Utilization of steel slag for Portland cement clinker production

Environmental Progress & Sustainable Energy, 2017

The feasibility of recycling the reduction slag, limestone sludge, iron-oxide sludge, and stone sludge produced in the manufacture of cement was investigated through compressive strength testing, differential thermal and thermogravimetric analysis, X-ray diffraction, and 29 Si nuclear magnetic resonance analysis. The major crystalline phases of ecocement clinkers, namely C 3 S, b-C 2 S, C 4 AF, and C 3 A, were observed. C 3 S content decreased and b-C 2 S and a-C 2 S content increased in the reduction slag. The compressive strength of EcoA pastes (ecocement contain 78% of limestone sludge, 19.51% of stone sludge and 2.49% iron-oxide sludge) was similar to that of commercial ordinary Portland cement. The Q 0 (270 ppm) species shifted to the Q 1 (280 ppm), and Q 2 (287 ppm) species during curing. The addition of stone sludge, iron-oxide sludge, and limestone sludge had no negative effect on the hydration of the cement pastes. In contrast, the addition of reduction slag negatively affected the formation of clinker minerals. Cement samples with reduction slag content of 1-7 wt % had lower 28-, 60-, and 90-day compressive strength than did the control mix. V

Journal of Hazardous Materials, 2004

The aim of the present research work was to investigate the possibility of adding red mud, an alkaline leaching waste, which is obtained from bauxite during the Bayer process for alumina production, in the raw meal for the production of Portland cement clinker. For that reason, two samples of raw meals were prepared: one with ordinary raw materials, as a reference sample ((PC) Ref ), and another with 3.5% red mud ((PC) R/M ). The effect on the reactivity of the raw mix was evaluated on the basis of the unreacted lime content in samples sintered at 1350, 1400 and 1450 • C. Subsequently, the clinkers were produced by sintering the two raw meals at 1450 • C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the red mud did not affect the mineralogical characteristics of the so produced Portland cement clinker. Furthermore, both clinkers were tested by determining the grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7, 28 and 90 days. The results of the physico-mechanical tests showed that the addition of the red mud did not negatively affect the quality of the produced cement.

Original method for steel production, which is implemented for close up to 90 percent of steel production, is the transformation of iron ore into iron in the blast furnace after the formation of steel in basic oxygen furnace. Today, the high volume of steel slags has become a critical problem in waste management. However, blast furnace slag due to its pozzolanic properties can be used for partial replacement of Portland cement. The purpose of this article is to process blast furnace slag and turn it into an effective material in the cement industry. The results showed that the physical processing of slag by grinding it into 75 microns and increasing alkalinity state by adding lime can lead to an increase of 117 percent in 11-day compressive strength of slag cement against unprocessed one. This conclusion is achieved through experiments conducted on 18 different samples.

Applied Sciences

A pyrometallurgical process was developed for the recycling of Ni bearing dusts and laterite ore fines by direct reduction smelting in DC (direct current) arc furnace. In the course of the performed industrial trials, besides the Ni-recovery in the liquid bath, slag composition was deliberately adjusted in order to produce a series of metallurgical slags with different chemical and mineralogical composition. The aim of this study was to investigate their suitability as clinker substitute in cement manufacturing. Examined parameters were slag FeOx content, basicity and applied cooling media (air, water cooling). A series of composite Portland and slag cements were manufactured in laboratory scale incorporating 20% and 40% of each slag, respectively; the rest being clinker of OPC (ordinary Portland cement) and 5% gypsum. The extended mineralogical analysis and microstructural properties of the produced slags were examined and correlated with the properties of the produced cements. The...

The use of selected secondary materials for improving the reactivity of cement raw mix, is a challenging subject. It is known that certain foreign elements exert a considerable effect on the cement raw mix burnability and clinker structure, even at low concentration. This work is part of a project on the use of selected minerals as a source of elements having a positive effect on the burnability of cement raw mix. The minerals, iron rich wolframite, stibnite and a wolframitestibnite assemblage, were selected in order to introduce W, Sb and S in the cement raw mix. One reference and twelve modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0 % w/w of the above minerals, were studied. Their effect on the burnability is discussed in Part I. The subject of this paper is their effect on the structure of the produced clinker. The XRD studies, performed in samples that were burned at 1450 o C, showed that the diffraction patterns correspond to a structure of a typical clinker, obtained at the above temperatures. In addition, samples sintered at lower temperature (1200-1400 o C) were examined in order to investigate the effect of the additives on the intermediate products. It is concluded that the added compounds affect mainly the structure of calcium aluminate and calcium aluminoferrite phases, due to their dissolution in the melt formed during the sintering. Scanning Electron Microscopy was used in order to examine the structure of the clinker and the distribution of the foreign elements in its main phases. It is shown that W and Sb are mainly concentrated in the solidified melt. In addition, bigger and more roundish alite crystals are found in these samples. These modifications are attributed to the effect of the added elements on the properties of the melt.

The dominant role of ordinary Portland cement is slowly decreasing in the construction industry in favor of substituted or composite cements. This is due to the added advantage or benefits of blended cements such as durability, cost and environmental friendliness. Steel slag, an industrial waste in the manufacture of steel and a major mineral admixture in Europe is not well utilized in Ghana because no extensive scientific research has been conducted into its alternate use. Meanwhile an estimated 5,000 tons of steel slag is dumped as waste every year for the past 20 years and it is gradually becoming an environmental challenge. This work has studied the alternate use of steel slag from Wahome Steel Works, a steel manufacturing company in Ghana, as a mineral admixture in Portland cement for construction applications. The physical properties of the slag such as specific gravity, Blaine indices and particle size distribution were studied. The chemical and mineralogical (XRF, XRD and SEM) analysis revealed that the slag is chemically suitable and contained the relevant minerals and phases. The slag-cement mixture required less water to form a workable paste and increased in setting time as slag content increased in the mix. The results also revealed that, water permeability decreased with increasing slag content.The slag-cement mix recorded lower compressive strengths at early ages but appreciated in strength at later ages, recording strength of 48.9 MPa at 30% replacement.

International Journal of Applied Ceramic Technology, 2009

A steel-making slag (basic oxygen furnace) obtained from the Kardemir Steelworks was modified to be used as a clinker additive in the cement industry. This study confirmed that the compressive strength values of concretes produced by addition of these steel-making slags up to 30 mass% were within the values of Grade-325 and Grade-425 steel-making slag cement. This is an attractive alternative for cement manufacturers, because calcined material is expensive, and slag substitutes are very often cheaper, in addition to its low or zero-greenhouse-gas emission.

Steel slag is the byproduct of the basic oxygen furnace and its disposal is cited as the biggest problem. Steel slag of Bokaro steel plant is characterized using X-ray diffraction analysis, X-ray fluorescence, electron microscope. The composition of the steel slag has the great influence on its cementitious properties. Mortar blocks are prepared with the replacement of cement by 5, 10, 15 and 20 % of steel slag. Cementitious properties of steel slag are checked by normal consistency, initial and final setting time, soundness, compressive strength. Silica modulus suggests that steel slag has significantly less amount of calcium silicate in its composition. The study reveals that fine steel slag can be utilized for cement replacement up to 10% does not show any adverse effect of the early as well as latter strength. Beyond 10% cement replacement would affect the compressive strength achieved after 90 days of curing. The study would help policymakers to adopt steel slag as a resource for partial replacement of cement.

2017

Alternative materials such as industrial wastes and by-products can be easily and economically utilised as raw material in Portland cement clinker manufacture. These materials are generated in abundance as a result of growing worldwide industrialisation. Two types of wastes from mining industry were used as secondary raw material in a concentration ranging from 1.4 to 3.5%. CEM I cements were obtained from these clinkers and compressive strength was determined. Different amounts varying between 3 and 7% of sludge generated in the effluent treatment plants of oil fields were added to a base raw mixture and the effect on the clinkering process was studied. The chemical and mineralogical compositions of the wastes and raw meals were determined. The raw mixes burnability containing different concentrations of wastes in various stages of burning in a laboratory furnace to form a Portland cement clinker was investigated. An improved burnability was noticed without affecting the clinker qu...

This study investigates the use of meta-schist as an alternative base material to cement clay in clinker production. First, the mineralogical differences between the reference cement clay, rich in silica but poor in iron and aluminium and the meta schist, rich in aluminium and iron and relatively poor in silica, were revealed by the XRD method. Two raw meal samples were prepared, one with ordinary raw materials (limestone and clay) ((RM)/Ref) and the other with meta-schist ((RM)/M) as a reference sample. The effects on the reactivity of the raw mix samples were evaluated on the basis of the unreacted lime content in the samples sintered at 1200, 1300, 1350, 1400 and 1450 °C. Then, two different clinker samples were produced by sintering the two raw mixtures at 1450°C. The relationships between the internal structures of the clinker samples determined by polarizing microscope (amount of porosity, distribution, grain structure of silicate phase crystals and variation of equivalent cry...