Microsoft Word C029098e doc Reference number ISO 1920 2 2005(E) © ISO 2005 INTERNATIONAL STANDARD ISO 1920 2 First edition 2005 04 15 Testing of concrete — Part 2 Properties of fresh concrete Essais d[.]
General
The consistence of the concrete is determined by one of the methods described below:
slump-flow test for high-fluidity concrete (see 4.7)
These methods are not applicable to foamed concrete, no-fines concrete or where the maximum aggregate size exceeds 40 mm.
Sampling
Samples for the tests shall be obtained in accordance with ISO 1920-1 Each sample shall be remixed before carrying out the tests.
Slump test
Fresh concrete is compacted into a conical frustum mold to assess its consistency As the cone is carefully withdrawn upwards, the amount the concrete slumps indicates its workability and fluidity This slump test is a key method for evaluating concrete quality and ensuring it meets construction standards.
The slump test is applicable to a range of consistence of concrete that corresponds to slumps of between
10 mm and 210 mm Outside this range, the measurement of slump may be unsuitable and other methods of determining the consistence should be considered
If the slump continues to change over a period of 1 min after demoulding, this test is not suitable
NOTE For high-fluidity concrete, the slump-flow test described in 4.7 is a more appropriate test
Note the calibration requirements associated with each apparatus
4.3.2.1 Mould, suitable of forming the test specimen, made of a metal not readily attacked by cement paste and not thinner than 1,5 mm
The mould can be constructed with or without a seam, ensuring versatility in manufacturing Its interior must be smooth and free from projections like protruding rivets or dents to ensure product quality Designed as a hollow frustum of a cone, the mould must meet specific internal dimensions for consistency and precision.
diameter of base: 200 mm ± 2 mm;
diameter of top: 100 mm ± 2 mm;
The base and top of the mold must be open, parallel, and perpendicular to the cone's axis to ensure proper alignment The mold should feature two handles at two-thirds of its height on the upper portion for easy handling For stability, it must be equipped with fixing clamps or foot pieces at the bottom to hold it securely in place during use Alternatively, a mold that can be clamped to the base is acceptable, provided the clamping mechanism can be fully released without moving the mold or disrupting the slumping concrete.
Before each use, visually inspect the mold to ensure it is clean, undamaged, and free of dents, ensuring optimal performance Additionally, the cone should undergo an annual check to verify that its dimensions and condition remain within specified tolerances, maintaining accuracy and safety in the molding process.
4.3.2.2 Tamping rod, straight, made of steel, having a circular cross-section with a diameter of
16 mm ± 1 mm, 600 mm ± 5 mm in length, and with rounded ends The rod may be extended with a handle of plastic conduit, provided that the overall length does not exceed 1 000 mm
The tamping rod shall be checked annually to ensure that its dimensions and conditions remain within tolerances
4.3.2.3 Funnel (optional), made of a non-absorbent material not readily attacked by cement paste
The funnel is designed with two co-axial conical frustums sharing a common diameter of 100 mm The larger ends of each frustum facilitate easy filling and accurate placement One frustum functions as the filling funnel, guiding materials seamlessly, while the other acts as a collar to securely attach the funnel to the outer surface of the mold This design ensures precise, stable operation during the molding process.
The funnel shall be checked annually to ensure that its dimensions and conditions remain within tolerances
4.3.2.4 Rule, graduated from 0 mm to 300 mm, at intervals not exceeding 5 mm, with the zero point being at the extreme end of the rule
4.3.2.5 Base plate/surface, rigid, flat, non-absorbent and smooth plate or other surface on which to place the mould
4.3.2.7 Re-mixing tray, of rigid construction and made from a non-absorbent material not readily attacked by cement paste
It shall be of appropriate dimensions such that the concrete can be thoroughly remixed, using the square- bladed shovel
4.3.2.8 Scoop, with a width of approximately 100 mm
4.3.2.9 Timer or other similar timing device, to allow time measurement to 1 s
The watch shall be properly calibrated at the time of test
To prepare the mould, dampen it and the base plate, then wipe away any excess water with an absorbent cloth Position the mould securely on a horizontal surface or base plate During filling, ensure the mould remains stable by clamping it or holding it firmly in place, using the foot pieces for support to prevent movement.
After obtaining the sample as per section 4.2, fill the mould in three equal layers, each about one-third of the mould's height when compacted Ensure the concrete is evenly distributed around the mould to promote uniform strength Tamp each layer with 25 strokes using a tamping rod, and distribute these strokes evenly across the cross-section to achieve proper compaction For the bottom layer, incline the rod slightly and perform about half of the strokes in a spiral motion toward the centre to enhance compaction Tamp the second and top layers thoroughly, ensuring the tamping strokes penetrate into the underlying layer for optimal density and stability.
In filling and tamping the top layer, heap the concrete above the mould before tamping is started
To prevent subsidence of the concrete below the top edge of the mould during tamping, always add extra concrete to maintain an excess above the mould's top Ensure that adding concrete to the top layer does not cause additional compaction of the material After tamping the top layer, smooth the surface by scraping it level with the mould using a sawing and rolling motion with the tamping rod Properly managing these steps ensures a uniform, well-compacted concrete surface.
Remove spilled concrete from the base plate or surface to ensure a clean working area Carefully remove the mold within 5 ± 2 seconds using a steady upward lift, avoiding any lateral or torsional movements to prevent damage to the concrete Adjust the lifting time as necessary according to local standards or national annex guidelines for optimal results.
The entire operation from the start of the filling to the removal of the mould shall be carried out without interruption and shall be completed within 180 s
After removing the mould, determine the slump (h) by measuring the difference between the height of the mould and the highest point of the slumped test sample, following ISO 1920 guidelines Depending on the national annex, measurements may be taken between the mould's height and the centre point or average height of the slump Record measurements to the nearest 10 mm, or 5 mm if specified by the relevant national annex for ISO 1920.
To ensure a valid concrete slump test, the specimen must exhibit a true slump, where the concrete remains substantially intact and symmetrical (see Figure 2a) If the specimen shears, indicating an invalid test, a new sample should be prepared, and the procedure repeated to obtain accurate results.
Record the true slump, h, as shown in Figure 1 to the nearest 10 mm, or 5 mm when required by the national annex
If two consecutive tests indicate that a portion of the concrete shears off from the specimen, the test should be considered invalid, as it signifies insufficient plasticity and cohesiveness in the concrete Such results suggest that the concrete does not meet the necessary properties for a reliable slump test, and the test should be redone to ensure accurate assessment of concrete consistency.
Figure 1 — Slump measurement a) True slump b) Shear Figure 2 — Forms of slump
The test report must include additional information beyond Clause 7 requirements, specifically the slump measurement, recorded to the nearest 10 mm (or 5 mm if specified by the national annex), or a notation indicating that the test resulted in a sheared slump Accurate documentation of slump is essential for quality control and compliance with testing standards.
Vebe test
To assess fresh concrete, it is compacted into a slump mold, which is then lifted to allow the measurement of its slump by placing a transparent disc over the surface and recording the slump value The vibrating table is activated, and the time taken for the disc’s lower surface to fully contact the concrete is measured, ensuring accurate consistency assessment.
Vebe time measurements falling below 5 seconds or exceeding 30 seconds indicate that this test method may not be suitable for assessing consistency In such cases, alternative testing methods should be considered to ensure accurate evaluation Accurate Vebe time ranges are essential for reliable consistency determination in concrete testing.
Note the calibration requirements associated with each apparatus
The Consistometer (Vebe meter) comprises a cylindrical container, as illustrated in Figure 3, item 1 It features an internal diameter of 240 mm ± 5 mm and a height of 200 mm ± 2 mm, crafted from a corrosion-resistant metal suitable for cement paste exposure The container's walls are 3 mm thick, with a base thickness of 7.5 mm, ensuring durability and accuracy in measurement.
Ensure the container is watertight, sufficiently rigid to maintain its shape during rough handling, and equipped with handles for easy handling It must be protected against corrosion and fitted with suitable foot pieces for secure clamping onto the vibrating table using wing nuts For the mould, as specified in section 4.3.2.1, the fixing clamps or foot pieces are not necessary.
Regular visual inspection of the mould before each use is essential to ensure it is clean, undamaged, and free of dents, maintaining quality and safety The disc component, shown in Figure 3, item 3, is a transparent, horizontal part attached to a vertically sliding rod (item 9), which moves through a guide sleeve (item 5) mounted on a swivel arm (item 13) This assembly can be securely fixed in position using a screw (item 15), ensuring precise operation and reliability during use.
The swivel arm supports a funnel, which aligns with the top of the conical mold when it is properly positioned in the container It is securely held by a holder and can be fixed in place with a set-screw, ensuring stability during use When correctly positioned, the axes of the rod, funnel, and container are aligned to facilitate precise pouring and efficient operation.
The testing apparatus includes a transparent disc measuring 230 mm ± 2 mm in diameter and 10 mm ± 2 mm in thickness, with a weight positioned directly above it to ensure the entire moving assembly (comprising the rod, disc, and weight) has a total mass of 2,750 g ± 50 g The rod is equipped with a scale graduated at least every 5 mm to accurately record the concrete slump Additionally, a vibrating table, sized at 380 mm ± 3 mm in length and 260 mm ± 3 mm in width, is supported on four rubber shock absorbers to facilitate proper testing conditions.
The vibrator unit (Figure 3, item 11) must be securely fixed beneath the base (Figure 3, item 10), which rests on three rubber feet, ensuring stable operation It should operate at a frequency of 55 Hz ± 5.5 Hz, producing a vertical vibration amplitude of approximately 0.5 ± 0.02 mm when an empty container is placed on top This setup is crucial for consistent vibration testing and accurate results.
The vibrating table shall be checked annually to ensure that the frequency and vertical amplitude remain within tolerances
All the elements of the vibration table shall be checked annually to ensure that their dimensions remain within tolerances
4.4.2.2 Tamping rod, straight, made of steel or other suitable metal, of circular cross-section, having a diameter of 16 mm ± 1 mm, 600 mm ± 5 mm in length, and with rounded ends
4.4.2.3 Stopwatch or clock, capable of recording time to an accuracy of 0,5 s
4.4.2.4 Remixing container, of rigid construction, made from a non-absorbent material not readily attacked by cement paste
4.4.2.5 Scoop, with a width of approximately 100 mm
Place the Vebe meter (consistometer) on a stable, vibration-free horizontal surface to ensure accurate measurements Ensure the container is securely fixed to the vibrating table using wing nuts, preventing any movement during testing Dampen the mould and position it inside the container, then carefully align the funnel over the mould and secure it in place by tightening the screw, preventing any displacement during operation.
During subsequent operations, ensure the mould (Figure 3, item 2) remains stationary until it is properly raised to prevent movement Additionally, avoid any concrete falling into the container (Figure 3, item 1) to maintain construction quality and safety.
To ensure accurate concrete testing, immediately fill the mold with the sample in three equal layers, each approximately one-third of the mold's height when compacted Tamp each layer with 25 strokes of a tamping rod, evenly distributing the strokes across the cross-section For the bottom layer, tilt the rod slightly and apply about half the strokes in a spiral motion toward the center to achieve proper compaction Tamp the second and top layers thoroughly so the strokes penetrate into the underlying layer, maintaining consistent density When filling and tamping the top layer, heap the concrete above the mold before beginning to ensure proper compaction and accuracy of test results.
Ensure sufficient concrete is added to maintain an even excess above the mold during tamping for optimal results After tamping the top layer, loosen the screw (Figure 3, item 6), lift and rotate the funnel (Figure 3, item 4) by 90°, then tighten the screw securely.
To remove the mould from the concrete, carefully raise it vertically using the handles within 5 to 10 seconds, ensuring no lateral or torsional movement Before removal, scrape off the concrete level at the top of the mould with a sawing and rolling motion of the tamping rod to achieve a smooth surface Proper technique prevents damage to the specimen and ensures accurate test results.
To ensure accurate documentation, record instances where the concrete shears, collapses, or slumps to the extent that it contacts the container wall, as illustrated in Figures 4(b), 4(c), and Figure 3 (item 1), respectively.
If the concrete has not slumped against the container wall (Figure 3, item 1) and a true slump has been achieved, as illustrated in Figure 4 (a), this result must be documented.
Degree of compactability test
Fresh concrete should be carefully placed in a container using a trowel, avoiding compaction during filling to ensure proper placement Once the container is full, the surface is leveled off with a trowel to match the top of the container The concrete is then compacted, and the height from the compacted surface to the container's upper edge is measured to assess the degree of compactability, ensuring optimal density and strength.
If the degree of compactability is less than 1,04 or more than 1,46, the concrete has a consistence for which the degree of compactability test is not suitable
4.5.2.1 Container, with parallel sides and a general shape as shown in Figure 6, made of metal not readily attacked by cement paste and having the following internal dimensions:
base: 200 mm ± 2 mm × 200 mm ± 2 mm;
The thickness of the base and walls shall be at least 1,5 mm
The bottom of the container may be perforated to facilitate emptying A suitable plastic plate to cover the bottom has then to be placed inside the container
The dimensions and condition of the container shall be checked at the time of test to ensure that they are within the tolerances
4.5.2.2 Trowel, with a flat blade (see Figure 5), or equivalent, e.g square-bladed shovel
To effectively compact concrete, use either an internal vibrator or a vibrating table An internal vibrator should operate at a minimum frequency of 120 Hz (7,200 cycles per minute), with the vibrating head's diameter not exceeding one-quarter of the smallest container dimension Alternatively, a vibrating table can be employed, functioning at a minimum frequency of 40 Hz (2,400 cycles per minute), ensuring proper consolidation of the concrete.
4.5.2.4 Remixing tray, of rigid construction, made from a non-absorbent material not readily attacked by cement paste
4.5.2.5 Straight edged scraper, having a length of greater than 200 mm
4.5.2.6 Rule, having a length of greater than 400 mm, having 1-mm subdivisions along its entire length with the zero point being at the extreme end of the rule
Clean the container and moisten the inner surfaces using a damp cloth
To fill the container, tilt the trowel sideways from each of the four upper edges in turn, avoiding tamping Once the container is full, remove excess concrete above the rim using a straight-edged scraper with a sawing motion to prevent compaction and ensure a smooth, level surface.
To ensure proper concrete compaction, utilize a vibrating table (reference method) or an internal vibrator until no further volume reduction is achievable During the process, prevent concrete from splashing or leaking to maintain mixture integrity and achieve optimal density.
After compaction, measure the distance between the surface of the compacted concrete and the upper edge of the container at the midpoint of each side, using a ruler accurate to the nearest millimetre Calculate the mean value of these four measurements to ensure consistent compaction assessment.
Dimensions in millimetres a) Before compaction b) After compaction
Figure 6 — Concrete in container, before a) and after b) compaction
The degree of compactability is given by Equation (1)
The degree of compactability, denoted as c, is a key parameter in assessing concrete performance It is influenced by the internal height of the container, represented as h₁, and the mean value, h₂, which is measured to the nearest millimeter Specifically, h₂ is the average distance from the surface of the compacted concrete to the upper edge of the container, providing essential data for evaluating compaction quality.
In addition to the information specified in Clause 7, the test report must include the internal height of the container, the distance measurement from the top of the container to the top of the compacted concrete, and the degree of compactability, accurately expressed to two decimal places.
Flow-table test
This test determines the consistence of fresh concrete by measuring the spread of concrete on a flat plate subjected to jolting
The flow test is applicable to a range of consistence of concrete that corresponds to flow values between
340 mm and 620 mm Outside this range, the measurement of flow may be unsuitable and other methods of determining the consistence should be considered
If the concrete segregates during the test, this test is not suitable (see 4.6.3)
A flow-table is a flat plate with a plan area of 700 mm ± 2 mm by 700 mm ± 2 mm, designed for placing concrete samples It is hinged to a rigid base, allowing the plate to fall from a fixed height to test concrete flow properties This setup, depicted in Figure 7, is essential for assessing the workability of fresh concrete according to standardized testing procedures.
The flow-table top must feature a metal surface with at least 2 mm thickness and a flatness within 1.5 mm, in accordance with ISO 1101:1983 and ISO 1920-3:2004, Annex B This surface should resist cement paste attack and rusting to ensure durability The moving part should have a mass of 16 kg ± 0.5 kg and be attached with a pin-hinge for weight verification The construction must prevent surface distortion, and the tabletop should be hinged to the base in a way that minimizes trapping of aggregate between the hinge surfaces, ensuring reliable performance during testing.
The center of the table should be marked with a cross, with lines parallel to the plate edges, and a central circle measuring 210 mm in diameter ± 1 mm.
Two hard, rigid blocks must be securely attached to the underside of the front corners of the table, serving as non-absorbent stops that do not deform when wet These stops are essential for transferring the tabletop's load to the base without causing deformation or distortion The base frame should be designed to direct this load safely to the supporting surface, minimizing any tendency for the tabletop to bounce or move when freely dropped, ensuring stability and durability.
Footrests shall be provided to assist in stabilizing the table when in use
The fall height of the tabletop, measured at the centre line of the front edge of the top place, shall be limited to
40 mm ± 1 mm by means of one or more stops
A robust handle or lifting mechanism must be installed to facilitate smooth and controlled lifting of the tabletop, preventing jerking motions This system should enable the tabletop to be lifted and lowered freely across the entire lifting height, ensuring safety and ease of use during operation Proper design of the lifting mechanism enhances functionality and user safety, making it an essential feature for optimal performance.
9 toe-board a Travel limited to 40 mm ± 1 mm
4.6.2.2 Mould, made of metal not readily attacked by cement paste or liable to rust and with a minimum thickness of 1,5 mm
The interior of the mold must be smooth and free from projections, including protruding rivets, and should be free from dents to ensure quality The mold is designed as a hollow frustum of a cone with specific internal dimensions to meet manufacturing standards Proper mold maintenance and adherence to design specifications are essential for achieving reliable and defect-free product outcomes.
diameter of base: 200 mm ± 2 mm;
diameter of top: 130 mm ± 2 mm;
Ensure the base and top of the mould are open, parallel, and perpendicular to the cone’s axis for accurate shaping The mould should be equipped with two metal footpieces at the bottom and two handles above for safe handling and stability Additionally, the mould can be clamped to the table, provided that it can be released easily without shifting the mould, to facilitate precise manual operations.
The tamping bar is constructed from a non-absorbing, hard material, featuring a square cross-section of 40 mm ± 1 mm and a minimum length of 200 mm Additionally, a section measuring 120 mm to 150 mm is tapered into a circular shape to form a comfortable handle This design ensures durability and ease of use, adhering to specified structural standards.
4.6.2.4 Scoop, with a width of approximately 100 mm
4.6.2.5 Sampling tray, with minimum dimensions 900 mm × 900 mm × 50 mm deep, of rigid construction and made from a non-absorbent material not readily attacked by cement paste
4.6.2.7 Rule, with a minimum length 700 mm, having at least 5-mm subdivisions along its entire length 4.6.2.8 Timer, with an accuracy of ± 1 s
For accurate results, place the flow table on a flat, stable surface free from vibrations or shocks Ensure the hinged top can be lifted to its designated limit and then freely fall to the lower stop, maintaining proper alignment Proper setup of the flow table is essential for reliable experiments and measurements.
`,,`,,,-`-`,,`,,`,`,,` - the table is supported such that, when the top of the table falls to the lower stop, there is minimal tendency for the top to bounce
Clean the table and the mould and dampen immediately prior to testing, but keep free from superfluous moisture
Ensure contact blocks are clean before use Place the mold centrally on the tabletop for accurate results Secure the mold in position by standing on the two foot pieces or using magnets to prevent movement during the process.
Fill the mould with concrete in two equal layers using the scoop, levelling each layer by tamping lightly
Use the tamping bar to compact the concrete in 10 layers, ensuring each layer is properly settled If needed, add additional concrete to the second layer to maintain an excess above the top of the mould, facilitating proper finishing Carefully scrape off the excess concrete with the tamping bar to level it with the upper edge of the mould Finally, clean any surplus concrete from the tabletop's free area for a smooth and precise finish.
Wait 30 s after scraping off the concrete, then slowly raise the mould vertically by the handles over a period of
To ensure accurate testing, raise the tabletop slowly to the upper stop without hard impact, then allow it to fall freely to the lower stop, repeating this cycle 15 times with each drop lasting between 2 and 5 seconds During the test, measure the maximum dimensions of the concrete spread in two directions, parallel to the table edges (d₁ and d₂), and record each measurement to the nearest 10 mm This process helps assess the concrete's spread consistency under controlled impact conditions.
To ensure concrete quality, inspect for segregation by observing if the cement paste separates from the coarse aggregate, forming a ring of paste extending several millimeters beyond the aggregate Reporting significant segregation indicates that the concrete is unsatisfactory and may compromise its structural integrity Regularly checking for paste segregation helps maintain concrete consistency and adherence to quality standards.
Determine the flow value (d 1 + d 2 )/2 and record to the nearest 10 mm
The test report must include essential details such as the jolting rate, measured in seconds per 15 jolts, along with dimensions d1 and d2 in millimeters It should also present the average test result, calculated as (d1 + d2) / 2, in millimeters Additionally, the report must contain a statement regarding any segregation identified during testing These requirements ensure comprehensive documentation in accordance with relevant testing standards.
Slump-flow test
This test method measures the slump-flow of high-fluidity concrete, including self-compacting and anti-washout underwater concrete It is applicable to concrete with a slump greater than 210 mm, providing essential data on its flowability and workability for quality assessment.
The fresh concrete is placed into a mould in the shape of a cone When the cone is withdrawn upwards, three measurements give indications of the consistence of the concrete:
time to flow to a diameter of 500 mm;
time to end-of-flow
4.7.3.1 Mould (slump cone), as described in 4.3.2.1
Regular annual inspections of the mould are essential to ensure its dimensions and condition stay within specified tolerances Before each use, a thorough visual check should be performed to confirm the mould is clean, undamaged, and free from dents These maintenance practices help ensure optimal mould performance and product quality.
4.7.3.2 Tamping rod, as described in 4.3.2.2
The tamping rod shall be checked annually to ensure that its dimensions and conditions remain within tolerances
4.7.3.3 Base plate, as described in 4.3.2.5
In addition, the base plate shall have minimum dimensions of 800 mm × 800 mm, and two circles having the same centre point shall be marked on its surface:
a circle having a diameter of 200 mm to aid the correct location of the mould;
a circle having a diameter of 500 mm for measuring the time to 500 mm flow of the concrete (see 4.7.4.4)
4.7.3.4 Callipers and measuring scale, with 1 mm increments
4.7.3.5 Measuring jigs (optional), as shown in Figure 11
NOTE Cut angle steel, for instance, is acceptable for these jigs
Measuring jigs may be omitted if the flow can be measured accurately with a measuring scale
3 plate a Measurement with a measuring scale b 90°
4.7.3.6 Container, such as a bucket, with a capacity of approximately 12 l
4.7.3.7 Stopwatches, two, capable of recording time to an accuracy of ± 0,1 s
The watch shall be in calibration at the time of test
4.7.4.1 Placement of mould (slump-cone) and plate
To ensure proper casting, clean and dampen the inner surface of the mould and the top surface of the plate, then wipe away any excess water with an absorbent cloth Position the plate on a stable, vibration-free surface, and use a level to accurately level the plate Place the mould centrally on the plate using the designated mark for precise alignment, setting the foundation for accurate and quality results.
After obtaining the sample, fill the mould by carefully pouring concrete into the cone, ensuring the process is completed within 2 minutes During filling, securely clamp or hold the mould in place by standing on the two foot pieces to prevent movement Careful filling is essential to avoid segregation and overfilling of the mould, ensuring accurate and reliable test results.
High-fluidity concrete should be added to the mould uniformly in one layer without tamping
Anti-washout underwater concrete should be added to the mould in three layers Rod each layer 25 times with a tamping rod as described in 4.3.3
The method of filling shall be recorded
4.7.4.3 Slump-flow measurements and calculation
To perform a slump test, first scrape off the top surface of the concrete to align with the top edge of the slump cone Carefully remove the cone by lifting it vertically once the concrete motion ceases Measure the concrete’s spread in the longest direction and at right angles to it, recording both diameters to the nearest 5 mm If the concrete's shape noticeably deviates from a circle or there is a significant difference between the two measurements, further assessment may be necessary.
50 mm or more, another test shall be conducted on a new sample taken from the same batch
The slump cone should be lifted within 2 to 3 seconds for a 300 mm sample If the sample tends to stick to the cone before dropping, it must be raised slowly over 10 seconds In cases where significant sample residue remains inside the cone, the test is considered void, and the reason must be documented A new test should be performed using a fresh sample from the same batch to ensure accurate results.
The slump-flow, which is the average of the two measurements, shall be calculated and rounded to the nearest 10 mm, or 5 mm when required by the national annex
4.7.4.4 Measurement of time to 500 mm flow
Measure the time from when the mold is first raised until the flow initially reaches the 500-mm diameter circle marked on the plate Use a stopwatch to record this interval with an accuracy of 0.1 seconds.
4.7.4.5 Measurement of time to end-of-flow
Measure the time from the beginning of the raising of the mould to the time when no further flow is observed Measure to an accuracy of 0,1 s, using a stopwatch
The test report must include essential details such as slump-flow, time to 500 mm flow, and time to end-of-flow, in addition to the information specified in Clause 7 It should also document any segregation observed through visual examination and specify the method used for filling and compacting the concrete These comprehensive details ensure accurate assessment of concrete properties and compliance with standards.
Principle
The fresh concrete is compacted into a calibrated rigid and watertight container and is then weighed
This test method may not be suitable for aerated concrete or very stiff concrete that cannot be compacted using normal vibration Caution is advised when applying this method to such types of concrete to ensure accurate results.
Apparatus
5.2.1 Container, watertight, of sufficient rigidity to retain its shape, made of metal not readily attacked by cement paste, having a smooth internal face, with the rim machined to a plane surface
The rim and base of the container must be parallel to ensure proper structure The internal diameter and height should each be at least four times the maximum aggregate size in the concrete, with a minimum measurement of 150 mm, to accommodate accurate testing and ensure consistent results.
The volume of the container shall be not less than 5 l The ratio of the diameter to the height of the container shall be 1,25 W d c /h c W 0,5
The container must be calibrated according to Annex B to determine its accurate volume (V) Calibration should be performed at the time of use to ensure precision To maintain accuracy, the container's calibration should be verified at least once a year.
5.2.2 Filling frame (optional), made of metal not readily attacked by cement paste, fitted tightly to the container
NOTE Filling can be simplified by using a filling frame.
To ensure proper concrete compaction in molds, various methods are recommended: an internal vibrator operating at a minimum frequency of 120 Hz, with a vibrating head no larger than one-quarter of the smallest mold dimension; a vibrating table functioning at a minimum of 40 Hz to achieve optimal compaction; a steel compacting rod, 16 mm ± 1 mm in diameter and 600 mm ± 5 mm in length, with rounded hemispherical ends for effective consolidation; or a compacting bar with a square or round cross-section weighing over 1.8 kg, suitable for hand compacting to achieve dense concrete, thereby ensuring structural integrity and durability.
5.2.4 Balance or scales, capable of determining the mass of the compacted concrete to an accuracy of
0,1 % of the mass of the concrete
5.2.5 Straight-edged scraper, made of steel not less than 100 mm greater in length than the maximum internal dimension of the top of the container
5.2.7 Remixing tray, of rigid construction and made from a non-absorbent material not readily attacked by cement paste
The tray shall be of appropriate dimensions such that the concrete can be thoroughly remixed using the square-mouthed shovel
Sampling
The samples for the tests shall be obtained in accordance with ISO 1920-1 The samples shall be remixed before carrying out the tests.
Procedure
Weigh the container to determine its mass, m 1 , and record the value indicated
When using a filling frame, ensure that the amount of concrete poured leaves a residual layer after compaction This leftover layer should be approximately 10% to 20% of the container's height, preventing overfilling and ensuring proper compaction Properly measuring the concrete volume in relation to the container height is essential for achieving optimal strength and durability in concrete testing.
Fill the concrete in a minimum of two layers
Compact the concrete immediately after placing it in the container in such a way as to produce full compaction of the concrete, with neither excessive segregation nor laitance Compact each layer by using one of the methods described in 5.4.3.2 or 5.4.3.3
Mechanical vibration ensures complete concrete compaction by eliminating large air bubbles on the surface, resulting in a smooth, glazed finish Proper vibration prevents excessive segregation, achieving a durable and high-quality concrete surface.
NOTE 2 To produce full compaction by hand, the number of strokes per layer required will depend upon the consistence of the concrete
Apply the vibration for the minimum duration necessary to achieve full compaction of the concrete Avoid over- vibration, which may cause loss of entrained air
Care should be taken not to damage the container The use of a filling frame is recommended
NOTE Laboratory tests have shown that great care is needed if loss of entrained air is to be avoided when using an internal vibrator
Ensure that the vibrator is kept vertical and not allowed to touch the bottom or sides of the container
To ensure proper concrete compaction, apply vibration only for the minimum necessary duration to achieve full consolidation Securely attach the container to the vibrating table to prevent movement during the process Avoid over-vibration, as it can lead to the loss of entrained air, compromising the concrete's strength and durability.
5.4.3.3 Hand compaction with compacting rod or bar
To ensure proper concrete compaction, distribute the strokes of the compacting rod uniformly across the mold's cross-section Avoid striking the bottom of the container or significantly penetrating previous layers during initial compaction Apply at least 25 strokes per layer to effectively eliminate entrapped air pockets After each layer, tap the container sides with a mallet to release large air bubbles and smooth out depressions, promoting uniform density and reducing voids.
After compacting the top layer, smooth it evenly with a steel float to achieve a level surface aligned with the container's top Skim the surface and rim with a straightedge for a clean finish, then wipe the exterior of the container to ensure it is tidy and ready for use.
5.4.5 Determining the mass and volume of the container
Weigh the container with its contents to determine its mass (m 2 ) and record the value indicated The volume,
V, of the container shall be determined in accordance with Annex B.
Test result
The density is calculated from Equation (2):
The density of fresh concrete (ρ_fr) is calculated using the formula ρ_fr = (m₂ - m₁) / V, where ρ_fr is expressed in kilograms per cubic meter In this equation, m₁ represents the mass of the empty container in kilograms, and m₂ denotes the combined mass of the container and the concrete sample, also in kilograms This method allows for an accurate determination of fresh concrete density essential for quality assessment and structural calculations.
V is the volume, expressed in cubic metres, of the container
The density of the concrete shall be expressed to the nearest 10 kg/m 3
Equations for calculating the volume of concrete per batch and the cement content per cubic metre are given in Annex C.
Test report
The test report must include essential details such as the calculated fresh density of the compacted concrete and, optionally, the consistency of the concrete Additionally, it should provide the calculated volume of concrete per batch if required, along with the calculated cement content of the concrete when necessary These parameters ensure comprehensive documentation of concrete quality and compliance with specified standards.
General
The methods described in this clause are applicable for concrete made with normal weight or relatively dense aggregates passing a 63-mm sieve
Neither method is applicable to concretes made with lightweight aggregates or aggregate with high absorption
This article discusses two testing methods that utilize apparatus based on Boyle-Mariotte’s law The first method, known as the pressure-gauge method, employs a pressure-gauge meter to measure pressure changes accurately The second method, called the water-column method, uses a water-column meter to determine pressure variations through water column height Both methods are effective for precise pressure measurements, making them essential tools in various engineering and scientific applications.
Sampling
When sampling fresh concrete, follow ISO 1920-1 guidelines to ensure accuracy If the concrete contains coarse aggregate particles larger than 63 mm, sieve a representative sample over a 63-mm sieve to obtain slightly more material than needed to fill the test container Perform the sieving carefully to minimize mortar loss and avoid wiping off adhering mortar from coarse aggregates to maintain sample integrity Remix the sample thoroughly before conducting any testing to ensure uniformity and reliable results.
Filling the container and compacting the concrete
The methods for compacting concrete within the container include using an internal vibrator operating at a minimum frequency of 120 Hz (7,200 cycles per minute), with the vibrating head diameter not exceeding one-quarter of the smallest mould dimension Alternatively, a vibrating table with a minimum frequency of 40 Hz (2,400 cycles per minute) can be used For manual compaction, a steel compacting rod or bar is recommended—specifically, a straight, circular cross-section rod with a diameter of 16 mm ± 1 mm, a length of 600 mm ± 5 mm, rounded hemispherical ends, or a square or round cross-section bar weighing more than 1.8 kg These methods ensure proper concrete compaction for structural integrity and quality.
To effectively place concrete, use a scoop to fill the container in three equal layers, minimizing entrapped air Immediately compact each layer to ensure full compaction, preventing segregation and laitance Employ the recommended compaction methods outlined in section 6.3.3 for optimal results.
Full compaction of concrete is achieved through mechanical vibration, which eliminates large air bubbles from the surface, resulting in a smooth, glazed appearance Proper vibration ensures the surface remains free from excessive segregation, indicating optimal compaction.
NOTE 2 The number of strokes per layer required to produce full compaction by hand, will depend upon the consistence of the concrete
Ensure the final layer of material is sufficient to fill the container completely without leaving excess If needed, add a small amount of extra concrete and compact it thoroughly to achieve a full, well-filled fill.
Compact the concrete by one of the methods described below
Apply the vibration for the minimum duration necessary to achieve full compaction of the concrete Avoid over- vibration, which may cause loss of entrained air
Care should be taken not to damage the container The use of a filling frame is recommended
NOTE Laboratory tests have shown that when using an internal vibrator, great care is needed if loss of entrained air is to be avoided
Ensure that the vibrator is kept vertical and not allowed to touch the bottom or sides of the container
Apply vibration for the shortest duration needed to ensure complete concrete compaction Ensure the container is securely attached to the table to prevent movement during vibration Avoid over-vibrating, as this can lead to the loss of entrained air and compromise concrete quality.
6.3.3.3 Hand compaction with compacting rod or bar
Distribute the strokes of the compacting rod evenly across the mold's cross-section to ensure uniform compaction Avoid striking the bottom of the container forcefully or penetrating deeply into previous layers during initial layer compacting Apply at least 25 strokes per layer to effectively remove entrapped air bubbles After each layer, tap the container sides with a mallet to eliminate surface bubbles and smooth out depressions caused by the rod, preventing the retention of trapped air while preserving entrained air within the concrete.
Pressure-gauge method
A known volume of air at a specified pressure is introduced into a sealed chamber containing an unknown volume of air within the concrete sample The pressure gauge dial is calibrated to display the resulting pressure as a percentage of air content This method allows for accurate measurement of the air voids in concrete, essential for assessing its durability and quality.
The apparatus shall be in calibration, using the procedure given in Annex E, at the time of the test
It is recommended that the apparatus be calibrated at a frequency dependent on use but at least once per year
The pressure-gauge method apparatus comprises a flanged cylindrical container made of durable steel or hard metal resistant to cement paste attack, with a minimum capacity of 5 liters The vessel's dimensions should feature a diameter-to-height ratio between 0.75 and 1.25, ensuring accurate pressure measurement during testing.
The vessel's outer rim and interior surfaces must be machined to a smooth finish to ensure optimal performance It is essential that the container is watertight and designed to withstand an operating pressure of approximately 0.2 MPa Additionally, both the container and cover assembly should be constructed for durability and safety under these pressure conditions.
`,,`,,,-`-`,,`,,`,`,,` - b) cover assembly, consisting of a flanged rigid cover, of steel or other hard metal not readily attacked by cement paste
The outer rim, lower surface of the flange, and interior surfaces must be machined to a smooth finish to ensure proper sealing The cover should include provisions for secure clamping to the container, creating a pressure seal that prevents air entrapment at the joint between the cover and container flanges Additionally, the assembly must be equipped with a pressure gauge calibrated to measure air content from 0% to at least 8%, with a preferred range up to 10%, ensuring accurate monitoring of internal pressure.
The scale of the gauge shall be graduated as follows:
0,5 % for the range (6 to 10) % d) air pump, a pressure pump which may be built into the cover
4 extension tubing for calibration checks
Figure 12 — Pressure-gauge method apparatus
6.4.2.3 Sampling tray, of minimum dimensions 900 mm × 900 mm × 50 mm deep, of rigid construction and made from a non-absorbent material not readily attacked by cement paste
6.4.2.5 Syringe, rubber, suitable for injecting water into the container either through valve A or valve B
6.4.2.6 Mallet, soft-faced, with a mass of approximately 250 g
6.4.3 Filling the container and compacting the concrete
Fill the container and compact the concrete in accordance with 6.3
Thoroughly clean the flanges of the container and cover assembly to ensure a proper seal Clamp the cover securely in place, checking that there is a tight seal between the cover and the container Close the main air valve, then open valve A and valve B to prepare for water injection Using a rubber syringe, inject water through either valve A or B until it flows out of the other valve, indicating the system is filled Lightly tap the apparatus with a mallet to expel any entrapped air, ensuring accurate and reliable testing results.
Ensure the air-bleeder valve on the air chamber is closed before pumping air into the chamber until the pressure gauge hand reaches the initial pressure line Allow the compressed air to cool to ambient temperature, then stabilize the gauge reading by adding or releasing air as needed, softly tapping the gauge to ensure accuracy Close both valve A and valve B, then open the main air valve, and sharply tap the sides of the container to stabilize the pressure reading After lightly tapping the pressure gauge, record the apparent air percentage (C1) Finally, open valves A and B to safely release the pressure before removing the cover assembly.
Water-column method
Water is introduced to a specified height above a compacted concrete sample of known volume within a sealed container, with a predetermined air pressure applied over the water The reduction in air volume inside the concrete is measured by observing the water level decrease, which is calibrated to indicate the percentage of air within the concrete sample This method provides an accurate assessment of the concrete's porosity and air content, essential for quality control in construction materials.
The testing apparatus must be calibrated at the time of testing following the procedure outlined in Annex F If the equipment has been relocated to a site with an elevation change of more than 200 meters from the previous calibration point, it must undergo recalibration as per Annex F requirements Regular calibration ensures accurate and reliable test results, complying with industry standards.
It is recommended that the apparatus be calibrated at a frequency dependent upon use, but at least once per year
The water-column method apparatus must include a flanged cylindrical vessel made of durable steel or other hard metals resistant to cement paste attack, with a minimum capacity of 5 liters The vessel's dimensions should ensure a diameter-to-height ratio between 0.75 and 1.25, as specified in Figure 13.
The flange's outer rim and upper surface, along with the vessel's interior surfaces, must be machined to achieve a smooth finish, ensuring optimal sealing and performance The container shall be watertight and designed to withstand an operating pressure of approximately 0.1 MPa Additionally, both the container and cover assembly should be sufficiently rigid to limit the pressure expansion constant, e, to no more than 0.1%, thus maintaining structural integrity under pressure.
`,,`,,,-`-`,,`,,`,`,,` - b) cover assembly, a flanged rigid conical cover, fitted with a standpipe
The cover must be made of durable steel or other hard metals that are resistant to cement paste attack It should feature interior surfaces inclined at a minimum of 10° from the flange surface to ensure proper sealing The outer rim, lower flange surface, and sloping interior face must be machined smoothly to achieve a tight fit Additionally, the cover should include provisions for secure clamping to the container, ensuring a pressure seal that prevents air entrapment at the flange joint A standpipe, integral to the system, can be a graduated glass tube or a uniform bore metal tube with an attached glass gauge for accurate fluid level measurement.
The graduated scale should display an air content range from 0% to at least 8%, ideally extending to 10%, to ensure accurate measurement It must be precisely graduated with divisions every 0.1% of air content, with each division spaced at least 2 mm apart to enhance readability and precision.
A convenient scale is to designate 25 mm as representing 1% of air content The cover should be equipped with essential components, including a suitable venting device for the air chamber, a non-return air-inlet valve, and a small valve for releasing water.
The applied pressure must be accurately indicated by a pressure gauge connected to the air chamber above the water column This gauge should feature graduations every 0.005 MPa, with divisions spaced at least 2 mm apart, and have a full-scale reading of 0.2 MPa to ensure precise pressure measurement Additionally, a deflecting plate or spray tube—a durable, non-corrodible disc of at least 100 mm in diameter—should be used to minimize disturbances to the concrete during water addition, maintaining the integrity of the testing process.
An appropriate brass spray tube can be used either as part of the cover assembly or installed separately, designed to ensure efficient water distribution The spray tube must be constructed to spray water onto the cover walls in a way that flows down the sides, minimizing disturbance to the concrete surface Additionally, an air (pressure) pump equipped with a lead should be connected to the non-return air-inlet valve on the cover assembly to facilitate proper airflow and pressure regulation.
6.5.2.4 Remixing tray, of rigid construction, made from a non-absorbent material not readily attacked by cement paste
It shall be of appropriate dimensions such that the concrete can be thoroughly remixed using a square- mouthed shovel
6.5.2.6 Container, fitted with a spout, having a capacity of 2 l to 5 l, to fill the apparatus with water 6.5.2.7 Mallet, soft-faced, with a mass of approximately 250 g
`,,`,,,-`-`,,`,,`,`,,` - a) Zero pressure b) System operating at pressure P c) Zero pressure after release of pressure P Key
The pressure-lowered level, H1, at pressure P, and the zero-pressure level, H2, are used to determine the material's volume, with the difference (H1 – H2) representing specific corrections When the container holds concrete, this difference equals C1, indicating the volume change due to pressure Conversely, for containers holding only aggregate and water, the difference equals G, the aggregate correction factor, to account for the presence of water and the aggregate's compressibility Understanding these measurements and correction factors is essential for accurate volume assessment in concrete and aggregate testing.
Figure 13 — Water-column method apparatus
6.5.3 Filling the container and compacting the concrete
Fill the container and compact the concrete as described in 6.3
Thoroughly clean the flanges of the container and cover assembly to ensure proper sealing If the spray tube is absent, position the deflecting plate centrally on the concrete and press it into contact Clamp the cover assembly securely to maintain a good pressure seal Fill the apparatus with water and tap lightly with a mallet to remove air from the interior surfaces Bleed the system through the small valve with the air vent open until the water level in the standpipe is zero Close the air vent, then apply the operating pressure using an air pump Record the initial gauge tube reading (h1), then release the pressure and check the gauge tube again If the second reading (h2) indicates 0.2% air content or less, record the result accordingly.
To determine the apparent air content, measure the difference (h₁ - h₂) and record it as C₁ to the nearest 0.1% air by volume If h₂ exceeds 0.2%, recalibrate by applying the operating pressure and taking gauge tube readings h₃ and h₄ after pressure release If the difference (h₄ - h₂) is 0.1% air content or less, record the value (h₃ - h₄) as the apparent air content; however, if this difference exceeds 0.1%, it may indicate leakage, and the test should be disregarded.
Calculations and expression of results
6.6.1 Air content of the sample tested
Calculate the air content, C c , of the concrete in the container from Equation (3):
C 1 is the apparent air content, expressed to the nearest 0,1 %, of the sample tested;
G is the aggregate correction factor, expressed to the nearest 0,1 %
The aggregate correction factors shall be determined as described in Annex G and Annex H
Express the air content as a percentage to the nearest 0,1 %
In some cases, when it is required by the national annex, the air content of concrete can be calculated as shown in Equation (4): abs fr c abs
= − × (4) where ρ fr is the density, expressed in kilograms per cubic metre, of fresh concrete calculated in 5.5; ρ abs is the absolute density of concrete which does not include air
6.6.2 Air content of the mortar fraction
When required, calculate the air content of the mortar fraction of the concrete, C m , from Equation (5): m c c m c c m
V_m represents the absolute volume, measured in cubic metres, of the mortar fraction components—cement, water, and fine aggregate—in concrete, excluding air It is calculated based on the original batch masses to ensure accurate measurement of the concrete mix's constituents.
V c is the absolute volume, expressed in cubic metres, of the constituents of the concrete, air-free, as determined from the original batch masses
Express the air content as a percentage to the nearest scale division.
Test report
In addition to the information required in Clause 7, the test report shall include the following:
identification of test method and procedure used, i.e pressure-gauge method or water-column method;
information relevant to the specific test, e.g altitude;
calculated air content (C c ) of the concrete;
when required, calculated air content of the mortar fraction (C m )
The test report must include essential information such as the identification of the test sample, the location and time of testing, and details about the test conditions Optional data may include the temperature of the remixed sample and observations on the sample's condition Additionally, the report should specify the method of compaction used during testing to ensure comprehensive documentation and compliance with testing standards.
for mechanical compaction, the duration,
For hand compaction testing, it is essential to record the number of strokes used during the process The identification of the person performing the test or the specific segment of the test should be documented to ensure accountability Any deviations from the standard test method must be noted accurately Additionally, the person conducting the test should declare that the procedure was carried out in accordance with ISO 1920-2, except for any deviations noted in section 7h, to ensure compliance and reliability of results.
informative) Examples of test reports and worksheets
Precision — Data for the density measurements
Precise data are provided in Table A.1, detailing fresh concrete density measurements obtained from the same sample Each test result reflects a single density determination, ensuring accurate and reliable measurement of fresh concrete density.
Table A.1 — Precision data for density of fresh concrete measurements Range Repeatability conditions a Reproducibility conditions b kg/m 3 s r kg/m 3 r kg/m 3 s R kg/m 3
The difference between two test results obtained from the same sample by a single operator using the same apparatus within the shortest feasible time interval should not exceed the repeatability value (r) more than once in 20 cases under normal and correct operating conditions Additionally, test results on the same sample conducted within the shortest feasible time interval by two different operators, each using their own apparatus, should differ by no more than the reproducibility value (R) on average once in 20 cases during proper method operation.
NOTE 1 The containers used complied with the requirements:
minimum thickness of metal: 4 mm;
radius between wall and base: 20 mm
NOTE 2 The precision data include the procedures of sampling, as well as the determination of the density of the fresh concrete
NOTE 3 For further information on precision, and for definitions of the statistical terms used in connection with precision, see
Calibration of the container for the density test
The apparatus shall be as follows:
B.1.1 Scales or balance, capable of weighing the container either empty or full of water to an accuracy of
Weight the empty container and glass plate to an accuracy of 0,1 % and record the indicated mass
Place the container on a horizontal surface and fill it with water at a temperature of 20 °C ± 5 °C Ensure the container is filled to overflowing, then slide a glass plate over it to exclude any air bubbles Remove any excess water from the outside of the container and plate to ensure accurate results.
Weigh the container, glass plate and water to an accuracy of 0,1 % and record the indicated mass
Calculate the volume of the container by dividing the total mass, expressed in kilograms, of water required to fill the container by 998
Express the volume, V, expressed in cubic metres, of the container to an accuracy of 0,1 %
The container shall be calibrated before initial use and at least annually thereafter
It is recommended that the balance be calibrated at least annually
Additional calculations for the density test
Once the density of the compacted fresh concrete has been determined, it is possible to use the result to calculate a) volume of concrete per batch; b) cement content
C.2 Calculation of volume of concrete per batch
If the volume of concrete produced per batch is required, it shall be calculated from Equation (C.1): b T fr,c
The volume of concrete produced per batch (Vb) is measured in cubic meters, reflecting the total amount of concrete generated The total mass of all constituents used in the batching process (mT) is expressed in kilograms, ensuring precise calculation of material quantities Additionally, the density of fully-compacted fresh concrete (ρfr,c) is specified in kilograms per cubic meter, which is essential for evaluating the concrete's workability and structural properties.
The result shall be expressed to an accuracy of 1 %
If the cement content of the fresh concrete is required, it shall be calculated from the formula: fr,c c c b T or m
C is the cement content, expressed in kilograms per cubic metre: ρ fr,c is the density, expressed in kilograms per cubic metre, of the fully-compacted fresh concrete;
Vb represents the volume of concrete produced per batch, measured in cubic meters The total mass of all constituents used in the batch is denoted as mT, expressed in kilograms Additionally, mc refers specifically to the mass of cement included in the batch, also measured in kilograms Understanding these parameters is essential for accurate concrete batching and quality control.
The result shall be expressed to the nearest 5 kg/m 3
Precision data for the water-column method are provided in Table D.1, which is essential for accurate air content measurements in concrete These data apply specifically to air content tests conducted using the water-column method on concrete samples that are taken from the same batch The measurements are performed on concrete that is compacted manually for each test, ensuring consistent and reliable air content determinations.
Table D.1 — Precision data for air content measurements Level Repeatability conditions a Reproducibility conditions b
When the same operator uses the same equipment to test a sample within the shortest practical time, the difference between two results should not exceed the repeatability value, r, more than once in 20 cases under normal and proper operating conditions Similarly, when two different operators use their own equipment to test the same sample within the shortest feasible interval, the results should differ by no more than the reproducibility value, R, on average, only once in 20 cases during normal and correct method operation.
NOTE For further information on precision, and for definitions of the statistical terms used in connection with precision, see
Calibration of apparatus — Pressure-gauge method
The calibration test should be performed regularly to ensure the accuracy of the air content readings on the pressure gauge dial Recalibration is not necessary when changing elevation or atmospheric pressure, as these factors do not affect the instrument’s calibration Frequent testing helps maintain precise measurements and reliable performance of the pressure gauge.
The apparatus shall be as follows:
E.2.1 Calibration cylinder, made of brass or other non-corrodible metal having a capacity of approximately
0,3 l, which may be integral with the cover assembly
E.2.2 Transparent plate, rigid and transparent, suitable for use as a closure for the container
Balances should be capable of weighing up to 1 kg with an accuracy of ± 0.5 g within the testing range, ensuring precise measurements for smaller samples Additionally, a calibrated balance capable of weighing up to 20 kg with an accuracy of ± 5 g is essential for larger quantities, providing reliable results across different weight ranges Proper calibration and measurement accuracy are crucial for maintaining consistency and reliability in testing processes.
E.3 Checking the capacity of the container
The capacity of the container is found by determining the mass of water, m w,con , required to fill it
Apply a thin layer of grease to the container's flange to ensure a watertight seal between the transparent plate and the container top Fill the container with water at ambient temperature, then carefully place the transparent plate over it to eliminate any convex meniscus, creating a smooth, bubble-free surface for accurate observations.
Wipe away surplus water and determine the mass of the container filled with water by weighing on the balance
E.4 Checking air content graduations on the pressure gauge
Screw the extension tubing into the threaded hole beneath valve A on the underside of the cover assembly and secure it to ensure a proper pressure seal Close the main air valve and open valves A and B, then add water through valve A to expel trapped air via valve B Pump air into the chamber until the pressure reaches the initial pressure line, then allow the air to cool and stabilize the gauge reading by adjusting the air volume as needed Finally, tap the pressure gauge lightly and close valve B to complete the process.
To calibrate the apparatus, remove water until the calibration cylinder is just filled or reaches a marked line, then determine the displaced water's mass, m_w,dis, by weighing it on a precision balance.
Control of water flow depends on the apparatus design: it can be managed by opening valve A and utilizing the main air valve for flow regulation, or by opening the main air valve and adjusting valve A Proper operation ensures efficient water flow management tailored to specific system configurations.
To release pressure in the container, open valve B; if an auxiliary tube is used for filling the calibration cylinder, open valve A to drain the tube back into the container, or close valve A immediately after filling the calibration vessel if it is integrated into the cover assembly The air volume in the container equals the displaced water volume; then, close all valves and pump air into the chamber until the pressure reaches the initial level before opening the main air valve The pressure gauge reading indicates the percentage of air, C₁, within the container, calculated as C₁ = (m_w,dis / m_w,con) × 100%.
When multiple determinations indicate the same deviation from the correct air content, reset the pressure gauge to the proper air content value and repeat the test Continue this process until the gauge reading matches the calibrated air content within 0.1%, ensuring accurate measurement.
Calibration of apparatus — Water-column method