Search

Capping Concrete Specimens For Compression Testing

By
KAUSHAL KISHORE
Materials Engineer, Roorkee

CAPPING THE CYLINDERS
It is required that the cylinders ends must be plane within 0.050 mm. The most common way of achieving this planeness requirement is to cap the ends of the cylinder as per ASTM C6176 with suitable materials. Three different capping materials are permitted (a) A thin layer of stiff Portland cement paste may be used on freshly molded specimens. (b) on hardened cylinders, either high-strength gypsum plaster or sulfur mortar may be used (c) A third method is, an elastomeric pad is placed within a metal retaining ring, and the assembly is then placed over the specimen end. The pad conforms to the shape of the cylinder end, but is prevented from spreading laterally by the metal retaining ring. This provides a uniform load across the specimen ends.

Continue Reading »

ULTRASONIC TESTING OF CONCRETE

By
KAUSHAL KISHORE
Materials Engineer, Roorkee

Fundamental principle
A pulse of longitudinal vibrations is produced by an electro-acoustical transducer, which is held in contact with one surface of the concrete under test. When the pulse generated is transmitted into the concrete from the transducer using a liquid coupling material such as grease or cellulose paste, it undergoes multiple reflections at the boundaries of the different material phases within the concrete. A complex system of stress waves develops, which include both longitudinal and shear waves, and propagates through the concrete. The first waves to reach the receiving transducer are the longitudinal waves, which are converted into an electrical signal by a second transducer. Electronic timing circuits enable the transit time T of the pulse to be measured.

Continue Reading »

Testing Concrete Cores

By
KAUSHAL KISHORE
Materials Engineer, Roorkee

The examination and compression testing of cores cut from hardened concrete is a well – established method, enabling visual inspection of the interior regions of a member to be coupled with strength estimation. Other properties which can be measured is also given in this paper.

IS: 456-2000 specified that the points from which cores are to be taken and the number of cores required shall be at the discretin of the engineer-in-charge and shall be representative of the whole of concrete concerned in no case, however, shall fewer than three cores be tested. Core shall be prepared and tested as described in IS: 516.

Continue Reading »

Concrete Mix Design – ITS Acceptance

By
KAUSHAL KISHORE
Materials Engineer, Roorkee

Concrete mix design is the process of choosing suitable ingredient of concrete and determining their relative quantities with the object of producing as economically as possible concrete of certain minimum properties, notable workability, strength and durability. It should be explained that an exact determination of mix proportions by means of table or computer data is generally not possible. The materials used are essentially variable and many of their properties cannot be assessed truly quantitatively. A Laboratory trial mix does not provide the final answer even when the moisture condition of aggregates are taken into account. Only a mix made and used on the site can guarantee that all properties of the concrete are satisfactory in every detail for the particular job in hand. In fact mix selection requires a knowledge of the properties of concrete and experimental data, and above all the experience of the expert who conduct the mix design. The selection of mix proportions is an art as much as a science. It is not enough to select a suitable concrete mix; it is also necessary to ensure a proper execution of all the operation involved in concreting. It cannot be stated too strongly that, competently used, concrete is a very successful construction material but, in the literal service of the word, concrete is not fool proof. The mix proportions once chosen, cannot expected to remain entirely immutable because the properties of the ingredients (cement, sand, aggregate, water and admixture) may vary from time to time.
Continue Reading »

Filed under Mix Design | 0 Comments

Water Proofing By Ferrocement

By
Er. KAUSHAL KISHORE
Materials Engineer, Roorkee

Ferrocement as a construction material has now gained acceptance in different applications, namely : housing, agriculture, marine, water supply, sanitation, water proofing treatment etc. Numerous studies published have built up confidence in the material resulting its wider application,

Traditional methods of roof water proofing by lime concrete and mud phuska with thin burnt clay tiles are very cumbersome, time consuming involved high labor cost and also due to non availability of traditional skills and good materials these methods of water proofing are now not very popular. Though bitumen felts are also provided for water proofing their life is less than five years and need frequent replacement.

Continue Reading »