Author: haroonkhan

This method has been used since 1944 and has undergone several revisions continuously. It has developed an identical procedure for angular or rounded aggregates, regular or light-weight aggregates and air-entrained or non-air-entrained concretes. The ACI mix design is based on certain factors which are established by field experience on large works. The factors are as…

Mix design of concrete is the process of selecting the required ingredients of concrete and finding their relative proportions with the aim of producing an economical concrete of certain strength and durability. It has been discussed earlier that concrete is based on two phases, viz., aggregate phase and paste phase. Workability of the concrete depends…

During 1976 there was only one type of cement available. Later OPC had been graded and the gain in strength after 28 days had been based on the grade and type of cement. The design was based on 28 days’ characteristic strength of concrete unless there was evidence to justify a higher strength for a…

The discussion so far has been centered on the modification of the properties of concrete using admixtures. Other chemicals that are used to enhance the performance are discussed in this section. Such chemicals are referred to as construction chemicals or building chemicals. Concrete-curing Compounds The measure adopted to prevent the loss of water from the…

Admixture and construction chemicals are chemicals added to the ingredients of concrete to obtain the desired strength and durability. Admixtures Of late concrete is used for varied purposes and is made suitable for different occasions and environments. Ordinary concrete is not as versatile and does not suit all purposes. Thus, admixtures and chemicals are added…

Water is an important ingredient of concrete. As a general guidance, if the water is fit for drinking, it is fit for making concrete. However, some water containing small traces of sugar is not suitable for concrete. Another yardstick adopted is that if the pH is between 6 and 8 the water is considered to be suitable.…

Fine aggregate is sand, which is usually obtained from rivers or lakes. Sometimes beach sand is also used. In places where sand is not available or a large quantity of sand is needed, crushed stone dust is used. The fineness modulus (F.M.) of sand should be around 2 to 3.2. The following limits may be…

As stated above, coarse aggregates are produced by the disintegration and crushing of rock. Coarse aggregates are usually those particles which are retained on an IS 4.75 mm sieve. Stones that are hard and durable such as granite, basalt, quartzite provide good coarse aggregate. Naturally available river gravels and shingle obtained from sea beaches after…

Aggregates may be classified as (i) normal weight aggregates, (ii) light-weight aggregates and (iii) heavy-weight aggregates. Normal weight aggregates can be further classified into natural and artificial aggregates. They are also classified as coarse or fine aggregates depending on the size. Natural and artificial aggregates are as follows:

Aggregates are the major and important constituent of concrete. They form the body of the concrete as it occupies 70–80% of the volume of concrete. Although aggregates were originally considered to be inert material, they have recently been found to be chemically active to some extent. Cement is the only factory-made component, whereas aggregates (both…