Alternative Concrete – Geopolymer Concrete


The general aim of this book is to make significant contributions in understanding and deciphering the mechanisms of the realization of the alkali-activated fly ash-based geopolymer concrete.


Alternative Concrete – Geopolymer Concrete
Emerging Research and Opportunities
Adrian LĂZĂRESCU, Henriette SZILÁGYI, Cornelia BAERĂ, Andreea HEGYI
Materials Research Foundations Vol. 109
Publication Date 2021, 138 Pages
Print ISBN 978-1-64490-152-6 (release date September 2021)
ePDF ISBN 978-1-64490-153-3
DOI: 10.21741/9781644901533

Portland cement based concrete is the most versatile, durable and reliable building material. Unfortunately, the production of Portland cement is environmentally unfriendly. An interesting alternative is provided by alkali-activated geopolymer materials (AAGM). This book focuses on fly ash-based alkali-activated geopolymer concrete, its production and characteristic properties. The re-use of waste materials and industrial by-products, such as fly ash, is not only economically of interest but also helps to reduce carbon dioxide emissions. The carbon footprint of these materials is much lower than that of concrete using ordinary Portland cement. They thus offer new sustainable solutions to the construction industry. The book references 132 original resources and includes their direct web link for in-depth reading.

Geopolymers, Geopolymer Concrete, Alkali-activated Geopolymer Materials (AAGM), Portland Cement, Fly Ash-based Geopolymer Concrete, Reduction of Carbon Dioxide Emissions, Concrete Applications, Self-Compacting Concrete, High-strength Concrete, High-performance Concrete


Table of contents

Introduction 6
Acknowledgement 10

Global Perspectives on the Production of Industrial By-Products in the Context of “Circular Economy” 1

Retrospective Regarding Research in the Field of Alkali-Activated Geopolymer Materials 4
2.1. Geopolymers and geopolymerisation – chemical characteristics 4
2.2. Geopolymers and geopolymerization – mechanical characteristics 7
2.3. Types of alkaline activators used in the synthesis of geopolymers 9
2.4. Alkali-activated geopolymer materials mix-design 10
2.4.1. Properties of the alkaline activator 10
2.4.2. Heat curing procedures 11
2.5. Properties of alkali-activated geopolymer materials 12
2.5.1. Mechanical properties of alkali-activated geopolymer materials 12
2.5.2. Durability of alkali-activated geopolymer materials 13
2.5.3. Remarks 13
2.6. Factors influencing alkali-activated geopolymer materials 13
2.6.1. Physical and chemical properties of fly ash 13
2.6.2. Alkaline activator and heat treatment properties 14
2.6.3. Mixing procedure 15
2.7. Alkali-activated geopolymer materials applications 15

Raw Materials Used in the Production of Alkali-Activated Geopolymer Materials 17
3.1. Why alkali-activation? 17
3.2. Portland cement and fly ash 18
3.2.1. Fly ash for cement 23
3.2.2. Fly ash for construction industry 24
3.2.3. Fly ash as type II addition for concrete 24
3.2.4. General conditions for producing fly ash 27

Development of Alkali-Activated Geopolymer Binder 33
4.1. General principles for the production of alkali-activated geopolymer materials 33
4.2. Alkali-activated fly ash-based geopolymer paste – raw materials characteristics 35
4.2.1. Fly ash (FA) 35
4.2.2. Alkaline activator (AA) 37
4.3. Alkali-activated fly ash-based geopolymer paste technology 40
4.4. Alkali-activated fly ash-based geopolymer paste characteristics 43
4.4.1. Alkali-activated geopolymer paste mixtures (AAGP) 43
4.4.2. Physical-mechanical properties of the alkali-activated geopolymer paste mixtures 46
4.4.3. Technological and mix-design influences on the performance of alkali-activated geopolymer binder 54 Influence of age on the compressive strength 54 Influence of the alkaline activator to fly ash ratio (AA/FA) on the compressive strength 56 Influence of the alkaline activators ratio (Na2SiO3/NaOH) on the compressive strength 57 Influence of the molar concentration of the NaOH solution on the compressive strength 59 Interdependence between molar concentration of NaOH solution and water in the mixture 62 Fly ash type influence on the compressive strength 65 Influence of fly ash physical properties on the compressive strength 67
4.4.4. Microscopic evaluation of alkali-activated geopolymer paste mixtures 69

Development of Alkali-Activated Fly Ash-Based
Geopolymer Concrete 74
5.1. Raw materials characteristics 74
5.2. Alkali-activated fly ash-based geopolymer technology 75
5.3. Alkali-activated fly ash-based geopolymer concrete mixtures 75
5.4. Alkali-activated fly ash-based geopolymer physical-mechanical properties 77
5.4.1. Fresh-state properties 77
5.4.2. Apparent density 78
5.4.3. Flash setting 79
5.4.4. Physical-mechanical properties of the alkali-activated geopolymer concrete mixtures 81
5.4.5. Microscopic evaluation 85
5.5. Technological and mix-design influences on the performance of alkali-activated geopolymer concrete 88
5.5.1. Influence of the molar concentration of the NaOH solution on the compressive strength 88
5.5.2. Influence of NaOH type on the compressive strength of AAGC mixtures 88
5.5.3. Influence of Na2SiO3/NaOH ratio on the compressive strength of AAGC mixtures 89

Research Regarding Alkali-Activated Fly Ash-Based Geopolymer Concrete Applications 92
6.1. Alkali-activated fly ash-based geopolymer panels 92
6.2. Alkali-activated fly ash-based geopolymer paving blocks 94
6.3. Legislative framework on the possibility of using alkali-activated geopolymer paving blocks 106

Conclusions and Final Remarks 107
References 113
List of Symbols 125
About the Authors 127

About the authors

PhD Eng Adrian Lăzărescu is Scientific Researcher at N.I.R.D. URBAN-INCERC, Cluj-Napoca Branch, Romania and PhD in Civil Engineering, granted at Technical University of Cluj-Napoca in the field of alkali activated geopolymer materials. His main interest is to study the possibility of producing this type of material using Romanian local materials, with the aim to assess the possibility of using fly ash as raw material in the production of innovative, new-alternative materials in the civil engineering field. Together with the team co-authors, the author was a member in several National Projects which targeted the use of industrial by-products in the production of alternative materials, within the Circular Economy and Sustainable Development principles. Also, within the research team of N.I.R.D. URBAN-INCERC, the author participated in extensive research programs on the development of cementitious materials with self-healing properties of microcracks (ECC – Engineered Cementitious Composites with Self-Healing Properties), self-healing cementitious materials, alternative thermal insulation products based on sheep wool and has coordinated numerous in-situ NDT and destructive investigations of buildings, respectively research on the quality of materials and products used in the construction industry.

PhD Eng Henriette Szilagyi is Senior Researcher and also the Manager of N.I.R.D. URBAN-INCERC, Cluj-Napoca Branch, Romania. A renowned practitioner in the field of concrete technology, her main research involves special concrete (self-compacting concrete, ultra-high-performance concrete, lightweight concrete, concrete with waste and by-products such as recycled glass, fly ash, recycled plastic and other innovative cementitious materials) and mortars, cements, admixtures, additives, building materials. She has published extensively on many aspects regarding concrete technology and sustainable development in the construction industry. She is Associate professor at Technical University Cluj-Napoca, Faculty of Civil Engineering; she also mentoring students in research projects, guidance for MSc Dissertation, PhD Thesis.

PhD. Eng Cornelia Baeră is Scientific Researcher at N.I.R.D. URBAN-INCERC, Timișoara Branch, Romania. Her main research interests involve the topic of high-performance concrete and mortars (Fibre reinforced concrete, Concrete with self-healing properties, Concrete with mineral additions, green concrete, Engineered cementitious composites (ECCs), etc.). The doctoral studies were performed at T.U. Cluj-Napoca, when she worked as a researcher at INCD URBAN-INCERC Cluj-Napoca Branch together with the team co-authors. Currently, her research interests extended towards the topic of Management in Production and Transportation, at Research Center in Engineering and Management, Politehnica University of Timișoara.

PhD Eng Andreea Hegyi is Scientific Researcher at N.I.R.D. URBAN-INCERC Cluj-Napoca Branch, Romania. Her main research interests involve studies regarding the durability of cementitious composites using hot-dip galvanized rebars, the development of ecological materials for the construction industry, studies regarding the parametric evaluation of self-cleaning cementitious composites using nano-TiO2 particles and the development of alternative thermal insulation materials based on sheep wool. Her expertise in research on the quality of materials and products used in the construction industry has opened new perspectives in studying new and alternative construction materials which comply with current legislation and further improving of existing ones in the field by addopting alternative solutions and by creating a “bridge” between traditional and modern construction materials.