( Reaffirmed 2002 ) IS:8272-1984 Indian Stan-dard SPECIFICATION FOR GYPSUM PLASTER FOR USE IN THE MANUFACTURE OF FIBROUS PLASTER BOARDS ( First Revision ) Gypsum Chairman DR S. K. CHOPRA Building Materials Sectional Committee, Representing BDC 21 Cement Research Institute of India, New Delhi Members SHRI K. D. BHAR~AVA Directorate of Mines and Geology, Ra.jasthan MINING ENGINEER ( Alternate ) All India Pottery Manufacturers' Association, SBRI K. K. BHATIA Calcutta SHBI N. I(. GUHA ( Alternate ) J & K Minerals Ltd, Jammu-Tawi SHXI A. M. BUTT SHRI B. L. TRAPPA ( Alternate ) Development Commissioner, Small Scale Industries, SHRI S. K. CHAI~RARORTY New Delhi SRRI L. T. I'. SINHA ( Alternate ) Engineer-in-Chief's Branch, Army Headquarters, SRRI R. P. CHANDA New Delhi SIIRI R. S. .IATHAR ( Alternate ) Geological Survey of India, Calcutta SI~RI G. J. CHANDAK SHRI P. N. MERTA ( Alternate ) Ministry of Railways DIRECTOR ( ARCH ) JOINT DTRIXTOR ( ARCH ) ( Alternate ) Directorate General of Techmcal Development, SH~I S. K. GHOSH New Delhi Smxr M. L. DABRAL ( Alternate ) Central Glass and Ceramic Research Institute DR S. K. GU~A ( CSIR ), Calcutta SJJRI S. I<. SOM ( Alternate ) Cement Research Institute of India, New Delhi DR ( SHRIMATI ) S. LAXMI Indian Institute of Architects, Bombay SHILI J. c. MALR.4N SHRI Y. R. KHIRWA~~AR ( Alternate ) RegiFati Research Laboratory, ( CSIR ) JammuDR ING S. K. MEHTA SRRI R. A. SAYANAN SHRI K. C. METAL Rajasthan Housing Board, Jaipur SHRI B. G. SHAnnrA ( Alternate ) ( Continuedon bags 2 ) @ Copyright 1985 INDIAN STANDARDS INSTITUTION This publication is protected under the Indian Copyright Act ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the nublisher shall be deemed to be an infringement of copyright under the said Act. ( Alternate ) IS:8272-1984 ( Contiwed from page 1 ) Members SRRI S. K. MITTAL Representing Rajasthan State Industrial Development Corporation Ltd, Jaipur SHRI L. K. MAHEBWARI ( Alternate ) Rai Plasters Ltd, Bikaner SHRI D. MOII'~A SHRI S. K. MOHT.~ ( Alternate ) Central Building Research Institute ( CSIR ), DR MOHAN Rar Roorkee DR MAXJEET Srxcrr ( Alternate ) National Buildings New Delhi DR A. V. R. RAO - Organization, SHRI J. SEN GUPTA ( Alternate) Rajasthan State Mines and Minerals Ltd, Bikaner SIiRI M. N. ROY Associated Instrument Manufacturers ( India ) Pvt SHRI A. V. S. R. SaS'rrc~ Ltd, New Delhi SHRI PALVINDER SINGH ( Alternate ) Sri Ram Institute for Industrial Research, Delhi SERI C. P. SHARDA SHRI P. K. MAIR ( Ahnate ) Central Public Works Department, New Delhi SURVEYOR OF WORKS-I ( NDZ ) Projects and Development India Ltd, Dhanabad, SHRI D. M. TRAKRE Sindri SARI S. CHANDRA ( Alternate ) Director General, IS1 ( &-o&o Member ) SRRI G. RAMAN, Director ( Civ Engg ) Secretary SHIH N. c. BaNDYOPADHYAY Deputy Director ( Civ Engg ), IS1 2 IS :8272-1984 Indian Standard SPECIFICATION FOR GYPSUM PLASTER FOR USE IN THE MANUFACTURE OF FIBROUS PLASTER BOARDS ( First Revision 0. FOREWORD ) 0.1 This Indian Standard ( First Revision ) was adopted by the Indian Standards Institution on 28 September 1981, after the draft finalized by the Gypsum Building Materials Sectional Committee had been approved by the Civil Engineering Division Council. 0.2 Gypsum building plasters are used extensil-cly in many countries of the world including Australia, Canada, United Kingdom, United States of America and USSR for general building operations and for the manufacture of preformed gypsum building products which have the specific advantages of lightness and high fire resistance. This specification applies to calcined gypsum plaster for use in the manufacture of fibrous plaster boards which are used as coverings for walls, ceilings and partitions in normally dry environments in buildings. 0.3 This standard w-as first published in 1976. This revision hasbeen taken up with a view to up-dating the standard based on the current knowledge on the subject. In this revision chemical composition and initial setting time of plaster have been modified. 0.4 In the formulation of this standard, due weightage has been given to international co-ordination among the standards and practices prevailing in different countries in addition to relating it to the practices in the field in this country. While formulating this standard assistance has been derived from AS A43-1963 `Gyp sum plaster for building purposes', issued by the Standards Association of Australia. 0.5 For the purpose of deciding whether this standard is complied with, the final 3 a particular requirement of value, observed or calculated, IS : 8272 - 1984 expressing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. `The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. 1. SCOPE 1.1 This standard prescribes sampling and tests for calcined fibrous plaster boards covered 2. CHEMICAL ( CaS04. trioxide the requirements and the methods of gypsum plaster used in manufacturing in IS : 8273-19847. COMPOSITION 2.1 The plaster shall consist essentially of calcium sulphate hemihydrate .&Hz0 ) and shall contain not less than 42 percent sulphur ( SOs ) as determined by the method described in IS : 1288- 1982:. exceed 10 2.2 Impurities insoluble in ammonium acetate shall not percent when tested by the method given in Appendix A. 2.3 The chloride content, expressed as sodium chloride shall not 0.2 percent when tested by the method given in Appendix B. 3. PROPERTIES exceed 3.1 Fineness - The residue retained on 600 more than 1 percent by mass when determined in Appendix C. 3.2 Compressive Strength when determined by the method less than 7.6 N/mmz. 3.3 pm IS Sieve shall not be by the method described The compressive strength of the plaster, described in Appendix D shall not be Setting Time 3.3.1 Initial Setting Time - When determined by the method given in Appendix E, the time of initial set of the plaster, unless otherwise agreed between the purchaser and the manufacturer, shall be between 20 and 35 minutes. *Rules for rounding off numerical values ( revised ). +Specification for fibrous gypsum plaster boards (Jirst revision ), SMethods of test for mineral gypsum ( second ruuision ). 4 IS : 8272 - 1984 4. SAMPLING 4.1 Lot In any consignment, all the packages of the gypsum plaster of the same class and type, and from the same batch of manufacture shall be grouped together to constitute a lot. 4.1.1 Samples shall be selected and tested separately from each lot to determine its conformity or otherwise to the requirements `of the specification. 4.2 The number of packages to be selected shall depend upon the size of the lot and shall co1 1 and 2 of Table I. TABLE 1 NUMBER LOT SIZE for the sample from a lot be in accordance with OF PACKAGES TO BE SELECTED FROM THE LOT SAMPLE SIZE (2) 3 4 5 7 10 (1) up to 100 101 to 150 151 to 300 301 to 500 501 and above 4.2.1 The packages for the sample shall be selected at random from the lot and in order to ensure the randomness of selection the procedures given in IS : 4905-1968* may be adopted. 4.3 Number of Tests 4.3.1 The contents of each package in the sample shall be thoroughly homogenized by mixing separately and sufficient quantity of gypsum plaster shall then be drawn from each package separately for carrying out the tests for setting time, compressive strength and fineness. These samples of gypsum plaster drawn from each package shall be kept separately and tested individually for each of the tests mentioned above. The samples should be placed immediately in clean, dry, air-tight containers for delivering to the laboratory. 4.3.2 The test for the remaining requirements shall be carried out on a composite sample prepared by thoroughly mixing equal quantities of gypsum plaster taken from each of the packages selected in the sample. *Methods for random sampling. IS: 8272 - 1984 as conformmentioned 4.4 Criteria for Conformity - A lot shall be considered ing to the requirements of this standard if the conditions in 4.4.1 and 4.4.2 are satisfied. 4.4.1 For test results on setting time, compressive strength and fineness, the average ( X) and the range ( R ) shall be calculated. From the corresponding average and range value for each characteristics the value of the expressions X f 0*4R shall be calculated. The value of the X - 0*4R as calculated above shall be greater than or equal expression and the value of the expression to the minimum limits specified, X + 0.4R shall be less than or equal to the maximum limit specified. 4.4.2 All the test results for composite sample shall satisfy ments. 5. PACKING AND MARKING remaining requirements tested on the the corresponding specification require- 5.1 The plaster shall be dry and free from lumps and shall be suitably packed in water-tight bags or containers. The following information shall be marked legibly on each package: a) Name of the manufacturer, b) Class of plaster, c) Date of manufacture, d) Net weight. 5.1.1 Mark. Each package may also be marked with the IS1 Certification and NOTE - The use of the IS1 Certification Mark is governed by the provisions of the Indian Standards Institution ( Certification Marks ) Act and the Rules and-ReguThe IS1 Mark on products covered by an Indian Standard lations made thereunder. 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 IS1 control which is devised and supervised by IS1 and operated by the producer. markrd products are also continuously checked by IS1 for conformity to that Details of conditions under which a licence for the standard as a further safeguard. use of the IS1 Certification Mark may be granted to manufacturers or processors, may be obtained from the Indian Standards Institution. 6 IS : 8272 - 1934 APPENDIX ( Clause 2.2 ) A METHOD FOR DETERMINATION OF IMPURITIES INSOLUBLE IN AMMONIUM ACETATE SOLUTION A-l. REAGENTS A-l.1 Ammonium Acetate Solution - Ammonium acetate shall be of the analytical reagent quality. It shall be prepared by dissolving acetate in 2 litres of distilled water conforming to 450 g of ammonium IS : 1070-1977". The solution shall be made distinctly alkaline by adding sufficient quantity of ammonium hydroxide, phenolphthalein being used as indicator. A-1.2 Ammonium ammonium~hydroxide A-I.3 Filter optional. A-2. Aid Hydroxide Wash Solution ( sp gr 0.88 ) to one litre. Analytical grade diatomaceous - Dilute silica. 100 ml of This is PROCEDURE A-2.1 Grind the sample so that it passes completely through 250 pm Take 4 g of dried sample in a beaker and add 350 ml of IS Sieve. ammonium acetate solution. The mixture shall be stirred thoroughly to loosen all solid matter from the bottom of the beaker. Weat the contents to approximately 70°C for 30 minutes, stirring being done frequently. To facilitate filtering, an accurately weighed sample of diatomaceous silica, say 2 g, may be added either before or during heating. By adding ammonia keep the solution alkaline as indicated by phenolphthalein. Using suction, filter the mixture through a tared Gooch crucible and wash the filtrate several times with warm ammonium acetate solution. Then thoroughly wash the filtrate with warm ammonium hydroxide washsolution. Dry the crucible alongwith the contents to constant mass in an air oven at 70°C. Cool in a desiccator and then -weigh. The mass of filter aid, if used, shall be subtracted. A-3. REPORT A-3.1 The ammonium OF TEST RESULTS in difference in mass shall give the impurities insoluble acetate solution and this shall be expressed in percentage. for water for general laboratory use ( second revision ). *Specification 7 D:8272-1984 APPENDIX ( Clause 2.3 ) METHOD B-l. REAGENTS Solution boil and cool. B OF CHLORIDES FOR DETERMINATION B-1.1 Silver Nitrate B-l.2 100 ml distilled water, 0.05 N. nitric acid in Strong Nitric Acid - Dilute 25 ml concentrated B-l.3 Dilute Nitric Acid B-l.4 B-l.5 1 : 99 ( v/v ). Ferric Alum Indicator Thiocyanate - volume. Ammonium NUTE - Approximately 40 percent mass per SoMion quality. - 0.05 N. All reagents shall be of analytical . B-2. PROCEDURE B-2.1 Take 1 to 6 g of sample in a beaker, add 5 to 20 ml of silver nitrate solution ( O-05 N ) depending on the chloride content. The amount of solution added should be 2-3 ml in excess of the amount Cover the beaker with glass and required to precipitate all the chloride. add the strong nitric acid ( 25 : 100 ) carefully. Heat the mixture gently on a hot plate and stir until the plaster is dissolved completely. Add 100 ml of hot water and digest the mixture for about 5 minutes with occasional stirring. Allow the contents to stand for a few minutes. and then filter the contents through a Buchner funnel. B-2.2 Wash the filtrate three times with dilute nitric acid ( 1 : 99 ) and finally with hot water until the residue is free from silver nitrate. Cool the filtrate to room temperature add transfer it to a porcelain dish. Add about 3 to 5 ml of ferric alum indicator and titrate the residual silver nitrate with ammonium thiocyanate solution ( 0.05 N ). During titration stir the solution vigorously with a glass rod until faint reddish-brown colour appears permanently. B-3. REPORT OF TEST RESULTS B-3.1 Calculate the chloride content as sodium chloride. Take one mP 0.05 N silver nitrate as equivalent to OX)02 923 goof sodium chloride. Average of three test results shall be reported as chloride content. 8 IS : 8272 - 1984 APPENDIX ( Clause 3.1 > METHOD FOR DETERMINATION C OF FINENESS C-l. C-l.1 PROCEDURE One hundred gram of the dried sample shall be shifted continuously on a 600 pm IS Sieve for five minutes. Air set lumps in the sample may be broken down with the 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. APPENDIX ( Clause 3.2 ) METHOD FOR DETERMINATION STRENGTH D OF COMPRESSIVE D-l. TEST SPECIMEN D-l.1 A sample of approximately 900 g shall be mixed with sufficient water to form a paste of standard testing consistency as described in Appendix F and shall be cast in five 50-mm cube mould conforming to IS : 10086-1982". The cubes shall be levelled off flush with the top of the moulds. The cubes in their moulds shall be retained over water in a closed vessel at room temperature for 24 hours. The specimens shall then be removed from the moulds and dried at a temperature of not more than 40°C. The specimens shall be weighed at intervals of not less than one hour and drying shall be considered complete when the mass has become constant to within 0.1 percent. D-2. PROCEDURE D-2.1 As soon as the cube specimens have been dried, they shall be cooled at room temperature ~for 15 minutes and their compressive strength determined. The rate of loading on the specimen shall be such that the breaking strength of the cube is reached in not less than 20 s .and not more than 80 s. *Specification for moulds for use in tests of cement and concrete. 9 IS : 8272 - 1984 D-3. REPORT D-3.1 The average compressive strength of the five cube specimens, If the shall be reported as the compressive strength of the sample. strength of one or two cubes vary more than 15 percent from the average of the five, they shall be discarded and the compressive strength shall be reported as the average of the remaining specimens. * , `: % METHOD APPENDIX ( Clause 3.3.1 ) FOR DETERMINATION E OF SETTING TIME -E-l. AP-PARATUS E-1.1 Setting Dish Any open container of uniform internal 10 mm manufactured from non-absorbent corrosion resistant and capable of retaining at least 200 g of mixture. E-1.2 Grooving of a stiff, parallel and manufactured depth of material Instrument - The grooving instrument shall consist sided, square edged blade, 0'5 f 0.05 mm in thickness from corrosion resistant material. instrument 03 2 0.05 is illustrated mm in Fig. 1. E-1.2.1 A suitable FIG. 1 GROOVINGINSTRUMENT 10 IS:8272-1984 E-2. PROCEDURE E-2.1 A mixture of standard testing consistency, as previously determined by the method described in Appendix F, shall be prepared by adding plaster to a known quantity of water and mixing by the method laid down in F-2.2. The mixture shall then be transferred to the setting dish and struck off level to a depth of 10 mm. Incisions 10 mm deep and at least 50 mm long shall be made with the grooving instrument in the mixture at convenient time intervals until the mixture commences to stiffen and then at one minute intervals until the mix stiffening has advanced to such an extent that the incisions, when once made, remain open for their full length and ~depth. E-2.2 Setting Time - The setting time shall be `reckoned from the time at which the plaster is added to the mixing water until the time at which the incision, when once made, remain open for their full length and depth. APPENDIX F 6 Clauses D-l .l and E-2.1 ) METHOD F-l. F-l.1 FOR DETERMINATION OF STANDARD CONSISTENCY TESTING APPARATUS mould shall be a hohow cylinder corrosion resistant material. The as given below: 35 mm ) 50 mm The base plate shall beof plate glass approximately Ring MouId - The ring manufactured from non-absorbent cylinder shall have the dimensions Internal Height diameter ( length F-l.2 Base Plate - 200 mm square. F-2. PROCEDURE be placed in a horizontal position F-2.1 The clean dry base plate shall with the ring mould centered on it. 11 IS :8272 -1984 F-2.2 Approximately 75 g of the plaster shall be shifted in 15 s into a -known volume of water in a mixing bowl and allowed to stand for a further 30 s while the bowl is tapped to dislodge air bubbles. The mixture shall then be spatulated for 60 s with a stiff bladed spatula and transferred to the ring mould, care being taken that the mould is completely filled. Two minutes from the time of starting the mix, the mould shall be lifted vertically and the mixture allowed to slump or spread over the base plate. One minute after the mould is lifted the maximum and minimum diameters of spread of the slumped mixture shall be measured. The procedures shall be repeated until a mix of standard testing consistency in accordance with F-3 is obtained. F-3. STANDARD CONSISTENCY F-3.1 The mixture shall be considered of standard testing consistency when the average of the maximum and minimum diameters of spread, obtained when tested in accordance with F-2 is within the limits ( 100 & 3 mm ). Standard testing consistency shall be expressed as the number of millilitres of water required to be added to 100 g of plaster. 12