Tailings after Iron Extraction in Bayer Red Mud by Biomass Reduction: Pozzolanic Activity and Hydration Characteristics

Bayer red mud (BRM) is a kind of solid waste with high hematite content, and its effective utilization is difficult due to the special physicochemical properties. In this work, Fe2O3 in BRM was reduced to Fe3O4 by biomass, and iron concentrate and high activity tailings were obtained after magnetic separation. The pozzolanic activity and hydration characteristics of the tailings were systematically studied. The results showed that the relatively stable polymerization structures of Si-O and Al-O in BRM are destroyed under the effect of biomass reduction at 650 °C, and some fracture bonds and activation points are formed in the structures. The aluminosilicate phases in the BRM were easy to transform into the active substances of Si and Al. The pozzolanic activity of tailings is greatly improved, and its pozzolanic activity index is 91%. High polymerization degree of gel and ettringite are formed since more active substances and alkali in the tailings promote the hydration reaction of cement-based cementitious materials, which made cementitious materials have dense matrix, good mechanical properties, and environmental performance. This work has realized the full quantitative utilization of BRM and provided a feasible way for the resource utilization of BRM.

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Rapid Evaluation of the Pozzolanic Activity of Bayer Red Mud by a Polymerization Degree Method: Correlations with Alkali Dissolution of (Si+Al) and Strength

Materials ◽

10.3390/ma14195546 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5546

Author(s):

Yaguang Wang ◽

Xiaoming Liu ◽

Zhiqing Xie ◽

Huimin Wang ◽

Wei Zhang ◽

...

Keyword(s):

Red Mud ◽

Activity Index ◽

Correlation Coefficients ◽

Evaluation Methods ◽

Pozzolanic Activity ◽

Infrared Spectrometry ◽

Polymerization Degree ◽

Strength Index ◽

Alumina Production ◽

Bayer Red Mud

A large amount of Bayer process red mud is discharged in the process of alumina production, which has caused significant pollution in the environment. The pozzolanic activity of Bayer red mud as a supplementary cementitious material is a research hotspot. In this work, a new method for Fourier-transform infrared spectrometry is used to determine the polymerization degree of Bayer red mud in order to evaluate its pozzolanic activity. Based on the results of the dissolution concentration of (Si+Al), strength index and polymerization degree of Bayer red mud, the relationships between different evaluation methods were analyzed, and the relevant calculation formulas of pozzolanic activity were obtained. The results showed that different evaluation methods can reflect the variation law of pozzolanic activity in Bayer red mud. The polymerization degree of Bayer red mud had a good linear relationship with the pozzolanic activity index obtained by the strength index and dissolution concentration of (Si+Al), respectively. The polymerization degree was negatively correlated with pozzolanic activity index and dissolution concentration of (Si+Al), and the correlation coefficients were greater than 0.85. Therefore, this method was found to be effective and hence can be used as a rapid and simple test for pozzolanic activity evaluation of Bayer red mud.

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Measurement of Pozzolanic Activity Index of Scoria, Pumice, and Rice Husk Ash as Potential Supplementary Cementitious Materials for Portland Cement

Advances in Civil Engineering ◽

10.1155/2017/6952645 ◽

2017 ◽

Vol 2017 ◽

pp. 1-13 ◽

Cited By ~ 9

Author(s):

Hieronimi A. Mboya ◽

Cecil K. King’ondu ◽

Karoli N. Njau ◽

Alex L. Mrema

Keyword(s):

Portland Cement ◽

Rice Husk ◽

Rice Husk Ash ◽

Activity Index ◽

Cementitious Materials ◽

Pozzolanic Activity ◽

Supplementary Cementitious Materials ◽

X Ray Diffraction ◽

X Ray ◽

Setting Times

This work investigated the properties of scoria and pumice as supplementary cementitious materials (SCMs) for Portland cement and compared to those of rice husk ash (RHA). X-ray fluorescence, X-ray diffraction, and pozzolanic activity index (PAI) tests confirmed the suitability of these two materials as potential SCMs. Scoria and RHA samples achieved over 75% PAI at 7 days whereas pumice did this after 28 days. Initial and final mean setting times observed for the composite cement blended with these materials were 166 and 285 min, respectively. These setting times are longer than that of ordinary Portland cement but shorter compared to that of common Portland pozzolana cement. The ultimate mean compressive strengths achieved at 28 days of curing were 42.5, 44.8, and 43.0 MPa for scoria, pumice, and RHA, respectively, signifying that these materials are good SCMs. Higher fineness yielded higher ultimate mean strength. For instance, a scoria sample with a fineness of 575 m2/kg achieved the strength of 52.2 MPa after 28 days.

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Calcinated Bentonite as Supplementary Cementitious Materials in Cement-Based Mortar

Journal of Applied Engineering Sciences ◽

10.2478/jaes-2021-0004 ◽

2021 ◽

Vol 11 (1) ◽

pp. 23-32

Author(s):

N. Mesboua ◽

K. Benyounes ◽

S. Kennouche ◽

Y. Ammar ◽

A. Benmounah ◽

...

Keyword(s):

Activity Index ◽

Cementitious Materials ◽

Sem Analysis ◽

Pozzolanic Activity ◽

Supplementary Cementitious Materials ◽

Partial Replacement ◽

Scanning Calorimetry ◽

Promising Alternative ◽

X Ray ◽

Hardened Properties

Abstract The construction industry consumes a large quantity of cement, which therefore leads to a high CO2 emission due to the cement manufacture. The partial replacement of cement by supplementary cementations materials (SCMs) is considered as the most promising alternative to reduce the environmental impact of this industry. This investigation aims to evaluate the performance of calcinated clay (calcined bentonite at 850 °C) used as partial replacement of cement in cement-based mortar. The evaluated performances include the physico-chemical and mechanical properties, as well as microstructural characteristics.. Various characterization tests, including laser granulometry, X-ray diffraction (XRD), and X-ray fluorescence spectrometry (XRF) have been investigated. In addition, the hardened properties of different mortar mixtures were also investigated. Mortar mixtures incorporating different calcinated clay percentages corresponding to 8, 10, 12, and 14%, by mass of total binder content, were proportioned. Termogravimetric analysis (TGA) and its derivative (DTG), Differential scanning calorimetry (DSC), and microstructural (Scanning electron microscopy (SEM)) analysis were carried out on samples of mortar mixtures. Furthermore, the 28-d hardened properties were assessed to assess the pozzolanic activity of the investigated mixtures. Strength activity index (SAI), DSC, and TGA analyzes are presented. The obtained results showed that all the mixtures exhibited adequate pozzolanic activity conforming to the ASTM C618 specifications.

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Research Progress on the Hydration of Portland Cement with Calcined Clay and Limestone

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1036.240 ◽

2021 ◽

Vol 1036 ◽

pp. 240-246

Author(s):

Jin Tang ◽

Su Hua Ma ◽

Wei Feng Li ◽

Hui Yang ◽

Xiao Dong Shen

Keyword(s):

Mechanical Properties ◽

Portland Cement ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Research Progress ◽

Hydration Reaction ◽

Hydration Products ◽

Early Hydration ◽

Calcined Clay ◽

Dense Microstructure

The use of calcined clay and limestone as supplementary cementitious materials, can have a certain influence on the hydration of Portland cement. This paper reviewed the influence of limestone and calcined clay and the mixture of limestone and calcined clay on the hydration of cement. Both limestone and calcined clay accelerate the hydration reaction in the early hydration age and enhance the properties of cement. Limestone reacts with C3A to form carboaluminate, which indirectly stabilized the presence of ettringite, while calcined clay consumed portlandite to form C-(A)-S-H gel, additional hydration products promote the densification of pore structure and increase the mechanical properties. The synergistic effect of calcined clay and limestone stabilize the existence of ettringite and stimulate the further formation of carboaluminate, as well as the C-(A)-S-H gel, contributed to a dense microstructure.

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The Effect of Substituting Rdf on the Physical and Environmental Properties of Coal Fly Ash

MRS Proceedings ◽

10.1557/proc-136-223 ◽

1988 ◽

Vol 136 ◽

Author(s):

Ashaari B. Mohamad ◽

David L. Gress

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Physical Properties ◽

Activity Index ◽

Coal Fly Ash ◽

Pozzolanic Activity ◽

Portland Cement Concrete ◽

Fly Ash Concrete ◽

Refuse Derived Fuel ◽

Cadmium And Lead

ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, respectively. Although the pozzolanic activity index of coal-RDF fly ash increases over normal coal fly ash, preliminary results show that the 28-day compressive strength of concrete with direct replacement of cement and sand decreases by up to 30%. Leaching tests on crushed concrete were conducted to evaluate the environmental effect of acid rain.

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Synergistic Excitation Mechanism of CaO-SiO2-Al2O3-SO3 Quaternary Active Cementitious System

Frontiers in Materials ◽

10.3389/fmats.2021.792682 ◽

2021 ◽

Vol 8 ◽

Author(s):

Fusheng Niu ◽

Yukun An ◽

Jinxia Zhang ◽

Wen Chen ◽

Shengtao He

Keyword(s):

Blast Furnace ◽

Blast Furnace Slag ◽

Steel Slag ◽

Cementitious Materials ◽

Test Block ◽

Hydration Reaction ◽

Alkaline Environment ◽

Granulated Blast Furnace Slag ◽

Cementitious System ◽

Furnace Slag

In this study, the influence of steel slag (SS) content on the strength of the cementitious materials was investigated. The quaternary active cementitious material (CaO-SiO2-Al2O3-SO3) was prepared using various proportions of steel slag (SS), granulated blast furnace slag (BFS), and desulfurized gypsum (DG). The mechanism of synergistic excitation hydration of the cementitious materials was examined using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The strength of the mortar test block was initially increased and decreased later with the increase of the SS content. Mortar test block with 20% steel slag, 65% granulated blast furnace slag, and 15% desulfurized gypsum with 0.35 water-binder ratio showed the highest compressive strength of 57.3 MPa on 28 days. The free calcium oxide (f-CaO) in the SS reacted with water and produced calcium hydroxide (Ca(OH)2) which created an alkaline environment. Under the alkaline environment, the alkali-activated reaction occurred with BFS. In the early stage of hydration reaction, calcium silicate hydrate (C-S-H) gel and fibrous hydration product ettringite (AFt) crystals were formed, which provided early strength to the cementitious materials. As the hydration reaction progressed, the interlocked growth of C-S-H gel and AFt crystals continued and promoted the increase of the strength of the cementitious system.

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Effect of Water-Soluble Carbon Nanotubes on the Mechanical Properties and early Hydration of Alkali-Activated Slag

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1000.118 ◽

2014 ◽

Vol 1000 ◽

pp. 118-121 ◽

Cited By ~ 1

Author(s):

Pavel Rovnaník ◽

Patrik Bayer

Keyword(s):

Mechanical Properties ◽

Carbon Nanotubes ◽

Cementitious Materials ◽

Water Soluble ◽

Strength Parameters ◽

Early Hydration ◽

Alkali Activated Slag ◽

Activated Slag ◽

Hydration Characteristics ◽

Alkali Activated

Alkali-activated slag (AAS) is a material which has great potential for use in building industry. The aim of this work was to gain new superior properties by the addition of carbon nanotubes (CNTs). This material can act as a microreinforcement improving mechanical properties of cementitious materials. The effect of 0–1 wt.% addition of CNTs on the mechanical properties, hydration characteristics and microstructure of AAS binder was determined. The addition of CNTs delays the setting of the binder and a partial deterioration of strength parameters was observed.

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