1、Designation: C1579 06 (Reapproved 2012)Standard Test Method forEvaluating Plastic Shrinkage Cracking of Restrained FiberReinforced Concrete (Using a Steel Form Insert)1This standard is issued under the fixed designation C1579; the number immediately following the designation indicates the year ofori
2、ginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method compares the surface cracking of fiberreinfor
3、ced concrete panels with the surface cracking of controlconcrete panels subjected to prescribed conditions of restraintand moisture loss that are severe enough to produce crackingbefore final setting of the concrete.1.2 This test method can be used to compare the plasticshrinkage cracking behavior o
4、f different concrete mixturescontaining fiber reinforcement.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is ther
5、esponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (Warning freshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.)
6、22. Referenced Documents2.1 ASTM Standards:3C125 Terminology Relating to Concrete and Concrete Ag-gregatesC143/C143M Test Method for Slump of Hydraulic-CementConcreteC192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC403/C403M Test Method for Time of Setting of Concre
7、teMixtures by Penetration ResistanceC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC995 Test Method for Time of Flow of Fiber-ReinforcedConcrete Through Inverted Slump Cone (Withdrawn2009)43. Summary of Test Method3.1 Panels of control concrete an
8、d fiber reinforced concreteare prepared in a prescribed manner and are exposed tocontrolled drying conditions after finishing. The drying condi-tions (See Note 1) are intended to be severe enough to induceplastic shrinkage cracking in test panels made of controlconcrete. The evaporation rate from a
9、free water surface ismonitored by pans placed next to the panels in the environ-mental chamber.NOTE 1An important parameter in this method is the rate ofevaporative water loss, which is controlled by the atmospheric conditionssurrounding the test specimens. Since the concrete specimens will notalway
10、s have the same rate of water evaporation as the pan of water (dueto evaporative and bleeding effects), the rate of evaporation of 1.0 kg/m2hfrom the pan of water represents the minimum evaporation rate that mustbe attained for this test (1).5The moisture loss from the concrete testpanels can also b
11、e monitored and reported, however, the rate of evapora-tion from the free surface of the water in the pan is the parameter thatshould be used to quantify the drying environment.3.2 The test is terminated at the time of final setting of theconcrete determined in accordance with Test Method C403/C403M
12、. At 24 h from initial mixing, the average crack widthis determined.3.3 A cracking reduction ratio (CRR) is computed from theaverage crack width for the fiber-reinforced concrete panelsand the average crack width for the control concrete panels.4. Significance and Use4.1 The test method is intended
13、to evaluate the effects ofevaporation, settlement, and early autogenous shrinkage on theplastic shrinkage cracking performance of fiber reinforcedconcrete up to and for some hours beyond the time of finalsetting (See Terminology C125).1This test method is under the jurisdiction of ASTM Committee C09
14、 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.42 on Fiber-Reinforced Concrete.Current edition approved April 1, 2012. Published October 2012. DOI: 10.1520/C1579-06R12.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of AST
15、M Standards, Vol. 04.02.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this hi
16、storical standard is referenced onwww.astm.org.5The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The measured values obtained from this
17、test may beused to compare the performance of concretes with differentmixture proportions, concretes with and without fibers, con-cretes containing various amounts of different types of fibers,and concretes containing various amounts and types of admix-tures. For meaningful comparisons, the evaporat
18、ive conditionsduring test shall be sufficient to produce an average crack widthof at least 0.5 mm in the control specimens (2, 5) (See Note 2).In addition, the evaporation rate from a free surface of watershall be within 6 5 % for each test.NOTE 2To achieve evaporation rates that result in a crack o
19、f at least0.5 mm in the control specimens, it may be necessary to use anevaporation rate higher than that discussed in Note 1.4.3 This method attempts to control atmospheric variablesto quantify the relative performance of a given fresh concretemixture. Since many other variables such as cement fine
20、ness,aggregate gradation, aggregate volume, mixing procedures,slump, air content, concrete temperature and surface finish canalso influence potential cracking, attention shall be paid to keepthese as consistent as possible from mixture to mixture.5. Apparatus5.1 Molds:5.1.1 For maximum coarse aggreg
21、ate size equal to or lessthan 19 mm, use a mold with a depth of 100 6 5mmandrectangular dimensions of 355 6 10 mm by 560 6 15 mm (SeeFig. 1). The mold can be fabricated from metal, plastic, orplywood.NOTE 3If plywood is used for molds, the plywood should have lowmoisture absorption. The mold should
22、be constructed to be lightweightand stiff. The molds, when properly constructed, should last for approxi-mately 50 uses.5.1.2 This test method is designed for aggregate less than orequal to 19 mm. For coarse aggregate greater than 19 mm, thedepth of the mold shall be at least 65 mm plus at least 2 t
23、imesthe maximum coarse aggregate size.FIG. 1 Specimen and Stress Riser Geometry (4, 5)C1579 06 (2012)25.2 Stress Riser and Internal RestraintsThe internal re-straints and stress riser shall be bent from one piece of sheetmetal, as illustrated in Fig. 1, or made from a solid piece ofsteel. The sheet
24、metal shall have a thickness of 1.2 6 0.05 mm(18 gauge) (See Fig. 1 and Ref 2). Two 32 6 1 mm highrestraints are placed 90 6 2 mm inward from each end of themold. The central stress riser is 64 6 2 mm high and serves asan initiation point for cracking. This sheet metal stress riserwith internal rest
25、raints shall fit at the bottom of the mold.5.2.1 Use form release oil to coat the metal insert and moldsides to reduce bond with concrete. The insert and mold areconsidered to be properly oiled when the entire surface iscoated and excess oil has been removed with a clean, dry rag.5.3 Variable Speed
26、Fan(s)The fan(s) used shall be capableof achieving a wind speed of more than 4.7 m/s over the entiretest panel surface area.5.4 Environmental ChamberThe use of a fan box in anenvironmental chamber is a method for producing a uniformairflow over the panel surface (See Fig. 2). A clear cover overthe p
27、anels will aid in obtaining uniform airflow and allow forobservation of cracking.Another method of producing uniformairflow is to use a specifically designed environmental chamberas shown in Fig. 3. A commercially available heater,humidifier, and dehumidifier can be used to maintain thespecified env
28、ironmental condition. This test is conducted usingeither apparatus shown in Fig. 2 or Fig. 3 by exposing thepanels to an evaporation rate of at least 1.0 kg/m2h (See Note1). For the standard test, the temperature must be maintained at36 6 3 C, the relative humidity must be 30 6 10 %, and thewind vel
29、ocity must be sufficient to maintain the minimumevaporation rate during the test.NOTE 4Before casting the concrete panels, atmospheric variables inthe environmental facility should be checked to determine that thenecessary evaporative conditions can be achieved. A wind velocity of 4.7m/s should be s
30、ufficient to achieve the minimum specified evaporationrate, but a higher wind velocity may be needed to obtain sufficient averagecrack width in some control panels.5.5 SensorsUse temperature, humidity, and wind velocitysensors to measure ambient air and concrete surface tempera-ture to the nearest 0
31、.5 C, relative humidity to the nearest 1 %,and air speed to the nearest 0.1 m/s.5.6 Vibrating PlatformAny device that can fully consoli-date the test panel that meets minimum frequency requirementsas stated in Practice C192/C192M for an external vibrator issuitable.5.7 Surface Finishing EquipmentAn
32、angle iron screedshall be used for the concrete after vibration. A magnesium,steel, or wood trowel shall be used for finishing the surface ofthe specimen after screeding.5.8 Monitoring PanA pan suitable for exposing water tothe air stream for each concrete test panel is required. The sidesof the pan
33、 shall be vertical. The pan shall be of sufficient sizeto expose at least 0.1 6 0.01 m2of water to the air stream. Theexposed lip of the pan shall not extend more than 5 mm abovethe water level at the start of the test.NOTE 5The test panels and monitoring pans can be placed in anenvironmental chambe
34、r designed for this test method (See Fig. 3) or thepans can be placed downstream from panels in a fan box (See Fig. 2).5.9 ScaleIf the rate of moisture loss from test panels isrequired by the specifier of tests, weigh test panels with a scalehaving a capacity of at least 100 kg and accurate to withi
35、n0.1 % of the test load. Weigh the evaporation rate monitoringpans with a balance or scale having a capacity of at least 3 kgand accurate to within 5 g.5.10 Crack Measurement ToolOptical hand-heldmicroscope, crack comparator, or image analysis system can beused. The measurement tool should be capabl
36、e of measuringcrack width to at least the nearest 0.05 mm. If an automatedimage analysis system is used, it should be demonstrated toprovide an accurate measurement. To demonstrate the accuracyof the measurement, the system shall be used to measure a 0.5mm notch that is machined into a piece of stee
37、l and thereported notch width shall be within 6 0.05 mm of themachined width.6. Sampling, Test Specimens, and Test Units6.1 Test PanelsCast test panels in accordance with theapplicable provisions of Practice C192/C192M, using the samesource of materials, preparation, mixing and finishing proce-dures
38、.6.2 Test UnitA test unit is comprised of at least twocontrol specimens and at least two fiber reinforced concretespecimens with the same mixture proportions. A group of twocontrol specimens has to be tested each time in order todetermine the plastic shrinkage crack reduction of fiber rein-forced co
39、ncrete.7. Procedure7.1 Determine the slump of each mixture in accordance withTest Method C143/C143M. If the slump is too low for aconcrete mixture containing fibers, use the time of flowthrough an inverted slump cone to measure workability inaccordance with Test Method C995.7.2 Fabricate specimens f
40、or setting time determination inaccordance with Test Method C403/C403M. If fiber reinforcedconcrete cannot be wet sieved readily, use the control concretespecimen to measure time of final setting of both the controland the fiber-reinforced mixtures. Place the time of settingspecimens in the air stre
41、am so that they are exposed to the sameenvironmental conditions as the plastic shrinkage panels.7.3 Fill the panel molds using one layer. Consolidate theconcrete with external vibration until the concrete is approxi-mately level with the top of the mold. Screed each specimenperpendicular to the stre
42、ss riser three times.7.4 After screeding, trowel specimens using a predeter-mined number of passes. If moisture loss from the panel is tobe determined, remove any waste concrete adhering to theoutside of the mold and weigh each panel while in the mold.7.5 Place a fiber reinforced concrete mixture pa
43、nel andcontrol mixture panel in the environmental chamber down-stream from the fan(s) (See arrangements in Figs. 2 and 3).7.6 Turn on the fan(s), which have been preset to achievethe air speed to obtain the required evaporative conditions (SeeNote 4). The evaluation of cracking commences at this tim
44、e.C1579 06 (2012)3FIG. 2 Example of Fan Box to Maintain Environmental Conditions (2) (Not to Scale)C1579 06 (2012)47.7 At the start of the test and at 30-min intervals, record airtemperature, relative humidity, and air flow speed at a location100 6 5 mm above each panel surface. If required by thesp
45、ecifier of tests, record the time at which cracking is firstobserved for each panel surface. Perform penetration tests atregular time intervals according to Test Method C403/C403M.Continue recording the environmental variables until the timeof final setting.7.8 The evaporation rate is determined by
46、initially weighingthe full monitoring pans at the start of the test and at 30-minintervals thereafter (3). Record the mass loss to the nearest 5 gat each weighing. To determine the evaporation rate duringeach time interval, divide the mass loss between successiveweighings by the surface area of the
47、water in the weighing panand the time interval between successive weighings (See Note6). The test is not valid if the average evaporation rate is lessthan 1.0 kg/m2h.NOTE 6Adjustments to wind velocity should be made if necessary tomaintain the evaporation rate at the required level. It is suggested
48、that themonitoring pans be placed on scales in the air stream for continuousmonitoring without periodic removal during testing. If this is not possible,the monitoring pan should be removed from the air stream, weighed, andreturned to the air stream within 15 seconds.7.9 After final setting occurs (u
49、se the later of the measuredtime of setting in the two specimens), record the atmosphericvariables, stop the fans, record the time, and determine the totalwater loss from the monitoring pans. If panel moisture loss isFIG. 3 Example of Chamber to Maintain Environmental Conditions (4)C1579 06 (2012)5to be determined, weigh the test panels in their molds. Store thepanels in the laboratory at 23 6 2 C and under plastic sheetsto minimize evaporation until time of crack width measure-ment.8. Quantification of Cracking8.1 Quantify the amount of cracking by measu
