Laboratory
The laboratory where preparation of specimens takes place shall be maintained at a temperature of
(20 ± 2)°C and a relative humidity of not less than 50 %
The moist air room or the large cabinet for storage of the specimens in the mould shall be maintained at a temperature of (20,0 ± 1,0)°C and a relative humidity of not less than 90 %
Storage containers used for curing specimens in water must be made from non-reactive materials with cement It is essential to maintain the water temperature at (20.0 ± 1.0) °C for optimal curing conditions.
In the laboratory, it is essential to record the air temperature and relative humidity at least once daily during working hours Additionally, the temperature and relative humidity in the moist air room or cabinet must be monitored every four hours to ensure optimal conditions.
Cement, CEN Standard sand (see 5.1.3), water and apparatus used to make and test specimens shall be at a temperature of (20 ± 2) °C
Where temperature ranges are given, the target temperature at which the controls are set shall be the middle value of the range.
General requirements for the equipment
Proper tolerances, as illustrated in Figures 1 to 5, are crucial for the effective functioning of equipment during testing procedures If routine measurements indicate that these tolerances are not achieved, the equipment must be either rejected, adjusted, or repaired Additionally, it is essential to maintain records of all control measurements.
Acceptance testing for new equipment must include measurements of mass, volume, and dimensions, with a focus on critical dimensions where specific tolerances are defined in this document.
In those cases where the material of the equipment can influence the results, the material is specified and shall be used
The approximate dimensions shown in the figures are provided as guidance to equipment manufacturers or operators Dimensions, which include tolerances, are obligatory.
Test sieves
Wire cloth test sieves conforming to ISO 3310-1 shall be of the sizes from ISO 565 given in Table 1 (series R 20)
Table 1 — Aperture of test sieves Square mesh size (mm)
Mixer
The mixer is designed with a stainless steel bowl that has a capacity of approximately 5 liters, featuring secure attachment mechanisms to the mixer frame for stability during operation It allows for precise height adjustments in relation to the blade, as well as the gap between the blade and bowl Additionally, the mixer includes a stainless steel blade that rotates around its own axis while simultaneously moving in a planetary motion around the bowl's axis, powered by an electric motor The blade operates at controlled speeds with opposite rotation directions, ensuring that the speed ratio between the two movements is not a whole number.
Blades and bowls shall form sets which shall always be used together
The gap between blade and bowl shown in Figure 1 shall be checked regularly The gap of
The term (3 ± 1) mm describes the proximity of the blade in an empty bowl to the wall In situations where direct measurement is challenging, simple tolerance gauges, also known as feeler gauges, can be effectively utilized.
NOTE The dimensions marked as approximate on Figure 1 are for the guidance of manufacturers
The mixer shall operate at the speeds given in Table 2 when mixing the mortar
Table 2 — Speeds of mixer blade
Rotation Planetary movement min -1 min –1
Moulds
The mould shall consist of three horizontal compartments so that three prismatic specimens
40 mm × 40 mm in cross section and 160 mm in length can be prepared simultaneously
A typical design is shown in Figure 2
The mould must be constructed from steel with wall thicknesses around 10 mm Additionally, the internal side faces of the mould should be case hardened to achieve a minimum Vickers hardness of HV 200.
NOTE 1 A minimum Vickers hardness value of HV 400 is recommended
The mould must be designed to allow for the safe removal of moulded specimens without causing any damage Each mould should include a machined steel or cast iron baseplate for stability When assembled, the mould must be securely and rigidly fastened to the baseplate to ensure proper functionality.
The assembly must be designed to prevent distortion and visible leakage during operation Additionally, the baseplate should ensure proper contact with the compacting apparatus table and maintain sufficient rigidity to avoid secondary vibrations.
NOTE 2 Moulds and jolting apparatus from different manufacturers may have unrelated external dimensions and masses, so their compatibility needs to be ensured by the purchaser
Each component of the mold must be clearly marked with identification stamps to aid in assembly and guarantee adherence to specified tolerances It is essential that similar parts from different mold assemblies are not swapped or interchanged.
The assembled mould must meet specific criteria regarding its internal dimensions and tolerances: the length should be (160 ± 1) mm, the width (40.0 ± 0.2) mm, and the depth (40.1 ± 0.1) mm Additionally, the flatness tolerance for each internal side face must not exceed 0.03 mm, and the perpendicularity tolerance relative to the bottom surface and adjacent internal face should be within 0.2 mm Furthermore, the surface texture of each internal side face must not be rougher than N8, as specified.
Moulds shall be replaced when any one of the specified tolerances is exceeded The mass of the mould shall accord with the requirement for the combined mass in 4.6
To prepare the cleaned mould for use, it is essential to apply a suitable sealing material to the outer joints, ensuring a secure seal Additionally, a thin film of mould oil should be applied to the internal surfaces of the mould for optimal performance.
NOTE 3 Some oils have been found to affect the setting of cement; mineral-based oils have been found to be suitable
A metal hopper with vertical walls, measuring between 20 mm and 40 mm in height, is essential for efficiently filling the mould The hopper walls should overlap the mould's internal walls by no more than 1 mm when viewed from above Additionally, the outer walls of the hopper must include a positioning mechanism to ensure accurate alignment over the mould.
For spreading and striking off the mortar two spreaders and a metal straightedge of the type shown in Figure 3 shall be provided
1 Striking off direction with sawing motion
Jolting apparatus
The jolting apparatus (a typical design is shown in Figure 4) shall conform to the following requirements
The apparatus features a rectangular table securely attached to two lightweight arms, pivoting at approximately 800 mm from the table's center At the center of the table's lower face, there is a rounded projecting lug, positioned above a small stop with a flat upper surface In its resting state, the normal line through the contact point of the lug and stop remains vertical, ensuring the table's top face is horizontal, with corner levels not deviating more than 1.0 mm from the mean level The table's dimensions are equal to or exceed those of the mould baseplate, and it includes a precision-machined upper surface along with clamps for secure mould attachment.
The combined mass of the table, including arms, empty mould, hopper and clamps shall be (20,0 ± 0,5) kg
The arms connecting the table assembly to the pivot must be rigid, constructed from round tubing with an outside diameter between 17 mm and 22 mm, as specified in ISO 4200 The total weight of the two arms, including any cross bracing, should be (2.25 ± 0.25) kg Pivot bearings should be of the ball or roller type and designed to prevent the entry of grit or dust Additionally, the horizontal displacement of the table's center due to pivot play must not exceed 1.0 mm.
The lug and the stop shall be made of through-hardened steel of at least HV 500 Vickers hardness value The curvature of the lug shall be about 0,01 mm -1
In operation, the table is raised by a cam and allowed to fall freely from a height of (15,0 ± 0,3) mm before the lug strikes the stop
The cam must be constructed from through-hardened steel with a minimum hardness of HV 400 Vickers, and its shaft should be supported by ball bearings that allow for a free fall of (15.0 ± 0.3) mm To minimize wear, the cam follower should be designed for durability The cam will be powered by a 250 W electric motor, operating at a consistent speed of one revolution per second, and will include a control mechanism and counter to ensure that each jolting period lasts exactly 60 seconds and consists of 60 jolts.
To ensure optimal functionality, the mould should be positioned on the table so that the longitudinal dimension of the compartments aligns with the direction of the arms and is perpendicular to the cam's axis of rotation It is essential to include suitable reference marks to assist in accurately positioning the mould, ensuring that the center of the central compartment is directly above the point of impact.
The apparatus must be securely positioned on a concrete block weighing approximately 600 kg and measuring about 0.25 m³, ensuring an optimal working height for the mold Additionally, the entire base of the concrete block should rest on an elastic pad, such as natural rubber, which provides effective vibration isolation to prevent external disturbances from impacting the compaction process.
To ensure a stable and vibration-free installation, the apparatus must be securely anchored to the concrete base using anchor bolts, with a thin layer of mortar applied between the apparatus base and the concrete.
The flexural strength testing apparatus must be able to apply loads up to 10 kN, ensuring an accuracy of ± 1.0% within the upper four-fifths of its load range Additionally, the loading rate should be maintained at (50 ± 10) N/s for optimal results.
The apparatus must include a flexure device featuring two steel supporting rollers, each with a diameter of (10.0 ± 0.5) mm, positioned (100.0 ± 0.5) mm apart, and a centrally located third steel loading roller of the same diameter The length of all rollers should range from 45 mm to 50 mm, as illustrated in Figure 5.
Figure 5 — Arrangement of loading for determination of flexural strength
The three vertical planes aligned with the axes of the rollers must be parallel, equidistant, and perpendicular to the test specimen's direction To ensure a uniform load distribution across the specimen's width without inducing torsional stresses, one supporting roller and the loading roller should have the ability to tilt slightly.
The testing machine for determining compressive strength must have an appropriate capacity and an accuracy of ± 1.0% of the recorded load in the upper four-fifths of its range, verified according to EN ISO 7500-1 It should ensure a load increase rate of (2,400 ± 200) N/s and include an indicating device that retains the failure value after unloading, achievable through a maximum indicator on a pressure gauge or a digital display memory Additionally, manually operated machines must be equipped with a pacing device to aid in controlling the load increase.
The ram's vertical axis must align with the machine's vertical axis, ensuring that the ram moves vertically during loading Additionally, the resultant forces should align with the specimen's center, while the lower machine platen's surface must remain perpendicular to the machine's axis throughout the loading process.
The center of the upper platen's spherical seating must align with the intersection of the vertical machine axis and the lower surface of the upper platen, maintaining a tolerance of ± 1 mm While the upper platen is designed to align freely upon contact with the specimen, it is essential that the relative position of the upper and lower platens remains constant during the loading process.
The testing machine must feature platens constructed from tungsten carbide or hardened steel with a minimum Vickers hardness of HV 600 These platens should have a thickness of at least 10 mm and dimensions of (40.0 ± 0.1) mm in both width and length The flatness tolerance across the entire contact surface with the specimen must not exceed 0.01 mm, adhering to ISO 1101 standards Additionally, the surface texture must fall within the range specified by ISO 1302, being no smoother than N3 and no rougher than N6.
Two auxiliary plates made of tungsten carbide or through-hardened steel, with a minimum Vickers hardness of HV 600 and a thickness of at least 10 mm, may be utilized It is essential to ensure that these auxiliary plates are centered accurately to the loading system axis within a tolerance of ± 0.5 mm Additionally, the alignment between the auxiliary plates must be maintained with a tolerance not exceeding ± 0.5 mm from their respective centers.
In situations where spherical seating is absent, obstructed, or exceeds a diameter of 120 mm in the testing machine, it is necessary to utilize a jig that complies with standard 4.9.
Compressive strength testing machine
The compressive strength testing machine must have an appropriate capacity and an accuracy of ± 1.0% of the recorded load in the upper four-fifths of its range, as verified by EN ISO 7500-1 It should achieve a load increase rate of (2,400 ± 200) N/s and include an indicating device that retains the failure value after unloading, either through a maximum indicator on a pressure gauge or a digital display memory Additionally, manually operated machines must be equipped with a pacing device to ensure controlled load increases.
The ram's vertical axis must align with the machine's vertical axis, ensuring that during loading, the ram moves vertically Additionally, the force resultant should pass through the specimen's center, while the lower machine platen's surface must remain perpendicular to the machine's axis throughout the loading process.
The center of the upper platen's spherical seating must align with the intersection of the vertical machine axis and the lower surface of the upper platen, allowing for a tolerance of ± 1 mm While the upper platen can adjust its position upon contact with the specimen, it is essential that the alignment between the upper and lower platens remains constant during the loading process.
The testing machine should be equipped with tungsten carbide platens or alternatively hardened steel platens with a Vickers hardness of at least HV 600 These platens must meet specific dimensional requirements, being at least 10 mm thick and 40 mm in width and length, with a tolerance of ± 0.1 mm Additionally, the platens must adhere to strict flatness and surface texture standards, with a flatness tolerance of no greater than 0.01 mm according to ISO 1101, and a surface texture between N3 and N6 as per ISO 1302.
Two auxiliary plates made of tungsten carbide or through-hardened steel, with a minimum Vickers hardness of HV 600 and a thickness of at least 10 mm, should be included These plates must be centered accurately to the loading system's axis within ± 0.5 mm and aligned with each other to a tolerance not exceeding ± 0.5 mm.
In cases where spherical seating is absent, obstructed, or exceeds a diameter of 120 mm in the testing machine, a jig that complies with standard 4.9 must be utilized.
The testing machine can feature multiple load ranges, with the maximum value of the lower range ideally set at about one-fifth of the highest value in the subsequent higher range.
NOTE 2 The machine should be provided with an automatic method for adjusting the rate of loading and with equipment for recording the results
To ensure proper adjustment during testing, the spherical seating of the machine can be lubricated, but care must be taken to avoid any movement of the platen under load It's important to note that lubricants designed for high-pressure conditions are not appropriate for this application.
In conventional testing machines, the terms 'vertical', 'lower', and 'upper' typically describe alignment along the vertical axis; however, it is important to note that machines with non-vertical axes are also acceptable for use.
Jig for compressive strength testing machine
When using a jig as specified in section 4.8, it must be positioned between the machine's platens to effectively transfer the machine's load onto the compression surfaces of the mortar specimen.
The jig incorporates a lower plate within its lower platen, while the upper platen transfers the load through an intermediate spherical seating This assembly is designed to slide vertically with minimal friction, ensuring smooth movement within the jig It is essential to maintain cleanliness in the jig, allowing the spherical seating to move freely so that the platen can initially adapt to the specimen's shape and remain stationary during testing All specifications outlined in section 4.8 are applicable when utilizing the jig.
Balance
Balance, capable of weighing to an accuracy of ± 1 g.
Timer
Timer, capable of measuring to an accuracy of ± 1 s
6 Spherical seating of the jig
7 Upper platen of the jig
9 Lower platen of the jig
11 Lower platen of the machine
Figure 6 — Typical jig for compressive strength testing
Sand
CEN Standard sands, produced in multiple countries, are essential for assessing cement strength as outlined in this document These sands must comply with the specifications of 'CEN Standard sand, EN 196-1' as detailed in section 5.1.3 Additionally, manufacturers of CEN Standard sand are required to conduct verification testing, which will be subject to inspection by an accredited certification body.
To address the challenges in fully characterizing CEN Standard sands, validation against the CEN Reference sand outlined in section 5.1.2 will be conducted through certification and verification testing, as detailed in Clause 11.
The CEN Reference sand, of which a limited stockpile is maintained as reference material, is a natural, siliceous sand consisting of rounded particles and has a silica content of at least 98 %
Its particle size distribution lies within the limits given in Table 3
Table 3 — Particle size distribution of the CEN Reference sand
NOTE Information on the CEN Reference sand may be obtained from Normensand GmbH, D-59269 Beckum, Germany
CEN Standard sand must meet the particle size distribution requirements outlined in section 5.1.2, determined through sieve analysis of a representative sample weighing at least 1,345 grams Sieving should continue until the amount of sand passing through each sieve is below 0.5 grams per minute.
The moisture content of sand must be below 0.2%, measured by the mass loss of a representative sample after drying at temperatures between 105 °C and 110 °C until a constant mass is achieved, and expressed as a percentage of the dried sample's mass.
Production determinations must be conducted daily to ensure compliance; however, these measures alone do not guarantee that CEN Standard sand performs comparably to CEN Reference sand To establish and uphold this equivalence, validation testing as outlined in Clause 11 is essential.
Cement
To ensure accurate testing, cement should be exposed to ambient air for the shortest time necessary If the cement needs to be stored for over 24 hours before testing, it must be kept in completely filled, airtight containers made from non-reactive materials.
The laboratory sample shall be homogenised, by machine or other means as described in EN 196-7, before taking sub-samples for testing.
Water
For validation testing, distilled or deionised water is required, while drinking water may be acceptable for other tests In the event of any disputes, distilled or deionised water will be the standard used.
Composition of mortar
The proportions by mass shall be one part of the cement (5.2), three parts of CEN Standard sand (5.1), and one half part of water (5.3) (water/cement ratio 0,50)
Each batch for three test specimens shall consist of (450 ± 2) g of cement, (1 350 ± 5) g of sand and
Mixing of mortar
Accurately weigh the cement and water using a balance, ensuring that when water is added by volume, it is dispensed with an accuracy of ± 1 ml Each batch of mortar should be mixed mechanically with a mixer, adhering to strict timing for switching the mixer on and off, which must be maintained within ± 2 seconds.
To mix the ingredients, begin by placing water and cement into the bowl, ensuring no loss occurs Once the water and cement are combined, start the mixer at low speed and record this moment as 'zero time.' After 30 seconds, gradually add sand over the next 30 seconds Then, switch the mixer to high speed and continue mixing for another 30 seconds.
'Zero time' marks the starting point for calculating the demoulding times of specimens and strength determination To prepare the mixture, pause the mixer for 90 seconds; during the initial 30 seconds, use a rubber or plastic scraper to remove mortar from the bowl's walls and bottom, then reposition it in the center After this, resume mixing at high speed for an additional 60 seconds.
NOTE 2 Normally these mixing operations are carried out automatically Manual control of these operations and timings may be used
Size of specimens
The test specimens shall be 40 mm × 40 mm × 160 mm prisms.
Moulding of test specimens
Immediately after preparing the mortar, mold the specimens by securely clamping the mold and hopper to the jolting table Using a suitable scoop, introduce the first of two layers of mortar, approximately 300 g each, into the mold compartments directly from the mixing bowl.
To achieve an even application of mortar, use a large spreader held nearly vertically, ensuring its shoulders touch the hopper's top while moving it back and forth across each mould compartment After spreading, compact the initial mortar layer with 60 jolts from the jolting apparatus For the second layer, add a surplus of mortar and level it with a small spreader, followed by another 60 jolts for compaction.
Gently lift the mould from the jolting table and detach the hopper, then use a metal straightedge to strike off any excess mortar Hold the straightedge almost vertically but slightly inclined in the direction of the strike, and use a slow, transverse sawing motion to remove the excess in both directions For a smoother finish, repeat the process with the straightedge held at a more acute angle.
The required number of sawing motions and the angle of the straightedge are influenced by the consistency of the mortar; stiffer mixtures necessitate more sawing motions and a sharper angle Additionally, fewer transverse sawing motions are needed for smoothing compared to striking off.
Wipe off the mortar left on the perimeter of the mould as a result of the striking-off
Label or mark the moulds for identification purposes
Handling and storage before demoulding
Place a plate of glass, steel or other impermeable material which does not react with cement of approximate size 210 mm × 185 mm × 6 mm on the mould
NOTE In the interest of safety, ensure that any glass plates used have ground edges
Immediately position each covered mould on a horizontal surface in the moist air room or cabinet, ensuring that the moist air circulates around all sides of the mould Avoid stacking moulds on top of one another, and ensure that each mould is removed from storage at the designated time for demoulding.
Demoulding of specimens
Store demoulded specimens for testing at 24 hours (or 48 hours if delayed demoulding is required) under a damp cloth until testing Clearly label specimens intended for water curing using water-resistant ink or crayon for easy identification later.
NOTE 2 As a check on the mixing and compacting operations and air content of the mortar, it is recommended that the specimens from each mould be weighed.
Curing of specimens in water
Submerge the marked specimens without delay in a convenient manner, either horizontally or vertically, in water at (20,0 ± 1,0) °C in the containers With horizontal storage, keep vertical faces as cast vertical
To ensure proper water access for specimen storage, place the specimens on gratings, maintaining adequate spacing between them It is essential that the water level above the upper faces of the specimens and the gaps between them never fall below 5 mm during storage.
To ensure accurate strength development testing of cements, it is essential to provide separate storage for different cement compositions unless proven otherwise Additionally, cements containing more than 0.1% chloride ion must be stored separately to prevent contamination and ensure reliable test results.
For initial filling and occasional topping up of containers, use tap water to maintain a consistent water level When storing specimens, ensure that no more than 50% of the water is replaced at any given time.
The installation must maintain a consistent storage temperature, and if a circulation system is utilized within the storage container, it should operate at the lowest possible flow rate to avoid visible turbulence.
For accurate testing, specimens should be removed from water no more than 15 minutes prior to the test, except in cases of delayed demoulding where a 48-hour period is applicable Ensure that any deposits on the test faces are cleaned off, and keep the specimens covered with a damp cloth until testing occurs.