Clinker Microstructure Research Articles

Preparation and properties of Portland cement from secondary recycle waste of rare earth tailing

Secondary recycle waste of rare earth tailing (RET) was used as raw material to prepare Portland cement. The phase composition and microstructure of clinker, mechanical strength and hydration characteristic of cement were investigated. The results indicated that the RET recycle waste increased the practical content of early-strength and high-durability mineral phases (C3S and C4AF) in clinker, which respectively rose from 45.3% to 67.5% and 6.1% to 10.6%, and significantly reduced the ratio of f-CaO from 0.4% to 0.23%, finally causing the intensity reduction of first exothermic peak of hydration, prolonging the appearing time of the second and third exothermic peak, and rising initial and final setting time. This RET recycle waste-fabricated cement generated high strength, and the improving rate of 1-day and 3-day compressive strength achieved to 81.2% and 60.3%, due to dense microstructure caused by fast hydration of rich C3S.

The influence of homogeneity of chemical and mineralogical composition of raw mixes on strength properties of Portland clinker

Factors affecting the clinker strength are of great interest. The implementation of the dry process attracts attention to the homogeneity of the chemical and mineralogical composition of raw mixes.Purpose: One of the main factors affecting the clinker hydraulic activity is the homogeneity of its chemical and mineralogical compositions. The aim of this work is to study clinkers prepared by different production methods in furnaces using wet and dry processes.Methodology: X-ray fluorescence analysis of chemical composition of mixes; X-ray powder diffraction analysis of clinker mineralogical composition; petrographic analysis of clinker microstructure;Research findings: The clinker structure obtained in drying furnaces is glomeroblastic. Minerals mostly generate clusters alternating with each other. Clinker crystallization is mediumcrystalline, unequigranular. Alite and belite can form both individual grains and aggregates.Research findings: The chemical composition heterogeneity of raw mixes directly affects the clinker mineralogical composition of microstructure, that has a significant impact on its hydraulic activity.

Cementron: Machine learning the alite and belite phases in cement clinker from optical images

The performance of cement hydrate depends on constituent phases, viz., alite, belite, aluminate, and ferrites present in cement clinker. Traditionally, clinker phases are analyzed from the optical image using empirical image processing techniques. However, the non-uniformity of images, variations in geometry, size of phases, experimental approaches, and imaging methods make it challenging to identify individual phases. Here, we present a machine learning (ML) approach to automatically and accurately detect the major clinker microstructure phases, namely, alite and belite, from optical microscopy images. To this extent, we create an annotated dataset of cement clinker by manually labelling alite and belite phases in microscopy images. We then demonstrate the use of supervised ML methods to train models for identifying alite and belite regions by using a small fraction of annotations on a single image. Further, we finetune the image detection and segmentation Mask R-CNN model using Detectron-2 by considering all the annotated images of the cement microstructure to develop a model for detecting cement phases, namely, Cementron. We demonstrate that Cementron, trained on literature data, generalized well on completely new data obtained from in-house experiments, demonstrating its wider applicability.

Application of optical microscopy techniques for the evaluation of raw materials for cement and concrete

Optical microscopy techniques play a prominent role in evaluation of Raw Materials for manufacture of cement and concrete. The present study mainly deals for the evaluation of cement clinker for its development of clinker phases, distribution of all the mineral phases, effect of cooling on clinker microstructure and also grindability of clinker which are helpful in determination of quality of clinker. A detailed study has also been carried out for limestone for its suitability for manufacture of cement and coarse aggregates using optical microscopy techniques for their suitability for concrete making. Studies have also been done for determination of glass content in blast furnace slag for its suitability for manufacture of Portland slag cement which is very good for marine constructions and the constructions in coastal areas. Based on the morphological features, different shapes, grain sizes and textures of clinker, limestone and coarse aggregates the results and conclusions have been arrived and the results provided have been implemented for the quality improvement.

Effect of Quartz in Clay on Grindability of Raw Mixes for Cement Production

High quartz content in clay substantially impacts the grinding of raw mix, quality of clinker and final cement produced. The presence of quartz requires very fine grinding and a long sintering time to react significantly, all of which are very expensive. This study assessed an extensive plant sample which involved a vertical roller mill to determine the correlation between quartz content in clay to the 90 μm residue, feed rate, clinker microstructure and mill power. The characterisation study performed on raw materials revealed three clay categories based on quartz content, namely low, normal and high quartz at (42.4%–48.8%), (57.1%–64.9%) and (81.5%–89.3%), respectively. The grinding test showed an increment of 90 μm residue for high-quartz clay. Meanwhile, high, medium and low feed rates generated the most coarse, coarse and fine products, respectively. Based on the distribution curve of mill products, high quartz content in clay significantly reduced the particles passing percentage. Coarser particles were observed to be present in mill products for the high-quartz category compared to the low-quartz clay and normal-quartz clay, signifying inadequate size reduction for the high-quartz clay in the vertical roller miller. The power consumption was higher (7.2 kWh/t–9.0 kWh/t) for grinding raw mixes that contained high-quartz clay than low-quartz clay. This study provided a significant relationship between grindability and the amount of quartz content in clay with the purpose of optimising the grinding process when dealing with high-quartz content in clay.

The effects of MgO, Na2O and SO3 on industrial clinkering process: phase composition, polymorphism, microstructure and hydration, using a multidisciplinary approach

The present investigation deals with how minor elements (their oxides: MgO, Na2O and SO3) in industrial kiln feeds affect (i) chemical reactions upon clinkering, (ii) resulting phase composition and microstructure of clinker, (iii) hydration process during cement production.Our results show that all these points are remarkably sensitive to the combination and interference effects between the minor chemical species mentioned above.Upon clinkering, all the industrial raw meals here used exhibit the same formation temperature and amount of liquid phase. Minor elements are preferentially hosted by secondary phases, such as periclase. Conversely, the growth rate of the main clinker phases (alite and belite) is significantly affected by the nature and combination of minor oxides. MgO and Na2O give a very fast C3S formation rate at T > 1450 K, whereas Na2O and SO3 boost C2SAfter heating, if SO3 occurs in combination with MgO and/or Na2O, it does not inihibit the C3S crystallisation as expected. Rather, it promotes the stabilisation of M1-C3S, thus indirectly influencing the aluminate content, too. MgO increseases the C3S amount and promotes the stabilisation of M3-C3S, when it is in combination with Na2O. Na2O seems to be mainly hosted by calcium aluminate structure, but it does not induce the stabilisation of the orhtorhombic polymorph, as supposed to occur. Such features play a key role in predicting the physical-mechanical performance of a final cement (i.e. rate of hydration and hardening) when used as a bulding material.

Evaluation of Clinker Microstructure Changes Resulting from Different Subsoil Contacts After Long-term Exposition to Polish Climate Conditions

A face wall is defined as an element applied inside or outside which should have an attractive look. The achievement of expected results is very difficult. Usually, during the first years of exploitation efflorescence appears, covering mostly clinker surface. This is primary efflorescence which should disappear within the first year of exploitation. Long-term observations led by the author on real objects indicate that this period is definitely longer, and efflorescence change depending on seasons of the year. The essential influence has the wall and subsoil contact area. This is an area especially endangered with rain and soluble compounds contained in water. The cyclic character of these changes influences the clinker microstructure. This paper deals with clinker microstructure changes resulting from ten years of exposition to external climate. There are three cases of wall and ground contact: a tight concrete band, humus layer, and gravel filter layer. The tests were performed on a field station located at the University of Science and Technology in Bydgoszcz. Three types of clinker walls with different mortars were analyzed. Six samples of bricks designed for wall erecting were taken as initial material for microstructure evaluation. The tests were led on 5mm thick face layer of bricks. Based on observation there were indicated areas of the biggest efflorescence intensity. Microstructure evaluation was done using mercury porosimetry method. The results obtained were used for comparative analysis of meso- and macropore share changes in clinker after ten years of functioning in external environment. These tests let us indicate the best solution taking into account the wall and ground contact.

Changes of Clinker Microstructure after Long-term Influence of External Environment

Contemporary clinker elements because of numerous colours and shapes give uncountable opportunities for architectural compositions. Apart from undeniable aesthetic values they are characterized with high resistance to environment influence. It is associated both with clinker microstructure as with adopted mortar types. By definition a facial wall has an attractive look which should be maintained during the whole period of the construction usage. However, it often occurs that the intended effect has not been reached. On majority of buildings during the first years of using there are efflorescence's appearing, covering mainly clinker surface. They are primary efflorescence's which should disappear during the first year of exploitation. The multi-year work led by the authors on real objects indicate that this period is definitely longer and efflorescence change according to seasons. The cyclic influence of salts changes the clinker microstructure. This work concerns the clinker microstructure and its changes resulting from ten years of exposition on external climate conditions. The researches were led on field station localized on area of the University of Science and Technology Bydgoszcz (Poland).

Comparative Study for Grinding of Two Cement Clinkers

The purpose of this work is the comparative study for grinding of two cement clinkers. X-ray fluorescence, physical and granulometric tests and optical microscopy were used to characterize the clinkers. Also grinding tests were carried out for ten samples to determine the parameters influencing grindability of its clinkers. The results of calculation of the energies of grinding according to the law developed by Von Rittinger and the study of the microstructure of the two clinkers shows good agreements. Indeed, frequent clusters of belite which indicate a lack of uniformity and fineness have an effect on lowering the grindability. The obtained analyses and the results enabled us to interpret the granulometry and the microstructure of clinker to control quality and resistance.

Properties of Recycled-Cement Produced from Waste Concrete

This research aims to find a new way of “turning trash into treasure” for the waste concrete. In the research, waste concrete was first ground, then, after analyzing its mineral composition, combined with some other ingredients according to the modulus of the cement clinker to become raw materials of cement. Mixed raw materials were made to be a thin cake, and then sent into high temperature furnace (HTF) to sinter for a certain period of time. Properties of cement, such as the compressive strength, required water of standard consistence and setting time were tested. The composition and microstructure of clinker were analyzed with X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) analysis. The experimental results showed that the main mineral components of clinker are C3S, β-C2S, CA2, CA, C3A, C4AF, the compressive strength of the recycled-cement is approximately equal to P.O32.5, there exists an optimum sintering temperature for the recycled-cement clinker with a given mix ratio of raw materials and content of seed crystal added,, and this temperature is usually much lower than the temperature adopted wildly in the cement plants.

Kinetic modelling of cement raw mix containing iron particles and clinker microstructure

This paper investigated the oxidation of iron particles contained in cement raw mix using stationary electric furnace. Results showed that oxidation kinetic of metallic particles in cement raw mix was limited by diffusion and occurred mainly in the transition zone. Complete oxidation of metallic particles in the raw mix can be achieved at about 800 °C. This is about 400 ° lower than that of abrasive slurry. The presence of CaO enhances the oxidation of metallic particles in raw mix. When used as raw mix component, abrasive slurry containing high metallic particles content can significantly influence the clinker minerals chemical composition, morphology and phases ratio. This is due to increased probability of localized high Fe 2O 3 concentration and consequently increased acidity of the liquid phase.

Mineral composition and microstructure of clinker from raw mix containing metallic particles

The influence of the presence of finely dispersed metallic particles on the mineral composition and microstructure of clinker minerals have been studied using chemical analysis and optical microscopy. The mineral composition to a great extent depends on the prevailing technological parameters: sintering temperature and concentration of Fe 2O 3. Abrasive slurry, containing finely dispersed metallic particles significantly influenced the mineral composition and microstructure of the cement minerals. The observed disintegration of the alite in general is attributed to the considerable increase in acidity of the liquid phase.

Applications of SEM/EDXA in cement clinker investigation

All the desired properties of cement primarily depend on the physicochemical characteristics of clinker from which the cement is produced. The mineralogical composition of the clinker forms the most important parameter influencing these properties.Optical microscopy provides reasonably accurate information pertaining to the thermal history of the clinker, while XRDA still remains the proven method of phase identification, and bulk chemical composition of the clinker can be readily obtained from XRFA. Nevertheless, all these microanalytical techniques are somewhat limited in their applications, and SEM/EDXA combination fills this gap uniquely by virtue of its high resolution imaging capability and possibility of instantaneous chemical analysis of individual phases.Inhomogeneities and impurities in the raw meal, influence of kiln conditions such as sintering and cooling rate being directly related to the microstructure can be effectively determined by SEM/EDXA. In addition, several physical characteristics of cement, such as rhcology, grindability and hydraulicity also depend on the clinker microstructure.

Microstructure and chemistry of unhydrated cements

Cement clinker microstructure is a major factor in determining resultant cement properties and may be modified by changes in clinker chemistry, burning regime and manufacturing processes.

Morphology and microstructure of autoclaved clinker and slag-lime pastes in presence and in absence of silica sand

Development of microstructure in four hydrothermal reactions has been undertaken using scanning electron microscopy. These are clinker, clinker-sand, slag-lime and slag-lime-sand hydrothermal reactions. The microstructure of clinker hydration products displayed crumpled foils and tabular masses of calcium silicate hydrates; few cubic crystals of hydrogarnet appeared only during the initial stage of the reaction. In clinker-sand mixture the C-S-H phase was the only product identified. In slag-lime hydration the microstructure displayed both of the hydrogarnet crystals and the C-S-H phase. The hydration of slag-lime-sand mixture (an optimum composition) was associated with the formation of ill-crystallized tobermorite and crystalline 11A tobermorite as the main products.