Maturity and compressive strength of concrete is tested through both destructive and non-destructive methods. Destructive test involve damaging some of an element or the structure. Some would like to carry them out by drilling into the surface or on purpose-moulded cubes, prisms or cylinders. It may not destroy the structure, but may damage the surface. Even in tests like rebound hammer strength, marks of indentation may be left on the surface.
Of late, non-destructive tests too have appeared on the technology scene. Certain physical characteristics of concrete structures can be related to strength including hardness, resistance to penetration of projectiles and ability to transmit ultrasonic pulses and X-rays.
The test is carried out on the specimen (generally a cube) cast simultaneously for compressive, flexural and tensile strength.
Ultratech cement has introduced a mobile concrete laboratory to provide assistance during concreting, advice on quality of materials required for concreting and mortar mix, test on fresh concrete (slump test) and test on hardened concrete (compressive strength and surface hardness non-destructive test).
The mobile lab is manned by an expert and can be booked in selected cities through an authorised dealer. Services, however, depend on material availability status. The results are available after seven days.
Protective sheets
Protecto Shutterite and Protecto Floorite are protective sheets laid under the surface while casting concrete slurry for roof slab and underneath the floor respectively. While casting concrete for roof slabs, there are chances of slurry seeping through the shutterings.
The general practice is to spread waste newspaper sheet prior to flowing the slurry. The 50 to 80 micron plastic sheet comes in sizes ranging from 50 to 100 sq. m is easily removable once the roof gets cured.
However, the Protecto Floorite is thicker, around 150 micron, and stays underneath the floor, acting as a protective layer against acidic or alkaline vapours. Tough built, it even protects the walls against damping and is a permanent protection for structures, especially in marshy and swampy lands, says Sanjeev Agarwal, Manager, Sales and Marketing of Manjushree Technopack Limited.