ENGINEERING MATERIALS BAA1312 &DAA1312 FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING, UCET
SYNOPSIS This subject is compulsory and basic subject in the field of construction. Engineering Material introduce the material that using in civil engineering. It covers characteristic, grading, effectiveness, processing, testing, strength and the others. Material that using is cement, aggregate in concrete, water, additives, fresh concrete, hardened concrete, concrete design mix, timber, type and characteristic of bricks and metal. • OBJECTIVES • Upon completion of this course, the students will be able to: • -Enhance basic knowledge of concrete, pre-cast concrete and its behavior. • -Practice the important concrete tests • -To know more about the things that should be taken in consideration for the construction using steel and other materials. FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING
ASSESSMENT Test 1 & 2 : 40% Quiz : 10% Assignment : 10% Exam (Final) : 40% ATTENDANCE Students must attend 100% of the classes. Students will be barred from taking / sitting for their final examination should they fail to attend classes without valid reason or given permission. FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING
INTRODUCTION • MATERIALS IN CONSTRUCTION • Modern building often comprise vast numbers of components, many pre-manufactured and simply assembled on site, while some, such as concrete, are manufactured in situ. In each case, satisfactory operation of building as a whole depends on the performance of the materials from which its components are made as well as on how they interact with each other in the building. • Before assessing the suitability of any one material for given situation, the performance requirements for that situation must identified. Such requirements might include: • Structural safety – the ability to withstand stresses resulting from gravity, wind, thermal or moisture movement, or other sources. • Health/safety – there should be no risk to health due to chemical or physical effect of the material both during and after construction. • Fire – the material must behave acceptable in resisting fire spread, release of dangerous substances in fire and retaining satisfactory structural stability • Durability – the material should fulfils the above performance criteria as required for the planned lifetime of the building • In addition to the above performance requirements of materials within the finished building, the following might also have to considered: • Availability/cost • Ease with which material can be incorporated into the building (buildability) • Environmental aspect – for example, energy demand of the material during manufacture and ability to conserve energy in use. FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING
CONCRETE • Introduction • Most widely used as construction material. • Obtained by mixing cement, water & aggregates • Then the mixture placed in a mould and allowed to cure • It became hard because of the chemical reaction that happened between water & cement. • The concrete afterwards grows stronger with the increasing of age.
CONCRETE • Advantages of Concrete • Economical in long run compared to other engineering material (low cost) • Possesses a high compressive strength • Corrosive & the weathering effects are minimal. • Fresh concrete can be easily handled & moulded in any shape / size. • Formwork can be re-used • Can be sprayed on & filled the cracks for repairing process. • Durable & fire resistant & requires little maintenance. • Can be pumped and hence it can be laid in the difficult position • Protection of embedded steel • Variety of finishes obtainable.
CONCRETE • Disadvantages using concrete: • Low tensile strength and cracks easily so it need to be reinforced with steel/brittleness • Fresh concrete shrinks when drying & hardened while it expands when it is wet. • Concrete expands and contracts with the changes of temperature. • Concrete under sustained load undergoes creep resulting reduction of pre-stress in the pre-stressed concrete construction. • Concrete is not entirely impervious to moisture & contains soluble salts, which may cause efflorescence. • Concrete is liable to disintegrate by alkali and sulphate attack. • The lack of ductility inherent in concrete. • Rather high density (though lower density types available.
CEMENT Introduction · Popular as building material. · Material with adhesive & cohesive properties. · To bind the sand & coarse aggregate together · To fill voids in between sand & coarse aggregate particle form a compact mass.
CEMENT • 2 Categories of Cement • Hydraulic Cement • Would set & hardened under water • Can be classified to 3 kind of cement that is: • 1) Natural Cement • 2) Portland Cement • 3) Aluminous Cement • High Alumina Cement • Quite different both in composition& properties from Portland Cement • Slow-setting but very rapid hardening & produces very high early strength • Contains a highest composition of Alumina (39%) beside others.
CEMENT There are 3 kind of concrete can be created using cement that are: Cement Grout - A mixture of cement & water Cement Mortar - A mixture of cement & sand & water to form a paste. Cement concrete - A composite product which is obtained by mixing of cement, water, inert matrix of sand and gravel / crushed stone.
CEMENT • PORTLAND CEMENT • Made by mixing substances containing Calcium Carbonate such as chalk / limestone, • with substances containing silica , alumina and iron oxide such as clay/ shale. • Clay/shale: • SiO2 Silica (silicon oxide) abbreviated S • Fe203 Ferrite (iron oxide) abbreviated F • Al203 Alumina (aluminium oxide) abbreviated A • Limestone/chalk • CaC03 Calcium carbonate abbreviated C • then the mixture heated and became clinker. • Clinker then grounded to powder. • The hardening Portland cement is a chemical process during which heat is evolved. Why is it called "portland" cement?Joseph Aspdin, an English mason who patented the product in 1824, named it portland cement because it produced a concrete that resembled the color of the natural limestone quarried on the Isle of Portland, a peninsula in the English Channel
CEMENT • The 4 main chemical compound are: • Dicalcium Silicate (C2S) • Slow strength gain – responsible for long term strength • 20% (Approximately percentage in OPC) • 260 (J/g) – Heat of hydration • Tricalcium Silicate (C3S) • Rapid strength gain – responsible for early strength ( eg: 7 days) • 55% (Approximately percentage in OPC) • 500 J/g (Heat of hydration) • Tricalcium Aluminate (C3A) • Quick setting (controlled by gypsum): susceptible to sulphate attack • 12% (Approximately percentage in OPC) • 865 J/g (Heat of hydration) • Tetracalcium Aluminoferrite (C4AF) • Little contribution to setting or strength; responsible for grey colour of OPC • 8% (Approximately percentage in OPC) • 420J/g (Heat of hydration)
TYPES OF PORTLAND CEMENT • There are many types of Portland cement such as following: • Ordinary Portland Cement • Has a medium rate of hardening • Suitable for most type of work • Can be attacked by acids & sulphates present in soil / groundwater • Sulphates also occur in clay bricks • Rapid – hardening Portland Cement • Similar chemical composition as OPC but different proportion • More finely grounded than OPC • This causes to the increased rate of early hardening • Setting & stiffening time for OPC similar to RHPC • It just that for RHPC, after the initial period the RHPC gains strength more rapidly. • Concrete made with RHPC develops in 7 days the same strength that it • Takes 28 days to develop in concrete made with OPC. • This high early strength is achieved by increasing the CS & CA content of • The cement and finer grinding. • Advantage is allows formwork to be struck earlier so providing savings either the quantity of formwork required / in time. • RHPC produce heat earlier than OPC, so can be used in cold weather • Stored & used in same way as OPC
CEMENT • White and Coloured Cement • Usually used for decorative work, pre-cast panels, coping, pavings • White cement is made by using china clay in place of ordinary clay. • This is to exclude impurities, especially iron & limestone • Needed care during curing as it is easily soiled coz it’s hard to clean • Plastic sheeting is excellent for curing & protection. • Coloured cements made by mixing pigments with Portland Cement. • Low Heat Portland Cement • Hardens & evolves heat slower than OPC because the proportion of • Dicalcium Silicate (C2S) was increased while the proportion of Tricalcium Silicate ( C3S ) & Tricalcium Aluminate ( CA ) ………………….. • It’s slow in development of strength because • But the ultimate strength is the same. • Useful for dam & other mass concrete construction • Portland – Blast furnace Cement • Made by grinding a mixture of OPC with selected granulated blastfurnace slag. • It has resistance to sulphate which can be found in………………………… • Hydrates slower than OPC so this cement evolves less heat and hardens slower than OPC.
Sulphate - Resisting Portland Cement • Applied at place where there Is expensive exposure to Sulphates such as used in concrete below ground • The proportion of SRPC higher content of Tetracalcium Aluminoferrite (C4AF) & reducing the Tricalcium aluminate (C3A) to a minimum. • SRPC has darker colour than OPC • Chemical constituents are different in proportions • Not resistant to acids same as OPC • Produces a little less heat than the other Portland cement & this can be an advantage in mass pours, deeps basements & foundation. • sulphate cement in poorly mixed & badly compacted will not assist it resistance to attack from chemical • Advise should be sought before using any admixtures with the cement, coz some will reduce its resistance to sulphate attack.
Masonry Cement • Consists of Portland cement with a fine inert admixture & air-entraining agent as a substitute for lime. • So it gives cement a consistent workability for use in mortars for brickwork & block work. • Mustn’t be used for concrete • High Alumina Cement • Darker than OPC • Stiffens at about the same rate as OPC • Contamination with Portland cement causes a “flash set” so all mixers, shovels & barrow must be carefully cleaned to remove any traces of ordinary cement. • Stored separately in clearly marked position • Admixtures shouldn’t be used • Rapid gain in strength is useful for in roof repairs of shops by providing a working surface in a few hours. • Also used in high temperature applications • Prohibited from being used for structural purposes.
Properties of Cement • a) Chemical Composition • The major substituents of cements are: • C3S – quick reaction • C2S – slow reaction • C3A - very quick reaction • C4AF - not very important C3S Strength C2S C3A C4AF Time
b) Fineness • v Fineness of cement is a measure of the sizes particles of cement. • v It is expressed in terms of specific surface of cement. • v Most important factor that will determines the properties of cement • v Process of Hydration • Since hydration starts at the surface of the cement particles it is the total surface area of cement that represents the material available for hydration • The finer the cement is ground, the greater will be its specific surface. • So the rate of hydration depends on the fineness of cement particles & for rapid development of strength higher fineness necessary. • Fineness cement leads to a stronger reaction with alkali reaction aggregate & makes a paste though not necessarily concrete, exhibiting a higher shrinkage & a creates proneness to cracking. • However, fine cement bleed less than a coarse one. • The fineness is the most important factor which determines the properties of cement: • Finer grinding increases the speed with which the various constituents reacts with the water • Fineness of grinding is of some importance in relation on the workability of concrete mixes. • Greater fineness increases the cohesiveness of a concrete mix • Finer grinding reduces the chances of bleeding of concrete • In some special type of cement the strength increases slowly than normal though they are finely grounded.
c) Hydration of cement • Heat is liberated as cement sets and hardened by reacting with water. • The rate of heat evolution as well as total heat depends on the compositon of cement. • The rate of hydration & the heat evolved increases with the fineness of cement but the total amount of heat liberated in unaffected by fineness. 5 1 2 3 & 4 C3S Hydration Rate of heat C3A Hydration Time
d) Setting time • The time from the addition of water to the initial & final setting stage. • Also refers to time of changes of the cement paste from a liquid to a rigid stage. • The setting process is accompanied by the temperature changes, hydration resolves in the formation of the gel around each parties of cement. • The means of controlling the rate at which cement stiffened by intergrinding a measured quantities of gypsum • Initial Setting • · Defined as the beginning of the noticeable stiffening in the cement paste. • It’s corresponds to a rapid rise in temperature. • · Normally takes about 45 – 175 minutes. • - • Final Setting Time • · Refers to completion of setting, which corresponds to the peak temperature in the cement paste. • · The stiffening of cement paste increases as the volume of the gel increases and the stage at which this is complete, the final hardening process begins. • · Normally takes between 3 hours to 10 hours for this to happen. • Hardening • Referred to the gained of the strength of the cement paste. • During the setting time the cement gained very little strength
Malaysian Standard for Cement Test (MS 7.13:1977) • Chemical Composition Test • Fineness Test • Setting Time Test • Strength Test • Soundness Test
Fineness Test • Minimum size of OPC is 225 m2/kg • Minimum size for RHPC is 325 m2/kg • Apparatus – Lea and Nurse or Blaine
AGGREGATE added up to 80% by volume in ordinary concrete to provide bulk CHARACTERISTIC - Must clean & durable & Free from organic impurities & dust (WHY?) - Coz it may prevent the cement paste from coating the aggregate properly - Also preventing bonding - Also lowering the strength of the concrete
TYPES OF AGGREGATES Fine Aggregates natural sand crushed rock crushed gravel that pass 5mm Bs Sieve dry vary in character depending on their location, method of extration & gradin “Sharp” sand has angular grains – used mainly for concrete “Soft” sand has smaller rounded grains – used for mortars & renderings Coarse Aggregate materials that retained on a 5mm sieve when dry. 10mm for small section work with a lot of close reinforcement 20mm for general work 100 – 150 mm for large reinforced pours All in Aggregate mixture of coarse & fine aggregate either as extracted / delivered not allowed for structural purposes Graded Aggregates natural agg. consist of different size of stones randomly mixed.
ADMIXTURE - Materials other than cement, water & aggregates - Added to the concrete mix to modify & to improve one/ more specific properties of concrete PURPOSE OF ADMIXTURE? • v To improve workability of fresh concrete • v To improve durability by entrainment of air • v To reduce the water required • v To accelerate setting & hardenin to produce high early strength • v To aid curing • v To impart water repellant / water proofing property • v To cause dispersion of the cement particles when mixed witH20 • v To retard setting • v To improve wear resistance ( hardness ) • v To offset / reduce shrinkage during setting & hardening • v To cause expansion of concrete and automatic prestressing of steel • v To aerate mortar / concrete to produce a light – weight product • v To impart colour • v To offset or reduce some chemical reaction • v To reduce bleeding • To reduce the evolution of heat
COMMONLY USED ADMIXTURE (TYPE) vAccelarator - added to increase the rate of hydration of concrete mix which then lead to the increases in the rate of development of strength and greater heat evolution. - And to shorten the setting time - Disadvantages is possible cracking due to heat evolution & Possibility of corrosion of embedded reinforcement - A good accelerator will accelerated the hydration of the C3S or C2S content of cement - The best know accelarator is calcium chloride
Water Reducing Admixture -used to reduce the amount of water necessary to produce a concrete of a given consistency -To increase the slump for a given water content -to obtain specified strength at lower cement content - Disadvantage is, careful control of air content and mixing time necessary
Superplasticizer - -by adding to a hydraulic binder , gives very high workability and allows a large decrease in water content for a given workability. - -enhances the hydration process - -allows the particles to be more workable - -less susceptible to segregation and bleeding problems.
Air entraining Admixtures - -An entraining concrete containing air in a rather special form of a bubble which trapped in concrete -Workability improved, easier placing, increased durability, better resistance to frost action,
Retarding Admixture - Prolong/delay the setting time of cement paste in concrete - used in hot weather to reduce any premature stiffening of the concrete & consequent loss of workability. - Disadvantages is may promote bleeding - Consist of the general chemical types: Calcium, sodium, potassium, or ammonium salts of lignosulphonic acid Hydroxy