INFLUENCE OF EXCESSIVE BLEEDING ON FROST SUSCEPTIBILITY OF CONCRETE INCORPORATING FERRONICKEL SLAG AS AGGREGATES

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1 INFLUENCE OF EXCESSIVE BLEEDING ON FROST SUSCEPTIBILITY OF CONCRETE INCORPORATING FERRONICKEL SLAG AS AGGREGATES Takayasu Sato*, Hachinohe Institute of Technology, Japan Kohei Watanabe, Hachinohe Institute of Technology, Japan Akihiro Ota, Hachinohe Institute of Technology, Japan Minoru Aba,Hachinohe Institute of Technology, Japan Yuki Sakoi, Hachinohe Institute of Technology, Japan 36th Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 211, Singapore Article Online Id: 3649 The online version of this article can be found at: This article is brought to you with the support of Singapore Concrete Institute All Rights reserved for CI Premier PTE LTD You are not Allowed to re distribute or re sale the article in any format without written approval of CI Premier PTE LTD Visit Our Website for more information

2 36 th Conference on Our World in Concrete & Structures Singapore, August 14-16, 211 INFLUENCE OF EXCESSIVE BLEEDING ON FROST SUSCEPTIBILITY OF CONCRETE INCORPORATING FERRONICKEL SLAG AS AGGREGATES Takayasu Sato*, Kohei Watanabe, Akihiro Ota, Minoru Aba and Yuki Sakoi *Hachinohe Institute of Technology, Japan 88-1, Ohbiraki, Myo, Hachinohe, Aomori Keywords: ferronickel slag, aggregate, bleeding, freezing and thawing resistance Abstract. In this paper, freezing and thawing resistance of concretes incorporating ferronickel slag as fine and coarse aggregates, are investigated. The durability factor of concrete according to JIS A 1148, decreased with increased bleeding amount, and the severe bleeding in excess of.3cm 3 /cm 2 aggressively impaired the frost resistance of air-entrained concrete, when the water to cement ratio and the slag volume fraction in fine and coarse aggregates are 6% and %, respectively. The decreased freezing and thawing resistance could be attributed to the internal defects originated by the up flow of bleeding water. It was confirmed that the excessive bleeding of fresh concrete is lowered the air void system such as extant air content and spacing factor in hardened concrete. 1. INTRODUCTION Ferronickel slag is a industrial by-product generated during smelting to ferronickel used in the manufacture of stainless steel and nickel alloys. In the late 198s, it has been studied for more effective use as aggregate for concrete. The ferronickel slag fine aggregate have been standardized in JIS A ) (Japanese Industrial Standard) as slag aggregate for concrete. While in recent years, from the viewpoint of use expansion of ferronickel slag, its coarse aggregate have been developed, and the standardization is investigated in actively research work. In previous studies using ferronickel slag coarse aggregate has been shown to increase of amount of bleeding of concrete and to decrease of freezing and thawing resistance of concrete with slag aggregate. When the bleeding is excessive, harmful effects will arise on concrete quality by producing the defects such as the formation of water channel, water pocket beneath the aggregates, and the increase of water to cement ratio near the top surface followed by the looseness of the top layer. It was considered that the detailed investigation is required for making durable concrete. The main purpose of this study is to indicate the fundamental properties of ferronickel slag aggregate as coarse aggregate and of the fresh concrete used ferronickel slag coarse aggregate. The influence of excessive bleeding on frost susceptibility of concrete used its slag aggregate was investigated from the determination of air void system. The combinational use of the ferronickel slag fine aggregates (JIS A 511-2) and the coarse aggregates was also studied. Hereafter, the ferronickel slag fine aggregates and the ferronickel slag coarse aggregates will be denoted as FNS and FNG, respectively. Hachinohe Institute of Technology, Japan

3 Type A-FNG B1-FNG B2-FNG Table 1 Manufacturing Process of FNG Manufacturing Process Overview Rotary kiln Water granulated Crushing machine Classifier (less than.75 mm) Kiln burning Air cooling Crushing machine Grading control Electric furnace Air cooling pit Crushing machine Grading control Electric furnace Air cooling pit Crushing machine Crushing machine Grading control (a) Rotary kiln method (b) Electric furnace method Fig. 1 Particle shape of FNG 2. CHARACTERISTICS OF FERRONICKEL SLAG AGGREGATE 2.1 Production of FNG Ferronickel slag aggregate is a by-product that is produced during the production of ferronickel from nickel oxide ore. Table 1 shows the schema of product process of ferronickel slag. In Japan, the ferronickel slag is produced by the rotary kiln method and the electric furnace method. From the rotary kiln method, the water granulated slag was manufactured from molten slag by kiln. From the electric furnace method, the wind granulated slag and the air cooling slag are manufactured. Originally, ferronickel slag aggregate had been limited to the fine aggregate from the manufacturing process. In recent years, ferronickel slag coarse aggregate (FNG) having excellent physical properties have been developed. In this study, three different types of FNG were investigated. One is produced by the kiln burning process using water granulated slag (hereinafter called A-FNG). Another is produced by the electric furnace slag with air cooling. However, in the melting process of ferronickel, CaCO 3 added to the raw materials, and CaO content in the slag adjusted to about by 2.5%, for improvement of aggregate quality (hereinafter called B1-FNG). The last one has twice crushing process after air cooling in the B1-FNG manufacturing procedure, in order to remove the porous parts in surface of slag coarse aggregate (hereinafter called B2-FNG). 2.2 Physical and chemical properties of FNG Fig. 1 indicates the FNG used in this study. The particle shape of FNGs used in this study was almost same with crashed stone. Table 2 shows the physical properties of FNGs, and it is satisfied the physical properties in JIS A 55 (crushed stone). As Table 2, the density of A-FNG is 2.54g/cm 3, and it was relatively small compared with that of crashed limestone. The density of B1-FNG and B2-FNG are 2.91 g/cm 3 and 2.97 g/cm 3, respectively. These densities are larger than that of crashed limestone. In addition, water absorption of B1-FNG is 2.74 %, and its value is larger compared with that of crushed limestone. However, water absorption of A-FNG and B2-FNG are 1.77% and 1.11%, respectively, and show a smaller value compared with that of crashed limestone. Furthermore, abrasion loss 2) and BS 4tf crashing value 3) of A-FNG and B2-FNG indicate an extremely low values. Especially, it can be observed that B2- FNG is improved the some physical properties compared with B1- FNG. This reason is the difference of the number of crushing process to remove the porous part in aggregate surface. Table 3 shows the chemical compositions of FNG used in this study. From this table, it is confirmed that the main chemical compositions of these FNGs are silicon dioxide, calcium oxide,

4 Test items Production method Table 2 Physical properties of FNS and FNG A-FNG B1-FNG B2-FNG Kiln Watercooling Coarse aggregate electric furnace air cooling electric furnace air cooling crushed stone (Limestone) Control magnesium oxide and so on. The chemical compositions of FNG are almost same that of FNS with same producing method, and it is satisfy the standard value in JIS A In this study, the leaching amount of harmful substances and the acid extractable contents of chemicals for FNGs were measured according to JIS K ) and JIS K ), respectively. The evaluate chemicals are cadmium, lead, hexavalent chromium, arsenic, total mercury, selenium, boron and fluorine. As a result, all harmful substances and content of chemicals are not detected, and these results provided the environmental safety of FNGs manufactured in this study. In addition, the test result for alkali-silica reactivity of aggregate, according to JIS A 1146 (mortarbar method) 6), used in this study was nonreactive. 3. MATERIALS AND MIXTURE PROPORTIONS OF CONCRETE Ordinary portland cement (density: 3.16g/cm 3 ) was used. Two types of FNSs, water granulated slag (kiln method : hereinafter called A-FNS) and wind granulated slag (electric furnace method : hereinafter called B-FNS), and two types of crashed lime sand were adopted as fine aggregate in this study, for blending and control compares with the FNS. Three types of FNG that is indicated in Table 2 was used, and crashed limestone were adopted as coarse aggregate in this study. Table 4 shows the combinational conditions of mixture proportions of concrete. The mixture proportions were planned with the combination of FNS volume fractions (, 25 % for A- FNS and, % for B- FNS), FNG volume fractions (, 5, % for A- FNG, B1- FNG, B2- FNG) and water to cement ratio (.45,.55,.6). The slump value and the air content were fixed in mm and 5. %, respectively. Furthermore, the case of 7 % air content was also planned for the concrete examined freezing and thawing resistance. FNS and FNG were replaced in absolute volume of fine aggregate and coarse aggregate, respectively. Control concrete was made with the volume fraction of crushed lime sand % and crashed limestone %. A-FNS Kiln Watercooling B-FNS Electric furnace breaking wind Fine aggregate crushed sand (Limestone) Control crushed sand* (Limestone) blending Gredig groups FNS 1.2 FNS 5 Density in oven dry condition[g/cm 3 ] Water absorption[%] Solid content[%] Solid volume content for shape determination[%] Mass of unit volume[kg/l] Fineness modulus Abrasion loss[%] BS 4tf crushing value[%] *A-FNS (FNS 1.2) and mixing Table 3 Chemical compositions of FNG Type Calcium oxide Magnesium oxide Total sulfur Total iron Metallic Silicon (CaO) (MgO) (S) (FeO) iron (Fe) dioxide (SiO 2 ) A-FNG B1-FNG B2-FNG JIS A Table 4 Combinational conditons of mixture of concrete (a) Series A (Rotary kiln method) (b)series B (Electric furnace method) FNS volume fraction(%) 25 W/C FNG - - volume A fraction(%) A- FNS volume fraction(%) W/C FNG B volume B1- fraction(%) B2- - -

5 4. TEST METHOD 4.1 Bleeding and Setting- time test Bleeding tests of concrete was also conducted to confirm the improvement of segregation resistance for the bleeding of concrete by the addition. Test was made with JIS A 1123 using 25 mm diameter by 285 mm high cylindrical container. The time of setting of concrete was examined in according with JIS A 1147 using Procter penetration resistance needles. The initial time of setting and the final time of setting were determined when the Procter penetration resistance reached 3.5 N/mm 2 and 28.4 N/mm 2, respectively. The samples used for test was the wet- screened mortar using 5 mm sieve. 4.2 Freezing and Thawing Resistance Test Freezing and thawing tests were conducted in according with JIS A 1148 procedure A (freezing and thawing in water, about 4 hours per 1 cycle). The test was started at an age of 14 days using by by 4 mm prisms. Three specimens were tested simultaneously representing each mixture and testing conditions. The change in the relative dynamic modulus of elasticity and the loss in mass were measured every 3 cycles up to the 3 th cycle. The relative dynamic modulus of elasticity P n and the percentage of loss in mass of concrete were calculated by the following Eq. 1 and Eq.2, respectively. f P = f 2 n 2 n (1) where, P n is the relative dynamic modulus of elasticity after n cycles freezing and thawing, f denotes the fundamental transverse frequency at cycle and f n denotes the fundamental transverse frequency after n cycles. W w w = w n n (2) where, W n is the percentage of loss in mass after n cycles freezing and thawing, w is the mass of specimen at cycle and w n is the mass of specimen after n cycles. The relative dynamic modulus of elasticity and durability Index (DF) are evaluated. In addition, the air void system such as spacing factor and air contents of hardened concrete, were measured according with ASTM C 457 (liner traverse method). 5. EXPERIMENTAL RESULTS AND DISSUCUSSION 5.1 Bleeding and setting time Fig. 2 shows the results of breeding tests for concrete with the slag aggregates. Fig. 2 (a) and (b) are in the case of useing slag produced by the rotary kiln method, and the case of using slag produced by the electric furnace process, respectively. From these results, it was found that the final amount of bleeding of concrete with FNG increased with the increase of FNG volume fraction, regardless of different type of FNG volume fraction. This phenomenon is due to the consolidation action by heavy FNS particles in freshly mixed concrete. The final amount of bleeding of concrete with FNS also increased with the FNS volume fraction, regardless of different type of FNG, compare to that of the concrete without FNG. Forthemore, in the case of water to cement ratio of 6%, the amout of bleeding of concrete mixed FNS valume fraction of 25% and FNG volume fraction of %, were indicated the excessive bleeding of about.45 cm 3 /cm 2. The unit water content of concrete with/ without slag aggregates shows in Table 5. In the case of FNG volume fraction of %, the unit water content of concretes increased, 13 kg/m 3, compare to FNG volume fraction of %, perhaps due to the increase of sand percentage in concrete and the grading condition of slag aggregates. From these

6 W/C=45% W/C=55% W/C=6% Volume fraction of FNS : % Volume fraction of FNS : 25% % % % % Volume fraction of FNG[%] (a) Series A (Rotaly kiln method) (b) Series B (Electric furnace method) Fig.2 The amount of bleeding water Volume fraction of FNS : % Volume fraction of FNS : % % % % % Volume fraction of FNG[%] Table 5 Unit water content of concrete (a) Series A (Rotaly kiln method) (b) Series B (Electric furnace method) FNS volume fraction(%) 25 W/C FNG volume A fraction(%) A results, the increase of amount bleeding of cocnrete with FNS / FNG is not only due to the heavy density of slag aggregate, but also due to the increse of unit water content of concrete with slag aggregate compare to that without slag aggregate. However, in the case of using combination with FNG and FNS, the unit water content of concretes decreased, 4 kg/m 3, compare to without FNS. The setting time of concrete with FNS and FNG is shown in Table 6 (a) and (b). The setting time of concrete with FNS and FNG is indicated the almost same as the result in the case of concrete without FNS and FNG. Therefore, it was cleared that the concrete incorporating FNS and FNG was hardly influenced to the setting situation of concrete. From the results, it was considered that the profile of freshly mixed concrete with FNG will be judged the almost same trend as compared with the previous standardized non-ferrous metal slag aggregates such as blast furnace slag. 5.2 Freezing and thawing resistance FNS volume fraction(%) W/C FNG volume fraction(%) B B B Table 6 Initial and final setting time of concrete (a) Series A (Rotaly kiln method) (b) Series B (Electric furnace method) FNS volume fraction(%) 25 FNS volume fraction(%) W/C W/C Initial 7:21 7:46 Initial 7:21 8:9 Final 1:4 11:3 Final 1:4 1:55 FNG FNG Initial 7:5 Initial 7:9 volume A-5 volume B1 5 Final 11:4 Final 1:18 fraction(%) fraction(%) Initial 8:1 7:43 Initial 7:13 7:57 A- B2- Final 11:24 11:5 Final 1:33 1:5 (hour : min) (hour : min) The results of freezing and thawing test of concrete with ferronickel slag aggregates are shown in Fig. 3 and Fig.4. Fig. 3 and Fig.4 indicate the results in the case of series A (produced by rotary kiln method) and B (produced by electric furnace method), respectively. The letter in parenthesis of figure legend indicates DF value for each mixture caluculated from the result of the relative dynamic modurus of elastisity. In the case of 5% of target air contents, the freezint thawing registance of concrete with FNG decreased with the increase of FNG volume fraction, regardless of different of serise A and B-1, compared to that of concrete with normal coarce aggregate. Especially, in the case of water to cement ratio of.6, the frost resistance of concrete showd the decrease greatly. However, the freezing thawing resistance of concrete with B-2 FNG indicated the aomost same level of the freezing thawing resistance of concrete with normal aggregate. Forethemore, the concrete with FNS and FNG

7 Relative dynamic modulus of elasticity [%] ID : W/C-FNS-FNG-Air (DF) (87) (71) (84) (56) (91) (77) Freezing and thawing cycle [N] (a) Volume fraction of FNS; % (b) Volume fraction of FNS; 25% Fig.3 Change of relative dynamic modulus of elastisity; Series A (rotaly kiln method) Relative dynamic modulus of elasticity [%] ID : W/C-FNS-FNG-Air (DF) (84) (62) (78) (45) (84) (69) Freezing and thawing cycle [N] Relative dynamic modulus of elasticity [%] ID : W/C-FNS-FNG-Air (DF) (87) (63) (8) B1-FNG (48) (8) (7) (91) B2-FNG Freezing and thawing cycle [N] (a) Volume fraction of FNS; % (b) Volume fraction of FNS; % Fig.4 Change of relative dynamic modulus of elastisity; Series B (Electric furnace method) indicated a slightly improvement in the freezing thawing resistance. In the other hand, in the case of 7% of target air contents, the frost resisntance of concrete indicated significant improvement for all mixture. Thus, it was considered that the frost resistance of concrete with FNS and FNG was able to improve by the increase of air contents in hardened concrete. Fig. 5 shows the relationship between durability factor (DF) and amount of bleeding water. From this result, the durability factor of concrete indicated the decrease with the increase of the amount of bleeding water. The occurrence of excessive bleeding water lead to create the weak zone around coarse aggregate in hardened concrete, and to increase the amount of frozen water. As a result, it was considered that the freezing thawing resistance of concrete decreased. Forethemore, DF of concrete for the same amount of bleeding water was arrenged in order to B2-FNG> A-FNG> B1-FNG. Thus, it was cleared that the influence on bleeding phenomenon was differ from type of FNG. Fig. 6 shows the relasonship between DF and the water absorption of corse aggregate. The mixture of concrete was the case of the constant of W/C and target air content. From this figure, it was cleared that the DF decreased with the increase of water absorption of corse aggregate. The incrase of water absoption of coarse aggregate lead to the decrease of frozen resistantce of concrete due to the increase of the freezing pressure in coarse aggregate and due to the movement un- frozen water to past part arround corse aggregate. Therfore, it was considered that the frost resistance of concrete was not affected by the amount of bleeding water and also by the quality of FNG. Fig. 7 shows the relationship the air content of hardened concrete and the amount of bleeding water, and Fig. 8 shows the relationship the spacing factor of hardened concrete measured according to ASTM C 457 and the the amout of bleeding water. From these results, it was cleared that the air content decreased, and spacing factor increased with the increase of the amout of bleeding water. These resutls indicated that the occurence of exessive bleeding water lead to movement and/or combine the air void in hardened concrete, and lead to the decrease of the frozen resistance of concrete. In addition, for the cocnrete with FNG, it was cleared that a need for reducing the amount of bleeding water, less than.3cm 3 /cm 2, for ensured spacing factor of 25 μm that was need for the improvement of the frozen Relative dynamic modulus of elasticity [%] ID : W/C-FNS-FNG-Air (DF) (83) (6) (75) B1-FNG (43) (75) (64) (84) B2-FNG Freezing and thawing cycle [N]

8 Durability factordf A-FNG B1-FNG B2-FNG Target air content : 5% Fig.5 Relationship between durabilty factor (DF) and amount of bleeding water Durability factordf Crushed lime stone A-FNS Volume fraction : % A-FNS Volume fraction : 25% B-FNS Volume fraction : % B-FNS Volume fraction : % W/C=55%, Target air content=5% Water absorption (Coarse aggregate) [%] Fig.6 Relationship between durability factor (DF) and water absorption of coarce aggregate Air content of hardened concrete [%] Target air content : 5% Series A [Kiln method] Series B [Electric furnace method] Fig.7 Relationship between air content of hardened concrete and amount of bleeding water Spacing factor[um] Target air content : 5% Series A [Kiln method] Series B [Electric furnace method] Fig.8 Relationship between spacing factor and amount of bleeding water resistnace of concrete. 6.CONCLUSION In this study, the experimental examinations of fundamental properties and durability of concrete incorporating ferronickel slag as aggregate conducted. The test results were summarized as follows. (1) FNG physical quality was found to satisfy the JISA55. FNG produced by the electric furnace method was able to improve the quality as coarse aggregate due to investigate the process for manufacturing (2) The amount of bleeding water of concrete with FNG and/or FNS indicated the trend of the increase due to the volume fraction of FNG and/or FNS, water to cement ratio and combination of FNS and FNG. (3) The frozen resistnace of concrete with FNG and FNS indicated the decrease with the increase of FNG volume fraction compare to that of concrete without FNG and FNS. Forthemore, the occurrence of excessive amount of bleeding water lead to decrease the frozen resistance of concrete due to the decrease of air content in hardened concrete.

9 REFERENCE 1) JAPAN INDUSTRIAL STANDARD, JIS A 511-2, Slag aggregate for concrete Part- 2: Ferronickel slag aggregate, Japan Industrial Standard, 23 2) JAPAN INDUSTRIAL STANDARD, JIS A 1121, Method of test for resistance of abrasion of coarse aggregate by use of the Los Angeles machine, Japan Industrial Standard, 27 3) BS Testing aggregate, methods for determination of a 4) JAPAN INDUSTRIAL STANDARD, JIS K 58-1, Test methods for chemicals in slags - Part 1: Leaching test method, Japan Industrial Standard, 25 5) JAPAN INDUSTRIAL STANDARD, JIS K 58-2, Test methods for chemicals in slags - Part 2: Test method for acid extractable contents of chemicals, Japan Industrial Standard, 25 6) JAPAN INDUSTRIAL STANDARD, JIS A 1146, Method of test for alkali-silica reactivity of aggregates by mortar-bar method, Japan Industrial Standard, 27