ASTM C 109 Compressive Strength of Hydraulic Cement Mortars(3)

held in position by suitable means.

6.Materials

6.1Graded Standard Sand:

6.1.1The sand(Note4)used for making test specimens shall be natural silica sand conforming to the requirements for graded standard sand in Specification C778.

N OTE4—Segregation of Graded Sand—The graded standard sand should be handled in such a manner as to prevent segregation,since variations in the grading of the sand cause variations in the consistency of the mortar.In emptying bins or sacks,care should be exercised to prevent the formation of mounds of sand or craters in the sand,down the slopes of which the coarser particles will roll.Bins should be of sufficient size to permit these precautions.Devices for drawing the sand from bins by gravity should not be used.

7.Temperature and Humidity

7.1Temperature—The temperature of the air in the vicinity of the mixing slab,the dry materials,molds,base plates,and mixing bowl,shall be maintained between73.565.5°F or [23.063.0°C].The temperature of the mixing water,moist closet or moist room,and water in the storage tank shall be set at73.563.5°F or[2362°C].

7.2Humidity—The relative humidity of the laboratory shall be not less than50%.The moist closet or moist room shall conform to the requirements of Specification C511.

8.Test Specimens

8.1Make two or three specimens from a batch of mortar for each period of test or test age.

9.Preparation of Specimen Molds

9.1Apply a thin coating of release agent to the interior faces of the mold and non-absorptive base plates.Apply oils and greases using an impregnated cloth or other suitable means. Wipe the mold faces and the base plate with a cloth as necessary to remove any excess release agent and to achieve a thin,even coating on the interior surfaces.When using an aerosol lubricant,spray the release agent directly onto the mold faces and base plate from a distance of6to8in.or[150to200 mm]to achieve complete coverage.After spraying,wipe the surface with a cloth as necessary to remove any excess aerosol lubricant.The residue coating should be just sufficient to allow a distinctfinger print to remain following lightfinger pressure (Note5).

9.2Seal the surfaces where the halves of the mold join by applying a coating of light cup grease such as petrolatum.The amount should be sufficient to extrude slightly when the two halves are tightened together.Remove any excess grease with

a cloth.

9.3After placing the mold on its base plate(and attaching, if clamp-type)carefully remove with a dry cloth any excess oil or grease from the surface of the mold and the base plate to which watertight sealant is to be applied.As a sealant,use paraffin,microcrystalline wax,or a mixture of three parts paraffin tofive parts rosin by mass.Liquify the sealant by heating between230and248°F or[110and120°C].Effect a watertight seal by applying the liquefied sealant at the outside contact lines between the mold and its base plate.

N OTE5—Because aerosol lubricants evaporate,molds should be checked for a sufficient coating of lubricant immediately prior to use.

If an extended period of time has elapsed since treatment,retreatment may be necessary.

N OTE6—Watertight Molds—The mixture of paraffin and rosin specified for sealing the joints between molds and base plates may be found difficult to remove when molds are being e of straight paraffin is permissible if a watertight joint is secured,but due to the low strength of paraffin it should be used only when the mold is not held to the base plate by the paraffin alone.A watertight joint may be secured with paraffin alone by slightly warming the mold and base plate before brushing the joint. Molds so treated should be allowed to return to the specified temperature before use.

10.Procedure

10.1Composition of Mortars:

10.1.1The proportions of materials for the standard mortar shall be one part of cement to2.75parts of graded standard sand by e a water-cement ratio of0.485for all portland cements and0.460for all air-entraining portland cements.The amount of mixing water for other than portland and air-entraining portland cements shall be such as to produce aflow of11065as determined in accordance with10.3and shall be expressed as weight percent of cement.

10.1.2The quantities of materials to be mixed at one time in the batch of mortar for making six and nine test specimens shall be as follows:

Number of Specimens

69

Cement,g Sand,g Water,mL

500

1375

740

2035

Portland(0.485)

Air-entraining portland(0.460)242

230

359

340

Other(toflow of11065)...... 10.2Preparation of Mortar:

10.2.1Mechanically mix in accordance with the procedure given in Practice C305.

10.3Determination of Flow:

10.3.1Determineflow in accordance with procedure given in Test Method C1437.

10.3.2For portland and air-entraining portland cements, merely record theflow.

10.3.3In the case of cements other than portland or air-entraining portland cements,make trial mortars with varying percentages of water until the specifiedflow is obtained.Make each trial with fresh mortar.

10.4Molding Test Specimens:

10.4.1Immediately following completion of theflow test, return the mortar from theflow table to the mixing bowl. Quickly scrape the bowl sides and transfer into the batch the mortar that may have collected on the side of the bowl and then remix the entire batch15s at medium speed.Upon completion of mixing,the mixing paddle shall be shaken to remove excess mortar into the mixing bowl.

10.4.2When a duplicate batch is to be made immediately for additional specimens,theflow test may be omitted and the mortar allowed to stand in the mixing bowl90s without covering.During the last15s of this interval,quickly scrape the bowl sides and tran …… 此处隐藏：3758字，全部文档内容请下载后查看。喜欢就下载吧 ……