Yield of Concrete There are various factors which affect the yield of concrete for a given proportion of concrete ingredients, such as Water-cement ratio Size of aggregate Method of compaction etc. Yield of concrete simply means the actual volume of concrete produced when a given proportion of concrete ingredients are mixed in a certain manner. … Read more
Concrete Placing Precautions The concrete, as it comes out of the mixer or as it is ready for use on the platform, is to be transported and placed on the formwork. Following precautions should be taken during placing of concrete. The formwork or the surface which is to receive the fresh concrete should be properly … Read more
Concrete for long have been specified by nominal mixes (mixes of fixed proportions which ensure adequate strength) and were arbitrarily applied with little regard to the required strength of concrete with water added to ensure workability. But for mixes of desired strength the three variable factors to be considered are: Water cement ratio and consistency … Read more
Vibrators are commonly used as a way of compacting concrete on site. In case of vibration, compacting gets effected by reduction in internal friction between various particles of concrete due to oscillation of particles which results in a dense and compact mass of concrete. Vibrations can either be Produced in the interior of the concrete … Read more
Surface Index of Aggregates Surface index of aggregates is another way to represent the specific surface of aggregate. This method was suggested by Murdock. Murdock provided some empirical numbers to represent the specific surface of different aggregates grading (as shown in the table below). Surface Index Values for Single Graded Aggregate TABLE-1 Sieve Size Within … Read more
Plastic shrinkage cracking (as shown below) is caused by rapid drying of the concrete surface. They can occur at any time of the year, from cooler low-humidity weather conditions to, in particular, hot weather conditions involving any one or a combination of high temperature, low humidity and wind. These types of cracks occur while the … Read more
Sandblasting Sand blasting is the process of roughening and cleaning the surface of old and set concrete (or in any corroded steel surface) by means of coarse sand and air applied under pressure of 90 to 100 pounds per square inch (6.33 to 7.03 kilogram per square centimeter) through a nozzle, so as to erode … Read more
Quality Control of Concrete Construction Quality of concrete construction on site can be accomplished in three distinct stages as follow Quality control before concreting Quality control during concreting Quality control after construction Stage-1 (Quality Control Before Concreting) This stage of quality control consists of two steps. Checking of specification requirements regarding excavation, forms, reinforcement and … Read more
Honeycomb Repair in Concrete Surface Honeycomb and larger surface voids require procedures resembling those for typical concrete repairs. But there’s nothing typical about the recommended approaches to repairing these voids. They vary greatly. While repairing voids or honeycomb in concrete surface, the most common question that arises is what should be the thickness of the … Read more
Objective To determine the Flexural Strength of Concrete, which comes into play when a road slab with inadequate sub-grade support is subjected to wheel loads and / or there are volume changes due to temperature / shrinking. Reference Standards IS: 516-1959 – Methods of tests for strength of concrete Equipment & Apparatus Beam mould of size … Read more