IS 12654: 1989 Indian Standard ( Reaffirmed 2000 ) LOWGRADEGYPSUM-USEINBUILDING -. . INDUSTRY-CODEOFPRACTICE ,' _ Vrm"rS 9TVS ml7 f+rbT sit7% a&r- -fffa tif@T f~?rti~f~wT--- UDC 691'311-431 : 006'76 I , ' @I BIS 1989 / BUREAU MANAK September 1989 OF INDIAN STANDARDS ZAFAR MARG . Price Group 2 BHAVAN, 9 BAHADUR SHAH NEW DELHI 110002 AMENDMENT NO. 1 MAY 2010 TO IS 12654 : 1989 LOW GRADE GYPSUM USE IN BUILDING INDUSTRY CODE OF PRACTICE (Page 3, Annex A, clause A-1.1, line 2) Substitute `sifted' for `shifted'. (CED 4) Reprography Unit, BIS, New Delhi, India Gypsum and Gypsum Based Products for Buildings Sectional Committee, BDC 21 FOREWORD This Indian Standard was adopted by the Bureau of Indian the draft finalized by the Gypsum and Gypsum Based Products had been approved by the Civil Engineering Division Council. Standards on 20 March for Buildings Sectional 1989, after Committee India is endowed with more than 1 200 million tonnes of mineral gypsum. Out of it, about High grade gypsum is required for the manufacture of 92 percent occurs in Rajasthan alone. However, large fertilizer, as an additive to Portland cement or for surgical, ceramic plaster, etc. deposits of low grade gypsum are available at several places in Rajasthan and are considered unsuitable for the above uses and hence remain unutilized. Studies carried out at Central Building Research Institute suitable plaster for use as masonry mortar and for making having purity less than 70 percent. ( CBRI ), Roorkee have shown that blocks can be produced from gypsum Considering the huge availability of low grade gypsum and its scope for utilization in the building construction, the Committee felt it necessary to bring out a code of practice on the use of low grade gypsum in building construction as this gypsum can be conveniently used as mortar and in This standard, it is expected, the manufacture of light weight blocks for non-load bearing walls. wquld help in promoting the wider use of low grade gypsum in low cost housing. For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expresisng the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 `Rules for rounding off numerical values (revised)`. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. IS 12654 : 1989 Indian Standard INBUILDING LOWGRADEGYPSUM-USE INDUSTRY-CODEOFPRACTICE 1 SCOPE 1.1This standard covers the preparation and physical requirements of calcined gypsum made from low grade gypsum and its use in masonry mortar, internal plaster and light weight blocks. 2 REFERENCES 2.1 The necessary Indian adjuncts Standards listed to this standard: Title Methods of test for mineral gypsum ( second revision ) Code of practice for preparamasonry use of and tion mortars (,first revision ) Glossary gypsum of terms relating to below are of calcium and magnesium, rials and minor impurities, chloride, sodium sulphate, gypsum anhydrite, etc. 5 PREPARATION OF GYPSUM OR GYPSUM and clayey matesuch as, sodium sodium carbonate, CALCINED PLASTER IS No. IS 1288 : 1982 IS 2250 : 1981 IS 2469 : 1976 ( jrst revision ) IS 2542 ( Part l/Set 1 to 12) : 1978 Methods of test for gypsum plaster, concrete and products: Part 1 Plaster and concrete (Jut revision ) 2/Set 1 to 8) : 1981 Methods of test for gypsum plaster, concrete and products: Part 2 Gypsum products (first revision ) Method of test for bustibility of building ( first revision ) non-commaterials 5.1 Gypsum should be calcined by methods, such as, open pan or rotary drum or kettle calcinators or by any other suitable method. Before calcination, gypsum should be crushed and ground generally to a fineness of about 60 percent passing through 150 pm 1s Sieve. Gypsum starts giving out steam after the removal of mechanically held water. The temperature of calcination should be controlled. Gypsum starts boiling at about 120°C and during the entire calcination process the maximum temperature should not exceed 170%. During the calcination process, the temperature remains constant when the entire charge boils vigorously. The calcination of gypsum is considered complete when boiling stops and the calcined material starts settling. N07'L - A fully covered pan with a chimney to avoid dust pollution with mechanical agitation is the modified design introduced recently by CUR1 in the open pan calcination process. In addition to improving the quality of product, this process also effects considerable saving in fuel consumption. IS 2542 ( Part 6 PHYSICAL REQUIREMENTS to the require- I$, I. 3808 : 1979 6.1 Gypsum plaster shall conform ments given in Table 1. 7 GYPSUM 7.1 7.1.1 Materials Gypsum Plaster MORTAR IS 8272 : 1984 Specification for gypsum plaster for use in the manufacture of fibrous plaster boards (jrst revision ) 3 TERMINOLOGY the purpose of 3.1 For dchnitions given in IS 2469 4 PURITY OF GYPSUM this standard, the Gypsum plaster shall conform ments given in Table 1. 7.1.2 Retarder to the require- : 1976 shall apply. A suitable quantity of retarder, such as, glue or citrate may be used for prolonging the setting time of mortar. 7.1.3 Sarzd 4.1 The purity of low grade gypsum when determined according to IS 1288 : 1982, shall be not less than 60 percent ( CaSO.r.2HsO ). major contains generally Such gypsum impurities, namely, silica, dolomite, carbonates 1 Sand of fineness modulus 1'75 to 2'0 is reGommended for preparing mortar. The sand shall IS :12654=198!I Table 1 Physical Requirements of Low Grade Gypsum Plaster (Clauses 6.1, 7.1.1 and8.1.1 ) Requirements 95'0 10 to 30 Method of Test, Ref to Annex A IS 2542 ( Part l/Set 1978 1 to 12) Sl No. i) ii) iii) Particulars Fineness, percentage passing through 150 micron IS Sieve, Min Setting time, minutes Compressive strength, N/mm', : Min 7.0 IS 8272 : 1984 ( Appendix D ) contain no harmful material in such quantity as to affect the strength or durability of mortar adversely. Iron pyrites, coal, alkali, organic impurities, mica, clay, shale or similar laminated materials shall not be present. 7.1.4 Water 7.4.2 Compressive Strength of Gypsum Mortar The average compressive strength of six 1 : 2 gypsum plaster and sand cubes ( by mass), determined according to the method described in IS 2250 : 1981 shall not be less than 2'5 N/mm2. 7.4.3 Weathering Test of Gypsum Mortar Potable water is generally considered satisfactory for mixing plaster and sand. It should be clean and free from suspended impurities. 7.2 Preparation of Mortar Gypsum plaster and sand should generally be mixed in the proportion of 1 : 2 by mass mixing of different materials shall be done preferably in a mechanical mixer. Gypsum plaster and sand shall be mixed dry in the required proporThe required tions to obtain a uniform colour. quantity of water shall than be added and the materials mixed thoroughly to produce a mortar of workable consistency. In case of mechanical mixing, the mortar shall be mixed for at least three minutes after addition of In the case of hand mixing, the mortar water. shall be thoroughly mixed for 5 to 10 minutes with addition of water. 7.3 Gypsum mortar specimens rnoulded in 50 mm cubes are subject to alternate wetting and drying cycles. One cycle comprises of 16 hours of drying the cubes in an oven at 42°C followed by one hour cooling and seven hours immersion in water. 7.4.3.1 Gypsum mortar cube shall not show any of deterioration, such as, crumbling, sign cracking, chipping, when tested up to 5 cycles of weathering test. For this test, observations should be made on six cubes. 7.5 Application of Gypsum Mortar Gypsum mortar is generally recommended for use as internal plastering and masonry work. It shall not be exposed to external weather conditions except where rainfall is very scanty. The field performance of gypsum mortar can be assessed by applying a mixture of 1 part of gypsum plaster and 2 parts of sand with 50 percent water ( all by mass) on a clean and wetted brick surface. The set mortar shall not show any visible shrinkage crack, chalking, when observed after 48 h of crazing, etc, application. `l'he set mortar shall adhere well with the masonry surface and shall not peel off after drying. 8 LIGHT BLOCKS WALL WEIGHT SOLID FOR NON-LOAD GYPSUM BEARING Consistency of Gypsum Mortar The working consistency of mortar is usually The judged by the worker during application. quantity of water should be enough to maintain the fluidity of the mortar during application but at the same time it shall not be excessive leading to segregation of aggregates from the gypsum plaster. The quantity of water required for maintaining consistency of fluidity will depend upon the masonry for which the mortar is used, for example, thinner joints will require greater fluidity and bed joints subject to heavy pressure may require stiffer mortar. 7.4 Physical Requirements 7.4.1 Setting Time of Gypsum Mortar The setting time of mortar, determined accordIS 2542 ing to the method described in ( Part l/Set 1 to 12) : 1978 shall not be less than one hour and greater than two hours. 2 8.1 Materials 8.1.1 Gypsum Plaster to cthe require- Gypsum plaster shall conform ments given in Table 1. IS:12654-1989 8.1.2 Water Potable factory 8.2 water is generally for mixing plaster. considered satis- 8.4 Physical Requirements 8.4.1 Comfiressive Strength The average compressive strength of three blocks when tested according to the procedure given in IS 2542 ( Part 2,%ec 1 to 8)-1981 shall not be less than 1'5 N/mm2. 8.4.2 Non-combustibility given Dimensions and Tolerances of the blocks 8.2.1 The Length mm nominal dimensions shall be as given below: Brradth mm 75 100 125 150 tolerances on and He@ht mm 300, Max in multiples of 100 When tested according to the procedure in IS 3808 : 1979, the blocks shall not: 700, Max in multiples of 100 a) cause the temperature readings of the furnace thermocouple to rise by more than 40°C above the initial furnace temperature, b) cause the temperature specimen thermocouple than 40°C above the temperature, or c) flame for more than 5 s. readings of the to rise by more initial furnace 8.2.2 f3'0 f1'5 8.3 The mm mm. on length shall be breadth and height Method Blocks of Casting of Gypsum 8.5 Visual Inspection Gypsum plaster with sand, saw dust, wood shavings, etc, or without any aggregate is mixed with sufficient quantity of water to form a uniform workable plaster or slurry. The wet mix is poured into well greased moulds in such a way that all the gaps are filled up properly. The superfluous material is removed with a spatula to give a smooth surface. The material after setting is demoulded and dried in air. All blocks shall be sound and free from cracks, broken edges and other imperfections that would render them unfit for use. 8.6 Application of Gypsum Blocks are recommended for use as walls or for inner leaf of in external walls. shall not be used or unprotected. blocks internal partition cavity construction 8.6.1 These 8.6.2 These gypsum blocks externally whether protected ANNEX -4 ( Table 1 ) METHOD A-l A-l.1 PROCEDURE FOR DETERMINATION OF FINENESS One hundred grams of dried sample shall be shifted continuously on a 150 t"rn IS Sieve for five minutes. Air set lumps in the sample may be broken down with fingers but nothing shall be rubbed on the sieve. The mass of the material retained on the sieve shall be expressed as a percentage of the original mass of the sample. Standard Mark The use of the Standard Mark is governed by the provisions of the Bureau of Indian Standards Act, 1986 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testing and quality control which is devised and supervised by BIS and operated by the producer. Standard marked products are also continuously checked by BIS for conformity to that standard as a further safeguard. Details of conditions under which a licence for the use of Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards. . 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