BUILDING MATERIALS & CONSTRUCTION UNIT -1 LECTURE SERIES: CEMENT

BUILDING MATERIALS & CONSTRUCTIONUNIT -1 LECTURE SERIES: CEMENT Lecturer: Eng. SIWILA Stephen Civil Engineering & Construction Department School of Engineering; Copperbelt university Mobile: 00260-972-470-543 Email: stephen.siwila@cbu.ac.zm

INTRODUCTION • Cement is a commonly used binding material in the construction. • Cement is obtained by burning a mixture of calcareous (calcium) and argillaceous (clay) material at a very high temperature then grinding the clinker so produced to a fine powder. • It was first produced by a mason Joseph Aspdin in England in 1924. He patented it as Portland cement.

Definition: Cement is a crystalline compound of calcium silicates and other calcium compounds having hydraulic properties

Uses of Cement Cement is used widely for the construction of various structures. Some of them are listed below: (i) Cement slurry is used for filling cracks in concrete structures. (ii) Cement mortar is used for masonry work, plastering and pointing. (iii) Cement concrete is used for the construction of various structures like buildings, bridges. water tanks, tunnels, docks, harbors etc.

Uses of Cement Cement is used widely for the construction of various structures. Some of them are listed below: (iv) Cement is used to manufacture lamp posts, telephone posts, railway sleepers, piles etc. (v) For manufacturing cement pipes, garden seats, dust bins, flower pots etc. cement is commonly used. (vi) It is useful for the construction of roads, footpaths, courts for various sports etc.

USES • Main use of cement is in the fabrication of concrete and mortars • Modern uses • Building (floors, beams, columns, roofing, piles, bricks, mortar, panels, plaster) • Transport (roads, pathways, crossings, bridges, viaducts, tunnels, parking, etc.) • Water (pipes, drains, canals, dams, tanks, pools, etc.) • Civil (piers, docks, retaining walls, silos, warehousing, poles, pylons, fencing) • Agriculture (buildings, processing, housing, irrigation)

Some History • Lime and clay have been used as cementing material on constructions through many centuries. • Romans are commonly given the credit for the development of hydraulic cement, the most significant incorporation of the Roman’s was the use of pozzolan-lime cement by mixing volcanic ash from the Mt. Vesuvius with lime. • Best known surviving example is the Pantheon in Rome • In 1824 Joseph Aspdin from England invented the Portland cement

History of cement and concrete • The early days: • Setting stone blocks without cementing them • Mud mixed with straw is the oldest cementing material used to bind dried bricks together • Pyramid of Cheops (3000 B.C).

Cheops, Giza • Stones were brought from Aswan and Tura using the Nile river • Built around 2566 B.C. • It would have taken over 2,300,000 blocks of stone with an average weight of 2.5 tons each • Total weight of 6 million tons • 30 years and 100,000 slaves to build it • Has a height of 482 feet (140m) • It is the largest and the oldest of the Pyramids of Giza • Mortars made by calcining impure gypsum

History of Cement and Concrete

Cement is a key concrete ingredient: • Paste = Cement + Water • Mortar = Cement + Water + Fine aggregate • Concrete = Cement + Water + Coarse and Fine aggregates • Thus Concrete is a mixture of Portland cement, water, aggregates, and in some cases, admixtures.

Portland Cement • Portland cement was named for the Isle of Portland, a peninsula in the English Channel where it was first produced in the 1800's. • Since that time, a number of developments and improvements have been made in the production process and cement properties.

Portland Cement • The production process for portland cement first involves grinding limestone or chalk and alumina and silica from shale or clay.

Portland Cement • The raw materials are proportioned, mixed, and then burned in large rotary kilns at approximately 1400°C-l500°C until partially fused into marble-sized masses known as clinker. • After the clinker cools, gypsum is added, and both materials are ground into a fine powder which is port land cement.

SUBSTITUTES • Cement competes in the construction industry with concrete substitutes e.g.: • Alumina • Asphalt • Clay brick • Fiberglass • Glass • Steel • Stone & Timber • Some materials like fly ash and ground granulated furnace slugs have good hydraulic properties and are being used as partial substitutes for Portland cement in some concrete applications

Raw materials required for manufacture of cement • Raw materials required for manufacture of cement are: • 1. Calcareous and • 2. Argillaceous material • Calcareous Materials: Calcareous materials are those materials which contain calcium or lime as their main constituents such as lime stone, chalk etc. • Argillaceous Materials: Argillaceous materials are those materials which contain alumina as their main constituents such as shale, laterite etc. It provides the required proportion of silica, clay, oxide of iron to the cement.

GEOLOGY (RAW MATERIALS) • The fundamental chemical compounds to produce cement clinker are: • Lime (CaO) • Silica (SiO2) • Alumina (Al2O3) • Iron Oxide (Fe2O3) Raw materials used in the production of clinker cement Fly ash: by-product of burning finely grounded coal either for industrial application or in the production of electricity

Clinker compounds in Type I portland cement (Macfadyen, 2006) www.recycleworks.org/images/flyash_concrete.gif

SOURCES OF CaCO3 • Sedimentary deposits of marine origin (limestone) • Marble (metamorphosed limestone) • Chalk • Marl • Coral • Aragonite • Oyster and clam shells • Travertine • Tuff • LIMESTONES • Originate from the biological deposition of shells and skeletons of plants and animals. • Massive beds accumulated over millions of years. • In the cement industry limestone includes calcium carbonate and magnesium carbonate. • Most industrial quality limestone is of biological origin. • The ideal cement rock 77 to 78% CaCO3, 14% SiO2, 2.5% Al2O3, and 1.75% FeO3. • Limestone with lower content of CaCO3 and higher content of alkalis and magnesia requires blending with high grade limestone

Proportion of mixing: • The ingredients are generally mixed in the ratio of two parts of Calcareous materials and one part argillaceous material. • Limestone and shale are first crushed and then they are mixed either in wet state or in dry state by grounding them together. • The mixture is then burnt in a rotary kiln at a temperature between 1400°C and l500°C. • Pulverized coal, gas or oil being used as the fuel. The clinker so obtained is first cooled and then gypsum (3 to 4%) is added and it is grounded to the required fineness

CEMENT CLINKERS

Main chemical Ingredients of Cement (Raw Stage)

Functions and Effects of Various Ingredients • Lime: It makes the cement sound and provides strength to the cement. Excess of it in original form causes the cement to expand and disintegrate. • Silica: It provides strength to the cement. In excess it slows down the setting of cement. • Alumina: It provides quick setting property to the cement. In excess it weakens the strength of cement. • Calcium Sulphate (Gypsum): It helps in increasing the initial setting time of cement.

Functions and Effects of Various Ingredients: • Iron Oxide: It provides colour, hardness and strength to the cement. • Magnesium Oxide: It provides colour and hardness to the cement. Excess of it in free state makes the cement unsound. • Sulphur Trioxide: In small quantity it makes the cement sound and in excess it makes the cement unsound.

Final compounds of Cement:

Final compounds of Cement: • C2S- Dicalcium silicate • 1. It hydrates slowly. • 2. It hardens more slowly • 3. It provides ultimate strength to the cement. • 4. It has more resistance to chemica1 attack. • C3S- Tricalcium silicate • 1. It hydrates more rapidly. • 2. It develops early strength. • 3. It generates heat more rapidly and has less resistance to chemical attack.

Final compounds of Cement: • C3A- Tricalcium Aluminate • It is fast reacting with large amount of heat generation. • It causes initial setting of cement. • It is weak against Sulphate attack. • C4AF- Tetra Calcium Aluminum Ferrite • It is comparatively inactive. • It has poor cementing value. • It is slow in reaction with small heat generation.

Main Properties of Cement • Fineness • Setting Time • Strength • Soundness • Heat of Hydration:

Different Types of Cement • Cements are considered hydraulic because of their ability to set and harden under or with excess water through the hydration of the cement’s chemical compounds or minerals. • There are two types: • (1)Hydraulic Cements: Those that activate with the addition of water And • (2)Pozzolanic: those that develop hydraulic properties when they interact with hydrated lime Ca(OH)2. • Definition: Pozzolanic material is any siliceous material that develops hydraulic cementitious properties when interacted with hydrated lime.

Different Types of Cement (cont.) • 1. Ordinary Portland cement. • 2. Rapid Hardening Portland cement • 3. Low Heat Portland cement • 4. Portland Blast Furnace slag cement • 5. Portland Sulphate resistant cement • 6. Air entraining Portland cement • 7. White and coloured cement • 8. High Alumina cement • 9. Pozzolana cement • 10. Oil well cement • 11. Quick setting cement • 12. Expanding cement

Different Types of Cement (cont.) • Ordinary Portland Cement: • It is also known as Normal setting cement. • It is general purpose cement suitable for all purpose. • It is used in Road pavements, buildings, culverts, water pipes, etc. • In the other sense it is used every where except in places where special properties of other types are required. • Out of the total consumption of different types of cement 90% of this type is used.

Different Types of Cement (cont.) • Rapid Hardening Cement: • Its manufacturing process is same as that of ordinary cement except chemical composition, degree of grinding and temperature of burning. • It contains less quantity of C2S and more quantity of C3S. • It is generally used where high early strength is required and so it is some times called as High Early Strength Portland cement. • It is used by concrete product manufactures, highway pavements which are to be opened early for road traffic and in cold weather concreting due to its high heat of hydration development.

Different Types of Cement (cont.) • Quick Setting Cement: • It has less proportion of CaSO4 (Gypsum) or a small % of Aluminium Sulphate is added at the time of grinding. • It is grounded much finer than ordinary Portland cement. • Its initial setting time is 5 minutes and final setting time is 30 minutes. • It is used for concreting under or in running water and only in special circumstances as it gives very little time for mixing

Different Types of Cement (cont.) • Low Heat Portland Cement: • This cement is so called because it develops low heat at the time of hydration. • It contains C3A and; C3S in less quantity because they develop early heat. • It develops strength quite late and so not advised to concrete structures as it requires shuttering and curing, for a longer period. • It is generally used in massive concrete structures such as dams, bridge, abutments, retaining walls etc.

Different Types of Cement (cont.) • Blast Furnace Slag Cement: • As the name indicates in this cement granulated blast furnace slag is grained along with cement clinkers. • Percentage of slag varies from 25 to 65%. • It is cheaper as compared to ordinary cement because waste product is used in it. • It can also be used in massive concrete such as dams, bridges etc. • It has a1so the capacity to resist Sulphate bearing soils, and water. Hence good for use in marine structures and construction in marshy areas

Different Types of Cement (cont.) • Sulphate Resistant Portland Cement: • It contains very low percentage of C3A and C4AF. Because when C3A and C4AF come in contact with sulphates they form Sulphur-aluminates causing swelling and disintegration. • It is used in canal lining, construction of pipe lines and culverts etc.

Different Types of Cement (cont.) • Air Entraining Portland Cement: • It is ordinary Portland cement mixed with small quantities or air entertaining materials during grinding. • It reduces the water requirement and has high resistance to weather. This cement is generally used in making insulated walls, roof slabs, and light weight concrete and the concrete which is subjected to freezing and thawing.

Different Types of Cement (cont.) • White and Coloured Cement: • In it white chalk and china clay are used instead of limestone and clay as these are having low percentage of Iron Oxide i.e.1 %. • Oil is used as fuel to avoid contamination of coal ash. • It is 3 to 4 times costlier than ordinary cement. • It is used for decorative floorings. Bridge railings, traffic curbs and aerodrome markings.

Different Types of Cement (cont.) • High Alumina Cement: • contains 35% to 45% of aluminates Bauxite and chalk or lime stone are mixed dry and heated till they melt and on cooling they form clinkers. These clinkers are then grounded to the required fineness. • It is dark in colour and initial setting time varies from 3 to 6 hrs. and final setting takes place with in 2 hours of the Initial set. • Its setting times are controlled by the rate of cooling of the fused product. It is highly resistant to heat and the strength is more.

Different Types of Cement (cont.) • High Alumina Cement: • It is high resistant to attack of sulphates. It gives high heat of hydration and, is also costlier than ordinary Portland cement. • It is used in structures subjected to the action of sea water, chemical and Sulphate bearing water. • It is generally used for chemical plants and in lining of furnaces. It can also be used in cold weather concreting

Different Types of Cement (cont.) • Pozzolana Cement: • Pozzolana is a naturally occurring material such as volcanic ash or Pumice stone or an artificial product such as burnt clay or shale containing siliceous and aluminous mineral substances. • As per BS 1489-1967, the proportion of Pozzolana material varies from 10 to 25% by weight of cement. • It increases the workability, reduces heat of hydration, and increases the water tightness. It also offers greater resistance against sulphatic action and sea water. • It is used in the construction of massive concrete structures such as dams, bridge abutments and retaining wall etc.

Different Types of Cement (cont.) • Oil Well Cement: • As the name indicates, it is used for cementing; oil wells. • It is used at greeter depth under high temperature and pressure. • As approximately 3hrs are required to, pump the cement to fill the space between steel tube lining and wall of the well, so it should not set during this period.

Different Types of Cement (cont.) • Oil Well Cement: • Iron Oxide is so adjusted that all the alumina is converted into C4AF and so proportion of C3A is very small, high increases the setting time of cement and also hardens quickly after setting. • It protects the oil well causing from corrosion and also help in supporting the oil well casing and thus reduce the tension, in steel pipes. • It also fills up the porous strata preventing water or gas from gaining access in the oil bearing strata.

Different Types of Cement (cont.) • Expanding Cement: • As per the name, its volume increases on hardening. • It takes about 15 days-for the expansion to occur fully but the time can be controlled by curing. • The upper limit of expansion is 1%. The agent which causes expansion is Calcium Sulpho-Aluminate (3CaOA12O33CaSO4) which is formed by the presence of calcium Sulphate with Calcium Oxide present in cement in sufficient quantity.

Best wishes & Thank you for your attention Compiled & presented by Eng. Stephen Siwila Mobile: +260-972-470-543 Email: ssiwilatabbie@yahoo.co.uk stephen.siwila@cbu.ac.zm

BUILDING MATERIALS & CONSTRUCTION UNIT -1 LECTURE SERIES: CEMENT