AS 1012.9:2014 pdf free download – Methods of testing concrete
6.2.1 General
Moulded caps shall be as thin as practicable, but not thicker than 6 mm. Only one layer of capping material shall be used on each surface requiring capping, but small depressions may be filled prior to capping. Moulded capped surfaces shall not depart from a plane by more than 0.05 mm.
6.2.2 Preparation of capping materials
Moulded capping materials shall consist of one of the following, subject to the limitations on use set out in Clause 6.4:
(a) Filled sulphur mixtures Mixtures of sulphur and at least 10% by volume of fine filler material such as fly ash, finely ground silica or fire clay, or cement may be prepared. The sulphur mixture shall be used at a temperature that ensures a suitable viscosity for capping.
(b) Portland cement mortar Mortar made from a mixture of one part of Portland cement and one part of fine sand, provided that the water-cement ratio does not exceed 0.35, may be prepared. The Portland cement shall be fresh, free from lumps, and shall comply with the requirements of AS 3972. The sand-cement mixture shall be mixed with water to form a stiff paste which shall be allowed to stand for not less than 0.5 h and not more than 2 h before use, to minimize shrinkage of the cap.
(c) High-alumina cement mortar Mortar made from one part of high-alumina cement and one part of fine sand, provided that the water-cement ratio does not exceed 0.35, may be prepared. The high-alumina cement shall be fresh and free from lumps. The sand-cement mixture shall be mixed with water to form a stiff paste which shall be allowed to stand for not less than 0.5 h and not more than 2 h before use, to minimize shrinkage of the cap.
(d) Cement pastes Portland cement or high-alumina cement paste or mixtures of these may be used to prepare caps if the cement used is fresh and free from lumps. The cement shall be mixed with water to form a stiff paste and used within 2 h.
(e) Special gypsum plasters Special high-strength gypsum plaster may be used to prepare a capping paste after being tested in the following manner:
(i) The plaster-water mixture, prepared in the same proportions as those used for capping, shall be compacted into a cube mould using a spatula. The dimensions from the sides of the cube shall be between 50 mm and 75 mm.
(ii) The specimen shall be demoulded after 0.5 h, stored in air, and tested 1 h after casting.
6.2.3 Plates and equipment
The plates and equipment used for moulded capping shall comply with the following requirements:
(a) Cement mortar or paste, and special gypsum plaster caps shall be formed against plate-glass, or a machined metal plane plate, at least 6 mm thick. The diameter of all such plates shall be at least 25 mm larger than the nominal diameter of the specimen, and the surfaces shall not depart from a plane by more than 0.05 mm.
(b) Caps made from sulphur mixtures shall be formed against a metal plate in which a recess has been machined. The thickness of the metal in the recessed area shall be at least 10 mm. The base of the recess shall be a circle whose diameter is approximately 5 mm greater than the nominal diameter of the specimen. The side of the recess shall slope to facilitate removal. The recessed area shall not depart from a true plane to an extent that results in caps with surfaces which themselves depart from a plane by more than 0.05 mm.
(c) Capping plates shall be thinly coated with mineral oil to prevent adhesion of the capping material to the plate.
(d) Alignment devices shall be used in conjunction with the plates to ensure that the specified perpendicularity of the cap to axis of the specimen is obtained.