Rheology of Cementitious Materials: Alkali-Activated Materials or Geopolymers

A clear alternative to reach the goal of sustainable development in the Construction Sector is the development of alternative building materials to Ordinary Portland Cement (OPC) in a more energetically as well as environmentally eco-efficient way. Alkaline cements (Alkali-Activated Materials, AAMs) and geopolymers meet these requirements; and they are based on the alkali activation of aluminosilicates (mainly waste and industrial by-products, such as blast furnace slag, fly ash and ceramic waste) in highly alkaline solutions. AAMs cements and concretes are notable for being very durable and mechanically resistant. However, to date their rheological behaviour is not well controlled and there is little understanding of it, with very disparate experimental data. Despite this, their rheological behaviour is not fully understood and little is known on the disparate data obtained in AAM pastes. Moreover, the common additives used in the preparation of OPC concretes and the rheology modifiers/controllers are also unstable in the AAMs systems. Understanding and controlling the rheology of the AAMs systems will ultimately determine whether they can be implemented in the market, and will open up greater competitive possibilities in a crisis-affected sector. A systematic study of the factors that affect the rheological properties of AAMs (pastes, mortars and concretes) is therefore necessary in order to ultimately develop more resistant and durable materials.

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Iron and Aluminium Production Wastes as Exclusive Components of Alkali Activated Binders—Towards a Sustainable Alternative

Sustainability ◽

10.3390/su13179938 ◽

2021 ◽

Vol 13 (17) ◽

pp. 9938

Author(s):

Nuno Cristelo ◽

Fernando Castro ◽

Tiago Miranda ◽

Zahra Abdollahnejad ◽

Ana Fernández-Jiménez

Keyword(s):

Co2 Emissions ◽

Building Materials ◽

Negative Impact ◽

Raw Materials ◽

Construction Materials ◽

Heat Of Hydration ◽

Sustainable Construction ◽

Alkaline Solutions ◽

By Products ◽

Alkali Activated

The sustainability of resources is becoming a worldwide concern, including construction and building materials, especially with the alarming increase rate in global population. Alternative solutions to ordinary Portland cement (OPC) as a concrete binder are being studied, namely the so-called alkali-activated cements (AAC). These are less harmful to the environment, as lower CO2 emissions are associated with their fabrication, and their mechanical properties can be similar to those of the OPC. The aim of developing alkali-activated materials (AAM) is the maximization of the incorporated recycled materials, which minimises the CO2 emissions and cost, while also achieving acceptable properties for construction applications. Therefore, various efforts are being made to produce sustainable construction materials based on different sources and raw materials. Recently, significant attention has been raised from the by-products of the steelmaking industry, mostly due to their widespread availability. In this paper, ladle slag (LS) resulting from steelmaking operations was studied as the main precursor to produce AAC, combined with phosphating bath sludge—or phosphate sludge (PS)—and aluminium anodising sludge (AS), two by-products of the surface treatment of metals, in replacement rates of 10 and 20 wt.%. The precursors were activated by two different alkaline solutions: a combination of commercial sodium hydroxide and sodium silicate (COM), and a disposed solution from the cleaning of aluminium extrusion steel dies (CLE). This study assesses the influence of these by-products from the steelmaking industry (PS, AS and CLE) on the performance of the alkali-activated LS, and specifically on its fresh and hardened state properties, including rheology, heat of hydration, compressive strength and microstructure and mineralogy (X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and Fourier transform infra-red. The results showed that the CLE had no negative impact on the strength of the AAM incorporating PS or/and AS, while increasing the strength of the LS alone by 2×. Additionally, regardless of the precursor combination, the use of a commercial activator (COM) led to more fluid pastes, compared with the CLE.

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Alkali Activation of Copper and Nickel Slag Composite Cementitious Materials

Materials ◽

10.3390/ma13051155 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1155 ◽

Cited By ~ 1

Author(s):

Tingting Zhang ◽

Shiwei Zhi ◽

Tong Li ◽

Ziyu Zhou ◽

Min Li ◽

...

Keyword(s):

Glass Phase ◽

Chemical Activation ◽

Cementitious Materials ◽

Mineral Admixture ◽

Alkali Activation ◽

Hydration Products ◽

Granulated Blast Furnace Slag ◽

Ft Ir ◽

Furnace Slag ◽

Alkali Activated

Alkali-activated copper and nickel slag cementitious materials (ACNCMs) are composite cementitious materials with CNS (copper and nickel slag) as the main materials and GGBFS (ground-granulated blast-furnace slag) as a mineral admixture. In this paper, the activity indexes of CNS with different grinding times were studied using CNS to replace a portion of cement. NaOH, Na2SO4, and Na2SiO3 activators were used to study the alkaline solution of the CNS glass phase. The effects of the fineness of CNS and the type of activator on the hydration of ACNCMs were investigated via physical/mechanical grinding and chemical activation. The hydration products of ACNCMs were analyzed via XRD, SEM, FT-IR, TG, and MIP. The results of the study revealed that the activity indexes of CNS ground with different grinding times (10, 30 and 50 min) were 0.662, 0.689, and 0.703, respectively. When Na2SiO3 was used as the activator, the glass phase dissolved the most Si4+, Al3+, and Ca2+, and the respective concentrations in the solution were found to be 2419, 39.55, and 3.38 mg/L. Additionally, the hydration products of ACNCMs were found to have a 28-day compressive strength of up to 84 MPa.

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Effect of NaOH Molarity on the Strength and Microstructure of Natural Pozzolan-Based AAC

MATEC Web of Conferences ◽

10.1051/matecconf/201820306017 ◽

2018 ◽

Vol 203 ◽

pp. 06017 ◽

Cited By ~ 1

Author(s):

Mohammed Ibrahim ◽

Megat Azmi Johari ◽

Mohammad Kalimur Rahman ◽

Mohammed Maslehuddin ◽

Mohamed Hatim Dafalla

Keyword(s):

Sodium Hydroxide ◽

Building Material ◽

Sodium Hydroxide Solution ◽

Alkaline Solutions ◽

Alkali Activation ◽

Material Research ◽

Natural Pozzolan ◽

Alkali Activated Binders ◽

By Products ◽

Alkali Activated

Alarming levels of greenhouse gas emissions has triggered change in the mode of direction of building material research. In this pursuit, alkali activated binders (AAB), synthesized by activation of industrial by products and natural materials in the presence of highly alkaline solutions, have offered viable alternative to OPC. However, there are quite a number of variables which controls the properties of these binders. Among these parameters, SS/SH ratio and molarity of sodium hydroxide solution plays a very important role in the development of these binders. Therefore, this research investigates the effect of SS/SH ratio, subsequently, molarity of SH solution on the properties of natural pozzolan based AAB. The NP was activated with sodium silicate to sodium hydroxide ratio (SS/SH) between 2.0 to 2.75. Subsequently, the molarity of SH solution was varied between 8 to 14. The development in strength was monitored on the specimens cured at 60 °C. SEM and EDS techniques were used to determine the nature of the binder formed during alkali activation. The results have shown that SS/SH ratio of 2.5 and 14 molar SH solution resulted in higher strength and finer microstructure as compared to others. Also, it was understood that there exists a suitable silica modulus of combined activator which results in higher polymerization.

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Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag

Materials ◽

10.3390/ma13051134 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1134 ◽

Cited By ~ 2

Author(s):

Ilda Tole ◽

Magdalena Rajczakowska ◽

Abeer Humad ◽

Ankit Kothari ◽

Andrzej Cwirzen

Keyword(s):

Compressive Strength ◽

Blast Furnace ◽

Portland Cement ◽

Sodium Silicate ◽

Blast Furnace Slag ◽

Ball Mill ◽

Efficient Solution ◽

Building Materials ◽

Furnace Slag ◽

Alkali Activated

An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.

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Comparison of Selected Properties of Portland Cement Based Materials and Alkali Activated Materials Based on Granulated Blast Furnace Slag

Materials Science Forum ◽

10.4028/www.scientific.net/msf.865.107 ◽

2016 ◽

Vol 865 ◽

pp. 107-113 ◽

Cited By ~ 1

Author(s):

Pavel Mec ◽

Jana Boháčová ◽

Josef Koňařík

Keyword(s):

Blast Furnace ◽

Blast Furnace Slag ◽

Water Glass ◽

Sodium Metasilicate ◽

Alkali Activation ◽

Granulated Blast Furnace Slag ◽

Cement Based Materials ◽

One Year ◽

Furnace Slag ◽

Alkali Activated

Alkali activated systems are materials formed by alkali-activation of latent hydraulic or pozzolanic materials. The outcome is a polymeric structure with properties comparable to materials based on cement.The principle of the experiment is to compare selected properties of alkali-activated materials based on blast furnace slag and using various types of activator (sodium water glass, potassium water glass, DESIL AL and sodium metasilicate) to binders based on white and Portland cements of the highest quality. The samples were left for one year in environments simulating the conditions in the interior and exterior. Selected physical-mechanical properties were evaluated and compared.

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Experimental Study on Compound Binding Material of Alkali Activated Metakaolin and Ground Granulated Blast Furnace Slag

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.287-290.1275 ◽

2011 ◽

Vol 287-290 ◽

pp. 1275-1279

Author(s):

Yong Jia He ◽

Lin Nu Lu ◽

Shu Guang Hu

Keyword(s):

Compressive Strength ◽

Blast Furnace ◽

Blast Furnace Slag ◽

Hydration Product ◽

Alkali Activation ◽

Granulated Blast Furnace Slag ◽

Binding Material ◽

Measurement Results ◽

Furnace Slag ◽

Alkali Activated

Compound binding material was prepared by the alkali activation of metakaolin and ground granulated blast furnace slag. Hydration product components, microstructure and mechanical properties of the hardened paste were investigated by IR, XRD, SEM, MIP, and compressive strength measurement. Results indicated that hydration products included C-S-H and geopolymer, and both of them were amorphous although there were differences in their structure and morphology. When the dosage of slag was less than 50%, the compressive strength of hardened paste increased as the dosage increased, which was mainly because C-S-H produced by the reaction of GGBFS and alkali filled void in geopolymer phase, and part of unreacted slag particles acting as microaggregate to prevent from extension of microcrack in the hardened paste, so the porosity of hardened paste decreased and compressive strength increased.

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Radiological and physico-chemical characterization of red mud as an Al-containing precursor in inorganic binders for the building industry

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp2102182k ◽

2021 ◽

Vol 36 (2) ◽

pp. 182-191

Author(s):

Ljiljana Kljajevic ◽

Miljana Mirkovic ◽

Sabina Dolenec ◽

Katarina Ster ◽

Mustafa Hadzalic ◽

...

Keyword(s):

Construction Industry ◽

Natural Radioactivity ◽

Red Mud ◽

Building Materials ◽

Raw Materials ◽

Construction Materials ◽

Polymerization Process ◽

Alkali Activation ◽

Silica Alumina ◽

Alkali Activated

The potential re-use of red mud in the building and construction industry has been the subject of research of many scientists. The presented research is a contribution to the potential solution of this environmental issue through the synthesis of potential construction materials based on red mud. A promising way of recycling these secondary raw materials is the synthesis of alkali-activated binders or alkali activated materials. Alkali-activated materials or inorganic binders based on red mud are a new class of materials obtained by activation of inorganic precursors mainly constituted by silica, alumina and low content of calcium oxide. Since red mud contains radioactive elements like 226Ra and 232Th, this may be a problem for its further utilization. The content of naturally occurring radionuclides in manufactured material products with potential application in the building and construction industry is important from the standpoint of radiation protection. Gamma radiation of the primordial radionuclides, 40K and members of the uranium and thorium series, increases the external gamma dose rate. However, more and more precedence is being given to limiting the radiological dose originating from building materials on the population these days. The aim of this research was to investigate the possible influence of alkali activation-polymerization processes on the natural radioactivity of alkali activated materials synthesized by red mud (BOKSIT a. d. Milici, Zvornik, Bosnia and Herzegovina) and their structural properties. This research confirmed that during the polymerization process the natural radioactivity was reduced, and that the process of alkali activation of raw materials has an influence on natural radioactivity of synthesized materials.

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The Leachability of Heavy Metals from Alkali-Activated Fly Ash and Blast Furnace Slag Matrices

Materials Science Forum ◽

10.4028/www.scientific.net/msf.851.141 ◽

2016 ◽

Vol 851 ◽

pp. 141-146

Author(s):

Jan Koplík ◽

Miroslava Smolková ◽

Jakub Tkacz

Keyword(s):

Mechanical Properties ◽

Heavy Metals ◽

Blast Furnace ◽

Fly Ash ◽

Blast Furnace Slag ◽

Inductively Coupled Plasma ◽

Emission Spectrometry ◽

Alkali Activation ◽

Furnace Slag ◽

Alkali Activated

The ability of alkali-activated materials (AAMs) to fix and immobilize heavy metals was investigated. Two raw materials were used to prepare alkali-activated matrices – high-temperature fly ash and blast furnace slag (BFS). NaOH served as an alkaline activator. Two heavy metals (Mn, Ni) were added in different amounts to find out the influence of dosage of heavy metal on the mechanical properties of the matrices and the leachability. Leachability was measured as concentration of heavy metals in leachates (ČSN EN 12457-4) by inductively coupled plasma/optical emission spectrometry (ICP/OES). Structure of prepared matrices was characterized by scanning electron microscopy (SEM). Increasing of addition of heavy metals led to decrease of mechanical properties of matrices. The leaching tests showed, that both matrices can immobilize Mn and Ni in dosages of 0.1 – 2,5%. Higher dosages caused deterioration of the matrices and increased the leachability. After alkali activation both heavy metals were transformed into the form of insoluble salts.

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A Review on the Effects of Various Supplementary Cementitious Materials on Physical Properties of Hardened Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.905.287 ◽

2014 ◽

Vol 905 ◽

pp. 287-291

Author(s):

Salim Barbhuiya ◽

Hamid Nikraz

Keyword(s):

Physical Properties ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Hardened Concrete ◽

Granulated Blast Furnace Slag ◽

Current Trends ◽

Fuel Ash ◽

Treatment And Disposal ◽

Furnace Slag ◽

By Products

The global development and current trends in social attitude are resulting in an increase in the amount of waste generated by society, the treatment and disposal of which are becoming a serious problem. Therefore, waste management is one of the most important aspects in ensuring sustainable development in todays world. Some of the industrial by-products, such as pulverised-fuel ash (PFA), ground granulated blast-furnace slag (GGBS) and microsilica (MS) can be used in concrete to improve its properties. In this paper the influence of various by-products on the physical properties of concrete is reviewed.

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