1、Designation: C1579 06 (Reapproved 2012)C1579 13Standard 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 ye
2、ar oforiginal 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. Scope Scope*1.1 This test method compares the surface cracking
3、of fiber reinforced concrete panels with the surface cracking of controlconcrete panels subjected to prescribed conditions of restraint and moisture loss that are severe enough to produce cracking beforefinal setting of the concrete.1.2 This test method can be used to compare the plastic shrinkage c
4、racking behavior of different concrete mixtures containingfiber reinforcement.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated wit
5、h its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. (Warning fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin andtissue upon p
6、rolonged exposure.)22. Referenced Documents2.1 ASTM Standards:3C125 Terminology Relating to Concrete and Concrete AggregatesC143/C143M Test Method for Slump of Hydraulic-Cement ConcreteC192/C192M Practice for Making and Curing Concrete Test Specimens in the LaboratoryC403/C403M Test Method for Time
7、of Setting of Concrete Mixtures by Penetration ResistanceC670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsC995 Test Method for Time of Flow of Fiber-Reinforced Concrete Through Inverted Slump Cone (Withdrawn 2009)43. Summary of Test Method3.1 Panel
8、s of control concrete and fiber reinforced concrete are prepared in a prescribed manner and are exposed to controlleddrying conditions after finishing. The drying conditions (See Note 1) are intended to be severe enough to induce plastic shrinkagecracking in test panels made of control concrete. The
9、 evaporation rate from a free water surface is monitored by pans placed nextto the panels in the environmental chamber.NOTE 1An important parameter in this method is the rate of evaporative water loss, which is controlled by the atmospheric conditions surroundingthe test specimens. Since the concret
10、e specimens will not always have the same rate of water evaporation as the pan of water (due to evaporative andbleeding effects), the rate of evaporation of 1.0 kg/m2h from the pan of water represents the minimum evaporation rate that must be attained for this test(1).4 The moisture loss from the co
11、ncrete test panels can also be monitored and reported, however, the rate of evaporation from the free surface of thewater in the pan is the parameter that should be used to quantify the drying environment.3.2 The test is terminated at the time of final setting of the concrete determined in accordanc
12、e with Test Method C403/C403M.At 24 h from initial mixing, the average crack width is determined.1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.42 onFiber-Reinforced Concrete.Current edition
13、approved April 1, 2012April 1, 2013. Published October 2012May 2013. Originally published in 2006. Last previous edition approved in 2012 asC157906(2012). DOI: 10.1520/C1579-06R12.10.1520/C1579-13.2 Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standard
14、s, Vol. 04.02.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 The last approved version of this historical
15、standard is referenced on www.astm.org.4 The boldface numbers in parentheses refer to the list of references at the end of this standard.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous ver
16、sion. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes sec
17、tion appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3 Acracking reduction ratio (CRR) is computed from the average crack width for the fiber-reinforced concrete panels and theaverage crack width f
18、or the control concrete panels.4. Significance and Use4.1 The test method is intended to evaluate the effects of evaporation, settlement, and early autogenous shrinkage on the plasticshrinkage cracking performance of fiber reinforced concrete up to and for some hours beyond the time of final setting
19、 (SeeTerminology C125).4.2 The measured values obtained from this test may be used to compare the performance of concretes with different mixtureproportions, concretes with and without fibers, concretes containing various amounts of different types of fibers, and concretescontaining various amounts
20、and types of admixtures. For meaningful comparisons, the evaporative conditions during test shall besufficient to produce an average crack width of at least 0.5 mm in the control specimens (2, 5) (See Note 2). In addition, theevaporation rate from a free surface of water shall be within 65 % for eac
21、h test.NOTE 2To achieve evaporation rates that result in a crack of at least 0.5 mm in the control specimens, it may be necessary to use an evaporationrate higher than that discussed in Note 1.4.3 This method attempts to control atmospheric variables to quantify the relative performance of a given f
22、resh concretemixture. Since many other variables such as cement fineness, aggregate gradation, aggregate volume, mixing procedures, slump,air content, concrete temperature and surface finish can also influence potential cracking, attention shall be paid to keep these asconsistent as possible from mi
23、xture to mixture.5. Apparatus5.1 Molds:5.1.1 For maximum coarse aggregate size equal to or less than 19 mm, use a mold with a depth of 10065 mm and rectangulardimensions of 355 6 10 mm by 560 6 15 mm (See Fig. 1). The mold can be fabricated from metal, plastic, or plywood.NOTE 3If plywood is used fo
24、r molds, the plywood should have low moisture absorption. The mold should be constructed to be lightweight and stiff.The molds, when properly constructed, should last for approximately 50 uses.5.1.2 This test method is designed for aggregate less than or equal to 19 mm. For coarse aggregate greater
25、than 19 mm, the depthof the mold shall be at least 65 mm plus at least 2 times the maximum coarse aggregate size.5.2 Stress Riser and Internal RestraintsThe internal restraints and stress riser shall be bent from one piece of sheet metal, asillustrated in Fig. 1, or made from a solid piece of steel.
26、 The sheet metal shall have a thickness of 1.2 6 0.05 mm (18 gauge) (SeeFig. 1 and Ref 2). Two 32 6 1 mm high restraints are placed 90 6 2 mm inward from each end of the mold. The central stressriser is 64 6 2 mm high and serves as an initiation point for cracking. This sheet metal stress riser with
27、 internal restraints shallfit at the bottom of the mold.5.2.1 Use form release oil to coat the metal insert and mold sides to reduce bond with concrete. The insert and mold areconsidered to be properly oiled when the entire surface is coated and excess oil has been removed with a clean, dry rag.5.3
28、Variable Speed Fan(s)The fan(s) used shall be capable of 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 an environmental chamber is a method for producing a uniform airflowover the panel surface (See Fig. 2). A clea
29、r cover over the panels will aid in obtaining uniform airflow and allow for observationof cracking. Another method of producing uniform airflow is to use a specifically designed environmental chamber as shown inFig. 3. A commercially available heater, humidifier, and dehumidifier can be used to main
30、tain the specified environmentalcondition. This test is conducted using either apparatus shown in Fig. 2 or Fig. 3 by exposing the panels to an evaporation rateof at least 1.0 kg/m2h (See Note 1). For the standard test, the temperature must be maintained at 36 6 3 C, the relative humiditymust be 30
31、6 10 %, and the wind velocity must be sufficient to maintain the minimum evaporation rate during the test.NOTE 4Before casting the concrete panels, atmospheric variables in the environmental facility should be checked to determine that the necessaryevaporative conditions can be achieved. A wind velo
32、city of 4.7 m/s should be sufficient to achieve the minimum specified evaporation rate, but a higherwind velocity may be needed to obtain sufficient average crack width in some control panels.5.5 SensorsUse temperature, humidity, and wind velocity sensors to measure ambient air and concrete surface
33、temperatureto the nearest 0.5 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 consolidate the test panel that meets minimum frequency requirements asstated in Practice C192/C192M for an external vibrator is suitable.5.7 Su
34、rface Finishing EquipmentAn angle iron screed shall be used for the concrete after vibration. A magnesium, steel, orwood trowel shall be used for finishing the surface of the specimen after screeding.5.8 Monitoring PanA pan suitable for exposing water to the air stream for each concrete test panel i
35、s required. The sides ofthe pan shall be vertical. The pan shall be of sufficient size to expose at least 0.160.01 m2 of water to the air stream. The exposedlip of the pan shall not extend more than 5 mm above the water level at the start of the test.NOTE 5The test panels and monitoring pans can be
36、placed in an environmental chamber designed for this test method (See Fig. 3) or the pans canC1579 132be placed downstream from panels in a fan box (See Fig. 2).5.9 ScaleIf the rate of moisture loss from test panels is required by the specifier of tests, weigh test panels with a scale havinga capaci
37、ty of at least 100 kg and accurate to within 0.1 % of the test load. Weigh the evaporation rate monitoring pans with abalance or scale having a capacity of at least 3 kg and accurate to within 5 g.5.10 Crack Measurement ToolOptical hand-held microscope, crack comparator, or image analysis system can
38、 be used. Themeasurement tool should be capable of measuring crack width to at least the nearest 0.05 mm. If an automated image analysissystem is used, it should be demonstrated to provide an accurate measurement. To demonstrate the accuracy of the measurement,the system shall be used to measure a 0
39、.5 mm notch that is machined into a piece of steel and the reported notch width shall bewithin 60.05 mm of the machined width.6. Sampling, Test Specimens, and Test Units6.1 Test PanelsCast test panels in accordance with the applicable provisions of Practice C192/C192M, using the same sourceof materi
40、als, preparation, mixing and finishing procedures.6.2 Test UnitA test unit is comprised of at least two control specimens and at least two fiber reinforced concrete specimenswith the same mixture proportions. A group of two control specimens has to be tested each time in order to determine the plast
41、icshrinkage crack reduction of fiber reinforced concrete.FIG. 1 Specimen and Stress Riser Geometry (4, 5)C1579 133FIG. 2 Example of Fan Box to Maintain Environmental Conditions (2) (Not to Scale)C1579 1347. Procedure7.1 Determine the slump of each mixture in accordance with Test Method C143/C143M. I
42、f the slump is too low for a concretemixture containing fibers, use the time of flow through an inverted slump cone to measure workability in accordance with TestMethod C995.7.2 Fabricate specimens for setting time determination in accordance with Test Method C403/C403M. If fiber reinforcedconcrete
43、cannot be wet sieved readily, use the control concrete specimen to measure time of final setting of both the control andthe fiber-reinforced mixtures. Place the time of setting specimens in the air stream so that they are exposed to the sameenvironmental conditions as the plastic shrinkage panels.7.
44、3 Fill the panel molds using one layer. Consolidate the concrete with external vibration until the concrete is approximatelylevel with the top of the mold. Screed each specimen perpendicular to the stress riser three times.7.4 After screeding, trowel specimens using a predetermined number of passes.
45、 If moisture loss from the panel is to bedetermined, remove any waste concrete adhering to the outside of the mold and weigh each panel while in the mold.FIG. 3 Example of Chamber to Maintain Environmental Conditions (4)C1579 1357.5 Place a fiber reinforced concrete mixture panel and control mixture
46、 panel in the environmental chamber downstream fromthe fan(s) (See arrangements in Figs. 2 and 3).7.6 Turn on the fan(s), which have been preset to achieve the air speed to obtain the required evaporative conditions (See Note4). The evaluation of cracking commences at this time.7.7 At the start of t
47、he test and at 30-min intervals, record air temperature, relative humidity, and air flow speed at a location 1006 5 mm above each panel surface. If required by the specifier of tests, record the time at which cracking is first observed for eachpanel surface. Perform penetration tests at regular time
48、 intervals according to Test Method C403/C403M. Continue recording theenvironmental variables until the time of final setting.7.8 The evaporation rate is determined by initially weighing the full monitoring pans at the start of the test and at 30-minintervals thereafter (3). Record the mass loss to
49、the nearest 5 g at each weighing. To determine the evaporation rate during eachtime interval, divide the mass loss between successive weighings by the surface area of the water in the weighing pan and the timeinterval between successive weighings (See Note 6). The test is not valid if the average evaporation rate is less than 1.0 kg/m2h.NOTE 6Adjustments to wind velocity should be made if necessary to maintain the evaporation rate at the required level. It is suggested that themonitoring pans be placed on scales in the air stream for continuous monitori
