STUDIES ON PHYSICAL PROPERTIES OF HOMOGENEOUS SAND MIXES ABSTRACT

Transcription

1 , t ityp t% \ OTITUTE 01 - en I LLIBRARV)(::-% 43, AL STUDIES ON PHYSICAL PROPERTIES OF HOMOGENEOUS SAND MIXES BY V. V. SUBBA RAO AND T. RAMMOHAN (Deprtment of Mech. Engg., Univ. College of Engg., Osmni University, Hyderbd ) Mnuscript received on August 5, 1973 ABSTRACT Effects of wter-cly rtio, prticle size nd bentonite content on the physicl properties of homogeneous snd mixes hve been investigted. Results of the investigtion indicte tht: (1) Wter-cly rtio is n importnt prmeter ffecting the physicl properties of homogeneous snd mixes. (ii) For given prticle size nd bentonite content, () green compression strength, green sher strength nd green hrdness ttin mximum round wter-cly rtio of 0.4, (b) permebility ttins mximum vlue, bulk density minimum round wter-cly rtio of 0-6. (iii) Riddled density, AFS flowbility, GF flowbility decrese rpidly wheres the compctbility increses rpidly' with the incresc in wter-cly rtio upto 0-6 nd then tend to ttin stedy vlue on incresing the wter-cly rtio further. (iv) For given wter-dy rtio nd bentonite content the properties vry with the increse in prticle size upto vlue round 400 microns nd then become insensitive to prticle size. (v) For given wter-cly rtio nd prticle size the physicl properties vry with increse in bentonite content upto vlue round 7% nd then remin constnt with furthtr increse in bentonite content. Attempts mde to interrelte the physicl prt,perties indicte tht: (1) A liner reltionship exists between green compression nd green sher strength, nd (ii) compctbility, GF flowbility nd Riddle density re linerly inter-relted. S Keywords: WtvtiCly Rtio; Bentonite; Swelling Index; Comrctbility; Flowbility. INTRODUCTION There hve been severl investigtions [1-3] in recent yers to determine the importnt fctors influencing the physicl properties of green moulding snd. Moulding snds in generl contin more thn three frctions of prticles nd the physicl properties of these snds re influenced to lrge extent by the grin size, grin distribution, type nd mount of bond used nd the moisture content. In order to understnd the fctors ffecting the properties nd behviour of moulding snd during mould preprtion, it E. I. Sc. I

2 48 V. V. SUBBA RAO AND T. RAMMOHAN is essentil to study the properties of homogeneous, binry, ternry, etc., system of snds. Erlier investigtors [4-6] hve reported tht the physicl properties of cly bonded snd re ffected not only by grnulr mteril but lso by the wter/cly rtio nd the percentge of cly in the snd mix. Attempts hve lso been mde by them to explin mny of the findings of snd-cly-wter reltionships using wter/cly rtio concept. No literture is vilble on the effen of wter/cly rtio nd bentonite percentge on the physicl properties of homogeneous snd mixes. Experiments were, therefore, crried out to study the effect of wter/cly rtio rnging from 0-2 to 1-0 on the physicl properties of homogeneous snd mixes contining different prticle size silic grins nd vrious percentge of bentonite (3% to 11%). Attempts were lso mde to interrelte the vrious physicl properties of bentonite bonded homogeneous mixes. EXPERIMENTAL DETAILS Mterils used. In Tble I re listed the detils of the homogeneous snd grins nd the cly used in the present investigtion. TABLE I () Detils of homogeneous snd grins used Averge Snd B.S. size of* smple sieve grin Remrks No. No. in micron A Single sieve snd smples were sieved C from silic snd obtined D from Tufron strem bed locted bout E km from Hyderbd (A.P.) F B * The verge size of the grin ws clculted on the bsis of the verge sizes of the Lo s of the two sieves, through one of which the snd pssed nd retined by nother.

3 Studies on Physicl Properties of Homogeneous Snd Mixes 49 (0 Cly used Bentonite of ph vlue 8, liquid limit 574, Swelling index 143-0% Bse exchnge cpcity 86 milliequivlents/100 g nd moisture 10.2% ws used in this investigtion. Mixing. Homogeneous snd mixes were prepred using snd muller of 5 kg cpcity. The following procedure ws dopted for prepring the snd mixes in the snd mixes. 1. Add the required mount of wter to silic snd nd mix for 3 minutes. 2. Add the required mount of bentonite to mix No. 1 nd mix for 5 minutes. Snd mixes thus prepred were stored in polythene bgs to prevent moisture loss, nd were subsequently used to determine the following physicl properties : 1. Green compression strength, 2. Green sher strength, 3. Green permebility, 4. Green hrdness, 5. Bulk density, 6. Riddled density, 7. AFS 8. ± OF Flowbility nd 9. Compctbility. Green compression nd sher strengths, green permebility nd green hrdness were determined using the Ridsdle universl snd strength testing mchine, premebility meter, nd hrdness tester respectively. Bulk density of snd mix ws clculted from the knowledge of the weight nd volume of AFS stndrd snd specimen. Riddled density ws clculted from knowledge of the weight nd volume of snd riddled through 3 mm sieve into stndrd AFS specimen tube. Compctbility of snd mix ws determined s follows : the snd ws riddled through 3 mm sieve into AFS specimen tube upto the brim nd

4 50 V. V. SUBBA RAO AND T. RAMMOHAN ws given 3 rms. The decrese in height of the snd column ws mesured. The compctbility vlue ws clculted using the expression : C Initil height of snd column finl compcted snd height Initil height of snd column in Fig. 1 is shown the principle of mesuring compctbility. / I i J ' 1 % 1. o I e, %.. s 2, I. r * % I d. 4.r,. 1 s. I t I * It e,.. V 1 %,.I,....., I 1. i 1. I, 1 4. I II I 4 IA. 3 I I, r r 4% 1.. e,.. P s 'I 1 I I se.2. t se. Ii, I S S AI I I P I / / I, t F IP I fl t. Pi 1 ( 11.. f 1 0. f 1 I.. 1. t r 1. % r 1 I $.5... At. I is 2. II '. I. I I #... S. ' 5..St 5 0 e. WA I 4 P.S.. - I t It ra t. C I 0.. : I. 9 :,. o... * A *. 1. h : FINAL HEIGHT p =to kg/cm 2 FIG. 1. Principle of mesuring compctbility. AFS flowbility ws determined by mesuring the decrese in height of the stndrd specimen due to the 5th blow of the AFS stndrd rmmer. To determine the + OF flowbility of snd mix the GF flowbility tube ws filled up with the mount of snd tht would mke stndrd AFS snd specimen nd subsequently ws given 3 rms. The

5 Studies on Physicl Properties of Homogeneous Snd Mixes 51 height of the snd specimen t the end of 3 rms ws mesured (hx). The flowbility ws evluted using the expression Flowbility % ho x 100 h-o hioo where ho = height of snd specimen t 0% flowbility hx = height of snd specimen t x% flowbility /too = height of snd specimen t 100% flowbility. In Fig. 2 is given the principle of mesurement of + GE + flowbility. (ho- hix, ".. S pi. hio o HEIGHT OF A FS SPECIMEN:h. HEIGHT OF TEST SPECIMEN :Fi x h x FLOWABI LIT Y / X 100 HEIGHT OF IDEAL SDECIMEN =h i.. Flo. 2. Principle ofmesuring CF flowbility. TEST RESULTS AND DISCUSSION In Figs. 3 to 16 re shown the plots were nlysed to determine nd bond content. test results in grphicl form. These the effect of wter/cly rtio prticle size Effect of wter/cly rtio. Figures 3 through 6 show the vrition of clifferent physicl properties of homovneous snd mixes of prticle si

6 52 V. V. SUBBA RAO AND T. RAMMOHAN p.. nd p, with wter/cly rtio t vrious bentonite percentges. From these figures one cn observe tht for prticulr bentonite percentge-- (1) the green compression strength, green sher strength nd green hrdness increse to mximum s the wter/cly rtio increses Lu Lu 0 e Ii OL_ *or ' tor- Nf WATEP/cLAY PATIO WATER/cI.Av PATIO FIG. 3. Effect of wter/cly rtio on green compression strength, green sher:strength, green hrdness, bulk density nd permebility ofbentonite bonded homogeneous snd $rins PU prti; size 426'1 /41

7 Studies on Physicl Properties of Homogeneous Snd Mixes J 4 2 E 0 C, 701_ WATER/CL AY PATIO _J 50L_ WATER/CLAY 0.8 RATIO FIG. 4. Effect of wter/ cly rtio on AFS flowbility, + OF + flowbility, riddled density nd compctbility of bentonite bonded homogeneous snd grins of prticle size nd then decreses with further increse in wter/cly rtio; the points of mximum green compression, green sher nd green hrdness occur round wter/cly rtio of 0. 4 t ll bent onitg percentges studied, 1.0

8 54 V. V SUBBA RAO AND T. RA.mmoHAN L. J I O. 8 ly 0 WATER/CLAY RATIO WATER/CLAY RATIO FIG. 5. Effect of wter/cly rtio on green compression strength, green sher strength, green hrdness, bulk density nd permebility of bentonite bonded homogeneous snd grins of prticle..ṅ/54e f.4,

9 Studies on Physicl Properties of Homogeneous Snd Mixes F- U 0 L.) WATE /CL AY RATIO WATER/CLAY RAT:0 FIG. 6. Effect of wter/cly rtio on AFS flowbility, + GF ± flowbility, riddled density nd compctbility of bentonite bonded homovneous snd grins of prticle size 201.5p.

10 56 V. V. SUBBA RAO AND T. RAMMOHAN (2) the green permebility increses to mximum with increse in wter/cly rtio from 0.2 to 0.6 nd then decreses with further increse in wter/cly rtio; the mximum permebility point occurs round wter/cly rtio of 0-6 t ll bentonite percentges studied, (3) the bulk density decreses to minimum s the wter/cly rtio increses from 0.2 to 0.6 nd then increses with further increse in wter/cly rtio; the minimum bulk density occurs t wter/ cly rtio of 0-6 t ll bentonite percentges studied; (4) riddled density, AFS flowbility nd + OF + flowbility decreses with increse in wter/cly rtio from 0-2 to 0-6 nd then does not vry pprecibly with further increse in wter/cly rtio; the sme trend is observed t other percentges of bentonite lso, nd (5) compctbility increses s the wter/cly rtio increses from 0-2 to 0.6 nd then remins lmost constnt with further increse in wter/cly rtio. This is true t other cly contents lso. All these conclusions re found to be vlid for ll prticle sizes employed in this investigtion. Effect of Prticle Size In Figs. 7 through 11 re shown typiclly the effect of prticle size t prticulr wter-cly rtio on the physicl properties of homogeneous snd mixes hving different percentges of bentonite. From these type of figures one cn conclude tht t given wter/cly rtio nd for prticulr cly content (1) the green compression strength, green sher strength, green hrdness nd compctbility decrese with increse in prticle size from 90;i to vlue round 400 p. ; however, with further increse in prticle size, these properties remin prcticlly unltered; (2) green permebility increses with increse in prticle size wheres the vrition of bulk density with increse in prticle size is not consistent; (3) riddled density, AFS flowbility nd + OF + flowbility increse s the prticle size increses upto vlue round 400 IL nd then Ternin lmost insensitive to ny further increse in prticle size,

11 Studies on Physicl Properties of Homogeneous Snd Mixes % C 0_43 5% er 7%. oh---- 9% )1 wi c Rtio:1.0 Ui Ui Ui L.5 Ui OCO 1 PARTICLE SIZE, microns PARTICLE SIZE, microns nu. 7. Effect of prticle size on green compression strength nd green sher strength of bentonite bonded homogeneous sndlgrins t wter/cly rtios of 0.6 nd 1-0. These conclusions re 'found to tie vlid t ll wter/cly rtios, viz., () 2 to 10v

12 58 V. V. SUBBA RAO AND T. RAmmomm4 ci PARTICLE SIZE, microns PARTICLE sizeimicrons - Fro. 8. Effect of prticle size on green hrdness nd green permebility of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.6 nd 1-0.

13 Studies on Physicl Properties of Homogeneous Snd Mixes 59. PARTICLE.sE,rnsicron.s PARTICLE SIZE, microns FIG. 9. Effect of prticle size on bulk density nd riddled density of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.6 nd 1-0.

14 60 V. V. SUBBA RAO AND T. RAMMOHAN Losiond 3% Cloy o----o 5% 7% *----to 11% 80 V X WIC Rtio:06 wic Rt 4) t. SO 200 4C0 600 PARTICLE SIZE ) M IC rons I #11) PARTICLE SIZE.,MiCrOrIS Fm. 10. Effect of prticle size:on AFS flowbility nd -1- GF - flowbility of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.6 nd 1.0.

15 Studies on Physicl Properties of Homogeneous Snd Mixes Legend 4( 3% % -- 7% -- 9% / 4 x 20 W/e Rtio= W/ C Rt io L C PARTICLE SIZE ) MiC rons Fm. 11. Effect of prticle size on compctbility of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.6 nd 1.0.

16 62 V. V. SUBBA RAO AND T. RAMMOHAN Effect of Bond Content In Figs. 12 to 16 re shown typiclly the effect of cly content t prticulr wter/cly rtio on the physicl properties of homogeneous snd 24 Leginid Pcrticlo sizo 851 p p 1) '-9 LP cr t- in I C 5 0 CLAY PERCENT CLAY PERCENT no. 12. Effect of cly content on green compression strength nd green sher strength of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.4 nd 1.0.

17 Studies on Physicl Properties of Homogeneous Snd Mixes 63 mixes of different prticle sizes. From this type of figures one cn infer tht for given prticle size (1) green compression strength, green sher strength, green hrdness nd compctbility increse with increse in cly content from 3% to 7% nd with further increse in cly content the increse in these properties is not pprecible, Lepnd i---k Po rt;rio S; Q R51 P W oso, ) cro 302 P viv up_p '28P 90 P wic Rotioz E Lu C 2 ts ! L CLAY PE PCEN CLAY PERLtNi FIG. 13. Effect of cly content on green permebility nd green hrdness of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.4 nd 1-0. I. I.Sc.-2

18 64 V.V. SUBBA RAO AND T. RAMMOHAN (2) green permebility, AFS flowbility, + GF +flowbility decrese with increse in bentonite content upto 7% nd then remin lmost constnt with further increse in bentonite content, nd (3) bulk density vrition with increse in cly cmtent does not follow ny definite trend. Legend Prtici. size 951 p 599 P P p 15 RQUO zip 'Sc 0 til J cr W/C Rtio: it CLAY PERCENT CLAY PERCENT Flo. 14. Effect of cly content on bulk density nd riddled density of bentonite bonecd homogeneous snd grins t wter/cly rtios of 0.4 nd 1.0.

19 Studies on Physicl Properties of Homogeneous Snd Mixes 65 The bove conclusions r ; vlid for ll the prticle sizes employed in this investigtion. A more or less similr trend is observed t other wter/ cly rtios lso. u CLAY PERCENT CLAY PERCENT Flo. 15. Effect of cly content of AFS flowbility nd + GT+ flowbility of bentonite bonded homogeneous snd grins t wter/cly rtios of 04 4 nd 1.0.

20 66 V. V. SUIII1A RAO ANO T. RAMMOHAN CLAY PERCENT FIG, 16. Effect of cly content on eompctbility of bentonite bonded homogeneous snd grins t wter/cly rtios of 0.4 nd 1.0.

21 Studies on Physicl Properties of Homogeneous Snd Mixes 67 Interreltion between Physicl Properties of Snd In foundry prctice, the determintion of physicl properties is 'essentil for snd control nd it is difficult to determine ll the physicl properties in the control lbortory. The physicl properties, in generl, re interrelted. A study of the literture indictes tht few ttempts hve been mde to relte the vrious physicl properties. Hence the physicl properties QIREEN COMPRE5SION STRENGTH,1b5iSCI H: \ FIG. 17. Interreltionship between green compression strength nd (5reenillepr strenitti of bentonite b94cd hoznogcnepus snd grins t =

22 68 V. V. SUBBA RAO AND T. RAMMOHAN of snd mixes obtined by using homogeneous snd grins were interrelted. In Fig. 17 through 23 re shown the interreltionships of vrious physicl properties for ll prticle sizes, ll cly percentges nd ll wtercly rtios employed in this investigtion. th Lu GREEN COMPRESSION STRENGTH, lbs/sq in Fm. 18. Interreltionship between green compression strength nd green hrdress of bentonite bonded homogeneous snd grins. (1) Green Compression nd Green Sher Sirength In Fig. 17 is shown the interreltion between green compression grength nd stun sher strength, It cgn 1?e observed from this figure tht

23 Studies on Physicl Properties of Homogeneous Snd Mixes 69 CT3 0 M. RIDDLED DENSITY, 911:1MS Flo. 19. Interreltionship 4twcfcli ricldled density nd AFS flowgbility 91 bcnionits boccled hornornc90 snd grins,

24 70 V. V. SUBBA RAO AND T. RAM AN 9 Legend Prticle size 851 P J ID P P 2015 p 128 P p RIDDLED DENSITY p gltms FIG. 20. Interreltionship between riddled density nd + GF bonded homogeneous snd grins. flowbility of bentonite n pproximtely liner reltionship exists between the two properties. The slope of the curve indictes tht the rtio of green compression strength tc) green sher strength is round 4,

25 Studies on Physicl Properties of Homogeneous Snd Mixes 71 t RIDDLED DENSITY, grms FIG. 21. Interreltionship between computbility nd riddled density of bentonite bonded homogeneous snd grins. (2) Green Compression nd Green Hrdness In Fig. 18 is shown the vrition of green hrdness with green compression strength. A study of this figure indictes tht the green hrdness vlue increse shrply with increse in green compression strength upto vlue of 95 nd ny further increse in yeen strenvh does not lter the green hrdness luch,

26 72 V. V. SUBI3A RAO AND T. RAMMOHAN tie is. 4 COMPACTABiLITY 9 % FIG. 22. Interreltionship between competftbility ncl bonded homogeneous snd grins. AFS Nisi/bility of bentonite

27 Studies on Physicl Properties of Homogeneous Snd Mixes 73 COMPACTABILITY 0/0 Fro. 23. Interreltionship between compctbility nd + CF bonded homogeneous snd grins. fiowbility of bentonite (3) Riddled Density nd Flowbility In Figs. 19 nd 20 re shown the interreltionships riddled density versus AFS flowbility nd riddled density versus + OF + flowbility respectively. From these figures one cn conclude tht : () AFS flowbility does not correlte well with riddled density, nd (b) + OF + flowbility increses linerly with riddled density,

28 74 V. V. SUBSA RAO AND T. RAMMORAN (4) Compctbility nd Riddled Density In Fig. 21 is shown the vrition of compctbility with riddled density. A study of the figure indictes tht n increse in riddled density decreses compctbility in liner mnner. (5) Compctbility nd Flowbility As flowbility nd compctbility mesure the decrese in height of snd column during compction, n ttempt ws mde to relte flowbility nd compctbility. In Figs. 22 nd 23 re shown the vrition of AFS flowbility nd +GF-F flowbility with compctbility vlue respectively. A study of the figures indictes tht () AFS flowbility does not correlte well with compctbility vlue. Compctbility increses upto vlue of 75 with decrese in AFS flowbility, (b) liner reltionship exists between + OF + flowbility nd cornpctbility, nd n increse in compctbility decreses flowbility. From Figs. 20, 21 nd 23, it is interesting to note tht compctbility, OF + flowbility nd riddled density re linerly interrelted nd they mesure one nd the sme property. CONCLUSIONS The results of the investigtion to study the effect of wter-cly rtio, prticle size nd cly content on the physicl properties of homogeneous snd mixes indicte the following: For given prticle size nd cly content, (l with increse in wter-cly rtio, the green compression strength, green sher strength, green hrdness nd green permebility increse to mximum nd subsequently decrese wheres bulk density decreses to minimum nd then increses; the mximum points of green compression strength, green sher strength nd green hrdness occur round wter-cly rtio of 0.4 while the mximum green permebility nd the minimum bulk density occur round wter-cly rtio of 0.6, nd (b) riddled density, AFS flowbility, + OF + flowbility nd compctbility vry with increse in wter-cly rtio upto vlue round 0.6 nd then remin insensitive to further increse in wter-cly rtio.

29 Studies on Physicl Properties of Ilomogeneo:ts Snd Mixes 75 For given wter-cly rtio nd bentonite content, (c) the properties vry with increse in prticle size upto vlue round 400m nd then become insensitive to prticle size. For given wter-cly rtio nd prticle size, (d) the physicl properties vry with increse in cly content upto vlue round 7% nd then remins constnt with further increse in cly content. The interreltionships of vrious physicl properties indicte tht (e) liner reltionship exists between green compression strength nd green sher strength, nd (f) compctbility, + GF + flowbility nd riddled density re linerly interrelted nd they mesure one nd the sme property. ACKNOWLEDGEMENT The uthors thnk Prof. Abid Ali, Principl, for providing fcilities to crryout this investigtion. REFERENCES [1] [2] (3] Yerly, B. C... Foundry, 1967, 94, 82. Seton, T. W.,, Trns. AFS, 1960, 68, 45. Sringesh, K... Ph.D. Thesis, Indin Institute of Science, Bnglore, [4] Wenninger, C. E. nd Volkmr, A. P. Trns. AFS, 1970, 78, 17. [5] Hofmnn, F. et t.. Trns. AFS, 1969, 77, 134. [6] Wenninger, C. E. nd Lng, W. J. Trns. AFS, 1969, 77, 39.