Production Of Blended Cements Research Articles

Feasibility study on the preparation of ternary blended cements with low-kaolinite calcined coal gangue and limestone

This paper presents a feasibility study on the production of ternary blended cements with low-kaolinite calcined coal gangue (CCG) and limestone, considering kaolinite contents varying from 11.7 % to 40.6 % in coal gangue (CG). The ternary systems were designed with 15 %, 30 %, 45 % and 60 % by mass of cement replaced by CCG and limestone with a fixed mass ratio of 2:1. The fluidity and compressive strength of the mortars were measured, followed by the strength efficiency analysis combined with CO2 emission. The potential hydration mechanism was revealed by analysing the hydration kinetics, hydrates and microstructural evolution of these ternary pastes. The results showed that it is possible to use low-kaolinite CCG and limestone to prepare ternary blended cements with adequate mechanical strength that can fulfill the 28-day strength requirement of 32.5 or 42.5 grade cement. In addition, Increasing the kaolinite content in CG can increase the substitution of cement up to 60 %. Microstructural studies indicated that the compressive strength of these ternary mortars at 3 and 7 days was mainly dominated by cement hydration and the pozzolanic reaction between CCG and portlandite (CH), respectively. The precipitation of carboaluminates from the synergy of CCG and limestone significantly reduced critical pore size and increased the volume fraction of fine capillary pores from 7 days, well supporting the strength development of the ternary mortar. The findings of this work underscores the potential of using low-kaolinite CCG as a supplementary cementitious material (SCM) to reduce carbon footprint in the field of construction, and also in contributing to a high-value green utilization of solid waste.

Durability analysis of sustainable mortars with biomass fly ash as high-volume replacement of Portland cement

Utilization of various supplementary cementitious materials was in the last decades considered beneficial for the replacement of the energy-intensive Portland cement to meet sustainable targets. However, structural changes in energy production and heavy industry in Europe significantly limit the availability of coal fly ash and blast furnace slag for blended cement production. On the other hand, the increasing production of biomass ash (BA) presents not only challenges for its disposal but also new opportunities for the concrete industry. In this paper, the durability of cement composites containing up to 70 wt% of BA as Portland cement (PC) replacement was analyzed, taking into consideration also microstructure and mechanical properties. The experimental results showed a preservation of good mechanical performance up to the 30 wt% limit. The freeze-thaw resistance was not affected significantly up to the 40 wt% BA dosage during the first 300 cycles. The analyzed composites also exhibited a good overall resistance to alkali silica reaction- and sulfate-induced expansion up to the 50 wt% PC replacement. BA can thus be considered as a prospective future alternative to coal fly ash and blast furnace slag to meet the sustainable development goals in the building industry.

Using ceramic demolition wastes for CO2-reduced cement production

This study focuses on assessing the pozzolanic potential of two types of ceramic demolition waste, namely terracotta roof tiles and sanitary porcelain, as substitutes for traditional calcined clays in blended and limestone calcined clay (LC3) cement production. Experimental methods employed include the modified Chapelle test and XRD for pozzolanic activity evaluation, flexural and compressive strength tests, capillary absorption measurements, and SEM for microstructure analysis. Mortars containing 10%, 20%, and 30% ceramic powders and 5%, 10%, or 15% limestone filler were tested. The findings showed that porcelain powders exhibited lower pozzolanic activity due to their lower surface area and higher firing temperature of the material. Up to 20% substitution of OPC with terracotta had minimal strength impact, with a 103% strength activity index (SAI) at 90 days. Ultrafine terracotta powder showed promise in LC3 production with up to 30% OPC substitution, achieving a 97% SAI after 90 days. The poor mechanical properties of porcelain-containing mortars were explained by surfactants present in sanitary porcelain. This research informs the cement and processing industries on the potential use of specific ceramic demolition waste materials in eco-cement production, offering insights into blended pozzolanic cements and LC3 formulations, with the goal of reducing the carbon footprint of cement manufacturing.

Review of the Effect of Grinding Aids and Admixtures on the Performance of Cements

Grinding aids (GAs) are polar chemicals introduced in cement mills in either liquid or powder form to improve on mill grindability efficiency. Studies have shown that some GAs not only help in grinding efficiency but also play vital roles in improving the product particle size distribution, product ability to flow in the mill, grinding energy reduction, and improvement on the separator efficiency. This review investigated the impacts of the GAs on the performance of some properties of cement when used as either mortar and/or concrete. The influence of the GAs incorporation in cement grinding on properties such as workability and setting times of the placed concrete and/or mortar has been covered in this review. The performance of GAs on ordinary portland cement (OPC) and blended cements with other supplementary cementitious materials such as pozzolana, fly ash, and slag has also been discussed. This is in view to tapping the maximum benefits of using GAs in cement production and use. This review work established that GAs have a positive influence on mill performance when properly applied. It further established that blended cements work better when dosed with additives such as GAs and/or quality improvers when compared to OPC. The review work demonstrated that some superplasticizers help in lowering the water demand in highly blended pozzolanic-based cements. The review finally recommended that the future course of action in the production of blended cements should apply GAs. This is in order to help produce highly replaced blended cements that are sustainable.

Continuous Assessment of the Environmental Impact and Economic Viability of Decarbonization Improvements in Cement Production

Growing awareness of the importance of mitigating climate change is driving research efforts toward developing economically viable technologies for reducing greenhouse gas emissions. The high energy consumption and carbon-intensive nature of cement manufacturing make it worthwhile to examine the environmental and economic characteristics of process improvements in cement production. This study examines the environmental impact of cement production and its economic considerations and demonstrates an IoT-inspired deployment framework for continuously assessing these. It contributes a practical approach to integrating sustainability into cement manufacturing and analyzes four different scenarios from a combination of two cement types (ordinary Portland cement, Portland-limestone cement) and two energy sources for thermal heating (coal, dried biosolids). It indicates that increased production and adoption of blended cement that has up to 15% limestone as an alternative to ordinary Portland cement can significantly reduce climate change effects from cement production (6.4% lower carbon footprint). In addition, significant emission reduction is possible with the use of waste from sewage sludge as a combustion fuel for heating in the cement production process (7.9% reduction compared with baseline). The information on environmental and financial trade-offs helps informed decisions on cement production improvements and can potentially contribute to greenhouse gas reduction targets.

Cement kiln dust in CIMENCAM Figuil (North Cameroon): characteristics and recycling as additives for blended cement production

This work presents the manufacture of CKD-blended cement from raw materials such as clinker, gypsum, marble and cement kiln dust (CKD) obtained from CIMENCAM Figuil, North Region of Cameroon. The raw materials were first characterized through XRF chemical analyses. Chemical tests (proportion of free lime, loss on ignition, sulfate, and insoluble residues), physical tests (fineness, consistency, setting time, and expansion), and compressive strength tests were carried out on manufactured CKD-blended cements and mortars. Clinker is composed of CaO (65.30%) and SiO2 (21.13%), with significant MgO (2.71%), Na2O + K2O (1.29%), SO3 (0.81%) and lime saturation factor of (97.9); which make this clinker good for cement production. Gypsum is composed of SO3 (36.32%) and CaO (33.92%) but contains very low proportion of impurities; it is therefore classified as low-impurities gypsum suitable for cement productions. The marble is dominantly composed of CaO (37.09%) with significant SiO2 (7.26%), SO3(2.40%), (2.36%), Fe2O3 (1.82%) and MgO (0.18%); it is classified as low-CaO calcitic-aluminosilicate and ferrosilicate bearing marble. The CKD is dominantly made up of CaO (46.0%) and SiO2 (11.62%) with significantly low Na2O + K2O (1.02%), and SO3(2.16%); this classifies it as low alkalies-sulfate cement kiln dust. The proportion of free lime, SO3, loss on ignition, and insoluble residues in the manufactured CKD-blended cements increase with an increase in the proportion of CKD. The blaine specific surface area (BSSA) (4797–6346 cm2/g) and the sieved residues (26.14–30.36%) show an increase with the proportion of used CKD. The compressive strength tests carried out on the prepared brick-shape hardened CKD-cement mortars (at 2, 7, and 28 days) show that, the resistance depends on the proportion of the used CKD (0% control, 5%, 10%, 15%, 20%… up to 50%). Pressures of 17.5 to 11.6 MPa was obtained in 2 days, 28.9 to 20.0 MPa in 7 days, and 35.5–23.3 MPa in 28 days.

A long-term study on structural changes in calcium aluminate silicate hydrates

Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO2 emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al2O3 and SiO2 contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C–A–S–H). Herein, spectroscopic and structural data for C–A–S–H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The 27Al MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C–A–S–H phase, secondary phases such as strätlingite, katoite, Al(OH)3 and calcium aluminate hydrate are present at Al/Si ≥ 0.03 limiting the uptake of Al in C–A–S–H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C–A–S–H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The 27Al NMR studies show that tetrahedrally coordinated Al is incorporated in C–A–S–H and its amount increases with the amount of Al present in the solution.

High-strength geopolymer concrete based on coal washing waste

In recent years, geopolymers have gained significant attention as an environmental-friendly alternative to Ordinary Portland Cement (OPC). Geo-Polymer Concrete (GPC) can be made using different aluminosilicate sources but using waste aluminosilicate sources not only helps to reduce environmental pollution, also leads to efficient waste management. Coal Washing Waste (CWW) refers to the waste that remains after coal washing process in the purification plants. CWW (if properly activated) can be used as a high potential aluminosilicate source to produce GPC or a supplementary cementitious material in the production of Blended Cement (BC). Hence, this study aims to investigate the use of CWW as a waste aluminosilicate source for manufacturing GPC. In this regard, CWW subjected to various methods of thermal activation and the obtained ash was used to produce GPC specimens. Thereafter, the mechanical and physical properties of CWW based-GPC were studied and also compared with conventional concrete. Furthermore, CWW ash was used as an OPC partial replacement (15 %) for BC production. The obtained results indicated that thermal activation conditions of CWW have a significant effect on the properties of the obtained CWW ash. Rapid and abrupt cooling of ash after heat treatment resulted in higher pozzolanic reactivity and thus higher compressive strength. Moreover, CWW ash-based GPC offers higher mechanical strengths, as well as excellent resistance to acidic conditions and low water absorption capacity. Furthermore, CWW ash-based GPC provides proper resistance to evaluated temperatures so that it is almost stable up to 800 °C.

Environmental Benefit Assessment of Blended Cement with Modified Granulated Copper Slag.

This study aimed to investigate the environmental impact of modified granulated copper slag (MGCS) utilization in blended cement production at a representative cement plant in China. Sensitivity analysis was performed on the substance inputs, and the life cycle impact assessment (LCIA) model was applied. A detailed comparative analysis was conducted of the environmental impact of cement production in other studies, and ordinary Portland cement production at the same cement plant. Results showed that calcination has the largest contribution impact of all the impact categories, especially in causing global warming (93.67%), which was the most prominent impact category. The life cycle assessment (LCA) result of blended cement was sensitive to the chosen LCIA model and the depletion of limestone and energy. In this study, producing blended cement with MGCS effectively mitigated the environmental impact for all the selected impact categories. Results also show a reduction in abiotic depletion (46.50%) and a slight growth (6.52%) in human toxicity. The adoption of MGCS in blended cement would therefore generally decrease the comprehensive environmental impact of cement, which contributes to the development of sustainable building materials.

Synergic effect between two pozzolans: Clinoptilolite and silica gel by-product in a ternary blend of a Portland cement system

Two types of SCMs such as clinoptilolite and silicagel by-product was incorporated in the OPC system and acted as pozzolanic materials. The individual effect of silicagel by-product led to the significant reduction of compressive strength due to soluble barrier layers made of CaF2 formed on the particles of OPC. In a ternary blend of a Portland cement system the synergetic effect of clinoptilolite and silicagel by-product led to the similar strength properties of hardened cement paste. Clinoptilolite acted as sorbent which sorb acidic fluoride ion impurities of silicagel by-product. This paper demonstrates the potential application of silicagel by-product and clinoptilolite as SCMs in the production of eco-friendly blended cements.

Uses of EAFS in production of blended cements

Uses of EAFS in production of blended cements

Utilization of alum sludge waste for production of eco-friendly blended cement

This work was focused on evaluating the suitability of replacing Portland cement (PC) by 5, 10 and 15 mass % of activated alum sludge waste (AAS) as a pozzolanic material. Exploitation of low-cost nanocomposite for bolstering the physical, mechanical, and stability against firing of PC–AAS-hardened composites was inspected. CuFe2O4 spinel nanoparticle with average particle size (~ 50 nm) was prepared. Inclusion of CuFe2O4 spinel in different PC–AAS-hardened composites bolsters their physicomechanical features at almost normal curing ages as well as their stability against firing. The positive impact of synthesized CuFe2O4 spinel was affirmed via TGA/DTG and XRD techniques, which indicated the presence of diverse hydration yields such as CSHs, CASHs, CFSH, and CuSH that enhance the overall physicomechanical characteristics and thermal stability of various PC–AAS-hardened composites. The composite containing (90 PC–10 AAS waste–2 CuFe2O4) offers many benefits from the economic and environmental view.Graphical abstract

A Life-Cycle Approach to Integrate Environmental and Mechanical Properties of Blended Cements Containing Seashell Powder

The adverse consequences of producing ordinary Portland cement (OPC) on the environment have introduced cement production as the fourth largest source of anthropogenic carbon emissions after petroleum, coal, and natural gas. Managing and reducing the environmental concerns regarding the impacts of cement production on the environment, namely the depletion of non-renewable fuel resources, consumption of natural raw materials, and releasing huge amounts of CO2 into the atmosphere should be, therefore, one of the key priorities of the cement industry. Application of locally available minerals and wastes that can be blended with OPC as a substitute could considerably reduce the environmental impact. The present study evaluates the potentiality of waste seashell to be used as an additive in the production of blended cement through a modified life cycle approach integrating environmental and mechanical performances. In this regard, 34 cements consisting of different blends of OPC, seashell powder (within the range of 4–30% by OPC mass), and natural pozzolan (up to 30% by OPC mass) were tested to identify the optimal dosage of OPC substitution. Environmental impacts of the cements were assessed through life-cycle analysis. The possibility of mitigating the carbon dioxide emissions in the production of cements, with similar mechanical performance compared to that of OPC, was evaluated by considering both the mechanical and environmental results. The outcome of this study introduced more environment-friendly and sustainable options for future cements.

Thermal performance of mortars/concretes containing calcined marl as alternative pozzolan

The solutions to the increasing problem regarding the energy demand of the world have been expected from the building sector with their consumption of a high amount of energy. Producing environmentally friendly and energy-efficient blended cements and using materials with high thermal performance in terms of insulation and thermal energy storage in buildings are some of these solutions. Calcined marl at the optimum temperature is an alternative pozzolan for blended cement production. The main purpose of this study is to determine how the thermal performance and mechanical properties of mortar/concrete are affected by using calcined marl as alternative pozzolan. For this purpose, mortars/concretes containing calcined marl blended cements were produced. The calcined marl replacement ratios of blended cements were 0, 10, 30 and 50 wt.%. In the study, the strengths and thermal performances of mortars/concretes containing calcined marl blended cements were determined. The test results were compared among themselves and with each other. From the test results, it was concluded that the thermal performances of the mortars/concretes containing calcined marl blended cements could be improved up to 50% replacement ratio without compromising the strength of considered materials.

Recycling of high quantities of wastepaper sludge ash for production of blended cements and alternative materials

Among low cost and widely available raw materials, wastepaper sludge ash is of key interest as potential construction material. These materials come from the paper recycling industry. In present study, wastepaper sludge ash (WSA) retrieved from UPM Chapelle Darblay Company located in the south of Rouen, France, were subjected to preliminary physicochemical characterization by X-ray fluorescence, laser granulometry and scanning electron microscope (SEM) imagery for particles morphology. Afterwards, the WSA considered as mineral addition was blended with cement, lime, and calcined kaolin for the highest possible dosages in WSA. The effects of reactivity were evaluated by means of mechanical strength measurements. Cylindrical samples were prepared with WSA mixtures and air-cured for 7, 14 and 28 days at ambient room temperature. WSA content ranged from 30%–95%. The samples obtained were subjected to unconfined compressive strength to verify the occurrence of reactivity and resistance. The results indicated that the strength increased along the curing time for all mixtures except for the reference sample in which 100% of WSA was used. The lime addition does not impact the unconfined compressive strength. As main results, on one hand, WSA and cement based mixtures with a weight ratio of 95/5 develop 2 MPa compressive strength and more during the curing time which suit for construction materials. On the other hand, with only 5% of calcined kaolin, a value of 9 MPa was attained after 28 days indicating that mixtures with calcined kaolin can be effectively used for building materials such as bricks or blocks. • Possible implementation of high volume of wastepaper sludge ash (WSA) in mixtures blended with cement and/or lime, or with calcined kaolin. • Wastepaper sludge ash and cement based mixtures with a weight ratio of 95/5 developed an unconfined compressive strength (UCS) more than 2 MPa after 28 days. • WSA and calcined kaolin based mixtures can also be employed for building materials. Their UCS strength was nearly 9 MPa after 28 days when only 5% of calcined kaolin was added.

Sustainable Opportunities for Sugar Industries Through Potential Reuse of Sugarcane Bagasse Ash in Blended Cement Production

Sugarcane bagasse ash is available in abundance and it has significant pozzolanic reactivity. However, bagasse ash is currently disposed of as a waste in the major sugar-producing countries and its use in industrial-scale blended cement production is highly limited. A systematic review of the potential of bagasse ash for use as a pozzolan in concrete and the translation of the all-inclusive research outcomes from earlier research studies to the industry can enable its wider acceptance. Hence, this study undertakes a comprehensive review on the use of sugarcane bagasse ash in concrete. The physical, chemical and pozzolanic characteristics of sugarcane bagasse ash and their effects on the properties of concrete are reported. The use of bagasse ash is found to result in a notable increment in the compressive and tensile strengths up to 20% replacement. Nevertheless, delay in setting times and reduction in workability are widely reported. The resistance of bagasse ash blended concrete against chloride ion penetration, water permeability and air permeability were also reviewed, and a considerable drop in the permeability was reported over the conventional cement concrete. Opportunities for the effective recycling of bagasse ash and their benefits in India, the second-largest sugar producer in the world, are presented.

Waste marble dust and recycled glass valorization in the production of ternary blended cements

The purpose of the present investigation is to examine the physicomechanical properties and the hydration development of ternary blended cements, composed by waste marble dust (WMD) and soda lime recycled glass (SLRG). Both wastes characteristics were investigated by means of chemical analysis, laser particle size analyzer and X-ray diffraction (XRD). Prior to their addition as substitutes for Ordinary Portland Cement (OPC), they were grounded to a specific surface area of 4000 cm2/g. Twelve different cement mixtures were produced, containing up to 20% of the above-mentioned wastes, in various proportions. The produced cements mixtures were evaluated, examining their setting times, standard consistency, soundness and compressive strength at 2, 7, 28, 56 and 90 days. The resistance to the alkali-silica reaction of the cement mixtures contained SLRG and the corresponding expansion was determined in prismatic mortar bars, at 38 °C, after 14, 28, 60, 90 and 180 days. The determination of their hydration evolution was accomplished by X-ray diffraction and thermogravimetric and differential thermal (TG/DTG) analyses. According to the results, WMD could be readily valorized together with SLRG as cementitious additions for cement replacement.

Physical and mechanical properties of cement containing regional hazelnut shell ash wastes

Turkey is ranked in the first place with two-thirds of the world hazelnut production. As the amount of shell obtained from shelled-hazelnut is almost equal to that of hazelnut by weight, the shell is a regionally important waste. The biomass is consumed as a fuel in some homes, workplaces, and public buildings with the help of specific caldrons. In the study, the use of ash was researched in the production of blended cement. For this purpose, blended cement mixtures containing hazelnut shell ash at the ratios of 0, 5, 10, 15, 20, 25 and 30% by weight of CEM I 42.5R ordinary Portland cement were prepared. The binary cementitious systems were assessed in terms of chemical, physical and mechanical properties. Hazelnut shell ash introduction increased the water demand up to 59% for standard consistency and reduced setting time up to 96% according to the ordinary Portland cement. Compressive strength results were remarkably reduced by an increase in the amount of ash. With over 5% of hazelnut shell ash introduction, the 28-d compressive strength value was found unsatisfactory (<42.5 MPa). The insufficient total amount of SiO2+Fe2O3+Al2O3 reduced the usage amount of the biomass ash in cementitious products due to having no pozzolanic characteristic. Hazelnut shell ash can be used as an alkaline set accelerator in concrete products as it is not steel-reinforced due to its high chlorine ion content.

Uses of EAFS in production of blended cements

In this investigation the goal is to prepare different blended cements by blending various mixes using electric arc furnace slag EAFS (90%OPC+10%EAFS) mixes, (80%OPC+20%EAFS) and (70%OPC+30%EAFS) .These materials are combined with different w/s ratios then poured into 1 inch cubic moulds and left within the moulds at room temperature (25±1oC) and 100% relative humidity for 1day.They are then taken out of moulds and cured under tap water for 3,7,28,90 and 180 days. For each hydration time, combined water, compressive strength, total porosity and bulk density .The X-ray diffraction patterns are then registered. The results show that the blends containing (90%OPC+10%EAFS) and (80%OPC+20%EAFS) are the best blended pastes.

Production of supplementary cementitious material as a sustainable management strategy for water treatment sludge waste

This paper investigates the application of Water Treatment Sludge (WTS), the main waste generated by water potabilization activities, for the development of a Supplementary Cementitious Material (SCM). The waste has been processed by calcining at a temperature range of 600 °C–800 °C for one hour. Chemical, mineralogical, physical, and morphological characterization has been performed to identify the potential pozzolanic activity of the calcined WTS and validate the application as SCM. Compressive strength tests have been performed in cement mortars with 14%, 35%, and 50% replacement of Portland cement by WTS. The WTS is a non-hazardous and non-inert waste, composed of SiO2, Al2O3, Fe2O3 and contains essentially quartz and kaolinite. Results confirmed the transformation of kaolinite into reactive amorphous phase by calcining. WTS calcined at 600 °C shows great potential to the production of SCM, confirmed by the chemical and physical analysis and the evidence of pozzolanic activity. The mechanical properties of mortars produced with 14% and 35% WTS calcined at 600 °C suggests a promising application in the production of blended and pozzolanic Portland cement.