GB2362643A

GB2362643A - Production of "green" cement

Info

Publication number: GB2362643A
Application number: GB0012952A
Authority: GB
Inventors: William Ajua Tasong
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-05-26
Filing date: 2000-05-26
Publication date: 2001-11-28
Anticipated expiration: 2020-05-26
Also published as: GB0012952D0; GB2362643B

Abstract

A hydratable cementitious composition is formed from a mixture of waste paper sludge ash and waste glass. Preferably the raw material mixture comprises 60-70 weight percent waste paper sludge ash and 30-40 weight percent waste glass. Optimum reactivity and performance are achieved when the raw materials (waste paper sludge ash and waste glass) are ground to a fine powder with particle size distribution in the range of 5-60 microns.

Description

" CEMENT PRODUCTION OF 'GREE'!'v

FIELD OF TITE INVENTIO'J

2362643 -r&Lie present iii,,.-eiitl;on relates t c, rfietliods 0 f producing 'green' or environmental cement using waste paper sludge ash and waste glass. The cii iroi-ia.intal cement lis f or use i n the industry, for example, to produce cementitious materials, such as mortar and conerete.

BACKGROUND

Portland --.E>i,-ient has been widely used in the construction indutry to produce cementitious materials for several decades. Howevere, ---ementitious materials prepared using Portland cement. have been "rom various forms of deterioration, subsequently observed to suffer. leading to failure in certain harsh or aggressive environments. For instance, Portland cement products are known to suffer from sulphate attack- leading to deterioration and subsequently failure in the presence of sulphates and humidity.

Furthermore, the production of Pu rt 1 and cement causes substantial damage to the environment due to emission or release of green house gases such as carbon dioxide. The process of Portland cement production also consume high quantities of energy. In adddition, the quarrying oil the raw materials used in the production of Portland cement also contribute significantly to the damage caused to the ---liv i ronment, Increase in environmental awareness over the past decade has resulted in increased legislations on the management of wastes and also in L L L increased control on the emission levels of green house gases. es are depleting at a fast rate. In addition, the increase increasing ressitance from 1 sites near their back yard the waste producers to find result, waste minimisation by Landfill sit i n.1 andif i A' 1 c c I Irm I I I I i t i. e S has further - It e'rnat ive rec.veling or costs t a x) together w i th to allow location of landfil increase the pressure on methods of disposal. As a.

re-used is now highly encouraged through out the world.

1 lhe application of waste materials such as ground granulated blastfurnace slag and fly ash as partial pozzolanic replacement of Portland cement has been widley used in cement and concrete technology over the past decade. This technique has resulted in a reduction in the quantity of Portland cement used in construction practice. This -he damage cause to tlie environment approach has been shown to reduce t and also the cost of construction, since Portland cement is the most expensive constituent of (-.,.onerete or mortar. However, Portland cement r,l-.,iiains a major constituent. of the cementitious material containing these partial pozzolanic replacement materials. It would therfor.c. be of great economic and environmental benefit to develope an alternative.ementitious material to Portland cement solely from waste materials.

Thus the principal aim of the currciit i nvent i on is to develope an environmentally friendly or 'green' cementitious material from wastes m Li L ,a'ei--'als, ior use in the construction industry, for example, to oduce or concrete. The method provided by this invent ion (W A Tasong) 1 ---em does riot suffer from sulphate ent i 1 iOllis material which allso se,,,,ei,al times more resistant to other noterious tau,k siicti as frost attack, corrosion, etc, as is the case and cellicilt. Herice the c eme n t. it io us mate. r i a 1 prepared c) th i S i liv e il t i oil i S s u i t ab 1 e f or- application in various eii,:ii,olirii(,,rit.s such as p r 1 cl e s a a t t a e. h a,, i cl. 1, ', j. at,,,, 1 '. 11 1, 0 r. 1 - 1 chemically 11 i gh sulphate, freezing 1 L. r a It. U re S, etc, W1-, i ell Port land e e lrl c n t, has been shown to be unsuitable. In addit _Jon the iriethods provided by the present invention has its Which ilivulve avoiding the use of large or release of green house gases Portland cement. The production of -g.. consumption. Hence, beside enei provided b y 'I h i S invention also (If quarried Material associated with the production of 41'ui.t,larid cement. also requires higi cost, the savings in c 1152 fil ( t 1 i cj d The p,loc.e-,s of pa p e i. i Invo 1 v c S t, ll c., c x t r a et i.j i i o L' - e 11 u.1Lj s c ibres f-roill wa.ste paper, materia.l. 1 arge quantities of waste paper S 1 lidge- -:c)iis i st J1 ng u f a su.,,ipc.iis i oil of the inorgarlic coat ing:s f rom Lhe .;as4e pap,-ip.11 us res idua 11 f ibres and i nk are produce as, of -he s Itidge, 8 i 1-1 (-., 1 lic 1. a.. ed 11 f 1 ul i d i s e, d s y s t. .. fri a t h i s p f 0 S S, -11 - . ---1 1 - - ill of 800 degree. C te) break down any dioxins. The ' '.' i 1_) i - 1 - a 1 lu r e- 's 1 1 111 P C "I have, ill the past, generall- ui ', i ii., wastc, pap I- 's ludg -, a sh it! (.- 1 C j a . 1. 1 1 -- A k_ J use ur- value, which is dtmped 1 U S t C ma t it i a a nd S 1 - ' he cii-x irot men' and J1 111k CUst both 1 kJ LI of a t.

will d u -at ion) .. 1 - ' '. I-J- i ile) ;, 1 e. LC c,:

aluminat- and . - i _ L - c 1- -- 3) /0 - -0, '1110% S;0z 111 11 -;; 1 ( S, 1 M.-5) r) 1 (: - -- 1 W PS A aku. c. () r (1 L 119 to the pr-esent invent ion 1 il 1 fle (produce cluring decomposition of carbonate m ion c c t akao 1 i ri o r cl d ii r i ng decompositi f 1 lle r at i On) and m' i 110 1, quant it-- i e s of sulphates, c. u ii., s i 1 i;,t a 1, c s, T1 i e c. 11 c fai e a 1 c-,-) mp o s i t ii c) n o f a major clement o.-?,ides w11 comprise about 20- oL 1 5 - 21 'S % AILCi..,,, Th.,- i-ria.jkji ment oxides etc. re, alsc aS components.

T- i( glass i 11 (1 U ss ', r Uu e' 11 i ons t..)nnes of waste c_. r a 1 ni i A xample, currently produce, 8 industry, fol, c., k CA, un torll-es of gla-ss packaging per aiiriuiit. The. lk)ut this -)ut v.i i '. Lei,t:.,-used in colitailler manu 'Lacture I- it is anticipated that, arid cuther spc,,Lif ications, uses will have to Le found, for over 100 twhousalld tonne/annuin, dumping in landfill -ideu Ill 1 4 ' S X, b e a,, li 1 - addill, i S 1 U IL,' to oil, s ign ' f icant quant ities of waste glass is alos produced a 1111 U a 1 1,,- f rom demolished buildings arid other sourc-es. The policies of most governments around the world is 4 1 A 1 l L c; sce, nc)i-.'ai)d"ill outlets for stjc.li waste materials.

Glass i.-., a sol id mat er 1 a 1 C:,)11 S i S L i ng of metal silicates or similar compounds. Me structure of c silicate glasses is generally considered t be a tlir L.(-- -(1 imell S 1 olla network of randon arrangement of Si04 t 'i a t L eas t t -s, 0 oxygen atoins o' each tetrahedron a4.tac.,tlc"d -C otil:"r silicon atoms. klur.iiio-silicate glasses include A104 -.(ill and bo-,osilij-at.e glasses incorporate both tetrahedral B04 Le, 1---r a h c. (1 units arid triangular BO,3.

L e cl micall. composition of a typical glass in terms of major element comprise of 35-96 weight % SiOz, 1-5 weight % A1203, 3-10 weigh', /% CaO, 0-15 weight % B203,0-60 weight % PbO, 1-3 weight % R203 (W A Tasong) 2_ and 4-20 weight % alkalis (Na + K). The other major element oxides such as Mg, Fe, etc., are also present as minor components. It should be noted that the proportions of the various major element oxide will vary, depending on the type of glass.

THE INVENTION The present invention relates to production of 'green' environental cement from waste paper sludge ash and waste glass for use in the construction industry, for example, to produce cementitious materials.

or an According to the present invention a process of preparing a hydratble cementious composition from a mixture. of waste paper sludge ash and waste glass is provided. The process generally comprises steps to process the raw materials, namely the waste paper sludge ash and the waste glass.

The waste. paper sludge ash produced at the incineration stage of the eycling process is lumppy or, coarse grained. In this state, paper. ree the WPSA is inert. In order to enhance its chemical reactity, the coarse grained or lumppy WPSA is ground to a fine powder. According to C the present invention, optimum react.i,,..ity is acheived for powders with a particle size distribution in the range of 5-60 microns. Similarly, t.he -wastle glass is ground to a fine powder (with a particle size distribution in the range of 5-60 microns) in order to achieve optimum --hemical reactivity.

According to the present. invention, a hydratable cementitious composition is formed from a mixture of waste paper sludge ash and waste glass. Preferably, the raw material mixture comprises of 60-70 weight percent. waste paper sludge ash and 30-40 weight percent waste glass According to the present. iii-,..,entiori, a chemical reaction occurs in the presence cif water between the mineral phases present in waste paper sludge ash (such as metakaolin, etc.,) and the mineral. phases present in the waste glass (such as borosilicate, etc.,) to form cementitious products. A chemical break down of waste paper sludge ash occurs in the presence of wate---. This chemical break results in the release into solution of alkalis, hydroxyl ions, etc., from the waste paper sludge ash. The alkalis and the hydroxyl ions released attack the glass, -iea(,.&, ing further alka.li metal and borate ions into solution. The lakli can in turn accelerate the attack on glass as well as activate the hydration process of other mineral phases also present in the niixture, such as inetakao'iiSi 4 1, etc. ions into 1 1 to release AI 3 1, so-Luition. It is proposed t h a t a series of chemical reactions (the nature still to be determined) take place within the mixture to 11ory"i products, such as calcium aluminate hydrates, a. 1 c. i um- a 1 U111 i 110 S j 1 i c at ' e hydrats, calcium silicate hydrates, calcium a-lumino-sulphates, etc. Ilk- is also proposed that a wide range of other c.ementitious compounds, whose exact nature is till to be determined are also expected Lo be formed from these chemical reactions.

3 (W A Tasong) CL A I N45 1. A green cement consists of a mixture of waste paper sludge ash and waste glass to form a hydratable cementitious composition.

Claims

2. A green cement as claimed in Claim 1 where the preferred mixture

consists of 60-70,eigbt percent wRste paper sludge ash and 30-40 weight percent waste glass.

3. A green cement as claimed in Claim 1 where the waste paper sludge ash is the residue obtained after combustion at temperatures in access of 800 degrees centigrade of the by-products (inorganic coating from waste paper plus residual fibre and ink) produced during the waste paper recycling process.

4. A green cement as claimed in Claim 1 where waste glass is glass produced by the Glass industry such as packaging glass or building glass.

A green cement as claimed in Claim 3 or Claim 4 where the waste paper sludge ash and waste glass are both fine powder with a particle size distribution in the range of 5-60 microns.