Properties of Hardened Concrete 1. Strength: Concrete is strong in compression but relatively weak in tension and bending. It takes a great deal of force to crush concrete, but very little force to pull it apart or cause bending cracks. Compressive strength is determined primarily by the amount of cement used, but is also … Read more
CEMENT AND CONCRETE – ARE THEY THE SAME? Many people think that cement and concrete are the same product – they are not. Cement is a dry powdered chemical that, when mixed with water, slowly reacts to form a new hard, solid compound. On the other hand, concrete is a mixture of cement blended with … Read more
PROPERTIES OF HARDENED CONCRETE The following are the properties of concrete in its hardened state, used by the designer during design process of reinforced concrete structure. 1. Compressive Strength The characteristics strength is defined as the strength of concrete below which not more than 5% of the test results are expected to fall. As per … Read more
Properties of Aggregates Approximately 75% of the volume of concrete is occupied by aggregates, so quality of aggregates plays an important role in determining properties of concrete. Aggregates are chemically inert, solid bodies held together by the cement. Aggregates come in various shapes, sizes, and materials ranging from fine particles of sand to large, coarse … Read more
CAUSES OF DISINTEGRATION OF CONCRETE The primary reasons that cause disintegration of concrete member are desribed below. 1. SULPHATE ATTACK Soluble sulphates are present in Ground water Soil Clay bricks Soluble sulphates react with Tricalcium Aluminate of cement I n the presence of moisture and form products which occupy much bigger volume than that of … Read more
FACTORS AFFECTING CHOICE OF CONCRETE FOR A STRUCTURE The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. 1. Economy Frequently, the foremost consideration is the overall cost of the structure. This is, of course, a function … Read more
Portland Pozzolana Cement 1. Pozzolana Pozzolana is a volcanic powder found in Italy near Vesuvius A pozzolanic material is essentially a siliceous or aluminous material which possess no cementitious properties. But it has the property when it combined with lime to produce a stable pozzolana compound it has definite cementitious properties. In the presence of … Read more
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
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