Concrete slump test

Last updated

The concrete slump test measures the consistency of fresh concrete before it sets. It is performed to check the workability of freshly made concrete, and therefore the ease with which concrete flows. It can also be used as an indicator of an improperly mixed batch. The test is popular due to the simplicity of apparatus used and simple procedure. The slump test is used to ensure uniformity for different loads of concrete under field conditions. [1]

Contents

A separate test, known as the flow table, or slump-flow test, is used for concrete that is too fluid (non-workable) to be measured using the standard slump test, because the concrete will not retain its shape when the cone is removed.

Procedure

The test is carried out using a metal mould in the shape of a conical frustum known as a slump cone or Abrams cone, that is open at both ends and has attached handles. The tool typically has an internal diameter of 100 millimetres (3.9 in) at the top and of 200 millimetres (7.9 in) at the bottom with a height of 305 millimetres (12.0 in).The cone is placed on a hard non-absorbent surface. This cone is filled with fresh concrete in three stages. Each time, each layer is tamped 25 times with a 2 ft (600 mm)-long bullet-nosed metal rod measuring 5/8 in (16 mm) in diameter. [2] At the end of the third stage, the concrete is struck off flush with the top of the mould. The mould is carefully lifted vertically upwards, so as not to disturb the concrete cone.

The concrete then slumps (subsides). The slump of the concrete is measured by measuring the distance from the top of the slumped concrete to the level of the top of the slump cone. [3] [4]

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.

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 the slump test is not appropriate. [1] [3] Very dry mixes having slump 0 – 25 mm are typically used in constructing pavements or roads, low workability mixes having slump 10 – 40 mm are typically used for foundations with light reinforcement, medium workability mixes with slump 50 – 90 mm, are typically used for normal reinforced concrete placed with vibration, high workability concrete with slump > 100 mm is typically used where reinforcing has tight spacing, and/or the concrete has to flow a great distance. [5] :68

Types of slump Types of concrete slump.jpg
Types of slump
CollapseShearTrue
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]

Limitations of the slump test

The slump test is suitable for slumps of medium to low workability, slump in the range of 5 – 260 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 (1.5 inch). [1]

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.

United States

In the United States, engineers use the ASTM C94, standard specification for ready-mixed concrete, and AASHTO specifications, address clump tolerances in detail. For diverse forms of concrete construction, different slumps are required. For example: for walls, slumps typically range from 4-in to 8-in. The American standards explicitly state that the slump cone should have a height of 12-in (300 mm), a bottom diameter of 8-in (200 mm) and an upper diameter of 4-in (100 mm). The soft SI conversions provided in the standard allow using the same dimension slump cones as those described in other standards. The ASTM standards also regulate the rigidity of the cone. It states in the procedure that when the cone is removed, it should be lifted up vertically, without any rotational movement at all. [6] 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).

United Kingdom and mainland Europe

In the United Kingdom, the standards specify a slump cone height of 300 mm, a bottom diameter of 200 mm and a top diameter of 100 mm. The British Standards do not explicitly specify that the cone should only be lifted vertically. The slump test in the British standards was first (BS 1881–102) and is now replaced by the European Standard (BS EN 12350–2). [7] The test should be carried out by filling the slump cone in three equal layers with the mixture being tamped down 25 times for each layer.

Other tests

There are many tests for evaluating slump in concrete: the flow table test (DIN 1048–1) uses similar, but differently-sized, apparatus, but the table on which the slump cone is placed is dropped several times after the slump cone is removed, and the measurement is of the diameter of the sample, not the height. [8] one example is the K-Slump Test (ASTM International C1362-09 Standard Test Method for Flow of Freshly Mixed Hydraulic Cement Concrete). [9] Other tests evaluating consistency are the British compacting factor test, [10] the Vebe consistometer for roller-compacted concrete (ASTM C1170), [11]

Another way of determining slump is to use an automated slump meter. Sensors and controls enable the meters to measure and display slump. Their reliability has by now earned them acceptance in various standard codes such as ASTM International. Some automated slump meters, such as the one by Verifi also can add water to the concrete mix in the delivery truck while in transit. In 2013 ASTM C94/C94M was revised to allow water additions during transit for trucks equipped with automated slump monitoring and measurement systems.

See also

Related Research Articles

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.

<span class="mw-page-title-main">Rebar</span> Steel reinforcement

Rebar, known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.

The NLGI consistency number expresses a measure of the relative hardness of a grease used for lubrication, as specified by the standard classification of lubricating grease established by the National Lubricating Grease Institute (NLGI). Reproduced in standards ASTM D4950(“standard classification and specification of automotive service greases”) and SAE J310(“automotive lubricating greases”), NLGI's classification is widely used. The NLGI consistency number is also a component of the code specified in standard ISO 6743-9“lubricants, industrial oils and related products — classification — part 9: family X (greases)”.

<span class="mw-page-title-main">Silica fume</span> Silicon dioxide nano particles

Silica fume, also known as microsilica, is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm. The main field of application is as pozzolanic material for high performance concrete.

<span class="mw-page-title-main">Ready-mix concrete</span> Concrete that is manufactured in a batch plant, according to a set engineered mix design

Ready-mix concrete (RMC) is concrete that is manufactured in a batch plant, according to each specific job requirement, then delivered to the job site "ready to use".

The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit.

Air entrainment in concrete is the intentional creation of tiny air bubbles in a batch by adding an air entraining agent during mixing. A form of surfactant it allows bubbles of a desired size to form. These are created during concrete mixing, with most surviving to remain part of it when hardened.

<span class="mw-page-title-main">Pipe (fluid conveyance)</span> Tubular section or hollow cylinder

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. "Nominal" refers to pipe in non-specific terms and identifies the diameter of the hole with a non-dimensional number. Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule. NPS is often incorrectly called National Pipe Size, due to confusion with the American standard for pipe threads, "national pipe straight", which also abbreviates as "NPS". The European and international designation equivalent to NPS is DN, in which sizes are measured in millimetres, see ISO 6708. The term NB is also frequently used interchangeably with DN.

The water–cement ratio is the ratio of the mass of water to the mass of cement used in a concrete mix:

<span class="mw-page-title-main">Geotechnical investigation</span> Work done to obtain information on the physical properties of soil earthworks and foundations

Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions; this type of investigation is called a site investigation. Geotechnical investigations are also used to measure the thermal resistance of soils or backfill materials required for underground transmission lines, oil and gas pipelines, radioactive waste disposal, and solar thermal storage facilities. A geotechnical investigation will include surface exploration and subsurface exploration of a site. Sometimes, geophysical methods are used to obtain data about sites. Subsurface exploration usually involves soil sampling and laboratory tests of the soil samples retrieved.

Fiber-reinforced concrete or fibre-reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers – each of which lend varying properties to the concrete. In addition, the character of fiber-reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation, and densities.

<span class="mw-page-title-main">Cast stone</span> Material simulating natural stone

Cast stone or reconstructed stone is a highly refined building material, a form of precast concrete used as masonry intended to simulate natural-cut stone. It is used for architectural features: trim, or ornament; facing buildings or other structures; statuary; and for garden ornaments. Cast stone can be made from white and/or grey cements, manufactured or natural sands, crushed stone or natural gravels, and colored with mineral coloring pigments. Cast stone may replace such common natural building stones as limestone, brownstone, sandstone, bluestone, granite, slate, coral, and travertine.

<span class="mw-page-title-main">Marsh funnel</span>

The Marsh funnel is a simple device for measuring viscosity by observing the time it takes a known volume of liquid to flow from a cone through a short tube. It is standardized for use by mud engineers to check the quality of drilling mud. Other cones with different geometries and orifice arrangements are called flow cones, but have the same operating principle.

Self-consolidating concrete or self-compacting concrete (SCC) is a concrete mix which has a low yield stress, high deformability, good segregation resistance, and moderate viscosity.

<span class="mw-page-title-main">Tremie</span> Equipment for underwater concrete placement

A tremie is a watertight pipe, usually of about 250 mm inside diameter, with a conical hopper at its upper end above the water level. It may have a loose plug or a valve at the bottom end. A tremie is used to pour concrete underwater in a way that avoids washout of cement from the mix due to turbulent water contact with the concrete while it is flowing. This produces a more reliable strength of the product. Common applications include the following.

<span class="mw-page-title-main">Flow table test</span> Concrete consistency test

The flow table test or slump-flow test is a method to determine consistency of fresh concrete. Flow table test is also used to identify transportable moisture limit of solid bulk cargoes. It is used primarily for assessing concrete that is too fluid (workable) to be measured using the slump test, because the concrete will not retain its shape when the cone is removed.

Copper slag is a by-product of copper extraction by smelting. During smelting, impurities become slag which floats on the molten metal. Slag that is quenched in water produces angular granules which are disposed of as waste or utilized as discussed below.

<span class="mw-page-title-main">Types of concrete</span> Building material consisting of aggregates cemented by a binder

Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.

<span class="mw-page-title-main">3D concrete printing</span>

3D concrete printing, or simply concrete printing, refers to digital fabrication processes for cementitious materials based on one of several different 3D printing technologies. 3D printed concrete eliminates the need for formwork, reducing material waste and allowing for greater geometric freedom in complex structures. With recent developments in mix design and 3D printing technology over the last decade, 3D concrete printing has grown exponentially since its emergence in the 1990s. Architectural and structural applications of 3D-printed concrete include the production of building blocks, building modules, street furniture, pedestrian bridges, and low-rise residential structures.

References

  1. 1 2 3 Gambhir, M. L. (2004). Concrete technology. Tata McGraw-Hill. pp. 127, 128. ISBN   9780070583740 . Retrieved 2010-12-11.
  2. W.B. Mckay; J.M. Mckay (1 January 1971). Building Construction Vol. Ii (Fourth ed.). Orient Longman Private Limited. p. 32. ISBN   978-81-250-0941-2 . Retrieved 9 June 2012.
  3. 1 2 3 4 5 "Slump test". The Concrete Society . Retrieved 2010-12-11.
  4. "California Test 555, Method of Test for Slump of Fresh Portland Cement Concrete" (PDF). June 2010.
  5. Lyons, Arthur (2007). Materials for architects and builders. Butterworth-Heinemann. ISBN   9780750669405 . Retrieved 2010-12-11.
  6. Tattersall, G.H. (1991). Workability and quality control of concrete. London: E & FN Spon. ISBN   978-0-419-14860-9.
  7. qpa.org; QPA BRMCA Committee Bulletin 3 Archived 2009-02-05 at the Wayback Machine
  8. Panarese, William C.; Kosmatka, Steven H.; Kerkhoff, Beatrix (2002). Design and control of concrete mixtures. [Skokie, Ill.]: Portland Cement Association. ISBN   978-0-89312-217-1.
  9. ASTM Complete Set. 2013 ISBN   9781622042715
  10. CSN EN 12350-4 - Testing fresh concrete - Part 4: Degree of Compactability
  11. ASTM C1170/C1170M-08 October 2008 Standard Test Method for Determining Consistency and Density of Roller-Compacted Concrete Using a Vibrating Table