AIR ENTRAINED CONCRETE A major advance in concrete technology in recent years is the introduction of tiny disconnected air bubbles into concrete called air entrainment. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing. Adding entrained air to concrete provides important benefits in both plastic and hardened concrete, … Read more
Shrinkage Of Concrete When concrete structures are not permanently water-saturated, it starts to lose moisture and starts to shrink from the time when the process of curing ceases. The 7 primary structural effects of shrinkage are as follow. 1. Joints Shrinkage of concrete between movement joints causes joints to open or makes it wider. Therefore … Read more
FLEXURAL STRENGTH TEST OF CONCRETE 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 & … Read more
Quality Control in 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
Engineering Properties of Aggregates Aggregates are used in concrete to provide economy in the cost of concrete. Aggregates act as filler only. These do not react with cement and water. But there are properties or characteristics of aggregate which influence the properties of resulting concrete mix. These are as follow. Composition Size & Shape Surface … Read more
Making of Test Cubes From Fresh Concrete IS-456 has laid down the acceptance criteria of quality concrete. In all the cases, the 28-days compressive strength shall alone be the criterion for acceptance or rejection of the concrete. 7 days compressive strength of concrete can be carried out in order to get a relatively quicker idea … Read more
Factors Affecting the Setting and Hardening of Portland cement (1) The Impact of Cement’s Composition The mineral composition of cement and their ratios are the main factors affecting the setting and hardening of cement. As mentioned above, various mineral components will reveal different characteristics when reacting with water. For example, the increase of C3A can … Read more
What Is Volume Batching of Concrete? Batching of concrete means measuring different ingredients of concrete (i.e. cement, sand, coarse aggregate and water) before mixing it. When this measurement is done on the basis of volume, we call it Volume Batching. Below are mentioned some of important points to remember before adopting volume batching method in … Read more
Needle Vibrator These concrete vibrators are also referred to as poker or immersion vibrator. These are extensively used in building industry. A needle vibrator consists of a cylindrical casing made of steel and is vibrated by means of a flexible drive with an outer tube run from an operating machine which can be run by … Read more
Types of Chemical Admixtures for Concrete Unlike mineral admixtures, which may be introduced as blended cements, chemical admixtures are typically added during the mixing process of concrete production. Depending upon the requirement, different types of chemical admixtures are manufactured such as air-entraining admixtures, accelerating admixture, water reducing admixture etc. To a civil engineer, description of … Read more