Introduction to concrete Definition of Concrete: Concrete is a mixture of cement, Aggregates (fine +coarse), water and air. Portland cement, water, sand, and coarse aggregate are proportioned and mixed to produce concrete suited to the particular job for which it is intended.

Cement Powder Cement + Water Cement Paste Cement Paste + Fine Aggregate (FA) Mortar Mortar + Coarse Aggregate (CA) Concrete Cement Paste Mortar

Advantages of concrete 1-Concrete has many environmental advantages, including durability, longevity, heat storage capability, and chemical inertness. 2-Ability to be Cast. -3-Fire resistant. 4-On-site fabrication. -5-Aesthetic properties -6-The raw materials used in cement production are widely available in great quantities. -7-Needs little or no finish or final treatments. -8-Chemically inert concrete doesn't require paint to achieve a given color; natural mineral pigments and coloring agents can be added at the mixing to provide a rainbow of options. -9-Low maintenance. -10-Can be reused or recycled: Concrete can be reused with bituminous asphalt as road base materials, can be recycled and reused by crushing into aggregates for new concrete or as fill material for road beds or site works.

Limitations of Concrete 1-Low tensile strength 2- Low ductility 3- Volume instability 4- Low strength-to-weight ratio

Portland Cement Cement is a pulverized material that develops binding forces due to a reaction with water. it is made by mixing substances containing CaCO3 with substances containing SiO2, Al2O3, Fe2O3 and heating them to a clinker which is subsequently. the term hydraulic cements referred to cements that harden by reaction with water and form a water-resistant product. Thus, Portland cement is a hydraulic cement capable of setting, hardening and remains stable under water.

Raw material for Portland Cement Raw material for P.C. is Calcium & Silica 2/3 Limestone, chalk, etc Calcium: (CaO+CO2) 1/3 Clays and shales Silica (SiO2+Al2O3+Fe2O3+H2O)

Manufacturing of Portland Cement 1- Raw materials are crushed, screened & stockpiled. 2- Raw materials are mixed with definite proportions to obtain “raw mix”. Then, they are mixed either dry (dry mixing) or by water (wet mixing). 3- Prepared raw mix is fed into the rotary kiln. 4- As the materials pass through the kiln their temperature is raised up to °C. The process of heating is named as “burning”. The output is known as “clinker” which is cm in diameter. 5- Clinker is cooled & stored. 6-Clinker is ground with gypsum (3-6%) to adjust setting time. 7- Packing & marketing.

REACTIONS IN THE KILN 100°C→ free water evaporates C°→ loosely bound water is lost from clay °C→decomposition of clay→SiO2 & Al2O3 600°C→decomposition of MgCO3→MgO & CO2 (evaporates) 900°C→decomposition of CaCO3→CaO & CO2 (evaporates) °C→liquid formation & start of compound formation. 1280°C→clinkering begins °C→clinkering 100°C→clinker leaves the kiln & falls into a cooler.