Application of high-temperature rapid catalytic technology to forecast the volumetric stability behavior of containing steel slag mixtures

Application of high-temperature rapid catalytic technology to forecast

the volumetric stability behavior of containing steel slag mixtures

Wen-Ten Kuo

, Chun-Ya Shu

Department of Civil Engineering and Disaster Mitigation Technology, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan, ROC

h i g h l i g h t s

High-temperature rapid catalytic technology can forecast expansion in a short time. Rapid catalytic technology can forecast steel slag instability in a short time.

The degradation rate of DSS with a high f-CaO content was greater than that for BOF. Steel slag critical value for the substitute amount was 20–30%.

Rapid catalytic technology can forecast the results of autoclave expansion.

a r t i c l e

i n f o

Article history: Received 1 July 2013

Received in revised form 4 September 2013 Accepted 24 September 2013

Available online 22 October 2013

Keywords:

High-temperature rapid catalytic technology

Basic oxygen furnace slag (BOF) Desulfurization slag (DSS) Free lime (f-CaO) Expansion

a b s t r a c t

Steel slag from the steel and iron industries often exhibits volumetric instability (expansion) due to long-term usage. Therefore, this study applied a high-temperature rapid catalytic technology to accelerate the hydration reaction to forecast the volumetric instability of steel slag in the shortest time. The steel slag included basic oxygen furnace (BOF) slag and desulfurization slag (DSS), which replaced 50% of natural river sand by weight for 1 to 4 days of high-temperature catalysis (100 °C) and autoclave expansion. In order to forecast more accurate results, a numerical regression was applied to crosscheck the test result and simulate a theoretical expansion value. The results showed that the specimens of each group rup-tured after a minimum of three days of high-temperature catalysis when the substitution amount was 30%. The expansion rupture warning value was within approximately 0.13–0.14%. The correlation coeffi-cient R2_{, obtained using a simulated expansion value, was greater than 0.9. The degradation rate of DSS}

with a high free lime (f-CaO) content was greater than that for BOF.

Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The civil engineering industry consumes hundreds of millions tons of natural sand every year. The supply and demand imbalance causes a continuous rise in price and promotes illegal and environ-mentally damaging mining by companies driven by economic interests. Therefore, it is urgently necessary to find suitable substi-tute products for natural sand. The specific weight of slag is 20% higher than that of dry saturated natural aggregate. Slag with a high Fe content also has a greater specific weight than does the dry saturated natural aggregate. The absorption and Los Angeles abrasion rates are equal to those of the natural aggregate. How-ever, the soundness loss is far lower than the code value for con-crete soundness loss (<12%)[1,2]. The previous property analysis shows that slag can be used as a substitute for natural aggregates. Basic oxygen furnace (BOF) slag and desulfurization slag (DSS),

byproducts of steel making, are produced during the separation of molten steel from impurities in steel-making furnaces [3]. In Taiwan, the annual slag output is approximately 1,600,000 tons, accounting for 25% of waste solids. After treatment, this slag can be used as aggregate[4]. This process can improve the reuse of waste material, reduce environmental pollution and destruction, limit the consumption of natural resources, and increase profits

[5,6]. Steel slag treatment and processing technology has been

ma-turely developed in recent decades, which has made it possible for slag to replace natural aggregate in road construction[7–10]and be used as a granular material in road base or sub-base courses

[9,11,12]and an aggregate in various asphalt mixes or pavement

surfaces[13–16]. Although slag is an attractive building material, its long term behavior and relevant environmental impacts must be considered [17]. The volume stability of steel slag has drawn great concern because cement cannot undergo any appreciable volume change after hardening[3]. The use of slag in this capacity is beneficial because it helps to conserve natural resources and re-duce the tonnage of slag grains that are stocked every year[18,19]. 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.conbuildmat.2013.09.030

⇑ Corresponding author. Tel.: +886 7 3814526x5233; fax: +886 7 3960300. E-mail address:[email protected](W.-T. Kuo).

Construction and Building Materials 50 (2014) 463–470

Contents lists available atScienceDirect

Construction and Building Materials

Steel slag contains free (unhydrated) lime (CaO) that can result in volumetric instability (expansion), which must be addressed by appropriate steel slag aging, testing and quality control to ensure its suitable use in construction[20,21]. Many studies have been conducted to stabilize steel slags so that they can pass the steam test, which consists of natural weathering[7,22], accelerated aging

[23], and treatment before cooling[24]or mixing with inert mate-rials[25,26]. The instability of non-water quenched slag is attrib-uted to the content of free lime and magnesium oxide [27,28]. These compounds are not hydrated during curing at normal tem-peratures[29]; consequently, abnormal expansion rupture occurs in the long term. To prevent expansion, the free lime content must be reduced by 2–3%, otherwise it cannot be used[30]. For certifica-tion, the Penn D.O.T. requires that all steel slag producers stockpile and test their steel slags after six months to ensure that there is no further expansion[31]. Wang[32]used an expansibility test and a pressure cooker test to accelerate the hydration reaction and ob-serve the volumetric change of slag. It has been demonstrated that the maximum expansion of slag can be used to evaluate its appli-cability. To forecast the maximum expansion in the shortest time, the relationship between the temperatures. The curing time, and chemical composition should be considered in the test to improve the forecasting confidence level and control the material quality. These considerations will allow steel slag to be used more safely in the concrete industry.

2. Materials and methods 2.1. Materials

The BOF and DSS slags used in this study were derived from a single Taiwan steel-making factory. The steel slag was crushed in a jaw crusher, and the ‘‘0– 5’’ mm fraction was used in this study. The material was identified as safe based on its toxicity characteristic leaching procedure (TCLP) leaching concentration. Ta-ble 1shows the chemical analysis and physical characteristics of the slag. The chemical composition contains SiO2,Fe2O3and CaO, accounting for about 90%, with

an elevated content of free lime, which is an important expansion source[17,18,33]. In the DSS have SO3ingredients; its content was 3.55%. SO3need at room

temper-ature water, in a long time, will have a reaction. Provisions of content cannot exceed 3.5%, or there will be the volume instability problems. The natural sand conforms to ASTM C33. The cement, Type I Portland cement produced by a Taiwan cement com-pany, conforms to ASTM C114-05.

2.2. Mix proportions

The reference mortar comprised cement, natural sand and water mixed at a ra-tio of 1:2.75:0.485 by mass. Other mixtures were prepared with natural sand replacing steel slag at 0%, 10%, 20%, 30%, 40% and 50% by mass. The mixture propor-tions of the mortar are summarized inTable 2.

2.3. Methods

The high-temperature rapid catalytic technology used in this study was auto-clave expansion, which conforms to ASTM C151 and high-temperature catalysis. Replaces the 0% to 50% of the BOF slag and DSS slag mixtures was placed in a cab-inet with constant temperature and constant humidity, and high-temperature catalysis was conducted at 100 °C and a relative humidity of 100%. Every other day, the specimen was taken out to measure its length. Transparent grids were used to quantize the rupture area of the specimens, and an image was recorded. Then, the specimen was replaced in the cabinet at constant temperature and constant humidity. The high-temperature catalysis was stopped until measurement was fin-ished on the fourth day. In addition, a theoretical expansion value was simulated by numerical regression to evaluate the expansion rupture warning value. After catal-ysis, the specimens underwent microanalysis. X-ray diffraction (XRD) analysis was performed, and verification was carried out with D-5000 data processing software and complete JCPDS data. Scanning electron microscopy (SEM) was used for imag-ing, and the X-ray derived from electron impact were used for energy dispersive analysis of X-ray (EDAX) to qualitatively analyze the chemical elements of the solid.

3. Results and discussion

3.1. High-temperature rapid catalysis

Steel slag must be used as a minority additive in Portland ce-ment because its chemical and mineralogical composition causes subsequent problems (delay in setting and expansion, in particu-lar)[34]. Therefore, it is assumed that volumetric instability in mixtures of steel slag is caused by excessive free lime. Free lime be-comes Ca(OH)2after it comes into contact with water for an ex-tended time, and volumetric expansion occurs. Different slag substitutes are used. The specimens are exposed to a high temper-ature to accelerate the reaction and find the volumetric instability as soon as possible.Table 1indicates that BOF and DSS have high concentrations of free lime, accounting for 3.24% and 15.95%,

Table 1

Chemical analysis and physical characteristics of slag, natural sand and cement. Oxides Chemical analysis (%)

BOF DSS Natural sand Cement

SiO2 16.68 17.57 76.60 20.87 Al2O3 0.38 5.90 13.50 4.56 Fe2O3 25.38 12.61 2.19 3.44 CaO 50.93 56.82 0.20 63.14 MgO 1.84 1.33 0.78 2.82 K2O 0.09 0.01 – – SO3 – 3.55 – – Cr2O3 – 0.14 – 2.06 TiO2 0.38 – 0.27 – Free CaO 3.24 15.95 – – Physical characteristics Specific gravity 3.04 2.17 2.63 3.15 Absorption (%) 5.70 21.50 2.40 – Table 2

Mixture proportions of steel slag mortar.

Mix No. Cement Water Natural sand BOF DSS kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 REF 541.1 262.43 1488.03 – – BOF10 541.1 262.43 1339.22 148.80 – BOF20 541.1 262.43 1190.42 297.61 – BOF30 541.1 262.43 1041.62 446.41 – BOF40 541.1 262.43 892.82 595.21 – BOF50 541.1 262.43 744.01 744.01 – DFS10 541.1 262.43 1339.22 – 148.80 DFS20 541.1 262.43 1190.42 – 297.61 DFS30 541.1 262.43 1041.62 – 446.41 DFS40 541.1 262.43 892.82 – 595.21 DFS50 541.1 262.43 744.01 – 744.01 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 Volumetric change (%) free lime (%) BOF10 DSS10 BOF20 DSS20 BOF30 DSS30 BOF40 DSS40 3.24 15.95

Fig. 1. Relationship between free lime and volumetric change after catalytic curing at 100 °C.

respectively.Fig. 1shows the relationship between free lime and volumetric change after catalytic curing at 100 °C. This figure shows the amount of all the different groups substituted steel slag mortar expansion after high temperature catalytic results. In the figure, there are four basic colors (red, orange, yellow, green), that represent 10–40% of the substitution. Other different colors represent several similar situation overlap after the results. As shown, the volumetric change in the substitute amount of BOF with a high free lime content exceeds 0.1%, and for DSS it is lower than 0.09%. This result indicates that the DSS expansion value is greater than that of BOF. And in DSS contains SO3ingredients. This is the reason for the occurrence of the

larger expansion.Figs. 2 and 3illustrate the relationship between catalytic time at 100 °C and volumetric change, suggesting that the volumetric change in the DSS substitute is almost greater than that of BOF. The expansion trend value was greater and steeper, indicat-ing that agindicat-ing and expansion were significant. The DSS had cracks on the second day, and the BOF had cracks on the second and third days when the natural sand content was greater than 30%.Table 3shows

0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 Break Break Break Volumetric change (%)

Curing time (days)

DSS10 DSS20 DSS30 DSS40

1 2 3 4

Fig. 2. Relationship of catalytic time and expansion of DSS (100 °C).

1 2 3 4 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 Break Break Volumetric change (%)

Curing time (days)

BOF10 BOF20 BOF30 BOF40

Fig. 3. Relationship of catalytic time and expansion of BOF (100 °C).

Table 3

The actual average expansion values under high-temperature catalysis for different substitute amounts of slag.

Day DSS (%) BOF (%)

REF 10 20 30 40 50 10 20 30 40 50

1 0.033 0.050 0.066 0.072 0.085 Break 0.058 0.062 0.075 0.070 Break 2 0.039 0.072 0.099 0.116 0.125 Break 0.059 0.066 0.096 0.122 Break 3 0.040 0.090 0.120 Break Break Break0.066 0.086 0.126 Break Break 4 0.041 0.102 Break Break Break Break 0.076 0.097 Break Break Break

Autoclave Expansion

0.0482 0.105 0.123 Break Break Break0.092 0.121 0.127 Break Break

Bold indicates autoclave expansion values to do with the high-temperature catalytic value the distinction. 10 20 30 40 50 0.08 0.09 0.10 0.11 0.12 0.13 Break Break Volumetric change (%) replaced (%) DSS BOF

Fig. 4. Illustrates the substitution amount and the volumetric change of the steel slag that was obtained from the autoclave expansion.

Fig. 5. Analysis results for the experimental and simulated expansion of DSS with different substitution amounts.

4. Conclusions

(1) High-temperature (100 °C) catalytic technology can be applied to clearly forecast the results of autoclave expansion. The correlation coefficient R2_{exceeds 0.9. This method can} be used to compensate for the deficiencies of simple site tools. The method is quicker and can save costs.

(2) After high-temperature catalysis, rupture occurred on the third day when the steel slag substitution amount was greater than 30%. The expansion rupture warning value was 0.13–0.14%. The critical value for the substitute amount was 20–30%. The aging caused by expansion may occur quickly. This phenomenon deserves some attention. (3) Most BOF specimens have dotted, claw-shaped rupture. The

rupture points are apparent and deep brown, similar to color of iron rust. A white color is distributed around, as shown in

Fig. 8. The DSS exhibits cracks or surface peeling, and the

rupture points are white. Sampling analysis shows that the main components of the white points are Mg(OH)2 and Ca(OH)2.

(4) For forecasting of the rupture area boundary, expansion ture may occur when the percentages of DSS and BOF rup-ture area are higher than 0.093% and 0.330%, respectively. (5) The results of SEM on the specimens suggest that Ca(OH)2

can instantly squeeze the surrounding hydration products during high-temperature rapid catalysis. This squeezing results in local stress concentrations and, finally, deforma-tion and rupture.

(6) The application of high-temperature rapid catalytic technol-ogy can accelerate free lime reaction and forecast expansion in a short time. Moreover, it can verify the volumetric stabil-ity of steel material and identify possible expansion risk before massive use, and it can forecast the durability of con-crete mixed with different amounts of steel slag used in place of aggregate.

Acknowledgement

The authors would like to thank the National Science Council of Taiwan for their financial support of this research under Contract No. NSC 101-2221-E-151-065.

References

[1] Wang WC, Liu CC, Lee C, Yu SK. Preliminary research of expansion problem and treated method of using slag as aggregate of concrete. TCI 2011 Conf on Concr Eng. 2011. A-001 [in Chinese].

[2]Chen L, Su MF, Lee WT, Huang WH. Field demonstration of pavement constructed using electric arc furnace oxidizing slag. Ind Pollut Control Eng Pract Technol Semin 1999:373–91 [in Chinese].

[3]Lun Y, Zhou M, Cai X, Xu F. Methods for improving volume stability of steel slag as fine aggregate. J Wuhan Univ Technol 2008;3:737–42.

[4]Siddique R. Utilization of waste materials and by-products in producing controlled low-strength materials. Resour Conserv Recycl 2009;54(1):1–8.

[5]Naganathan S, Razak HA, Hamid SNA. Properties of controlled low-strength material made using industrial waste incineration bottom ash and quarry dust. Mater Des 2012;33:56–63.

[6]Naganathan S, Razak HA, Nadzrian AH. Effect of kaolin addition on the performance of controlled low-strength material using industrial waste incineration bottom ash. Waste Manage Res 2010;28(9):848–60.

[7]Alexandre J, Boudonnet JY. Les laitiers d’aciérie LD et leurs utilisations routières. Laiti sidér 1993;75:57–62.

[8]Shen DH, Wu CM, Du JC. Laboratory investigation of basic oxygen furnace slag for substitution of aggregate in porous asphalt mixture. Constr Build Mater 2009;23:453–61.

[9]Shen W, Zhou M, Ma W, et al. Investigation on the application steel slag-fly ash-phosphogypsum solidified material as road base material. Hazard Mater 2009;164(1):99–104.

[10] US federal environment protection agency. Use of recycled industrial materials in roadways. <http://www.epa.gov/osw/conserve/rrr/imr/pdfs/roadways.pdf>. 2010.

[11]Suer P, Lindqvist J, Arm M, et al. Reproducing ten years of road ageing-accelerated carbonation and leaching of EAF steel slag. Sci Total Environ 2009;407(18):5110–8.

[12]Motz H, Geiseler J. Products of steel slags an opportunity to save natural resources. Waste Manage 2001;21:285–93.

[13]Ahmedzade P, Sengoz B. Evaluation of steel slag coarse aggregate in hot mix asphalt concrete. Hazard Mater 2009;165(1–3):300–5.

[14]Xue Y, Wu S, Hou H, et al. Experimental investigation of basic oxygen furnace slag used as aggregate in asphalt mixture. Hazard Mater 2006;138(2):261–8. [15]Huang Y, Bird R, Heidrich O. A review of the use of recycled solid waste materials in asphalt pavements. Resour Conserv Recycl 2007; 52(1):58–73.

[16]Ivanka Netinger. Utilisation of steel slag as an aggregate in concrete. Mater Struct 2011;44(9):1565–75.

[17]Chaurand P, Rose J, Briois V, Olivi L, Hazemann JL, Proux O, et al. Environmental impacts of steel slag reused in road construction: a crystallographic and molecular (XANES) approach. Hazard Mater 2007;139(3):537–42.

[18]Motz H, Geiseler J. Products of steel slags an opportunity to save natural resources. Waste Manage 2001;21(3):285–93.

[19]Waligora J, Bulteel D, Degrugilliers P, Damidot D, Potdevin JL, Measson M. Chemical and mineralogical characterizations of LD converter steel slags: a multi-analytical techniques approach. Mater Charact 2010;61(1):39–48. [20]Wang G. Use of steel slag as a granular material: volume expansion prediction

and usability criteria. Hazard Mater 2010;184(1-3):555–60.

[21]Ameri M. Laboratory studies to investigate the properties of CIR mixes containing steel slag as a substitute for virgin aggregates. Construct Build Mater 2012;26(1):475–80.

[22]Verhasselt A. Sous-produits industriels pour la réalisation de mélanges liés de fondation: laitiers de haut fourneau concassés, scories LD et cendres volantes. Centre de Recherche Routière Bruxelles Compte Rendu 1991:33.

[23]Da Silveira NO, e Silva MVAM, Agrizzi EJ, De Lana MF, De Mendonça RL. ACERITA(R) – steel slag with reduced expansion potential. Revue De Metallurg-Cahier D Inf Tech 2004;101(10):779–85.

[24] Sorrentino F, Gimenez M. Mineralogy of modified steel slags. In: Proceedings of the 11th Int Congr on the Chem of Cem (ICCC): Durban; 2003: p. 2139-47.

[25] Deneele D, de Larrard F, Rayssac E, Reynard J. Control of basic oxygen steel slag swelling by mixing with inert material. In: Proceedings of the 4th Europ Slag Conferen: Oulu; 2005: p. 187–98.

[26] Rayssac E, Auriol JC, Deneele D, de Larrard F, Ledee V, Platret G. Valorisation de laitiers d’aciérie de conversion ‘‘LD’’ dans les infrastructures routières. Laiti sidér. 2008; 92: 8–21.

[27]Geiseler J. Use of steelworks slag in Europe. Waste Manage 1996;16:59–63. [28]Auriol JC. Expansion volumique de la chaux et de la magnesia vives (libres) lors

de leur hydratation. Laitiers sidér 2004;85:6–12.

[29]Chengmu L, Wangjun L. Discussion on quality & expansiveness of expansive material-magnesium oxide. Des Hydroelectri Power Stan 2005;21(3):95–9. [30]Svanera M. An innovative system for the re-use of slag from the Electric Arc

Furnace. Metall Ital 2012;2:37–43.

[31] Beaver Valley Slag.http://www.bvslag.com/SlagExpansion.pdf.

[32]Wang G. Determination of the expansion force of coarse steel slag aggregate. Construct Build Mater 2010;24:1961–6.

[33] Shi CJ, Qian J, High performance cementing materials from industrial slags – a review. Resour conserv recycl 2000; 29(3): p. 195–207.

[34]Shi CJ. Steel slag – its production, processing, characteristics, and cementitious properties. J Mater Civ Eng 2004;16(3):203–36.

[35]Mu SB, Sun ZY, Su XP. A study on the microstructure and expanding mechanism of highly free-calcium oxide cements. J Wuhan Univ Technol 2001;23(11):27–30 [in Chinese].