rice husk ash cement 25-657

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    ATMlCRdFlCHEREFERENCE\ LIBRARY . A project of Volunteers in dsia

    Ri c = e Hu s k + As h Ce me n t. .. b y R a y S mi t h4 1 e, 8P u b 1 ished b y : *

    , Intermediate TechnolcYgy Dgvelopment Group (ITDG)*

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    Av ' a i l a b l e f r o m: i , p -Intermediate Technnlogy.Pubiications ,~9 King Street ;L o n d o R WC / E 8 H N- E N GL A ND "

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    RReproduction .of this ,.tnicrof iche document .in anyf o r m is s u b j e c t t o t h e s a me r e s t r i c t i o n s a s t h o s e ,of t h e original d o c u me n t . 0

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    RICE HUSK ASH CE ME NT sP r o g r e s sin .d ev e lo p m en t i .L&d a p p lh t ibn . (

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    .. A report .on site visits to';- India, Nepal and Pakistan

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    bY k. G. SmithBuilding*ResearchEs$$blisl?mentWatford.

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    I\ -Intermediate Technolog; Development Group Limited\.-.,.,~\ .9 King Street ". ', I_ ; (.i;, - -"f&jy,d~ ,;3i_ ' '. , ' _, I '

    Publica.tions Ly$mi& _ '* .> @Intermediate Technology-. "

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    Printed by Steers Limiied, &inters, Rugby: i--%,;.. I e.I

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    The use of the ash r.esulting from burning rice, *husk as a cementitious binder in conjunction with_ lime*has Abeen receiving/increasing.attention over." recent years.n attractive prospectalternative .eement village-scale'n ,- technology-using a rea.dily available agriculturalwaste titerial. The heed for s'uch mater"lals 'is

    " b clear;.as the conventional binder, Portland cementVL. '* is.--common,ly unava.ilable, or, expensive part.icu,lgr,$y.in rural cpmmunities /,where, indeed, its high-, s.trGngth, -ra etting >properties are not ofprimary, impor to -the'a _ Simpie civil ,lo-w-rise building oreeriqg.work typically undertakeninth'ese,,areas. * %'~" 9-t..:$ Yme - :research andhevelopment work into rice

    ash (RHA):.cement technology has beenundertaken by a vqriety of institution& andindividuals, principally in the ,Indiansub-continent, and several attempts have been made./ ...

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    \ \ to commeraialise 'and ~dis'seminate the technology.,\ Reports on this work are sparse,. and* in particular\\there has been' a .lackof independent comparaive'batak on the various approaches used; these., itw ll be seen'from this report, contain significant.diff erences in terms-of the final product and' thepraduction process used.. These differing-L approhches were adopted for good reason and, as'inall appropriate technologies, it is unlikely thata single process -will emerge as being the uniquesolution for all situations. This report is not,therefore, intended to be a guide to the F'best-buy" in RHA cement technology but is an attempt tobring_ togeth,er comparative-' data on' the variousinitiatives for the benefit of those contemplatingthe us" of.such a material in their- own region..I_._The report ,_--must be r.ead with all 'the usual~~~*'~ -.,cautions; in particular the laboratory-.tests:were 'performed on -'grab ' samples and'should not be seenas defi'nitive or statistically significant.Our thanks are due to those ~people and5institutions visited who gave

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    -a 'sta-te-of-the-art' review of .rice.husk ashcement technology and production in the Indiansub-continent. .Twelv,evisited to diskuss specific locations' wereresearch and development.Visits t-u pilot' and commercial production plantswere included,: and sampies were collected forlater analysis in the UK. . ',.--Some,o-f the c,cmpleted

    '-'~~~.~~catio,~,,,,,b:u"t research. still -awa'itedsome was being applied.'Commercial pr*oduction was often held up throughnon-delivery of raw materia~l, failure of powersupplies or mechanical breakdown, but some ricehusk ash cement-was being made, sold and used., , *Research workers had found that it was necessaryto limit the tempsrafure of the burning husks tono "more than.700 C to obtain an amorphous ashwhich would b.e reactive with lime, .although in.some production processes this,,exceeded. temperature was"I \It had been found that the .ash needed s'everal.,

    --hours of grinding to produce a sufficiently finepowder: The period in practice'using ball millsvaried between 1.5 and 5 ,hourti. '>

    IIn most cases the cementwas made. by mixing onepart of lime.,with two parts of rice husk ash (by,weight) . Sometimes ordinary Portland cement wasused in place of lime. It was commonly( recommended .that for building use, one. part ofrice husk ash cement shoul'd be mixed with 3 partssand (by volume).The rice husk, ash' cement' is much cheaper thanordinary Portland cement for .a'given weight and ?nspite, of richer mixes being used 'in practice it isstill cheaper to make mortars from the rice huskash -cement. .'Capital investment of some L12,OOOmay be required for a complete plant.,'& ,.1Results of tests in-UK laboratories are given andare compared with manufacturers' claims and withrequirements in the most relevant Indian andBritish Standard Specifications. b.

    IThe rice husk-,aSh cements often exceeded therequirements of the Indian Standard forLime-Pbzzolana Mixture. In general they should besuitable for use in making mortars, renderings forwalls, and some lower 7tr-ength ' requirementcpncrete.- , '

    ..It is recommended that the technology.-be appliedin other rice-growing countries of the world. ~r-'\ .

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    . ,CONTENTS d u

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    . PageINTRODt?CTION 1SITE VISITS . 2'i

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    2.1 INDIA c 21 .2.2 NEPAL szdL1 15

    _'2.3 PAKISTAN 15&MP$RISON bF PRODUXJTION METHODSmD RECOMMENDATIONS F& USE h 28TESTING OF SAMPLES IN UK 'isRESULTS OF UK LABORATORY TESTS1 " 29COMPARISON OF PRODUCERS' DATA aWITH UK RESULTS 310COMPAtiISON OF EXPERIMENTAL DATA -WITH STANDARDS REQUIREMENTS A_ .' 31

    RECOMFENDATIONS 36- rTABLES

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    ECONOMICS 32CONCLUSIONS, 340 . .1

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    / KEY T.0 INSTITUTES i1 * . ,/ I.Yt /II'wI&JB~A .i,.,.,.,.,ll*.11,','I,I $ ,i' .A 1 Cement Research Institute .o;f India, ,NebDelhi .'I B.? Indian Institute,,pf T&bnology, Kanpur -1-. c- - Birla Institutey'of- Scientsfic Reseaych, \..Ranchi ,, 7.. D *r Central Buildin Researkh .I.nstitute,.. Roorkeq

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    E Res;eprch Cen$re for Applied ' Science and .* - "--_>\ ,,*,. -Tech%olqpy, Ka'thmandue. .PAKISTAN ,

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    Pak'istan 'Council for Scientific and iiIndustrial Research, Karachi\ I5 L

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    i i ./Throughout the world eighty million tonnes of husk- . //

    become available each -year .during the /processingof rice. Some is used as packaging or fuel, but-the greatest proportion i-s' dumped as a wasteby-product. -4

    z-*.Several institutes have investigated. dieproperties of the ash of the burnt husk, which ccontains a high proportion of sili,ca, and therehas. been some commercial exploitation of itspozzofanic reaction -with lime to form amaterial of potential use in the

    and discussed: -

    'recommended.'

    Developmentcurrentf cemeptitiousdevelopment It was already known that

    publications -gavesituation and a confusing picture of thethere was no '.overall comparativereview of the subject.'potential benefi.ts ITIS r,ecognised the' _of making these materials inIndia, and also in other rice growing areas ofdeveioping countries to increase the supply of cbuilding materials, especially where ordinary rPortland cement was expensive or scarce. Such usewould also effectively dispose'of and-utilise, anagricultural. waste,'improve rural economy and .*generate employment, with low capital cos;ts. ITIS-wished to be in a position to make recommendationsSO, in 1982'the author, a member of the staff ofthe -Overseas Division, BRE, visited India, Nepal .and Pakistan to gain first-hand information.

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    r of N,ew SouthJWales, 'accompanied the author for !... part of th>e '-v?sit. ,", ,/ .23 SITE/VISITS d ,.. . i'Discussi,o'ns' on research into th.e various *- procdsse& were held at six insti'tutes and visitswere made to inspect the commerc'ial enterprises *'utilis'ing the process' of each institute.(Figgre 1) The map .shows the location of iplaces visited,Land/other centres of :information,.c This section ofthe report describes, discussions and site. v%isits .I 'i P"ut a more methods,t' ,properties detailed compari,so$ of

    d ;,'-: ,of the products- and economics is madein later sections. I .r

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    at:the; same location, limestonerought in and/burnt in kilns under the'same Isupervision' as, .used .in burning husks, "lime. from the

    calcium silicateToo high a proportion of lime inwith -ash : was said to delay" theof strength of the product in use, andatio of 1:2 /l,ime:ash was used,: _'/'/in sufficiently fast reaction,&tes between._ lime it was necessary to. rind the ash inmill for one. hour,' t n add lime, and

    BYmilling for a furth half hour to mix,~-Entrepreneurs were encouraged to xash for 1;5 hours to be more certain ofning the necegsary k _fin ness. They were alsoed -to obtain a ball mill of slightly# largerify than that requir d for continuous use, tod '-downs and thet-ions in electric .power /

    inevitable inter,rup- .supply.. ,Such a mill isavailable in India8 read --made,x 1.5 m with a 15kW mot,2% its size being 1.5 ,. _ -_'A two tonne per day .for rural use adjareckoned -to be ithe miplant would'be run by

    Such. ,a .one lime kiln operatoThe Institute listedof which the ~ballwas the most expen at &5,000,allocation of nincluded boundaccommodation,

    - up from the earli' priced at- L5OO. brought ,the total offixed capital to r "- The annual costs of run forper year at 90%'capacity ng the plant 330 daysere also indicated. 'Rawmaterials were a small rt of the wholesen as. chargestransportation only, so

    per annum would, costa limestone plusCinder for burning limestone would 'cost+1,300; electricity., chi for the ball' mill," was {calculated- at A2201 ,seems to be anunderestimate.

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    \ I-. i*-. II ;, q..rqely due to,wear of thebe a-nticipated at L.750, la:

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    ball mili shell, I which might last only threeyears. Salaries of 42,250,. and similar -amounts.for interest- on loans and for Opackaging plus anumber of smaller items would give a tota,l annualcost -of &12,000 or 219 per- tonne. With anestimated selling price of 227 per tonne thiswould yield w-return*on investment of 32%.L LIThe above selling price was .m&h lower than thelowest price for ordinary Portland cement (OPCj ofat least L40- per-,--tonne. One third of the .OPCproduction in India must now be sold on the openma.rket '(since February 19821, and it commands aneven higher price,cemen.t therefore up to about'L95.per tonne. RHAappears :. very -' attracti-tie--e,conomically. .-- :T .' ..

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    Agreements had been signed with entrepreneurs \infour States-for plants with 4,4, 3.and 10 tonnesper .day-capacities 'respectively. Agreements aremade with a payment by entrepreneurs for plantcommissioning, routine testing., exam=ination ofsamples for the first month or so, and occasionaltesting and advice later. -Laboratory tests.,wereto ASTM, for wa.ter retention, water demand,fineness, camp-ressive strength, slump Ip flow

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    table) , and lime reactivity of ash (at 50-C). . No + ' )/specific standard for RHA-cement existed but theproducts were., generally assessed by therequirements of~IS, 4098. Specification for L&me -Pozzolana Mixture- There. was little feedback-ofdetailed information from plants at the time ofthe vfsit, except from one which' .WaS visited' -.later, as part of the review. The larger planfwhich had ,two mills, each +,1.8 x 1.8 m, was *.repsrted to be not working; due to some mechanicalfailure. c-7, , ...Si_x more parties-were about to sign agreements and,@:further 400 .ekquiries "had been received. a.:: I--. - . cIt was- envisaged,that in rurai communities village -bpeople would briricj',$heirrice to*a local.mill, andcould purchase RHA cementi.from the adjacent plant,:taking it to their' villages ys i l-g the sametransport as for the rice. -^1 I1LExperiments car'ried- out '"by the .,1-ns ti tutedemonstrated the -fairly successful- use of RHAcementnsand mixes for r.enderings,(@1:3 by volume).'Althbugh cracks- had appeared in some ele'vations,the -renderings -seemed well attached t0 th.,e

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    : brickwork. FairLfaced brickwork built "with RHA .

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    4. - cement:sa=nd, mortar -2) .' 'showed satisfactory 'performance as a mortar.- y RHAr2 -cement was not recommended for reinforced concrete ' c 1,-work. I - 0 4. '.'I2 a' Production,Plant Al '( *usiny technology of" ..Institute A), \i--Approxima+tely eight workers were seen to be busily'..:.-engaged.ia spite Eight incineratol?sSwere being operated, . '

    :0 of rain and wind. at;.the. time of- thevisit, which made

    i (Figure 5&.working* cond&,tions difficult '1

    in .ft was obser.vexthat unburnt husk was..and around- the bottom area of, r some ci _,2 I'Two brizk-built lime kilns wer& it

    .yj c%--._ the:giteTwas 'to1 the 'design. of .th.e 'Jhadi *-and

    +I$s.Iadustries Commission, .,yilla-gew'8rker.s preferred but,&+ not us-ed,_ince thethe other-which was built to

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    their own traditional design:" 3-t was 3.25m 'h

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    ~ ReSe&ch Ifistitute B. - iAn, amorphous ash,less than 750C, obtained by burning husks atwas claimed to be desirable, butUse, of any type of ash .which might becomea*vailable was *._'.considered. This was because ricehusk was being increasingly used as a fyel, sothat it might not be cheaply available in a few 8 .years * time,for, burning in special incinerators. .4Consequently a technique which could .be modified'" .according todprevailing conditions was advocated.Although 2 hours grinding was adequate foramorphous ash, longer ceriods of grinding, of 6hours or so, could be effective in increasing thestrength of cements made from more. crystallineash. To conserve energy and,improve efficiency ofproduction, appropria-te min~imu-m grinding--times ~--should be used for each particular ash'. up to 10%carbon had not proved,deleterious. ,Where husk was availab.1.e,,,".-,eontrolsufficiently low temperature woureactive ash which needed little,to obtain adequate .-:.cement fcylindrical met31 wire mesh basket, 1.2 m high-and0.6 m in diameter, lined,.w-ith.a--finer wire netting 2to retain husks, set in' a mild steel frame onlegs, and with a perforated metal chimney up thecentre had. proved successful as an incinerator(Figure 7). To operate, a fire was kindled at thebase between the'legs. A damper w...

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