Concrete slump testFrom Wikipedia, the free encyclopedia

A tester performing a concrete slump test.

The concrete slump test is an empirical test that measures the workability of fresh concrete.

More specifically, it measures the consistency of the concrete in that specific batch. This test is performed to

check the consistency of freshly made concrete. Consistency is a term very closely related to workability. It is a

term which describes the state of fresh concrete. It refers to the ease with which the concrete flows. It is used

to indicate the degree of wetness. Workability of concrete is mainly affected by consistency i.e. wetter mixes

will be more workable than drier mixes, but concrete of the same consistency may vary in workability. It is also

used to determine consistency between individual batches.

The test is popular due to the simplicity of apparatus used and simple procedure. Unfortunately, the simplicity

of the test often allows a wide variability in the manner that the test is performed. The slump test is used to

ensure uniformity for different batches of similar concrete under field conditions,[1]:127,128and to ascertain the

effects of plasticizers on their introduction.[1]:134 In India this test is conducted as per IS specification.

Apparatus

Metal mould, in the shape of the frustum of a cone, open at both ends, and provided with the handle, top

internal diameter 102 mm, and bottom internal diameter 203 mm with a height of 305 mm. A 610 mm long

bullet nosed metal rod, 16 mm in diameter.[2]

[edit]Procedure

Slump cone

 

Tamping procedure

 

Removing cone

 

Height measurement

The test is carried out using a mould known as a slump cone or Abrams cone. The cone is placed on a

hard non-absorbent surface. This cone is filled with fresh concrete in three stages, each time it is tamped

using a rod of standard dimensions. At the end of the third stage, concrete is struck off flush to the top of

the mould. The mould is carefully lifted vertically upwards, so as not to disturb the concrete cone.

Concrete subsides. This subsidence is termed as slump, and is measured in to the nearest 5 mm.[1]:128[3]

[edit]Interpretation of results

The slumped concrete takes various shapes, and according to the profile of slumped concrete, the slump

is termed as true slump, shear slump or collapse slump. If a shear or collapse slump is achieved, a fresh

sample should be taken and the test repeated. A collapse slump is an indication of too wet a mix. Only a

true slump is of any use in the test. A collapse slump will generally mean that the mix is too wet or that it

is a high workability mix, for which slump test is not appropriate.[1]:128[3] Very dry mixes; having slump 0 –

25 mm are used in road making, low workability mixes; having slump 10 – 40 mm are used for

foundations with light reinforcement, medium workability mixes; 50 - 90 for normal reinforced concrete

placed with vibration, high workability concrete; > 100 mm.[4]:68

Collapse Shear True

In a collapse slump the

concrete collapses

completely.[3]

In a shear slump the top portion of

the concrete shears off and slips

sideways.[3]

In a true slump the concrete simply

subsides, keeping more or less to

shape.[3]

[edit]European classes of slump

According to European Standard EN 206-1:2000 five classes of slump have been designated, as

tabulated below.[4]:69

Slump class Slump in mm

S1 10 - 40

S2 50 - 90

S3 100 - 150

S4 160-210

S5 ≥220

[edit]Limitations of the slump test

The slump test is suitable for slumps of medium to high workability, slump in the range of 25 – 125 mm,

the test fails to determine the difference in workability in stiff mixes which have zero slump, or for wet

mixes that give a collapse slump. It is limited to concrete formed of aggregates of less than 38 mm

(1 inch).[1]:128

[edit]Differences in standards

The slump test is referred to in several testing and building codes, with minor differences in the details of

performing the test.

[edit]United States

In the United States, engineers use the ASTM standards and AASHTO specifications when referring to

the concrete slump test. The American standards explicitly state that the slump cone should have a height

of 12-in, a bottom diameter of 8-in and an upper diameter of 4-in. The ASTM standards also state in the

procedure that when the cone is removed, it should be lifted up vertically, without any rotational

movement at all.[5] The concrete slump test is known as "Standard Test Method for Slump of Hydraulic-

Cement Concrete" and carries the code (ASTM C 143) or (AASHTO T 119).

Workability of Fresh Concrete by Slump TestPosted in Civil Engineering Tests |   Email This Post

WORKABILITY

Slump test is used to determine the workability of fresh concrete. Slump test as per IS: 1199

– 1959 is followed.The apparatus used for doing slump test are Slump cone and Tamping

rod.

Procedure to determine workability of fresh concrete by slump test.

i) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil.

ii) The mould is placed on a smooth, horizontal, rigid and nonabsorbent surface.

iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to

one-fourth of the height of the mould.

iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are

distributed evenly over the cross section).

v) After the top layer is rodded, the concrete is struck off the level with a trowel.

vi) The mould is removed from the concrete immediately by raising it slowly in the vertical

direction.

vii) The difference in level between the height of the mould and that of the highest point of

the subsided concrete is measured.

viii) This difference in height in mm is the slump of the concrete.

Reporting of Results

The slump measured should be recorded in mm of subsidence of the specimen during the

test. Any slump specimen, which collapses or shears off laterally gives incorrect result and if

this occurs, the test should be repeated with another sample. If, in the repeat test also, the

specimen shears, the slump should be measured and the fact that the specimen

sheared, should be recorded.

Typical Questions

Ques 1. What is the ideal value of slump?

Answer 1 In case of a dry sample, slump will be in the range of 25-50 mm that is 1-2

inches. But in case of a wet concrete, the slump may vary from 150-175 mm or say 6-7

inches. So the value of slump is specifically mentioned along the mix design and thus it

should be checked as per your location.

Slump depends on many factors like properties of concrete ingredients – aggregates etc.

Also temperature has its effect on slump value. So all these parameters should be kept in

mind when deciding the ideal slump

Ques 2. How does a superplasticizer effect the slump of concrete?

Answer 2 Value of Slump can be increased by the addition of chemical admixtures like mid-

range or high-range water reducing agents (super-plasticizers) without changing the

water/cement ratio.

Ques 3. How much time one should take to raise the cone?

Answer 3 Once the cone is filled and topped off [ excessive concrete from top is cleared ]

raise the cone within 5-10 seconds.

Ques 4. What are the dimensions of the cone used in Slump Test?

Answer 3 The dimensions are

Top Diameter – 10cm

Bottom Diameter – 20cm

Height – 30cm

Sampling  ProceduresSampling  (or  obtaining)  concrete  for  theslump   test should   be   accomplished   accord-ing  to  ASTM  C  172.  In  this  TRAMAN, onlythe  procedure  of  sampling  from  a  revolvingdrum truck mixer (TM) or agitator is discussed.If you should ever need to sample from a pavingmixer,  open-top  truck mixer,  or  other  type  ofequipment,  be  sure  to  refer  to  the  most  recentASTM  C 172.Samples  taken  for  the  test  specimens  mustbe   representative   of   the   entire batch.   Thisis  accomplished  by  taking  the  samples  at  twoor  more  regularly

spaced  intervals  during  dis-charge   of   the   middle   portion   of   the batch.Sample  by  repeatedly  passing  a  scoop  or  pailthrough the entire discharge stream. Compositethese  samples  into  one  sample  for  testing  pur-poses.  Be  sure that  the  first  and  last  por-tions  of  the  composite  sample  are  taken  asquickly  as possible,  but  never  exceeding  15min.  If  it  is  necessary  to  transport  the  sam-ples  away  from  the  mixer  to  the  place  wherethe  slump  test  is  to  be  performed, combine  thesamples and remix them with a shovel to ensureuniformity.Testing ProceduresFigure  15-40.-Slump  cone.to  thetest  loadis   applied perpendicularlongitudinal axis of a standard size, premolded,and-properly  cured concrete  beam.  From  this  test,the  flexural  strength,  expressed  in  terms ofmodulus  of  rupture  and  given  in  psi,  can  bereadily calculated. As with the compression test,only  the  procedures  to  prepare  the  test  beams  cor-rectly  will be  discussed  in  this  TRAMAN.SLUMP TESTSThe slump test is performed on newly mixedconcrete. To perform the test, you need a slumpcone  and  a  tamping rod.  The  slump  cone  (fig.15-40) should be made of galvanized steel, 12 in.in height, with a base opening 8 in. in diameterand the top opening 4 in. in diameter. Both thetop  and  bottom  openings  are  perpendicular  to  thevertical  axis  of  the  cone. The  tamping  rod  is  astraight, steel rod that is 5/8 in. in diameter andapproximately 24  in.  in  length.  One  end  of  therod  is  rounded  to  a  diameter  of  5/8  in.  (Do notsubstitute  a  piece  of  rebar.)Perform  the  slump  test  according  to  ASTMC 143.  Be  sure  to  start  the  test  within  5  minafter   obtaining   the   final   portion of   the   com-posite   sample.    In  performing  the  test,  firstdampen  the  slump cone  and  place  it  on  a  flat,moist,   nonabsorbent,   rigid   surface.   From thecomposite  sample  obtained  and  while  standing  onthe  two  foot  pieces  of  the cone,  fill  the  cone  inthree layers, each approximately one third of thevolume  of  the cone.  In  placing  each  scoopful  ofconcrete,  rotate  the  scoop  around  the  top edgeof  the  cone  as  the  concrete  slides  from  it  toensure  even  distribution  of concrete  within  themold.Rod  each  layer  with  25  strokes  of  thetamping   rod (using   the   rounded   end),   anduniformly  distribute  the  strokes  over  the  en-tire cross  section  of  each  layer.  Rod  the  bottomlayer throughout its depth. Rod the second layerand  the  top  layer  each  throughout  its  depth  sothat  the  strokes  just penetrate  into  the  under-lying   layer.   In   filling   and   rodding   the   toplayer, heap  the  concrete  above  the  mold  beforethe  rodding  is  started.  If  the  rodding results

ASTM C387 / C387MAbstract

This specification covers the production, properties, packaging, and testing of packaged, dry,

combined materials for concrete and mortars. Concrete mixtures covered by this specification includes

high-early strength concrete, normal strength concrete, normal weight concrete, high-strength mortar,

and mortars for unit masonry. The purchaser shall specify the material desired as concrete, high

strength mortar, or mortar for use with unit masonry, and the respective physical requirements.

Materials used as ingredients in packaged, dry, combined materials for mortar and concrete shall be

composed of aggregates, air-entraining admixtures, blended cement, chemical admixtures, fly ash,

ground granulated blast-furnace slag, hydrated lime, latex and powder polymer modifiers, masonry

cement, mortar cement, Portland cement, and silica fume. All aggregates shall be dried, without

disintegration, to specific moisture content The proportions of cementitious material and aggregate

shall be such that the strength requirements will be met. Packaged, dry, combined materials for

concrete, high strength mortar and mortar for use with unit masonry shall conform to the respective

compressive strength requirements. Scales conforming to the standards will be used for sampling

concretes from a single batch using a sufficient quantity. A slump test will be performed to check if

additional water is required. In sampling mortar, the contents of an entire package of dry, combined

material for mortar for unit masonry or for concrete mortar shall be used. Mortar mixing equipment,

which must be provided with a bowl positioning adapter, shall be used to ensure clearance for the

largest size aggregate in the mix being tested. The specification includes the following testing methods

for mortar: compressive strength, density and yield, air content, and water retention.

This abstract is a brief summary of the referenced standard. It is informational only and not an official

part of the standard; the full text of the standard itself must be referred to for its use and application.

ASTM does not give any warranty express or implied or make any representation that the contents of

this abstract are accurate, complete or up to date.

1. Scope

1.1 This specification covers the production, properties, packaging, and testing of packaged, dry,

combined materials for concrete and high strength mortar. The classifications of concrete and mortar

covered are defined in Section 3.

NOTE 1—The scope of this standard does not cover mortars for unit masonry. Dry preblended mortars

for unit masonry are covered by Specification .

1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard.

The values stated in each system may not be exact equivalents; therefore, each system shall be used

independently of the other. Combining values from the two systems may result in non-conformance

with the standard. Some values have only SI units because the inch-pound equivalents are not used in

practice.

1.3 The following safety hazards caveat pertains only to the test method portion of this

specification. This standard does not purport to address all of the safety concerns, if any, 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 prior to use.

2. Referenced Documents (purchase separately) 

ASTM Standards

C33 Specification for Concrete Aggregates

C39/C39M Test Method for Compressive Strength of Cylindrical Concrete Specimens

C91 Specification for Masonry Cement

C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-

mm] Cube Specimens)

C125 Terminology Relating to Concrete and Concrete Aggregates

C138/C138M Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete

C143/C143M Test Method for Slump of Hydraulic-Cement Concrete

C144 Specification for Aggregate for Masonry Mortar

C150 Specification for Portland Cement

C173/C173M Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method

C185 Test Method for Air Content of Hydraulic Cement Mortar

C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory

C207 Specification for Hydrated Lime for Masonry Purposes

C231 Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method

C260 Specification for Air-Entraining Admixtures for Concrete

C270 Specification for Mortar for Unit Masonry

C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency

C330 Specification for Lightweight Aggregates for Structural Concrete

C494/C494M Specification for Chemical Admixtures for Concrete

C566 Test Method for Total Evaporable Moisture Content of Aggregate by Drying

C595 Specification for Blended Hydraulic Cements

C618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete

C702 Practice for Reducing Samples of Aggregate to Testing Size

C989 Specification for Slag Cement for Use in Concrete and Mortars

C1116 Specification for Fiber-Reinforced Concrete and Shotcrete

C1157 Performance Specification for Hydraulic Cement

C1240 Specification for Silica Fume Used in Cementitious Mixtures

C1329 Specification for Mortar Cement

C1437 Test Method for Flow of Hydraulic Cement Mortar

C1438 Specification for Latex and Powder Polymer Modifiers in Hydraulic Cement Concrete and Mortar

C1600/C1600M Specification for Rapid Hardening Hydraulic Cement

C1714/C1714M Specification for Preblended Dry Mortar Mix for Unit Masonry

Keywords 

aggregate-cement aggregate combinations; cement mortars; combined concrete/mortar materials;

concrete admixtures; concrete, packaged; concrete specifications; dry combined concrete/mortar

materials; mortar-cement mortar; mortar, packaged; packaged dry combined materials; packaged

concrete/mortar materials; Aggregate--specifications; Cement mortars--specifications; Combined

concrete/mortar materials; Concrete admixtures--specifications; Concrete construction

materials/applications--specifications; Dry combined concrete/mortar materials; Mortar--specifications;

Packaged dry combined materials

The slump test is the most well-known and widely used test method to characterize the workability of fresh concrete. The inexpensive test, which measures consistency, is used on job sites to determine

rapidly whether a concrete batch should be accepted or rejected. The test method is widely standardized throughout the world, including in ASTM C143 in the United States and EN 12350-2 in Europe.         The apparatus consists of a mold in the shape of a frustum of a cone with a base diameter of 8 inches, a top diameter of 4 inches, and a height of 12 inches. The mold is filled with concrete in three layers of equal volume. Each layer is compacted with 25 strokes of a tamping rod. The slump cone mold is lifted vertically upward and the change in height of the concrete is measured. Four types of slumps are commonly encountered, as shown in Figure 3. The only type of slump permissible under ASTM C143 is frequently referred to as the “true” slump, where the concrete remains intact and retains a symmetric shape. A zero slump and a collapsed slump are both outside the range of workability that can be measured with the slump test. Specifically, ASTM C143 advises caution in interpreting test results less than ½ inch and greater than 9 inches. If part of the concrete shears from the mass, the test must be repeated with a different sample of concrete. A concrete that exhibits a shear slump in a second test is not sufficiently cohesive and should be rejected.

       The slump test is not considered applicable for concretes with a maximum coarse aggregate size greater than 1.5 inches. For concrete with aggregate greater than 1.5 inches in size, such larger particles can be removed by wet sieving.         Additional qualitative information on the mobility of fresh concrete can be obtained after reading the slump measurement. Concretes with the same slump can exhibit different behavior when tapped with a tamping rod. A harsh concrete with few fines will tend to fall apart when tapped and be appropriate only for applications such as pavements or mass concrete. Alternatively, the concrete may be very cohesive when tapped, and thus be suitable for difficult placement conditions.       Slump is influenced by both yield stress and plastic viscosity; however, for most cases the effect of plastic viscosity on slump is negligible. Equations have been developed for calculating yield stress in terms of slump, based on either analytical or experimental analyses. Since different  rheometers measure different absolute values for the yield stress of identical samples of concrete, the experimental equations are largely depended on the specific device used to measure yield stress. 

Advantages:   • The slump test is the most widely used device worldwide. In fact, the test is so well known that often the terms workability and slump are used interchangeably, even though they have different meanings. • Specifications are typically written in terms of slump. • The slump test is simple, rugged, and inexpensive to perform. Results are obtained immediately. 

• The results of the slump test can be converted to yield stress in fundamental units based on various analytical treatments and experimental studies of the slump test. • Compared to other commonly used concrete tests, such as for air content andcompressive strength, the slump test provides acceptable precision. Disadvantages: • The slump test does not give an indication of plastic viscosity. • The slump test is a static, not dynamic, test; therefore, results are influenced by concrete thixotropy. The test does not provide an indication of the ease with which concrete can be moved under dynamic placing conditions, such as vibration. • The slump test is less relevant for newer advanced concrete mixes than for more conventional mixes.