CPT Unit 3D

• Cement


  An inorganic, greyish-fine powder made of finely ground calcareous materials (limestone) and argillaceous materials (silica and slate)
• Cement


  An active component in concrete
• Cement


  When combined with water, it acts as a binder, forming a paste that solidifies via the hydration process, forming concrete
• Cement should not be confused with concrete and mortar, but it is an important component of these two products
• Mortar


  A mixture of sand and cement
• Concrete


  Includes rough aggregates
• Cement


  • Plays a crucial role in construction materials and is used for buildings, harbors, bridges, runaways, and roads
• With developing countries, cement is one of the largest commodities used
• Ancient builders


  Relied on natural cement made from crushed lime and pozzolanic materials (volcanic ash) which harden underwater, creating hydraulic cement
• Egyptians


  Used cementing materials obtained by burning gypsum (calcium sulfate hydrate)
• Greeks and Romans


  Used cementing materials derived from burning limestone
• These ancient materials lacked the strength and durability provided by modern Portland cement
• Portland Cement was patented

  21 October 1824
• Cement remains a cornerstone in construction, facilitating the development of robust and enduring structures that define our modern world
• Cement


  • Gives strength to the masonry, i.e., building units (bricks and stones)
• Cement


  • Acts as an excellent building material
• Cement


  • Offers good resistance to moisture
• Cement


  • Possesses good plasticity (quality of being molded or shaped)
• Cement


  • Has early stiffness and hardness
• Cement


  • Is easily workable
• Lime (C): Calcium oxide (CaO)


  The major constituent of cement with the highest percentage (60-67%) and is sourced from limestone, chalk, or marl
• Lime


  Provides strength when it reacts with water, promoting quick setting
• Excessive lime (free lime)

  Leads to changes in volume (expansion) after hardening, potential cracking, and disintegration
• Silica (S): Silicon dioxide (SiO2)


  Imparts high durability and strength (through the formation of di-calcium and tri-calcium) to cement with a percentage of 15-25%
• Silica


  Is sourced from clay, sand, or shale
• Silica


  Enhances the concrete's elastic strength, making it resilient and the plasticity of the material during mixing
• Excess silica


  Can increase the strength and setting time of concrete
• Alumina (A): Alumina oxide (Al2O3)


  Is used for the initial setting with a 3-8% percentage
• Alumina


  Is sourced from clay, shale and other materials
• Alumina


  Acts as a flux to lower the clinker's temperature during burning
• Excess of alumina


  Can weaken the cement, leading to a very fast setting time without achieving full strength
• Iron (F): Iron (III) oxide or Ferric oxide (Fe2O3)


  Provides a greyish color, hardness, and strength with a percentage of 0.5-6%
• Iron


  Is sourced from clay, shale, or other materials
• Gypsum: Calcium sulphate (CaSO4)


  Increases the setting time of green concrete with a percentage of 1-4%
• Magnesia: Magnesium oxide (MgO)


  Is present in small quantities (0.1-4%)
• Magnesium oxide


  Regulates the setting time, enhances strength, controls expansion, and improves sulfate resistance (forms stable compounds that resist the attack of sulfate ions in soil or water)
• Alkalis (K20, Na2O)


  Minor constituents, with a percentage of 0.4-1.3%. Accelerating the setting time and high content may increase the amount of water required for normal consistency, thus affecting the workability of the paste
• Sulfur trioxide (SO3)


  Constitute 1.3-3%, reacts with water to form sulfuric acid, which reacts with calcium hydroxide during hydration to form calcium sulfate (sulfate attack)
• Ordinary Portland Cement (OPC)


  The predominant building material, valued for its versatility, reliability, and widespread availability
• OPC manufacturing process


  Involves grinding clinker, a blend of calcined limestone and clay, with the addition of gypsum to regulate the setting time