Measurement of cement s particle size distribution by the buoyancy weighing-bar method

Transcription

1 Measurement of cement s particle size distribution by te buoyancy weiging-bar metod *Rondang Tambun, Nofriko ratama, Ely, and Farida Hanum Department of Cemical Engineering, Faculty of Engineering, University of Sumatera Utara, Jl. Almamater Kampus USU Medan 20155, Indonesia; *Corresponding Autor: rondang_tambun@yaoo.com / rondang@usu.ac.id Abstract One of te important caracteristics of cement quality is particle size distribution. Tere are several simple metods to measure te particle size distribution of cement based on te Stokes diameter, like Andreasen pipette metod, sedimentation balance metod, centrifugal sedimentation metod, etc. A major disadvantages of tese metods are tey are time consuming process and require special skills. article size distribution also can be analyzed by using a different principle troug microscopy, laser diffraction/scattering metods and Coulter counter metod. Even tese metods produce igly accurate results witin a sorter time, owever, te equipments are expensive. In te present study, it as developed a new metod to overcome te problem. Te metod is te buoyancy weiging-bar metod. Tis metod is a simple and cost-effective. Te principle of te buoyancy weiging-bar metod tat te density cange in a suspension due to particle migration is measured by weiging buoyancy against a weiging bar ung in te suspension, and te particle size distribution is calculated using te lengt of te weiging-bar and te time course cange in te te apparent mass of te weiging bar. Tis apparatus consists of an analytical balance wit a ook for underfloor weiging, and a weiging bar, wic is used to detect te density cange in suspension. Te result obtained sow tat te buoyancy weiging bar metod is suitable for measuring te particle size distribution of cement, and te result is comparable to tat of determined by settling balance metod. Introduction Key words: buoyancy, cement, particle size distribution, weiging-bar One of te important caracteristics of cement quality is te particle size distribution. Tere are several simple metods to measure te particle size distribution based on te Stokes diameter, like Andreasen pipette metod (Society of Eng. Jpn, 1988), sedimentation balance metod (Fukui et al., 2000), centrifugal sedimentation metod (Arakawa et al., 1984), etc. However, all tese metods are time consuming and require special skills. On te oter and, te particle size distribution can be analyzed using a different principle troug microscopy (Kuriyama, et al., 2000), laser diffraction/scattering metod (Minosima, et al., 2005), and Coulter counter metod (Oira, et al., 2004). Tese metods require numerous samples to accurately determine particle size distribution. Altoug te laser diffraction/scattering and Coulter counter metods produce igly accurate results witin a sorter time, te equipments for tese metods are extremely expensive. Hence, a simple and cost effective metod to determine te particle size distribution of cement is in ig demand. In tis study, it was developed a new metod to measure te particle size distribution by using te buoyancy weiging-bar metod (BWM). In tis metod, density cange in a suspension due to particle migration is measured by weiging buoyancy against te 112

2 weiging-bar ung in a suspension. Ten te particle size distribution is calculated using te lengt of te weiging-bar and te time-course cange in te apparent mass of te weiging-bar (Motoi et al., 2010, Obata et al.,2009, Oira et al., 2010, Tambun et al., 2011, Tambun et al., 2012a, 2012b). In tis experiment, te initial buoyant mass of te weiging-bar W0 depends on te particles between te top and bottom of te weiging-bar in a suspension. Te initial density of suspension ρs0, initial buoyant mass of te weiging-bar W0, and initial apparent mass of te weiging-bar G0 in a suspension at t = 0 are given by te following equations. S0 L C 0 L, W0 VBS0, (2) G 0 VBB W0 VB( B S0 ), (3) were ρl and ρ are te liquid density and te particle density, respectively. C0 is te initial solid mass concentration of suspension, ρb is te density of te weiging-bar in suspension, and VB is te volume of te weiging-bar. Te solid mass concentration of suspension C(t) decreases wit time because large particles settle. Te density of suspension ρs, buoyant mass of te weiging-bar W, and apparent mass of te weiging-bar G in a suspension at time t are expressed as C( t) S( t ) L L, (4) ( S W t) V B ( t), G( t) VBB W ( t) VB( B S( t)). (6) Te solid mass concentration of suspension C(t) becomes zero once all te small particles also settle. Te final density of suspension ρs, final buoyant mass of te weiging-bar W, and final apparent mass of te weiging-bar G in a suspension at t = are given by te following equations. S L, (7) W V B L, (8) G VBB W VB( B L). (9) Equation (10) sows te mass balance of settling particles in a suspension (Allen., 1990). xmax xi v( t C0 C( t) C0 f ( dx C0 f ( dx. (10) xi xmin Te left side in Eq. (10) is te quantity of particles tat move onto te bottom side of te weiging-bar. Te first term on te rigt side represents te mass of particles larger tan particle size xi among te particles tat move, wile te second term on te rigt side is te mass of particles smaller tan particle size xi among te particles tat move. From Eqs. (2), (5), (8), and (10), xmax xi v( t W0 W ( t) ( W0 W ) f ( dx ( W0 W ) f ( dx, (11) xi xmin were v( is te settling velocity of te particle and f( is te mass frequency of te particle size x. Differentiating Eq. (11) wit respect to te time t gives dw x i v( ( W0 W ) f ( dx. (12) dt xmin From Eqs. (11) and (12), (1) (5) 113

3 dw W W R t. (13) dt Te apparent mass of te weiging-bar, wic is given by Eq. (6), gradually increases from G0 to G. Te volume and density of te weiging-bar are constant values. Differentiating Eq. (6) wit respect to time t gives dg dt dw dt. (14) Terefore, according to Eqs. (6), (13), and (14), G V W dg t G dt dg t dt B B R R, (15) were GR = VBρB-WR. Te value of GR is calculated from te tangent line based on Eq. (15). Te cumulative mass oversize is xmax G0 GR R 100 f ( dx D, (16) x G0 G were D is te cumulative mass undersize. article size x is given by Stokes formula 18Lv( x, (17) g ( ) L Te settling velocity of te particles v( is calculated using Eq. (18) v(, (18) t were is te lengt of te weiging- bar and t is te time lapse. From Eqs. (17) and ( 18), time t is an inverse function of particle size x. Te particle size distribution of te suspended particles is calculated using te particle size at eac time and ten plotting te corresponding cumulative mass undersize D. Materials and Metods rocedure Figure 1 scematically illustrates tis experiment. Te weiging tools was weiging bar ( φ 10.0 mm x mm, submerged lengt: mm) wic was composed of aluminum (density: 2700 kg/m 3 ). Figure 1. Scematic diagram of te experimental apparatus 114

4 Te particle suspension was placed in a 1000 ml measuring glass cylinder (diameter: 65.0 mm). Te analytical balance (minimum readout mass 0.1 mg) ad a below balance weiging ook for anging measurement. Te sample material was cement (density: 2500 kg/m 3 ). Etanol and metanol were used as a dispersion liquid, and te influence of etanol and metanol concentrations were investigated. Te etanol and metanol concentrations were 99.8% ( p.a), 70%, 50% and 30%. Te suspensions ad a solid concentration of 10 kg/m 3 (ca. 1 wt.%) (Oira et al., 2010). To prepare a suspension, a 1000 ml liquid and te particles to be tested were mixed in a glass cylinder. Using a anging wire, wic did not extend due to te weigt of te weiging-bar, te weiging-bar was ung from te analytical balance. Te room temperature was approximately 298 K. After torougly stirring te suspension using an agitator, te weiging-bar was set wit te balance. Te measuring data, wic consist of time t and te corresponding mass of te bar GB, were recorded. Te measuring time was two ours and te data were collected every 60 second intervals. After te measurement, te particle size distribution was calculated based on te above described teory. As comparison metod, te particle size distributions were also measured by using te settling balance metod. Results and Discussion Figure 2 sows te cange wit time in te apparent mass of weiging-bar GB wen cement was used. Figure 2(a) was te te apparent mass of te weiging-bar as a function of time using etanol (p.a) as liquid, and Figure 2(b) was te te apparent mass of te weiging-bar as a function of time using metanol (p.a) as liquid. Bot of te figures sow tat te apparent mass of te weiging-bar increased until all te cement particles settled below te lower end of te weiging-bar, and ten te apparent mass of te weiging-bar became constant. Te cange in te apparent mass was due to te cange in te buoyant mass against te weiging-bar as well as particle settling. a. Using etanol as liquid b. Using metanol as liquid Figure 2. Apparent mass of te weiging-bar as a function of time (a. Using etanol as liquid b. Using metanol as liquid) Figure 3 and 4 sow te influence of etanol and metanol concentration at determination of cement particle size distributions by using te BWM. Te solid line indicates te distribution measured by te settling balance metod. Te result obtained sow tat te concentration of etanol and metanol influence te particle size distributions of cement. Te etanol (p.a) and metanol (p.a) gave te close result to tat measured of settling balance metod. Hence, BWM can measure te particle size distribution of cement by using etanol and metanol as liquid. 115

5 Figure 5 sows te particle size distributions determination of cement by BWM using etanol (p.a) and metanol (p.a). Te results sow tat te etanol (p.a) gave te closer result to tat measured by settling balance tan metanol (p.a). Hence, te etanol is more suitable as liquid in determination of cement s particle size distributions by using BWM. Figure 3. Influence of etanol concentration at cement particle size distributions measurement by using BWM Figure 4. Influence of metanol concentration at cement particle size distributions measurement by using BWM Figure 5. article size distributions measurement of cement using etanol (p.a) and metanol (p.a) 116

6 Conclusions Te study investigates te influences of concentration of etanol and metanol as liquid in particle size distribution measurement of cement by BWM. From tis study, te following results were concluded: 1. Te particle size distributions of cement could be measured by BWM using etanol and metanol as liquid, and te particle size distributions obtained were comparable to tose measured by settling balance. 2. Te iger concentration of etanol and metanol gave te better result tan te lower concentration. 3. Te particle size distributions of cement by BWM using etanol (p.a) as liquid gave te closer result to tat measured by settling balance metod tan metanol (p.a) as liquid. Acknowledgements Te autors would like to tank Ministry of Researc, Tecnology, and Higer Education of Republic Indonesia for Researc Grant, under enelitian Fundamental sceme, References Allen, T. (1990). article Size Measurement, Fourt edition, Capman and Hall, London, pp Arakawa, M., Simomura, G., Imamura, A., Yazawa, N., Yokoyama, T., Kaya, N. (1984). A New Apparatus for Measuring article Size Distribution based on Centrifugal Sedimentation, Journal of te Society of Materials Science of Japan, 33, Fukui, K., Yosida,H., Siba. M., Tokunaga, Y. (2000). Investigation about Data Reduction and Sedimentation Distance of Sedimentation Balance Metod, Journal of Cemical Engineering of Japan, 33, Kuriyama, M., Tokanai, H., Harada, E. (2000). Maximum Stable Drop Size of seudoplastic Dispersed ase in Agitation Dispersion, Kagaku Kogaku Ronbunsu, 26, Minosima, M., Matsusima, K., Sinoara, K. (2005). Experimental Study on Size Distribution of Granules repared by Spray Drying: Te Case of a Dispersed Slurry Containing Binder, Kagaku Kogaku Ronbunsu, 31, Motoi, T., Oira, Y., Obata, E. (2010). Measurement of te Floating article Size Distribution by Buoyancy Weiging Bar Metod. owder Tecnology, 201, Obata, E., Oira, Y., Ota, M. (2009). New Measurement of article Size Distribution by Buoyancy Weiging Bar Metod. owder Tecnology, 196, Oira, Y., Furukawa, K., Tambun, R., Simadzu, M., Obata, E. (2010). Buoyancy Weiging- Bar Metod: A article Size Distribution Measurement using New Settling Metod. Journal of te Sedimentological Society of Japan, 69, Oira, Y., Takaasi, H., Takaasi, M., Ando, K. (2004). Wall Heat Transfer in a Double- Tube Coal-Slurry Bubble Column, Kagaku Kogaku Ronbunsu, 30, Society of Cemical Engineering of Japan. (1988). edition, Maruzen, Tokyo, Japan, pp Cemical Engineering Handbook, 5 t Tambun, R., Motoi, T., Simadzu, M., Oira, Y., Obata, E. (2011). Size Distribution Measurement of Floating articles in te Allen Region by a Buoyancy Weiging Bar Metod. Advanced owder Tecnology, 22, Tambun, R., Nakano, K., Simadzu, M., Oira, Y., Obata, E. (2012). Sizes Influences of Weiging Bar and Vessel in te Buoyancy Weiging-Bar Metod on Floating article Size Distribution Measurements. Advanced owder Tecnology, 23, Tambun, R., Simadzu, M., Oira, Y., Obata, E. (2012). Definition of te New Mean article Size based on te Settling Velocity in Liquid. Journal of Cemical Engineering of Japan, 45,