SOUTH AFRICAN NATIONAL STANDARD

Transcription

1 ISBN Any reference to SABS SM is deemed to be a reference to this standard (Government Notice No of 8 November 2002) SOUTH AFRICAN NATIONAL STANDARD Concrete tests Consistence of freshly mixed concrete Slump test Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: Fax: SABS

2 Table of changes Change No. Date Scope Amdt Amended to change the designation of SABS standards to SANS standards, with no technical changes. Acknowledgement The SABS Standards Division wishes to acknowledge the valuable assistance derived from publications of the following organizations: The British Standards Institution The International Organization for Standardization Foreword This South African standard was approved by National Committee SABS SC 59A, Construction standards Cement, lime and concrete, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This edition is technically identical to the first revision (SABS SM 862-1:1994). SANS 5862 consists of the following parts under the general title Concrete tests Consistence of freshly mixed concrete: Part 1: Slump test. Part 2: Flow test. Part 3: Vebe test. Part 4: Compacting factor and compaction index. Reaffirmed and reprinted in July This standard will be reviewed every five years and be reaffirmed, amended, revised or withdrawn.

3 Concrete tests Consistence of freshly mixed concrete Slump test 1 Scope This part of SANS 5862 specifies a method of determining the slump of freshly mixed concrete, mixed both in the laboratory (see SANS ) and on site. NOTES 1 The test method applies to plastic and cohesive concrete that has a measured slump of not less than 5 mm and not more than 175 mm. 2 The test method applies to plain and air-entrained concrete, made with aggregates of low, normal or high density and of maximum nominal size 40 mm. 3 The test method is not applicable to superplasticized concrete, since it is very difficult to measure aerated concrete and no-fines concrete. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of SANS All standards are subject to revision and, since any reference to a standard is deemed to be a reference to the latest edition of that standard, parties to agreements based on this part of SANS 5862 are encouraged to take steps to ensure the use of the most recent editions of the standards indicated below. Information on currently valid national and international standards can be obtained from the SABS Standards Division. SANS , Concrete tests Part 1: Mixing fresh concrete in the laboratory. SANS , Concrete tests Part 2: Sampling of freshly mixed concrete. 3 Definitions For the purposes of this part of SANS 5862, the following definitions apply: 3.1 aerated concrete concrete made light and cellular by the addition of a prepared foam or by the generation of gas within the unhardened mixture 1

4 3.2 aggregate of high density aggregate that contains materials such as barytes, magnetite, hematite, limonite, ilmenite, iron or steel, and that has a particle density that exceeds kg/m aggregate of low density aggregate with a particle density of less than kg/m 3 and that contains materials such as: a) expanded or sintered clay, shale, diatomaceous shale, perlite, vermiculite, or slag; b) natural pumice, scoria, volcanic cinders, tuff, or diatomite; and c) sintered fly ash or industrial cinders 3.4 aggregate of normal density aggregate that is neither of high density nor of low density 3.5 air-entrained concrete concrete that has microscopic air bubbles intentionally incorporated during mixing, usually by the use of a surface-active agent 3.6 no-fines concrete a concrete mixture that contains little or no fine aggregate 4 Apparatus 4.1 Mould, that is made of a metal that is not readily attacked by cement paste, is of thickness at least 1,6 mm, and has a smooth internal surface. The mould (see figure 1) is in a form of a frustum of a cone, with the following nominal internal dimensions: a) diameter of base: 200 mm ± 2 mm; b) diameter of top : 100 mm ± 2 mm; and c) height: 300 mm ± 2 mm. The base and the top are open and parallel to each other and at right angles to the axis of the cone. The mould has two suitable hold-down footpieces at the bottom, to permit it to be held steady, and handles at two-thirds of its height, to facilitate lifting it up vertically from the test specimen. Alternatively, use a mould that can be clamped to a baseplate, if the clamping arrangement can be removed without movement of the mould. 4.2 Tamping rod, that is made of straight steel, is of nominal diameter 16 mm and of length 600 mm ± 2 mm, and that has at least one hemispherical end. 5 Sampling Obtain a representative composite sample of the freshly mixed concrete in accordance with SANS Determine slump as soon as possible after sampling and re-mixing. 2

5 6 Procedure 6.1 Before starting with the test, ensure that the interior surface of the mould is clean and damp but free from superfluous moisture. Place the mould on a clean, smooth, horizontal, rigid and nonabsorbent surface that is free from vibration and shock. While the mould is being filled, hold it firmly in place by standing on the footpieces or by any other suitable means. NOTE A levelled metal plate, of adequate size to support the slumped concrete, placed on a bed of sand, is a suitable surface. 6.2 Fill the mould with a composite sample (see clause 5) in three layers, each approximately onethird of the height of the mould. Tamp each layer with 25 strokes applied with the hemispherical end of the tamping rod, distributing the strokes uniformly over the cross-section of the layer. Tamp each layer throughout its depth, ensuring that when the second and third layers are being tamped, the strokes penetrate into the underlying layer. While tamping the third layer, ensure that excess concrete is maintained above the top of the mould, if necessary by adding more concrete while tamping. 6.3 After the top layer has been tamped, so strike off the excess concrete, using a sawing and rolling motion of the tamping rod, that the mould is completely filled and level. Without disturbing the concrete in the mould, clean off the concrete around the base of the mould, that may have leaked or spilled during the tamping. 6.4 Demould the concrete by raising the mould vertically, slowly and carefully, in 5 s to 10 s, in such a manner as to impart minimum lateral or torsional movement to the concrete. The entire process, from moulding and demoulding, should be carried out within 150 s. 6.5 Immediately after demoulding, measure the slump of the concrete to the nearest 5 mm, by determining the difference in the height of the mould and the highest point of the specimen under test. If the specimen collapses or lateral shearing of concrete occurs, consider the test invalid and repeat it on a fresh sample of concrete. If, during two consecutive tests, collapsing or lateral shearing of the test specimen occurs (see figure 2), the concrete lacks the necessary plasticity and cohesiveness for the slump test to be applicable. NOTE An indication of cohesiveness and workability of the mix can be obtained if, after the slump measurement has been completed, the side of the concrete is tapped gently with the tamping rod; a wellproportioned concrete, which has an appreciable slump, will gradually slump further, while a badly proportioned mix is likely to fall apart. 7 Expression and reporting of results Calculate the slump of the test specimen during the test, using the formula Slump = h h m s where h m is the height of the mould, in millimetres; and h s is the height of the slumped test specimen, in millimetres. Report the slump of the concrete to the nearest 5 mm. 3