tion. The highest conductivity was found for the sample obtained from GPMK, amounting to 2.14 x 10-2 Ω-1cm-1 at 700 oC. The corresponding activation energies of conductivity for this sample amounted to 0.33 eV in the temperature range of 500-700 oC. The geopolymer synthesized from metakaolin has good ionic conductivity values, which recommends it for use as an alternative material for an SOFC (Solid Ox-ide Fuel Cell)

Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review

Chemically activated materials (often termed as geopolymer) have received attracting attentions in civil, material and environmental research fields as a toolkit alternative to traditional Portland cement in specific applications. This paper presents a comparative review on silico-aluminophosphate (SAP) geopolymers in terms of definition, chemistries involved during geopolymerization, mechanical performance, durability, environmental impacts, and their potentials in applications relative to conventional alkali-aluminosilicate (AAS) geopolymers. Recommendations for future applications are also highlighted. It is found that S-A-P gels with six-coordinated aluminum environment dominate in SAP geopolymers, while the aluminum in N-A-S-H gels formed in the AAS geopolymers is characterized by four-coordinated features. Besides, the slow performance development of SAP geopolymer matrix under ambient temperature curing can be compensated through incorporating additional countermeasures (e.g., metal sources) which allow the tailored design of such geopolymers for certain in-situ applications. Generally, the calcium-bearing C-(A)-S-H gels co-existing with N-A-S-H gels are dominant in AAS geopolymers, while the S-A-P gels enhanced by phosphate-containing crystalline/amorphous phases are the main products in SAP geopolymers. The SAP geopolymers show their environmental friendliness relative to the AAS geopolymers due to the utilization of phosphate activators that require lower production energy relative to silicate-containing activators. However, the higher cost of phosphate activators may confine the applications of SAP geopolymers in some exquisite or special fields

Development of Alkali-activated Foamed Lightweight Mortar Tungsten Mining Waste Mud-based Incorporating Expanded Cork

In this study, an Alkali-activation of tungsten mining waste mud (TMWM) was combined with aluminium powder (Al) as a blowing agent (gas foaming method). The synthesis of inorganic alkali-activated foamed mortar (AA-FM) and alkali-activated lightweight foamed mortar (AALW-FM) was achieved by incorporating expanded granulated cork (EGC) and one type of river sand < 2 mm. Al powder was added first to the dry mix with the mass used varying from 0.1 g to 0.5 g. Precursors and activators were included to produce a homogeneous mixture, which was placed into a mould (100x100x60 mm3), and cured in the oven at 60° C for 24 hours. The influence of two main parameters (Al powder contents and cork particles) on the AA-FM and AALW-FM properties (compressive strength, density, expansion volume and pore size distribution) were investigated. The compressive strength of the foams in the case of highly porous structures of the AALW-FM and AA-FM achieved 4.1MPa and 13.2MPa respectively, for samples with a larger amount of Al powder (0.5g). Open celled hardened of the AALW-FM and AA-FM with 0.5g Al shows a high porosity of 40% and 81% respectively. Therefore, tungsten mining waste-based alkali-activated foams shows potential as a thermal insulation material in certain situations. Keywords: Tungsten mining waste, Alkali-activated, Foamed Material