Lecture 1. Introduction To Concrete Technology
CIV-E2020 Concrete technology (5 cr)(1/28)Lecture 1. Introduction to concrete technologyPrepared by:D.Sc. Fahim Al-Neshawy,Reviewed by:Prof. Jouni PunkkiAalto University School of EngineeringDepartment of Civil EngineeringA: P.O.Box 12100, FIN-00076 Aalto, Finland
CIV-E2020 Concrete technology (5 cr)(2/28)Table of ContentsLecture 1.Introduction to concrete technology . 11.1Definitions . 31.2European standards for concrete. 41.3Main uses of concrete . 51.3.1Concrete cast in situ and precast concrete (ordinary concrete) . 51.3.2Special concretes . 61.4History of Concrete . 71.5Compressive strength classes - Concrete families . 111.6Advantages and limitations of concrete . 111.7Review of the concrete mix design methods . 121.7.1Concrete mix design procedure (Nykänen method) . 131.7.2Concrete mix design procedure (Building Research Establishment (BRE)-method) . 201.8References . 28
CIV-E2020 Concrete technology (5 cr)(3/28)1.1 DefinitionsDefinition of ConcreteConcrete is a mixture of cement (9 – 15%), water (15 – 16%), fine aggregate (sand, 25 – 30%), coarseaggregate (gravel or crushed rocks, 30 – 45%), air (2 – 6%) and chemical admixtures in which thecement and water have hardened by a chemical reaction – hydration – to bind the nearly (non reacting) aggregate.Figure 1-1. Basic ingredients of concreteDefinition of CementPortland cements are hydraulic cements, meaning they react and harden chemically with the additionof water. Cement contains limestone, clay, rock and iron ore blended and heated to 1200 to 1500 C .The resulting product "clinker" is then ground to the consistency of powder. Gypsum is added tocontrol setting time.Definition of Fine AggregateNormally called sand, this component can be natural sand or crushed stone, and represents particlessmaller than 4.0 mm. Generally accounts for 30%-35% of the mixture.Definition of Coarse AggregateMay be either gravel or crushed stone. Makes up 40%-45% of the mixture, comprised of particlesgreater than 4mm.
CIV-E2020 Concrete technology (5 cr)(4/28)Definition of Chemical AdmixturesMaterials added to alter the properties of concrete including: Air entraining admixtures: add microscopic air bubbles to the concrete, enhancing itsresistance to freeze/thaw cycles and makes the concrete easier to finish.Set accelerators: speed the set-time of the mixture, enabling finishing operations to beginsooner, useful during cold weather pours.Set retarders: have the opposite effect, slowing the set and enabling delivery to distantsites and finishing during hot weather.Water reducers: are used to reduce the amount of water required to produce a givenslump. They also provide a ball bearing effect, making the concrete easier to finish, andproduce better cement hydration. By reducing the amount of water required,cementamounts can be reduced because concrete strength is directly related to thewater/cement ratio.Definition of Mineral AdmixturesMineral admixtures include fly ash, hydrated lime, silica fume and ground blast furnace slag. Many ofthese materials have cement-like properties, increasing the strength and density of the finishedconcrete. They generally improve the workability, density and long-term strength of concrete, at theexpense of set time and early strengths.Definitions of Workability of ConcreteACI (American Concrete Institute) defines the workability of concrete as ‘the property of freshly mixedconcrete or mortar which determines the ease and homogeneity with which it can be mixed, placed,consolidated and finished. A concrete is said to be workable if: It can be handled without segregationIt can be placed without loss of homogeneityIt can be compacted with specified effortIt can be finished easily1.2 European standards for concreteThe concrete standards are being implemented across Europe to create harmonization between allEuropean countries and remove trade barriers between members. This harmonization will create andpromote opportunities to increase free trade throughout the European Community.
CIV-E2020 Concrete technology (5 cr)(5/28)Figure 1-2. The European Standards for concrete1.3 Main uses of concrete [ 1]Concrete is the second most widely used substance after water and over six milliard tons of concreteis produced each year. Concrete is specific to different applications like new construction, repair,rehabilitation and retrofitting. Concrete building components in different sizes and shapes includewall panels, doorsills, beams, pillars and more. Post-tensioned slabs are a preferred method forindustrial, commercial and residential floor slab construction. It makes sense to classify the uses ofconcrete on the basis of where and how it is produced, together with its method of application, sincethese have different requirements and properties.1.3.1Concrete cast in situ and precast concrete (ordinary concrete)Cast-in-site concrete is an unhardened state, like ready-mix, and is placed in molds. Ready mixedconcrete is proportioned and mixed off the project site. It finds application in foundations and slabson-ground, walls, beams, columns, floors, roofs, bridges, pavements, and other infrastructure. ReadyMixed concrete is durable and hard wearing and is used for variety of applications owing to its crackresistance and durability. Situ concrete is cast in place, on site. Precast concrete finds application inconcrete curtain walls, exterior cladding and structural walls, as it monolithic and can be easily used1T. Hirschi, H. Knauber, M. Lanz, J. Schlumpf, J. Schrabback, C. Spirig, U. Waeber (2005). Sika - Concrete Handbook. Onlineat: 093-338c-87291f770d6bfa97/Fact 1 concrete handbook.pdf
CIV-E2020 Concrete technology (5 cr)(6/28)for two-way structural systems. It is also adjustable to post tensioning and easily adapts to anybuilding shape.Figure 1-3. The 605 metres high, the Burj Khalifa skyscraper in Dubai will be the world’s tallestbuilding. Burj Khalifa's construction used 330,000 m3 of concrete. [ 2]1.3.2Special concretesA special concrete is a concrete made with special ingredients or by a special process may be ideallysuited to some special needs. Special concretes are used in modern times, for increased strength andconstruction of skyscraper or special structures. The special concretes include (among other things): 2Concrete for traffic areasSelf-compacting concrete (scc)Frost and freeze/thaw resistantconcreteHigh strength concreteSlip formed concreteWaterproof concreteFair-faced concreteMass concreteFiber reinforced concreteHeavyweight concretehttps://en.wikipedia.org/wiki/Burj Khalifa Underwater concreteLightweight concreteRolled concreteColoured concreteSemi-dry concrete for precastmanufacture of concrete productsConcrete with enhanced fire resistanceTunnel segment concreteMonolithic concreteGranolithic concrete
CIV-E2020 Concrete technology (5 cr)(7/28)The difference between the ordinary and special concrete is shown in Table 1.Table 1. Difference between the ordinary and special concrete.1.4 History of Concrete [ 3]The history of cement and concrete spans over 5,000 years, from the time of the Egyptian Pyramids topresent day decorative concrete developments. Concrete has been used for many amazing thingsthroughout history, including architecture, infrastructure and more.3000 BC - Egyptian PyramidsThe Egyptians were using early forms of concrete over 5000 yearsago to build pyramids. They mixed mud and straw to form bricksand used gypsum and lime to make mortars.3Concrete History Timeline – online at: near-timeline.html
CIV-E2020 Concrete technology (5 cr)300 BC - 476 AD-Roman ArchitectureThe ancient Romans used a material that is remarkably close tomodern cement to build many of their architectural marvels, suchas the Colosseum, and the Pantheon. The Romans also used animalproducts in their cement as an early form of admixtures.1824-Portland Cement InventedJoseph Aspdin of England is credited with the invention of modernportland cement. He named his cement portland, after a rockquary that produced very strong stone1836-Cement TestingThe first test of tensile and compressive strength took place inGermany1850 Concrete road1850 - The first concrete roads appeared in Austria.1865 - in England1891 - in Bellefontaine, Ohio US1854 First reinforced concreteWilliam B. Wilkinson, an English plasterer, erected a smallreinforced concrete two-story servant's cottage.He reinforced the concrete floor and roof with iron bars and wirerope. This is credited as the first reinforced concrete building.(8/28)
CIV-E2020 Concrete technology (5 cr)1889 Alvord Lake BridgeThe first concrete reinforced bridge was built in San Francisco.Alvord Lake Bridge still exists today, over two hundred years afterit was built!1901 Column clamp - Concrete formArthur Henry Symons designed a column clamp to be used withjob-built concrete forms1902 Rotary kiln – for ement productionThomas Edison was a pioneer in the further development of therotary kiln, which allows for continuous production cement1913-Ready Mix concreteThe first load of ready mix was delivered in Baltimore, Maryland.The first patent for a concrete pump was filed. This made concretetransportation easy and allowed on site mixing.1915 Colored concreteLynn Mason Scofield founded L.M. Scofield, the first company toproduce color for concrete.Their products included color hardeners, colorwax integral color,sealers, and chemical stains.1928 Pre-stressed concrete1928 - Eugene Freyssinet - French civil engineer - successfullydevelops pre-stressed concrete and built two air hangars withbarabolic curved shape at Orly Airport - Paris.(9/28)
CIV-E2020 Concrete technology (5 cr)1930-Air Entraining AgentsAir entraining agents were used for the first time in cement toresist against damage from freezing and thawing.1970's-Fiber ReinforcementFiber reinforcement was introduced as a way to strengthenconcrete.1980’s Self-compacting concreteThe mid 1980’s - Japan: the development of self-compacting1993 – Sweden : Research into self-compacting concrete, vibratingfree concrete, Europe’s first bridge built of self-com pactingconcrete was Swedish.1980's Superplasticizers and Silica fumeSuperplasticizers were introduced as admixtures. and silica fumewas introduced as a pozzolanic additive. The "highest strength"concrete was used in building the Union Plaza constructed inSeattle, Washington.1999 Polished concreteThe first installation of a polished concrete floor in the US was a40,000-square-foot warehouse floor for the Bellagio in Las Vegas.The popularity of polished concrete has soared in just the few shortyears it has been around, it is now being used in retail locationsand even residential homes(10/28)
CIV-E2020 Concrete technology (5 cr)(11/28)1.5 Compressive strength classes - Concrete families [ 4]Accordding to SFS-EN 206:2014, concrete is classified with respect to its characteristic compressivestrength at 28 days of 150 mm diameter by 300 mm cylinders ( fck,cyl) or the characteristic compressivestrength at 28 days of 150 mm cubes ( fck,cube), tested in accordance with EN 12390-3 may be used forclassification.Table 2. Compressive strength classes for normal-weight and heavy-weight concreteMinimum characteristiccylinder strength.fck,cyl [N/mm2]Minimum characteristic150 mm cube strength.fck,cube [N/mm2][ 5] Minimum characteristic100 mm cube strength.fck,cube 1.6 Advantages and limitations of concreteConcrete is an artificial stone-like material used for various structural purposes. Basic advantages andlimitations of concrete are as follows.45SFS-EN 206:2014 A1:2016:en - Concrete. Specification, performance, production and conformityBetoninormit 2016 – BY 65, Suomen Betoniyhdistys ry
CIV-E2020 Concrete technology (5 cr)(12/28)Some advantages of concrete are given below in brief: Concrete is economical when ingredients are readily available in most of the places.Concrete’s long life and relatively low maintenance requirements increase its economicbenefits.Concrete is not as likely to rot, corrode, or decay as other building materials.Concrete has the ability to be molded or cast into almost any desired shape and casting ofconcrete and can be manufactured to desired strength.Building of the molds (framework) and casting can occur on the work-site, which reduces cost.Concrete is a non-combustible material, which makes it fire-safe and able to withstand hightemperatures (Cracking starts at 550 C, popouts over chert or quartz aggregate particles at600 C and spalling at 800 C) [ 6].Concrete is resistant to wind, water, rodents, and insects. Hence, concrete is often used forstorm shelters.Maintenance cost of concrete is almost negligible.As a sound proofing material lightweight concrete could be used.Limitations of concrete: Compared to other binding materials, the tensile strength of concreter is relatively low.Concrete is less ductile.The weight of compared is high compared to its strength (low strength-to-weight ratio).Concrete may contain soluble salts. Soluble salts cause efflorescence.Concrete is susceptible to cracking.1.7 Review of the concrete mix design methodsThe objective in designing concrete mixtures is to determine the most economical and practicalcombination of readily available materials to produce a concrete that will satisfy the performancerequirements under particular conditions of use. Quantities of materials for the production ofrequired quantity of concrete of given mix proportions can be calculated by absolute volume method.This method is based on the principle that the volume of fully compacted concrete is equal to theabsolute volume of all the materials of concrete, i.e. cement, sand, coarse aggregates and water. Theformula for calculation of materials for required volume of concrete is given by:6Evaluating fire damage to concrete structures. Online ures tcm45-343618.pdf
CIV-E2020 Concrete technology (5 cr)Where:𝑉𝑉𝑐𝑐𝑐𝑐𝑐𝑐 (13/28)𝑄𝑄𝑐𝑐𝑒𝑒𝑒𝑒 𝑄𝑄𝐹𝐹𝐹𝐹 𝑄𝑄𝐶𝐶𝐶𝐶 𝑄𝑄𝑤𝑤 ��𝑐𝑐𝑐 𝑆𝑆𝐹𝐹𝐹𝐹 𝑆𝑆𝐶𝐶𝐶𝐶Vcon Absolute volume of fully compacted freshconcrete, [m³]Qcem Mass of cement, [kg]QW Mass of water, [kg]QFA Mass of fine aggregates, [kg]QCA Mass of coarse aggregates, [kg]Scem, SFA and SCA are the specific gravities of cement,fine aggregates, and coarse aggregates respectivelyVAir the volume of the air contentThis method of calculation for quantities of materials for concrete takes into account the mixproportions from design mix for structural strength and durability requirement.This section covers mix design fundamentals common to the Finnish - Nykänen and BRE (BuildingResearch Establishment, UK) mix design methods.1.7.1Concrete mix design procedure (Nykänen method)Nykänen method (7): Developed by professor Arvo Nykänen (1912 – 1990)1st version of the proportion method was developed in 1945 and the publications about themethod during the years 1947 and 1948The new version of the methods established in 1955 because of the changes in the code ofpractices and the development of concrete technologySpecified concrete propertiesA properly proportioned concrete mix should possess the following qualities:i.ii.iii.Acceptable workability of the freshly mixed concreteDurability, strength, and uniform appearance of the hardened concrete result from thestructural design processEconomy.The requirement (input) for the Nykänen method are:7Arvo Nykänen, talven taitaja ja suhteituksen isä. Online at kanentalven-taitaja-ja-suhteituksen-isa
CIV-E2020 Concrete technology (5 cr) (14/28)The 28 days compressive strength of the concrete (nominal strength)The slump of the fresh concrete mass (workability), shown in Table 3.The 28 days compressive strength of the cement usedThe air-content of concrete (generally assumed 2% for normal concrete)The grading and the moisture content of the aggregatesThe amount of absorbing water in the aggregates (generally estimated to be 0.4 %)Any other information about the concrete structureTable 3. The permissible slump for various types of concrete in relation to their use 8Concrete structuresReinforced foundation walls and footingsPlain footings, caissons and substructure wallsSlabs, beams, thin reinforced walls and building columnsPavements and floor laid on groundHeavy mass constructionConsistency (Slump), [mm]MaximumMinimum12550100251507575257525Example - Procedure for concrete mix designProportion a concrete mix with a 28 day compressive strength of 35 MPa and a slumpof 90 mm, made with ordinary Portland cement with cement strength of 49,5 MPa.Grading of the aggregate is presented in Figure 1-7. All aggregates are dry, absorbing 0.8%, not crushedStep 1. Calculating the proportioning strength:The proportion strength is calculated using the following equation:Where:KsKtKKcem8𝐾𝐾𝑠𝑠 𝑘𝑘𝑡𝑡 𝐾𝐾 𝑘𝑘𝑐𝑐𝑐𝑐𝑐𝑐 1.2 35 42.5 36 𝑀𝑀𝑀𝑀𝑀𝑀49.5is proportion strength for the concrete mixis the target strength factor, kt 1.2is the nominal strength of the concrete (28d compressive strength)is the cement strength factor(kcem (42.5/N), where N is the 28d cement strength in MPa, according to Nykänenproportioning formulaACI 211.1 - 91 (Reapproved 2009), “Standard Practice for Selecting Proportions for Normal, Heavy weight, and MassConcrete”, specifically Chapter 6, “Procedure” and Appendix 1, “Metric (SI) System Adaptation. Online crete mix design guide.pdf
CIV-E2020 Concrete technology (5 cr)(15/28)Step 2. Choice of the aggregates and calculating of the grading factor (H)Selecting the maximum coarse aggregate size: The maximum size of coarse aggregate that can beused in a mix depends on the size, shape, and reinforcing of a concrete member.Figure 1-4. Maximum coarse aggregate size.Maximum aggregate size (Dmax) should not be larger than:i)ii)iii)iv)1/5 the minimum dimension of structural members such as beams columns, frames etc. (b/5)1/3 the thickness of a concrete slab (h/3)3/4 the clearance between reinforcement bars (3S/4)3/4 the concrete cover depth (3C/4) the clearance between reinforcing steel and the concretingforms (molds).These restrictions limit maximum aggregate size to 32 mm, except in mass applications. In manycountries, the largest available sizes vary 16 mm to 32 mm(9).For the laboratory concrete mix design, the maximum aggregate size is the sieve size that passes 95%of the combined aggregate.Speci
1.3.1 Concrete cast in situ and precast concrete (ordinary concrete) Cast-in-site concrete is an unhardened state, like ready-mix, and is placed in molds. Ready mixed concrete is proportioned and mixed off the pro
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