BS EN 13286-41:2021 pdf free download – Unbound and hydraulically bound mixtures Part 41: Test method for the determination of the compressive strength of hydraulically bound mixtures.
5 Apparatus
5.1 Compression testing machine
The precision of the machine and the load indication shall he capable of loading and measurement to accuracy of± 1%.
NOTE 1 Test specimens of hydraulically bound mixtures can be either cylindrical or cubical, with nominal dimensions as small as 50 mm (diameter) and as large as 300 mm (height), and with ultimate compressive strengths varying from 0,5 N/mm2 to normal concrete strengths. Machines complying with EN 12390-4 can he suitable for stronger specimens.
The machine shall have two steel loading platens with faces having a Rockwell hardness of at least 55 HRC for a depth of approximately 5 mm. The loading platens shall be at least as large as, and preferably larger than, the faces of the specimen to which the load is applied. The surface flatness of the platens and the surfaces by which they are supported shall be 0,03 mm or better.
NOTE 2 Auxiliary platens having a minimum thickness of 25 mm and fulfilling the same requirements as the original platens can be used.
The upper platen shall have a spherical seating of dimension such that the deformation of the platen under normal loading does not exceed the tolerance of flatness. The combination of the upper platen and spherical seating shall be designed to permit easy alignment of the platen to the specimen but to become immobile as the force on the specimen increases. The seating shall have its centre at the surface of the platen, or at a point whose distance from the platens is less than 1 mm. The diameter of the seating shall not exceed 150 mm.
Provision shall be made for positive location of specimens at the centre of the lower platens; visual alignment shall not be used.
6 Test specimen
7.5 Specimen positioning
Excess moisture shall be wiped from the surface of the specimen before placing in the test machine.
All testing machine bearing surfaces shall be wiped clean and any loose grit or extraneous material removed from the surfaces of the specimen that will be in contact with the platens or auxiliary platens if used.
No packing shall be used between the specimen and the platens or auxiliary platens.
Cube specimens shall be compressed perpendicularly to or in the direction of casting and the direction recorded.
The specimen shall be centred on the lower platen or auxiliary platen to an accuracy of 1 % of the designated size of the cube or diameter of cylindrical specimens.
At the moment of contact between the specimen and the upper platen, the spherical seating shall be adjusted to achieve uniform contact between the specimen and upper platen.
7.6 Loading
The load shall be applied in a continuous and uniform manner without shock so that rupture occurs within 30 s to 120 s of commencement of loading.
When using manually controlled testing machines and as specimen rupture is approached, any tendency for the selected rate of loading to decrease shall be corrected by appropriate adjustment of the controls.
When using automatically controlled testing machines, the rate of loading shall be periodically checked to ensure that the rate is constant.
The maximum force, F, sustained shall be recorded.
The time between the removal of the test specimens from their curing condition and loading should be minimized in order to avoid loss of moisture.