Tests Applied on Concrete for Strength and Workability
SAMPLING The first step is to take a test sample from the large batch of concrete. This should be done as soon as discharge of the concrete commences. The sample should be representative of the concrete supplied. The sample is taken in one of two ways: For purposes of accepting or rejecting the load: Sampling after 0.2 m3 of the load has been poured. For routine
ACI Method Concrete Mix Design & Mix Ratio
Mix design can be defined as the process of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible. One of the ultimate aims of studying the various properties of the materials of concrete, plastic concrete and hardened concrete is to
Planning & Site Preparation for Concrete
The most important step in placing concrete is planning. Always plan every step before any concrete is delivered. Proper planning avoids delays, wastage, segregation and problems which develop from these. Proper concrete planning also eliminates problems of Delay, Segregation and Wastage. Workers on the site should always wear protective clothing, strong boots and
Types of Admixtures of Concrete & Cement
A material other than water, aggregates, or cement that is used as an ingredient of concrete or mortar to control setting and early hardening, workability, or to provide additional cementing properties. Admixtures are generally used to alter the properties of concrete (such as increased workability or reduced water content, acceleration or retardation of setting time,
Types and Uses of Special Concrete
Special Concrete means the concrete used or made for special cases, such as: Frequently, concrete may be used for some special purpose for which special properties are more important than those commonly considered. Sometimes, it may be of great importance to enhance one of the ordinary properties. These special applications often become apparent as new
Hot Weather Concreting
ACI 305 “Hot Weather Concreting” defines hot weathers as any combination of the following conditions that tends to impair the quality of the freshly mixed or hardened concrete: The success of many hot-weather concreting operations depends on the steps taken to slow the cement hydration reactions within the concrete and to minimize the rate of evaporation of
Cold Weather Concreting ACI 306 - Cold Weather Concrete
ACI 306 “Cold Weather Concreting” defines cold weather concreting as a period when for more than three (3) consecutive days, the following conditions exist: The average daily air temperature is less than 5°C (40°F) and, The air temperature is not greater than 10°C (50°F) for more than one-half of any 24 hour period. ete placed during cold weather will develop
Creep in Concrete and Effects of Creep of Concrete
Concrete creep is defined as: deformation of structure under sustained load. Basically, long term pressure or stress on concrete can make it change shape. This deformation usually occurs in the direction the force is being applied. Like a concrete column getting more compressed, or a beam bending. Creep does not necessarily cause concrete to fail or break apart. Creep
Definition and Types of Concrete Shrinkage
Concrete is subjected to changes in volume either autogenous or induced. Volume change is one of the most detrimental properties of concrete, which affects the long-term strength and durability. To the practical engineer, the aspect of volume change in concrete is important from the point of view that it causes unsightly cracks in concrete. We have discussed elsewhere the
Definition and Methods of Curing of Concrete
Curing can be described as keeping the concrete moist and warm enough so that the hydration of cement can continue. More elaborately, it can be described as the process of maintaining a satisfactory moisture content and a favorable temperature in concrete during the period immediately following placement, so that hydration of cement may continue until
How to Determine Maturity of Concrete
One of the methods to determine the strength of concrete is to find maturity of concrete. Maturity of concrete is defined as Summation of product of age and temperature (Curing). Concrete Maturity = ∑ (Time x Temperature). Hydration can take place at minimum of -10°C, below this water crystals (ice) do not react with cement. Datum Temperature = -10°C, If
Corrosion in Concrete Reinforcement
The basic problem in Reinforced concrete structures is the corrosion of steel reinforcement. The main cause of this corrosion is intrusion of water inside the RC structures. The corrosion of steel reinforcement can be judged by peculiar cracking of concrete structures. At last stage of corrosion, the steel reinforcement becomes exposed and the extent of corrosion
Concrete Slump Test - Theory and Lab Test
A slump test is a method used to determine the consistency of concrete. The consistency, or stiffness, indicates how much water has been used in the mix. The stiffness of the concrete mix should be matched to the requirements for the finished product quality. Slump is a measurement of concrete's workability, or fluidity. It's an indirect measurement of concrete
Durability of Concrete and Effects of Durability of Concrete
Durability is defined as the capability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties. It normally refers to the duration or life span of trouble-free performance. Different concretes require different degrees of durability depending on the exposure environment and properties desired. For
