1、Standard Method of Test for Water Retention by Liquid Membrane-Forming Curing Compounds for Concrete AASHTO Designation: T 155-13 ASTM Designation: C156-11 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b T 155-1
2、 AASHTO Standard Method of Test for Water Retention by Liquid Membrane-Forming Curing Compounds for Concrete AASHTO Designation: T 155-13 ASTM Designation: C156-11 1. SCOPE 1.1. This test method covers laboratory determination of the efficiency of liquid membrane-forming compounds for curing concret
3、e, as measured by their ability to reduce moisture loss from mortar specimens during the early hardening period. 1.2. The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information purposes only. 1.3. This standard may involve hazardous
4、 materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations pr
5、ior to use. WarningFresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 85, Portland Cement T 71, Effect of Organic Impurities in Fine Aggregate on Strength of Mortar 2.2. ASTM Stan
6、dards: C305, Standard Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency C778, Standard Specification for Standard Sand D1475, Standard Test Method For Density of Liquid Coatings, Inks, and Related Products D1644, Standard Test Methods for Nonvolatile Conten
7、t of Varnishes D1653, Standard Test Methods for Water Vapor Transmission of Organic Coating Films E178, Standard Practice for Dealing with Outlying Observations 3. SIGNIFICANCE AND USE 3.1. The moisture retaining ability of a product as determined by this test method is used to assess the suitabilit
8、y of materials for contributing to an appropriate curing environment for concrete. The laboratory test method is used both in formulating and in specifying or qualifying curing products. This test method gives the user a measure of the ability of tested curing materials to impede the escape of moist
9、ure from a hydraulic cement mortar. Since it is desirable to retain moisture in fresh 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 155-2 AASHTO concrete to promote the hydration process, failu
10、re of the product to minimize the escape of moisture may lead to loss of strength, cracking, shrinkage, or low abrasion resistance of the hardened concrete, or a combination thereof. 3.2. Many factors affect the laboratory test results. Test results obtained may be highly variable as indicated by th
11、e precision statement. Critical factors include the precision of the control of the temperature, humidity, and air circulation in the curing cabinet; preparation and sealing of the mortar specimens; the age and surface condition of the mortar specimen when the curing product is applied; and the unif
12、ormity and quantity of application of the curing membrane. 4. APPARATUS 4.1. Mechanical Mortar Mixeras described in ASTM C305, or a larger size mixer operating on the same principle. 4.2. MoldsMolds shall be made of metal, glass, hard rubber, or plastic and shall be watertight and rigidly constructe
13、d to prevent distortion during molding of the specimens or handling the mold containing fresh mortar. They shall have a minimum surface area of 12 000 mm2(18.6 in.2) and a minimum depth of 19 mm (3/4in.). The top surface shall be round, square, or rectangular with length not more than twice the widt
14、h. The top of the mold shall have a rim to provide a firm level surface to support the wood float and to facilitate the grooving and sealing steps of the procedure. The rim shall be parallel with the bottom surface of the mold. Note 1Take care to avoid use of an excessive amount of oil, grease, or m
15、old release compound on molds, particularly along the top rim where sealing compound will be applied. Use of masking tape on the top rim during application of release compound to prevent contamination has been found to be expedient. 4.3. Glovesof rubber or plastic to be worn while molding the specim
16、ens. 4.4. Tamperof a nonabsorptive, nonabrasive material such as medium-hard rubber or seasoned oak rendered nonabsorptive by immersion for 15 min in paraffin at approximately 200C. The tamper shall be rectangular with a 25-by-50-mm (1-by-2-in.) cross section and it shall be a convenient length (150
17、 to 300 mm (6 to 12 in.). 4.5. Wood Floatapproximately 75 by 280 by 20 mm thick (3 by 11 by 3/4in.). Note 2A commercial wood float equipped with a substantial handle can be readily reduced to these dimensions. The float shall be resurfaced or replaced when there is noticeable wear to the floating su
18、rface. 4.6. Brushmedium-soft bristle 50-mm (2-in.) paintbrush to brush the surface of the specimens prior to sealing. 4.7. Curing Cabinetmaintained at a temperature of 37.8 1.1C (100 2F) and a relative humidity of 32 2 percent. The curing cabinet shall be of a design that allows movement of conditio
19、ned air such that the solvent from the curing compound will be readily evaporated and eliminated from the system. Air circulation shall be equivalent for all specimens. 4.8. Balancehaving a capacity to determine the mass of a filled specimen mold to the nearest 0.1 g or less. 4.9. ApplicatorFor spra
20、y application, any apparatus that can be used to apply the curing compound uniformly and with minimum overspray is acceptable. For brush or roller application, use the equipment recommended by the curing compound manufacturer. 2015 by the American Association of State Highway and Transportation Offi
21、cials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 155-3 AASHTO 4.10. SpoonA stainless steel serving spoon having a bowl 75 to 100 mm (3 to 4 in.) long and 50 to 75 mm (2 to 3 in.) wide for transferring the mortar from the mixing bowl to the mold. 5. MATERIALS 5.1. Portl
22、and cement conforming to the requirements for Type 1 of M 85. 5.2. Graded standard sand conforming to the requirements of ASTM C778. 5.3. Sealing compound that will not be affected by the curing material and that effectively seals against moisture loss between the boundary of the specimen and the ed
23、ge of the mold. Note 3Issue embedding wax, readily available from scientific supply houses, is a convenient and reliable sealant. 6. CONDITIONING 6.1. The temperature of the room and of all materials when used in this test shall be 23 2C (73 4F) unless otherwise specified, and the room humidity shal
24、l be 50 10 percent. 7. NUMBER OF SPECIMENS 7.1. A set of three or more test specimens shall be made in order to constitute a test of a given curing material. Note 4When more than one set of specimens is to be prepared, each set should be handled as a group throughout the preparation to make the elap
25、sed time between molding and application of the curing product as uniform as possible. This may require mixing the mortar for each set separately. 7.2. For determining the quantity of curing compound to be applied (MA), calculate the total top surface area of the specimen, including the seal and the
26、 rim of the mold, in square millimeters using appropriate geometric formulae. Note 5The area (A) used in calculating the mass loss per unit area (L) is calculated in Section 14.3 from the surface dimensions measured inside the seal of the specimen. 8. PROPORTIONING AND MIXING MORTAR 8.1. Proportioni
27、ngDetermine the sand content of the mortar by adding dry sand to a cement paste having a water-cement ratio of 0.40 by weight to produce a flow of 35 5 in 10 drops. Determine the flow in accordance with T 71. Discard the mix used to determine the proportion of sand to cement. Note 6This mix is disca
28、rded because it is thought that the age and the mixing history of the mortar where the curing compound is applied, measured from the first addition of water, affects the final results and must be controlled. 8.2. MixingCombine the components of the mortar in a mortar-mixing machine to produce a homo
29、geneous mortar not more than 6 min from the time the water and the cement are combined. Note 7A generally effective sequence is to add the cement to all of the water in the mixing bowl and allow it to stand for 30 s. Then, mix at low speed for 30 s and, without stopping the mixer, add the sand withi
30、n 30 s and continue mixing for 1 min. Stop the mixer for 1 min. During the first 15 s, scrape down the sides of the bowl. Finish by mixing for an additional 1 min and promptly begin molding the specimens. 2015 by the American Association of State Highway and Transportation Officials.All rights reser
31、ved. Duplication is a violation of applicable law.TS-3b T 155-4 AASHTO 9. PREPARING SPECIMENS 9.1. Thoroughly clean the molds before each use. Use of a mold release is acceptable provided that care is taken to avoid its application to the top rim of the mold to prevent interference with sealing of t
32、he edge. 9.2. Half fill the mold and spread the mortar with the back of the spoon to create a layer of approximately uniform thickness. Tamp over the entire surface with one stroke of the 25-by-50-mm (1-by-2-in.) face of the tamper per 1000 mm2of surface area rounded to the nearest integer. Place a
33、second layer of mortar, sufficient in amount to slightly overfill the mold, and tamp in a similar manner. Using the 25-mm- (1-in.) wide by 150- to 300-mm- (6 to 12-in.) long edge of the tamper, fill the indentations made by the tamping, and level the surface by pressing down firmly with a series of
34、contacts across the entire surface. Strike off the specimen level with the top of the mold using a wood float with one pass only, in the direction of the long axis of the specimen for rectangular molds, using a sawing motion of the float. Keep the 75-mm (3-in.) face of the float firmly in contact wi
35、th the mortar and edges of the mold so the float creates a uniformly dense surface free of voids and cracks. 9.3. Immediately after molding, wipe the outside surfaces of the molds clean and then place the specimens in the curing cabinet maintained at the conditions specified in Section 4.7. The spec
36、imens shall be level and not subject to vibration. The spacing between the individual specimens and between the specimens and the side walls of the cabinet shall be between 50 and 175 mm (2 to 7 in.). Within these limits, the spacing shall be the same for all specimens. Use dummy specimens to fill a
37、ny empty spaces in the cabinet. 10. SURFACE PREPARATION AND EDGE SEALING 10.1. Remove the specimens from the cabinet immediately upon disappearance of the surface water and lightly brush the surface using sufficient force to remove the laitance and glaze but not so as to scarify the mortar surface.
38、If surface water appears upon brushing, return the specimen to the cabinet. When the water brought to the surface by the brushing operation disappears, immediately remove the specimen and then brush again. The mortar shall be free of surface water but shall not be dry below the surface. The proper s
39、urface condition will be attained when brushing does not bring free water to the surface or does not produce smearing when rubbing an area with the fingertip. Note 8The exposure time in the cabinet and the initial moisture loss that will result in the proper surface condition is characteristic of th
40、e curing cabinet used and other testing conditions related to the laboratory performing the test. Uniformity of test surface conditions may be maintained by setting an expected exposure time or initial moisture loss. When any test condition is changed (sand, cement, or the like), a new exposure time
41、 or initial moisture loss, or both, shall be determined. 10.2. Form a V-shaped groove approximately 3 mm (1/8in.) deep and not more than 3 mm (1/8in.) wide between the edge of the mortar specimen and the mold. Fill the groove with the sealing compound. The sealing compound shall not extend more than
42、 6 mm (1/4in.) from the edge of the mold onto the surface of the specimen. Note 9To cut out the groove for sealing, the tip of a pointed trowel, a pointed spatula, a pointed triangular can opener, or a “hawksbill point” ground on the end of a spatula or knife blade have all been reported to be effec
43、tive. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 155-5 AASHTO 11. APPLICATION OF CURING MATERIAL 11.1. Liquid Membrane-Forming Compounds: 11.1.1. Determine the density of the curing compound
44、, Dm, in accordance with ASTM D1475. 11.1.2. Calculate the mass of the curing compound to be applied (MA) to the nearest 0.1 g based on the specified application rate, the total surface area calculated per Section 7.2, and the density of the curing compound, Dm. If no rate is specified, apply the cu
45、ring compound at the rate of 0.2 L/m2(gal/200 ft2). The method of application shall be in accordance with the manufacturers recommendations. 11.1.3. Immediately after sealing, weigh the specimen to the nearest 0.1 g (M1), then uniformly apply the curing compound at the specified rate of application.
46、 Application shall be made expeditiously to only one specimen at a time. Note 10It is desirable to use a spray booth or a laboratory hood to control overspray and solvent fumes, especially for curing compounds that are sprayed. However, the velocity of air movement in the vicinity of the specimen mu
47、st be kept at a minimum so as to prevent, as much as possible, significant loss of volatiles during spraying and before the final weighing. Spraying shall be accomplished with the minimum pressure and flow rate of air with which an acceptable spray pattern can be attained. 11.1.4. Determine the prop
48、er coverage by comparing the initial mass of the specimen (M1), before applying the curing compound to the mass after coating. The final mass shall equal the initial mass of the specimen plus the predetermined mass of the curing compound to be applied. This will necessitate frequent weighing of the
49、specimen during application as full coverage is approached. In the case of brush application, proper coverage may be determined by weighing the container, brush, and curing compound before and after application of the compound to the specimen. Total time for application shall not exceed 2 min. Weigh to the nearest 0.1 g (M2). If the final amount of curing compound applied differs from the calculated amount for the specified coverage by more than 10 percent, the specimen shall be discarded. Note 11In previous versions of this
