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MINISTRY OF EDUCATION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS MAI HONG HA RESEARCH ON USING RECYCLED STEEL SLAG IN BA RIA VUNG TAU FOR ROAD CONSTRUCTION Field of study Code Speciality : Transport engineering : 9580205 : Highway and urban road engineering SUMMARY OF DOCTORAL THESIS HA NOI – 2019 This research is completed at : University of transport and communications Supervisors: AssocProf.Dr La Van Cham University of Transport and Communications Reviewer 1: Reviewer 2: Reviewer 3: The thesis will be defended before Doctoral-Level Evaluation Council at University of Transport and Communications at … hours……Day……Month……Year…… The thesis can be read at : National Library of Vietnam Library of University of Transport and Communications INTRODUCTION Rationale According to the development planning for Viet Nam Steel Industry during 2007 – 2015 with a vision until 2025, if the steelmaking factories in South Vietnam alone all operated with the capacity of 4-5 million tons/year, then they would discharge approx million tons of steel slag each year An average of 0.5-1.0 million tons per year of steel slag is discharged in Viet Nam and in Ba Ria -Vung Tau province, the amount is about 0.3-0.5million tons/year Unless there were proper solutions to reuse this source of waste, the storage would be costly and plenty of land would be wasted While automobile road construction is in need of various kinds of materials, these traditional natural material are becoming scarce Therefore, the thesis “Research on using recycled steel slag in Ba Ria-Vung Tau for road construction” is esential with scientific and practical significance Aims of the research To study experiences of many countries in the world in using steel slag as an aggregate in road pavement construction; To combine the theoretical research with analysis of experiments in lab and on site on recycling steel slag from steel factories in Ba Ria-Vung Tau in roadbase construction; On that basis, to evaluate possibility of replacing macadam aggregate by steel slag in roadbase construction and propose pavement structures using steel slag recycled from the steel factories in Ba Ria-Vung Tau Targets and scope of the research - The physio-mechanical properties and technical specifications necessary for design, construction and acceptance of roadbase and pavement using recycled steel slag from electric arc furnace steel factories in Ba Ria-Vung Tau; and - Suitable reinforcement solutions to improve the physio-mechanical properties of steel slag to satisfy technical requirements of aggregates in road base construction in Ba Ria-Vung Tau Scientific and practical significance 4.1 Scientific significance - The experiment results have proved that it is possible to use the recycled steel slag from steel factories in Ba Ria-Vung Tau as aggregate for roadbase layers; - The effectiveness of cement reinforcement with types of aggregate; steel slag, steel slag with fine sand and steel slag with stone dust has been analyzed A suitable ratio of 4-6% cement by mixture mass is recommended 4.2 Practical significance - Having determined the technical specifications of steel slag from steel factories in Ba Ria-Vung Tau to be recycled in roadbase construction; - Having proposed some pavement structures using recycled steel slag from steel factories in Ba Ria-Vung Tau; and - Having contributed to enriching the knowledge on using steel slag for roadbase construction in Viet Nam, and serving as good reference for research and teaching on materials and pavement structures Outline of the research The thesis is comprised of the Introduction, main chapters, the Conclusions and Recommendation, the Direction for Furrther Research, the Reference and the Appendix OVERVIEW OF STEEL SLAG AND ITS USE IN ROAD CONSTRUCTION 1.1 Steel slag Steel slag, a by-product of steel making, is produced during the process of the molten steel being separated from impurities in the steel-making furnace The slag occurs as a molten liquid which melts and is a complex dissolving process of silicates and oxides but it solidifies upon cooling Steel slag formation process looks like lava eruption, thus steel slag is called ‘artificial magma’ in scientific reports overseas 1.2 Studies on steel slag overseas 1.2.1 Chemical properties 1.2.1.1 Chemical composition Ana Mladenović, Tahir Sofilić, R Alizadeh, H Motz, etc have analyzed the chemical and mineral composition of steel slag in their studies The chemical composition of steel slag includes CaO, Fe xO y, MgO, MnO 2, SiO and Al O3 , in which the main substances are CaO, SiO và Fe x O y, accounting for about 80% of the steel slag weight The mineral composition of steel slag includes Wustite (FeO), Calcium Silicates (2CaO.SiO 2, C2 S and 3CaO.SiO 2, C3S), Brownmillerite (Ca (Al,Fe) 2O ,C AF) and Mayenite (12CaO.7Al O 3, C12 A7 ) 1.2.1.2 Physical and mechanical properties The physio-mechanical properties of steel slag have been investigated by many scientists overseas like Gurmel from the UK; Lykoudis, V Maruthachalam from Greece, Tahir Sofilić from Croatia, Maslehuddin from Saudi Arabia, H Motz from Germany, etc The study results show that the specific gravity of steel slag is between 3.3-3.5 g/cm3, the porous bulk density is 1500kg/m3, the voids is 31-45%, the water absorption is 1-2%, and the pH degree is 10-12 1.2.2 Oversea studies on steel slag used as aggregate in roadbase construction According to EUROSLAG, the amount of steel slag discharged in 2010 was about 21.8 million tonnes, 87.0% of which was reused In some European countries, like Figura 1.11 Applications of steel slag in Europe Germany and France, the reuse rate was over 90% In general, about 48.0 % of the steel slag was used in road construction while the rate was 32.4% in Japan, 49.7% steel slag of the United States was used for the upper and lower roadbase, 16% was used as aggregate for asphalt concrete, and in China the rate was approx 29.5% According to Ebenezer Akin Oluwasola, steel slag is qualified to serve as aggregare for lower roadbase construction due to its high internal friction and draining ability To increase the reuse rate of steel slag in China, Weiguo Shen [37] experimented to use steel slag reinforced with fly ash and phosphogypsum (a waste by-product from production of phosphoric acid and phosphate fertilizer) in upper roadbase construction The experiment results show that the compressive strength of the reinforced samples has increased from 1.86MPA at Day to 8.38MPA at Day 28, completely meeting Chinese standards of the upper roadbase The splitting tensile strength and elastic modulus are a little lower than those of cementreinforced macadam, but much exceed Chinese requirements set in “Specifications of Asphalt Pavement Design for Highway- JTJ014-97” Besides, many other scientific studies in the world all acknowledge that steel slag can be applicable to road construction, e.g aggregate for asphalt concrete, surface for low-grade roads, or upper and lower roadbase for pavement 1.3 Inland studies on steel slag In Viet Nam, the initial legal documents and standards have acknowledged applicability of steel slag in road construction, e.g TCVN 6705:2009; Document No 31/BXD-VLXD dated June 07, 2011 by Vietnam Ministry of Construction; Decision No 430/QĐ-BXD promulgating the technical specifications of “Cast iron and steel slag used as buliding materials” According to Le Thanh Truong , after melted in the electric arc furnace at 1600oC, steel slag has similar mineral composition to that of cement, which is not available in natural materials The Green Materials Ltd Co has sent steel slag samples to VILAS laboratory to analyze and identify hazardous components The analysis results when compared with QCVN 07:2009/BTNMT reveal that the inorrganic hazardous components have not been detected or if present, fall much lower than the limit value In his doctoral thesis, Nguyen Van Du studied steel slag to replace coarse aggregate in asphalt concrete In 2011, Dr Tran Van Mien and his partners from the Material Section, HCMC University of Technology in coordination with Le Phan Company Lld Co conducted a study on use of steel slag as aggregate to replace macadam in asphalt concrete From 2013 to 2015, the Ministry of Transport assigned HCMC University of Transport to implement a ministry-level research project entitled “Study on steel slag from steel factories to be recycled as a material in roadbase construction” led by Dr Nguyen Quoc Hien and me, a doctoral candidate as the main participant The project was accepted and graded Level B by the Minisstry of Transport The project results and recommendations are as follows Steel slag can absolutely be recycled as a building material in production of cement concrete, asphalt concrete and in roadbase construction; If steel slag is processed by a suitable technology, it can be used in the road subbase layers according to the aggregate principle like Grade II macadam 1.4 Objectives of the research To study the properties of steel slag after recyled from the steel factories in Ba Ria - Vung Tau (BRVT) to be used in roadbase construction To investigate solutions to improve the physio-mechanical properties of steel slag so that it can satisfy the technical requirements when used as aggregate for various roadbases RESEARCH ON PHYSICAL, MECHANICAL AND CHEMICAL PROPERTIES OF RECYCLED STEEL SLAG 2.1 Studying properties of steel slag discharged at steel factories in Ba RiaVung Tau The steel slag under survey, study and evaluation comes from the Electric Arc Furnace (Electric Arc Furnace steel slag is abbreviated as EAF steel slag) The recyled steel slag samples are collected from the building material factory of the Green Materials Ltd Co (located in Tan Thanh district, Ba Ria-Vung Tau province) 2.1.1 Steel slag properties Within the research scope, in comparison with the related standards, a survey of the physio-machenical properties of steel slag, including particle composition, specific gravity, bulk gravity, and so on has been conducted in addition with an analysis of its chemical composition 2.1.2 Testing results Testing results are summarized in Table 2.5: Specific gravity Bulk dry specific gravity Bulk saturated surface dry specific gravity Water absorption Bulk density Voids Moisture Maximum bulk dry specific gravity (proctor compaction test) Index: Wl; Ip; PP Content of dust, mud and clay Los Angeles abrasion and impact Sample 10 Sample Sample Sample Sample Sample Sample Sample Unit Sample Testing specification Sample Table 2.5: Physio-machenical properties of steel slag g/cm3 3.47 3.66 3.66 3.68 3.50 3.52 3.41 3.55 3.58 3.49 3.29 3.35 3.34 3.42 3.19 3.29 3.16 3.28 3.30 3.23 g/cm3 3.34 3.44 3.42 3.49 3.28 3.36 3.23 3.36 3.38 3.31 % kg/m3 % % 1.54 1823 47.5 2.98 2.52 1877 48.7 3.41 2.61 2.10 2.81 1.96 2.31 2.26 2.38 2.26 1906 1837 1975 1799 1806 1874 1886 1800 47.8 50.1 43.6 48.9 47.0 47.2 47.4 48.4 3.62 3.54 3.57 3.67 3.54 3.65 3.37 3.42 g/cm3 2.36 2.43 2.48 2.45 % 0.4 1.2 1.6 0.6 % 22 22 21 22 g/cm 2.50 2.50 2.50 2.45 2.43 2.43 1.6 0.5 0.7 1.2 1.1 0.7 22 19 21 22 21 22 none Sample Sample Sample Sample Sample Sample 10 % Sample Elongation and flakiness content Elastic modulus In-lab CBR (K = 0.98) Sample Unit Sample Testing specification Sample 0.8 1.1 1.2 0.9 0.7 0.6 1.8 0.3 1.6 1.0 MPa 225.88 230.59 226.74 285.17 231.57 239.60 244.71 232.70 318.80 246.23 % 111.58 90.35 85.92 88.98 90.28 117.98 89.07 103.86 98.24 93.30 Table 2.6 Particle composition of steel slag Remain (%) Sample Sample Sample Sample Sample Sample Sample 10 100 Sample 1, steel slag is alkaline, so if it is used as aggregate, it must be reinforced by cement or lime 2.2.4 Evaluation and remarks of steel slag’s effect on the environment Based on the research results stated in the Overview and earlier in this chapter, some remarks and evaluation are given below Steel slag does not contain substances harmful to the environment (according to the research by Tahir Sofilić); Radionuclides content found in steel slag is lower than the limit (according to Decision No 430/QĐ-BXD dated May 16, 2017 by the Ministry of Construction); Testing and analysis results of the recylced steel slag from the steel factories in BRVT province show that hazardous substances are not detected or lie within the limit range 2.3 Conlusions of Chapter (1) The physio-machenical properties of recycled steel slag from the steel factories in BRVT are similar to those of macadam aggregate in the southeastern region, a common material in roadbase construction According to TCVN8859:2011, most specifications of steel slag meet the technical requirements of Class I macadam aggregte (except for the CBR index); (2) Due to the characterisitics of steel slag and the recycling technology currently in use in BRVT, the steel slag aggregate lacks small sized particles (0.05 4.1.5 Evaluation and remarks The results of field testing on the test section have demonstrated that - Under the same compacting, the density of the macadam aggregate base is higher than that of the steel slag base; - With the roadbase of the same thickness, the subgrade of the same strength and under the same construction conditions, there is a little diffrence between the elastic modulus recorded on the macadam aggregate base and that on the steel slag base; - After ye ars of exploitation, the elastic modulus does not decrease, the flatness of pavement with steel slag base reaches the limit, the road surface is stable and still well exploited without any sign of damage 4.2 Proposing pavement structures using steel slag The reseach and testing results in lab and on site pressented in Chapter 2, Chapter and earlier Chapter have proved that steel slag can be used as aggregate in roadbase construction Hereinafter, the doctoral candidate continued investigating the scientific fundamentals and practices in order to propose typical pavement structures using steel slag, which ensure the technical requirements, reduce impacts on the environment and save resources 4.2.1 Proposed pavement structures 4.2.1.1 Pavement structures for rural roads 21 Table 4.16 Pavement structures for rural roads Parameters Structure KC1 Subgrade KC2 Subgrade KC3 Materials for each layer Cement concrete with stone 1x2, #>30Mpa, or Cement concrete with steel slag, #>30MPa Flatness making layer Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement Steel slag reinforced with 4-6% cement, or Steel slag aggregate Subgrade Compacted sphalt concrete 12.5mm Compacted asphalt concrete 19mm Asphalated with or layers as per TCVN 8863:201 Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement, or Steel slag aggregate Steel slag reinforced with 4-6% cement; or Steel slag aggregate Subgrade Asphalated with layers as per TCVN 8863:2011 Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement, or Steel slag aggregate Steel slag aggregate Thickness in cm 18 22 13 16 18 14 18 45 67 1.52.5 14 18 15 30 3.03.5 14 18 15 30 Subgrade Subgrade KC4 Subgrade Cement concrete with stone 1x2, #25-30Mpa, or Cement concrete with steel slag, #25-30MPa Flatness making layer Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced 18 20 13 16 18 Scope of application The design follows 230/QD-BGTVT The traffic flow is designed (Nn) of 100 200 vehicles/day&night Applicable to roads with heavy vehicles (the axle is more than 6000 Kg) exceeding 10 % The design follows Decision 230/QDBGTVT The traffic flow is designed (Nn) of 100 200 vehicles/day&night Applicable to roads with heavy vehicles (the axle is more than 6000 Kg) exceeding 10 % The design follows Decision 230/QDBGTVT The traffic flow is designed (Nn) of 100 200 vehicles/day&night Applicable to roads with heavy vehicles (the axle is more than 6000 Kg) exceeding 10 % The design follows Decision 230/QDBGTVT The traffic flow is designed (Nn) of 50 100 vehicles/day&night Applicable to roads with heavy vehicles (the axle is 22 Parameters Structure Materials for each layer Thickness in cm with 4-6% cement KC5 Subgrade Steel slag aggregate Subgrade Cement concrete with stone 1x2, #25Mpa, or Cement concrete with steel slag, #25MPa Flatness making layer Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement Steel slag aggregate Subgrade 15 18 16 18 13 14 16 14 16 Scope of application more than 6000 exceeding 10 % Kg) The design follows Decision 230/QDBGTVT The traffic flow is designed (Nn) lower than 50 vehicles per day and night Applicable to roads with heavy vehicles (the axle is more than 6000 Kg) exceeding 10 % 4.2.1.2 Pavement structures for automobile roads Table 4.17: Pavement structures for automobile roads Parameters Structure KC6 Subgrade KC7 Subgrade Materials for each layer Compacted asphalt concrete 12.5mm Compacted asphalt concrete 19mm Asphalated with or layers as per TCVN 8863:201 Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement Steel slag reinforced with 4-6% cement, or Steel slag aggregate Subgrade Cement concrete, # fr=4.5 5.0 Mpa,or Cement concrete + steel slag, # fr=4.5 5.0 Mpa Flatness making layer Steel slag + fine sand reinforced with 6% cement, or Steel slag + stone dust reinforced with 4-6% cement Steel slag reinforced with 4-6% cement, or Steel slag aggregate Subgrade Thickness in cm 56 78 1.52.5 15 20 Scope of application For pavement of high grade A1 The design follows 22TCN 211-06 or 22TCN 274-01 The elastic modulus is required of 140 160 Mpa 16 35 20 25 13 16 25 15 30 The design follows Decision 230/QDBGTVT Applicable to heavy vehicles and lighter means 23 4.2.1.3 Pavement structures for motorways and roads under heavy load Pavement structures applied for motorways and roads under heavy load are given in Table 4.1 Steel slag aggregate serves only the subbase Table 4.1 Pavement structures for motorways Parameters Structures KC8 Materials for each layer Sanding layer Polymer asphalt concrete 12.5mm/SMA Compacted asphalt concrete 19mm ATB25 layer SAMI layer Steel slag + stone dust reinforced with 4-6% cement Steel slag + fine sand reinforced with 4-6% cement Steel slag reinforced with 4-6% cement, or Steel slag aggregate Subgrade Thickness in cm 2.2 67 10 15 18 Scope of application For pavement of high grade A1 The design follows 22TCN 211-06 or 22TCN 274-01 The elastic modulus is required of 180 Mpa 16 20 16 30 4.2.2 Technology for construction and exploitation of pavement using steel slag 4.2.2.1 Construction technology It is recommended to use machinery for construction of steel slag layers Reinforced materials are mixed at a batching plant Steel slag aggregate is scattered by a spreader Compaction should ensure the required density There should be solutions to reduce cracking of the asphalt concrete surface by SAMI layer or timely cutting For the steel slag aggregate base, the technology for construction and acceptance is proposed similar to that for the maccadam aggregate base 4.2.2.2 Exploitation technology The technology for exploitation and maintenance of pavement using steel slag does not differ from that of the traditional pavements in current use locally 4.3 Conlusions of Chapter (1) Pavement with steel slag aggregate base has been designed, constructed and evaluated after years of exploitation, and compared with pavement with macadam aggregate base The field experiment results show that the steel slag aggregate base is similar to the macadam aggregate base; (2) pavement structures using steel slag with ensured technical requirements have been proposed; (3) Parameters of steel slag and cement-reinforced steel slag have been determined 24 CONCLUSIONS AND RECOMMENDATIONS A NEW CONTRIBUTIONS BY THE THESIS (1) Having determined that the aggregate made of steel lag, recycled by the Green Materials Company, Ba Ria-Vung Tau, satisfies the requirements for aggregate used in roadbase construction This finding contributes to saving natural resources and reducing environmental polution (2) Series of experiments were conducted to determine the compressive strength (Rn), splitting tensile strength (Rech) and elastic modulus (E) of the following types of aggregate: + Steel slag aggregate reinforced with cement, + Steel slag aggregate reinforced with cement and fine sand, and + Steel slag aggregate reinforced with cement and stone dust Regression equations have been established, proving that the steel slag aggregate, which is reinforced with cement and stone dust, achieves the highest modulus, and recommending a reasonable ratio of 4% - 6% cement (3) Field experiments on the test section with macadam aggregate replaced by steel slag aggregate have produced good results (4) It is proposed to use steel lag aggregate for the base of pavement B LIMITATIONS The field experiments using steel slag aggregate for roadbase have been conducted, but the solution of using steel slag reinforced with cement and fine sand or stone dust has been experimented only in laboratory, not yet able to be tested on site C RECOMMENDATIONS A standard process for construction and acceptance of pavement base using recycled steel slag should be developed D DIRECTION FOR FURTHER STUDY Conducting field experiments to evaluate the solution of using steel slag reinforced with cement and fine sand or stone dust in roadbase construction PUBLICATIONS BY THE AUTHOR Mai Hong Ha, Nguyen Thi Thuy Hang (2018), “Study on using recycle steel slag in cement treated aggregate material for road pavement subbases”, Transportation Science and Technology Journal , No 27+28, 05/2018, pages 149-155 Nguyen Thi Thuy Hang, Phan Duc Hung, Mai Hong Ha (2016), “Gradation correction of steel slag aggregate concrete ”, The Builder Journal, No 293&294, 3&4/2016, pages 68-72 Nguyen Thi Thuy Hang, Phan Duc Hung, Mai Hong Ha (2016), Determine the mechanical properties of concrete using steel slag as coarse aggregate, Construction Journal, No 55, 2/2016, pages 31-35 Nguyen Thi Thuy Hang, Phan Duc Hung, Nguyễn Hồng Vũ, Mai Hong Ha (2016), “Flexural behavior of reinforced concrete beams made with steel slag coarse aggregate”, The Builder Journal, No 285&286, 7&8/2015, pages 49-53 Nguyen Thi Thuy Hang, Phan Duc Hung, Mai Hong Ha (2016), Study on the physical and mechanical properties of concrete using steel slag as coarse aggregate, Pavement Material Recycle and Reuse Conference-12th PMRRC, National I-Lan, 10/2016 ... 28, completely meeting Chinese standards of the upper roadbase The splitting tensile strength and elastic modulus are a little lower than those of cementreinforced macadam, but much exceed Chinese... compressive strength exceeds 4.0MPa 3.3.5.2 Analysis of the splitting tensile strength Rech Similarly conducted as desribed above, the splitting tensile strength of Figure 3.32: General diagram of... effect on Rech 16 Figure 3.32 is a general diagram of the splitting tensile strength Rech versus cement ratio and age At Day 14, the splitting tensile strength of XC reinforced with 6-8% cement and