Production Of Blended Cements Research Articles

A Review on Pyroprocessing Techniques for Selected Wastes Used for Blended Cement Production Applications

Pyroprocessing is an important stage in cement manufacturing. In this process, materials are subjected to high temperatures so as to cause a chemical or physical change. Its control improves efficiency in energy utilization and hence enhances production for good quality assurance. Kilns used in cement manufacturing are complex in nature. They have longer time constants, and raw materials used have variable properties. They are therefore difficult to control. Additionally, the inclusion of various alternative fuels in burning makes the process more complex as the fuel characteristics remain inconsistent throughout the kiln operation. Fuel intensity standards for kilns using fuel oil are very high, ranging from 2.9 GJ to 7.5 GJ/ton of clinker produced. Grinding of clinker consumes power in the range of 2.5 kWh/ton of clinker produced. These and other pyroprocessing parameters make cement production costly. The pyroprocessing process in kilns and the grinding technologies therefore have to be optimized for best processing. This paper discusses the cement manufacturing and grinding processes. The traditional kiln technologies and the current and emerging technologies together with general fuel and energy requirements of cement manufacturing have been discussed. From the discussion, it has been established that the cement manufacturing and grinding technologies are capital‐intensive investments. The kiln processes are advanced and use both electricity and natural fuels which are expensive and limited factors of production. The raw materials used in cement manufacturing are also limited and sometimes rare. The calcination of the raw materials requires external energy input which has contributed to the high cost of cement especially to low‐income population in the developing countries. Self‐calcining materials, in which the pozzolanic materials burn on their own, are potential pozzolanic materials with great potential to lower the cost of cement production. Such materials, as shown from the previous research study, are rice husks, broken bricks, spent bleaching earth, and lime sludge. There is a need, therefore, for research to look into ways of making cement using kiln processes that would use this property. This will be cost‐effective if successful. It can be done at micro‐ and small‐scale enterprise.

A Comparative Study: Blended Cements Containing Analcime and Clinoptilolite

The demand to blended cements is increasingly widespread due to clean environment and energy saving. In the future, this demand will not be met by currently additives on the market. For this reason, alternative additives will always be needed. The aim of this study is to provide a contribution for additive variety used in sustainable blended cement productions. Therefore, in this study, natural zeolite type clinoptilolite (C) which is widely used in blended cement production and different natural zeolite type analcime (A) are compared. These zeolites are natural pozzolans with volcanic tuff origin. Firstly, pozzolanic activities, mineralogical structures, physical and chemical properties of zeolites were determined. And then, the heat of hydration, setting times and compressive strength tests were performed on samples prepared by using Portland cement (PC) and natural zeolite blended cements. The replacement ratios of zeolites used in test samples are 0, 10, 30 and 50% of Portland cement weight. According to results of pozzolanic activity tests, the compressive strengths of lime-zeolite (pozzolan) mixtures were determined as 6.30MPa for analcime and 9.02MPa for clinoptilolite. The heats of hydration of blended cements containing analcime were lower than that of blended cements containing clinoptiloite and that of Portland cement at all replacement ratios. The setting times of blended cements containing analcime were determined as shorter than that of blended cements containing clinoptiloite and that of Portland cement. The compressive strengths of mortars containing analcime blended cements were slightly higher than that of mortars containing clinoptilolite blended cements. The optimum strength values of mortars containing both zeolite blended cements were obtained at 10% replacement ratio. According to the results obtained from the study, analcime exhibits similar properties to clinoptilolite. In some cases, due to these similar properties, analcime may be an alternative additive to clinoptilolite which is widely used in blended cement industry.

Valorization of demolition ceramic wastes and lignite bottom ash for the production of ternary blended cements

The present investigation aims to the utilization of demolition ceramic wastes (DCW) and coal bottom ash, derived from lignite combustion in power plants (LBA), for the development of ternary blended cements. The wastes under investigation were initially characterized by chemical analysis, X-ray diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM). After their grinding to a specific surface area of about 4000 cm2/g, various cement mixtures were prepared substituting Portland cement up to 20%. The physico-mechanical properties of the produced blended cements were examined by means of standard consistency, initial and final setting times, soundness and compressive strength, after curing at 2, 7, 28, and 90 days. The hydration evolution study was accomplished using X-ray diffraction and TG/DTG analyses at various ages. The results showed that both DCW and LBA could be valorized for the production of ternary blended cements, thus presenting significant environmental benefits in waste management practice.

Complex Characterization and Behavior of Waste Fired Brick Powder-Portland Cement System.

Two waste fired brick powders coming from brick factories located in Argentine and Czech Republic were examined as alternative mineral admixtures for the production of blended cements. In pastes composition, local Portland cements (Argentine and Czech) were substituted with 8–40%, by mass, with powdered ceramic waste. For the ceramic waste-Portland cement system, workability, the heat released, pozzolanity, specific density, compressive strength, hydrated phases, porosity, and pore size distribution were tested. The relevance of the dilution effect, filler effect, and pozzolanic activity was analyzed to describe the general behavior of the pozzolan/cement system. The properties and performance of cement blends made with finely ground brick powder depended on the composition of ceramic waste and its reactivity, the plain cement used, and the replacement level. Results showed that the initial mini-slump was not affected by a low ceramic waste replacement (8% and 16%), and then it was decreased with an increase in the ceramic waste content. Brick powder behaved as a filler at early ages, but when the hydration proceeded, its pozzolanic activity consumed partially the calcium hydroxide and promoted the formation of hydrated calcium aluminates depending on the age and present carbonates. Finally, blended cements with fired brick powder had low compressive strength at early ages but comparable strength-class at later age.

The Influence of Production Parameters on Pozzolanic Reactivity of Calcined Clays

Abstract Calcined clays are gaining increasing interest as future supplementary cementitious materials for the production of blended cements. Besides the mineralogy, the right production conditions can affect the pozzolanic activity of calcined clays. In this paper, the pozzolanic reactivity of two calcined natural clays in dependence of burning temperature, residence time in the furnace, cooling conditions and particle size of the final product is investigated. The highest pozzolanic reactivity was found at calcination temperatures between 600 and 800°C. While different cooling conditions had no identified effect on reactivity, decreased particle size and residence time increased the reactivity.

Chemical composition and physicomechanical characteristics of sawdust ash blended cement

The production of blended cement by incorporating sawdust ash (SDA) in Ordinary Portland Cement (OPC) clinker, during manufacturing of cement was investigated. Sawdust was collected from sawmill industry at Olope Marun, Ogbomoso, Oyo State, Nigeria. It was burnt to ash and then added as percentage replacement for OPC clinker. Chemical and physical properties of both SDA and OPC clinker were determined. The production of the SDA – blended cement was carried out by intergrinding 5–25% by weight of SDA with OPC clinker during cement manufacturing. The blended cement produced was analyzed for chemical composition and physical properties. The chemical compositions of SDA – blended cement with 5–25% SDA replacement were 19.96–22.52% for silicon oxide, 5.57–5.72% for aluminum oxide, 3.47–3.63% for iron oxide, and 65.39–57.28% for calcium oxide. The physical properties of SDA – blended cement were 5–7 mm for soundness, 391–410 m2/kg for fineness, 27.6–30.0% for consistency, 45–160 min for initial and 75–210 min for final setting time, 2.5–2.2 for specific gravity, and 1.33–1.45 for loss on ignition. The compressive strength of blended cement with 5–25% SDA replacement ranged from 5.2 to 9.9, 11.2–27.8, 13.9–44.0, 14.3–56.0, 15.8–58.9, 20.4–62.4, and 23.6–65.2 N/mm2 for 1, 3, 7, 14, 28, 56, and 90 days, respectively while the flexural strength ranged from 1.8 to 2.3, 2.5–5.3, 2.8–6.3, 3.4–7.4, 3.5–8.9, 3.9–10.1, and 4.1–11.5 N/mm2, respectively. The partial replacement of OPC clinker with SDA during cement manufacturing was established. A maximum replacement level of 15% by weight of cement gave desirable engineering properties.

Usability of alternative admixtures for the potential production of blended cements

This paper studies how pozzolan materials can be mechanically activated. For this, two major grinding technologies and different types of artificial pozzolans, such as red brick dust, granulated blastfurnace slag and sheet glass, were used. Observed properties were chemical and mineral composition, amorphousness, particle size and specific surface area. Pozzolan activity of selected materials was compared by evaluation of the reaction with lime using X-Ray diffraction (XRD) analysis and differential thermal analysis (DTA).

Properties of mixtures of cement with various raw materials

This paper presents possibility of utilization of selected Czech and Slovak industrial and natural raw materials in blended cement production. The cement blends were prepared using 75 wt. % of cement and 25 wt. % of a substituent. The paper is focused only on test results of the laboratory-prepared blended cements. The influence of admixture on hydration process was observed by calorimetric measurement of heat evolution during hydration process within 24 hours. The hydration products of water-cured samples for 28 days were determined by thermal analysis. Further properties, such as short and long-term compressive strengths and setting period, were determined.

Chemical and Physical Characteristics of Blended Cements Produced from Softwood Ash

In an attempt to convert agricultural residue to alternative binding material for use in construction industry, this research considered the use of wood ash from Anacardium- occidentale (kaju) wood which is softwood as a pozzolan in cement production. In this study, the chemical composition (silica (SiO.), aluminum oxide (AI,O,), ferric oxide (Fe,O,), calcium oxide (CaQ), magnesium oxide (MgO), sulphur trioxide (SO,), sodium oxide (Na,O) and potassium Oxide (K,O)) of the ashes and the clinker was investigated. The production of blended cements were carried out in the factory by replacing 5- 50% by weight of Ordinary Portland Cement Clinker with the ashes during the manufacturing process. The cement without wood ash serves as the control. The physical characteristic (fineness, initial and final setting times, heat of hydration and residue on 45um sieve), and the chemical composition of the blended cements were also investigated. The results showed that Anacardiumoccidentale ash (AOA) was a suitable material for use as pozzolan since it satisfied the requirement for such a material by having a combined SiO, Fe,O,and Al,O,of more than 70% according to ASTM C 618. The AOA blended cements satisfied standard requirements for up to 20% replacement level. It was concluded that the wood ash was suitable for use in the production of blended cements.

Characteristics of Blended Cements Produced from Selected Hardwood Ashes

In an attempt to find an alternative binding material for construction industry, this study considered the use of wood ash from three different hardwoods namely: Tectonagrandis, Cassia siamea and Vitellariaparadoxa as a pozzolan in cement production. The study investigates the chemical composition (silica (SiO2), aluminum oxide (Al2O3), ferric oxide (Fe2O3), calcium oxide (CaO), magnesium oxide (MgO), sulphur trioxide (SO3), sodium oxide (Na2O) and potassium Oxide (K2O)) of the ashes and the clinker. The production of blended cements were carried out in the factory by replacing 5- 50% by weight of Ordinary Portland Cement Clinker with the ashes during the manufacturing process. The cement without wood ash serves as the control. The physical characteristic (fineness, initial and final setting times, heat of hydration and residue on 45µm sieve), and the chemical composition of the blended cements were also investigated. The results showed that all the wood ashes (Tectonagrandis ash (TGA), Cassia siamea ash (CSA) and Vitellariaparadoxa ash (VPA)) were suitable material for use as pozzolan since they satisfied the requirement for such a material by having a combined SiO2, Fe2O3 and Al2O3 of more than 70%. The TGA, CSA and VPA blended cements satisfied standard requirements for up to 20% replacement level. It was concluded that all the wood ashes were suitable for use in the production of blended cements.

Utilization of Alumina Industrial Waste in Production of Blended Cement.

Utilization of Alumina Industrial Waste in Production of Blended Cement.

Development and characterization of blended cements containing seashell powder

This study evaluates potentiality of waste seashell to be used as additives in production of blended cement. Cements with binary blends of ordinary Portland cement (OPC) and seashell powder (up to 30% by mass) as well as ternary blends of OPC, seashell powder (up to 7% by mass) and natural pozzolan (up to 30% by mass) were developed and their characteristics were investigated in terms of density, fineness, specific surface, chemical composition, and setting time. Properties including compressive strength, flexural strength, and water demand were determined for mortars made of the developed cements. All the properties characterized for the blended cements were compared with those of the OPC as well. Setting time of all the blended cements was higher than that of the OPC, which is beneficial for construction in hot climate. All the blended cements containing seashell powder, presented compressive strength relatively close to that of the OPC at all three ages of 3, 7, and 28 days, demonstrating competitiveness of the produced blended cements with OPC. Results indicate that seashell powder can be used as cement replacement in developing blended cements not only to enhance sustainability and reduce costs of production, but also to promote the properties and performance of concrete.

Portland metakaolin cement containing dolomite or limestone – Similarities and differences in phase assemblage and compressive strength

The scarceness of high-quality limestone obliges the cement industry to consider alternative supplementary cementitious materials (SCMs) for the production of blended cements. This study investigated the potential usage of dolomite instead of limestone as an addition to Portland metakaolin cement by measuring the development of the compressive strength and phase assemblages at 5°C, 20°C or 38°C. Laboratory grade materials were used to identify potential differences in the impact of the carbonate on the phase assemblages. As with limestone, a strength increase was observed when dolomite is added at temperatures >5°C due to the formation of additional carbonate AFm phases and the stabilization of ettringite. Differences were observed in the amount and type of the carbonate AFm and AFt phases formed. Thermodynamic modelling in combination with the experimental results indicate that the dolomite and limestone affect Portland metakaolin cement in a similar way, with the reactivity being the major difference between the two carbonate sources. This indicates that with regard to the strength development up to 90days dolomite can be used instead of limestone to replace parts of a Portland metakaolin cement.

Determination of Pozzolanic Activity for Using Natural Zeolite Analcime in Sustainability Additive Cement Products

It is known that the cement industry is responsible for 5-8% of world CO2 emissions and also for intensive energy consumption. For this reason, cement productions need to sustainability studies. Mineral admixtures added to cement as partial replacement material enable to sustainable blended cement productions due to used less amount of cement. Mineral admixtures with pozzolanic property are also preferred in terms of increasing cement performances. This situation corresponds to improved performance of cement and concrete products as well as saving energy, reducing world CO2 emissions. In recent years, the cement industry has been using natural zeolites extensively as pozzolanic materials. Analcime is known as second valuable zeolite mineral after from clinoptilolite in natural zeolite groups The aim of this study is to determinate the pozzolanic properties of analcime and to investigate whether it has potential availability in sustainable blended cement production. The clinoptilolite was used with comparison purpose in this study. Blaine values, densities, chemical composions, pozzolanic activities, mineralogical structures of analcime and clinoptilolite which are subject of study were determined. Accordance with TS 25, which contains pozzolan conformity criterias, 7-days average compressive strength values of lime-pozzolan mixture samples were determined. The datas obtained shown that, the 7-days average compressive strengths of lime-zeolite (pozzolan) blended samples are 9.02 MPa for clinoptilolite and 6.3 MPa for analcime. The total content of Si02 + Al2O3 + Fe2O3 was 77.3% for clinoptilolite and 73.16% for analcime. Accordingly, analcime which is a natural zeolite satisfies to puzolan conformity criterias in TS 25 has the potential to be an alternative to clinoptilolite which is more widely used in cement productions.

Properties of Portland cement pastes enriched with addition of calcined marl

Increasing global production of Portland cement and the necessity to reduce CO2 emissions have resulted in the need to increase the production and application of blended cements enriched with supplementary cementitious materials (SCMs). Recently, polymineral clays, which are abundantly available across the globe, have gained attention as promising raw materials for the production of SCMs. In this study, the effect of marl on the properties of hardened Portland cement was investigated. The Portland cement pastes enriched with marl (5–20%) calcined at 400–800°C and ground up to 250–800m2/kg showed better physical-mechanical properties than those enriched with metakaolin. This study demonstrates the potential of calcined marl to be used as an effective pozzolan additive for Portland cement.

Limestone calcined clay cement as a low-carbon solution to meet expanding cement demand in emerging economies

This paper aims at assessing the return on investment and carbon mitigation potentials of five investment alternatives for the Cuban cement industry in a long-term horizon appraisal (15 years). Anticipated growing demand for cement, constrained supply and an urgent need for optimisation of limited capital while preserving the environment, are background facts leading to the present study. This research explores the beneficial contribution of a new available technology, LC3 cement, resulting from the combination of clinker, calcined clay and limestone, with a capacity of replacing up to 50% of clinker in cement. Global Warming Potential (GWP) is calculated with Life Cycle Assessment method and the economic investment's payback is assessed through Return on Capital Employed (ROCE) approach. Main outcomes show that projected demand could be satisfied either by adding new cement plants—at a high environmental impact and unprofitable performance— or by introducing LC3 strategy. The latter choice allows boosting both the return on investment and the production capacity while reducing greenhouse gas (GHG) emissions up to 20–23% compared to business-as-usual practice. Overall profitability for the industry is estimated to overcome BAU scenario by 8–10% points by 2025, if LC3 were adopted. Increasing the production of conventional blended cements instead brings only marginal economic benefits without supporting the needed increase in production capacity. The conducted study also shows that, in spite of the extra capital cost required for the calcination of kaolinite clay, LC3 drops production costs in the range of 15–25% compared to conventional solutions.

Use of oxyfuel combustion ash for the production of blended cements: A synergetic solution toward reduction of CO2 emissions

In this paper, it is investigated the possibility of reusing ashes, issued by an oxyfuel combustion process aimed at mitigating CO2 emission, as substitutes for natural pozzolan in the production of low-CO2 blended cements. To this end, the oxyfuel plant (a 95 kWth pilot-scale fluidized bed reactor) was operated under controlled conditions by feeding blends of anthracite or lignite and biomass corn stover. Characterization of fly and bottom ashes revealed that the latter showed properties able to make them considerable for obtaining blended cements by mixing them with Portland clinker and natural gypsum. The cements were subjected to pozzolanicity and hydration tests for curing times ranging from 2 to 28d at 20° and 40°C. X-ray fluorescence and diffraction, differential thermal–thermogravimetric analyses and scanning electron microscopy were employed as characterization techniques. With reference to a standard blended cement, and with particular eye on the blended cement containing bottom ashes obtained from the lignite–biomass mixture combustion, it was observed a good similarity in the ability of the silico-aluminous fraction to react with Ca(OH)2 produced by Portland clinker hydration, to yield the desired calcium silicate hydrates among the hydration products.

Ocena sposobnosti drobljenja recikliranega stekla pri proizvodnji mešanih cementov

The replacement of primary raw materials in cement production is a current topic. Potentially usable raw materials include recycled glass. The disadvantage of glass is its tendency to aggregate. The conventional method for the production of blended cement is separate grinding and then homogenizing the components. However, in this case aggregated fine glass in the cement composites acts only physically and mechanically as a filler rather than as an active pozzolan. An interesting option to prevent the formation of aggregates formed from glass is co-grinding. This procedure is not very common in practice. Various ingredients of blended cements have widely different grindabilities, and it is therefore better to grind them separately. The aim is to compare the co-grinding and separate grinding of a combination of Portland clinker and recycled glass. The grindability was tested on clinker, glass, and blended cements prepared by co-grinding and by separate grinding. The results of the experiment show that by co-grinding the components of blended cement with the addition of 20 % of recycled glass as a pozzolan, a synergy effect caused by the various mechanical properties of the components occurs. The aggregation of grains is less significant than during separate grinding and it leads to a better grinding effect. This knowledge can by utilized in the design and processing of new blended cements. Also, co-milling the glass-cement system can eliminate the stage of homogenization, and, therefore save energy.

Assessment of hardened characteristics of raw fly ash blended self-compacting concrete

Summary Fly ash is widely used as a supplementary cementitious material in concrete. Due to the implementation of new thermal power plants as a consequence of electricity demand, generation of fly ash is noticeably increased. In addition to pozzolana blended cement production, it is very imperative to use raw fly ash in concrete. Earlier research studies investigated the performance of processed fly ash in blended cement production as well as in concrete. In general, ground fly ash is used in blended cement production. A comprehensive study on the performance evaluation of raw fly ash in self-compacting concrete is not available in the existing literature. Moreover, utilization of raw fly ash in special concrete such as self-compacting concrete is essential to comprehend the performance of raw fly ash blended concrete compared to ordinary Portland concrete. Additionally, it will help to achieve maximum utilization of raw fly ash as a supplementary cementitious material rather than disposal as a waste, which eventually leads to several environmental issues. In the study, raw fly ash was collected and is directly used in development of self-compacting concrete. Two mixes were cast and hardened characteristics of blended concrete were investigated. Results from the study showed comparable performance with control concrete. Furthermore, significant reduction in chloride permeability was observed for raw fly ash blended concrete.

Management and valorisation of wastes through use in producing alkali‐activated cement materials

AbstractThere is growing global interest in maximising the re‐use and recycling of waste, to minimise the environmental impacts associated with waste treatment and disposal. Use of high‐volume wastes in the production of blended or novel cements (including alkali‐activated cements) is well known as a key pathway by which these wastes can be re‐used. This paper presents a critical overview of the urban, agricultural, mining and industrial wastes that have been identified as potential precursors for the production of alkali‐activated cement materials, or that can be effectively stabilised/solidified via alkali activation, to assure their safe disposal. The central aim of this review is to elucidate the potential advantages and pitfalls associated with the application of alkali‐activation technology to a wide variety of wastes that have been claimed to be suitable for the production of construction materials. A brief overview of the generation and characteristics of each waste is reported, accompanied by identification of opportunities for the use of alkali‐activation technology for their valorisation and/or management. © 2016 Society of Chemical Industry