Transcript of " Recent Advances in Concrete Technology"
Staff De evelopme Progr ent ramme ( (SDP) onRECENT ADVANCES IN CONC C A N CRETE T TECHN NOLOGY Y 16-27 April, 20 007 Sponsored b by All In ndia Co ouncil fo Tech or hnical E Educati ion (AICTE New D E), Delhi Coo ordinator JOB THOMA AS Div vision of C Eng Civil gineering g School o Engine S of eering Coc chin Univ versity of Science and Te f e echnolog gy Coochin – 6 022, Kerala 682 , www.civ vil.cusat. .ac.in
Fast track concrete technology Prof. A.R.Santhakumar Emeritus Professor of Civil Engineering IIT (Madras),600 036 India Email: firstname.lastname@example.org. AbstractConstruction is the ultimate objective of design and machinesmake accomplishment of that task possible. The efforts of theengineer who designs a project , and the constructor, whobuilds the project are directed towards the same goal: creationof some infrastructure that will improve the quality of life formankind and serve the purpose for which it is built in asatisfactory manner. Construction is the ultimate objective andmachines and methods make accomplishment of that objectivepossible. The constructor must select the proper equipment toprocess materials and build the structure economically.Whereas most manufacturing companies have a permanentfactory a construction company carries its factory with it fromsite to site depending on job requirement.1. INTRODUCTIONIn order to supply the required land for accommodating the hugepopulation, and to provide ample infrastructure and communityfacilities to substantiate an acceptable standard of living, commercialoperations and other necessary developments, many critical locationswhich may be unsuitable for development to most internationalyardsticks, are built with very large sized and high-rise buildings. Thefollowing situations are some of these examples.
FIBER REINFORCED CONCRETE FOR RETROFITTING Dr. C.Antony Jeyasehar R.Balamuralikrishnan Professor and Head, Sr.Lecturer E-mail: email@example.com E-mail:firstname.lastname@example.org Dept. of Civil and Structural Engineering Annamalai University, Annamalainagar- 608 002 Tamilnadu, India Telephone No: 91-4144-239732 Fax No: 91-4144-2397321. IntroductionThe use of randomly oriented, short fibers to improve the physical properties of a matrix isan age – old concept. For example, fibers made of straw or horsehair have been used toimprove the properties of bricks for thousand of years. In modern times, fiber – reinforcedcomposites are being used for a large variety of applications. The composite could be a claybrick reinforced with natural fibers or a high – strength, fiber – reinforced ceramiccomponent used in space shuttle. The fiber reinforced composites made with the primarilyPortland cement – based matrices. The matrices can consist of any of the following:1. Plain Portland cement2. Cement with additives such as fly ash or condensed silica fume3. Cement mortar containing cement and fine aggregate4. Concrete containing cement, fine and coarse aggregates.The presence of micro cracks at the mortar-aggregate interface is responsible for the inherentweakness of plain concrete. The weakness can be removed by inclusion of fibers in thematrix. The fibers help to transfer loads at internal micro cracks. Such a concrete is calledfiber reinforced concrete. Thus the fiber-reinforced concrete is a composite materialessentially consisting of conventional concrete or mortar reinforced by fine fibers.The fibers can be broadly classified as1. Metallic fibers2. Polymeric fibers3. Mineral fibers4. Naturally occurring fibersMetallic fibers are made of either steel or stainless steel. The polymeric fibers in use includeacrylic, carbon, nylon, polyester, polyethylene and polypropylene fibers. Glass fiber is thepredominantly used mineral fiber. Various types of organic and inorganic naturally occurringfibers such as cellulose are being used to reinforce the cement matrix.Fiber reinforced concrete (FRC) has been used since the 1960’s (ACI 544.1, 1996), althoughuse was generally limited to warehouse floor or pavement overlays. Steel, glass, carbon and
Polymer Modified Concrete for RetrofittingDr. C.Antony Jeyasehar R.BalamuralikrishnanProfessor and Head, Sr.LecturerE-mail: email@example.com E-mail:firstname.lastname@example.org Dept. of Civil and Structural Engineering Annamalai University, Annamalainagar- 608 002 Tamilnadu, Tel. No: 91-4144-239732, Fax No: 91-4144-2397321. IntroductionIn virtually all cases of concrete deterioration, the problem is associated with corrosion ofsteel reinforcement. It is well established that steel reinforcement well embedded in goodquality concrete is protected from corrosion by the passivating nature of the highly alkalinecement matrix. Therefore, whenever, possible, it is desirable from both technical andeconomic considerations deteriorated reinforced concrete should be repaired withimpermeable highly alkaline cement based materials closely matched in properties to theparent concrete. However there are many instances where repair composition containingpolymers, either as admixtures for cementation systems or as high strength binders (foradhesive mortars and grouts) are the most appropriate. Over the past twenty years, manydifferent polymers have been used in a range of applications in the repair and maintenance ofbuilding and other structures. With out the unique properties of some of the polymer systems,many of the repairs undertaken would, with out doubt, have been much more costly and havetaken much longer to carry out.To realistically appraise the position of concrete repair technology and the complex fabric ofproblems it faces today, we must pause periodically to review where we are and where wemight be going. The majority of the faults and problems are caused by lack of attention todesign details, specifications and poor in-site workmanship. Material, although important, isless of an evil. Material, per se, does not problem; the end product made from a material - therepaired structure - performance. The concern should not be solely with repair, materialthemselves, but with the uses to which they are being put, with the gray area of overlapbetween material properties, and the end engineering product - the repaired structure.Experience world-wide now confirms that even when specific national code requirements ofdurability in terms of concrete cover and concrete quality are achieved in practice, there is anunacceptable high risk of premature deterioration of concrete structures exposed toaggressive conditions. Deterioration of concrete and corrosion of reinforcement have thusbecome the major causes of loss of serviceability and safety of reinforced and prestessed
LIGHTWEIGHT CONCRETE: MATERIALS, PRODUCTION CHARACTERISTICS, PROPERTIES AND APPLICATIONS Kunhanandan Nambiar E K1ABSTRACT: In concrete construction, self-weight usually represents a large proportion of the total load in thestructure and hence, any attempt to reduce the self-weight of the structure is undoubtedly considered as anadvantage. In addition to reducing stresses through the life time of the structure, the total weight of material tobe handled during construction is also reduced, which consequently increases the productivity. Further more,lightweight concrete offers better thermal insulation, seismic resistance and fire protection than ordinaryconcrete.INTRODUCTION Lightweight concrete can also be classified according to the purpose for which it is to be used: Practical range of densities of lightweight we distinguish between structural lightweightconcrete (LWC) varies between 300kg/m3 and 1850 concrete (ASTM C 330-89) and concrete used inkg/m3. Basically there is only one way of making non-load bearing walls (concrete used in masonryconcrete lighter – the inclusion of air in its units, ASTM C 331-89) , for insulation purposescomposition. However this air-entrainment can be (ASTM C 332-87), and the like. The strength andachieved by three different ways viz. ; (i) by density ranges of these concretes are given in Tablereplacing the ordinary aggregate with a hollow 1. The essential feature of insulating concrete is itscellular or porous aggregate that includes voids coefficient of thermal conductivity which should bewithin its body, this is termed ‘lightweight aggregate below about 0.3 J/m2s oC/m (Neville, 1995)concrete’; (ii) by omitting finer sizes from theaggregate grading thereby creating ‘no fines . Table 1 Classification based on useconcrete’; (iii) by introducing gas/air bubbles in theplastic mix of cement/ cement-filler slurry (aerated Type ofconcrete) or by introducing pores due to excessive Insulating Masonry Structural LWCwater proportion in the mortar (microporites), bothafter setting leaves a cellular structure, termed as Density 1400-‘cellular concrete’ (Shrivastava, 1977). A general <800 500-800 range, kg/m3 1800classification of lightweight concrete is presented inFig. 1.1. Out of these, lightweight aggregate concreteand aerated concrete are the most popular classes. Strength 0.7-7 7-14 ≥17 range, MPa Lightweight concrete Also, classification based on strength is given in Table 2. Lightweight Cellular No-fines aggregate concrete concrete concrete Table 2 Classification based on strength Aerated Microporites Moderate Type of Insulating Structural concrete strength LWC concrete concrete concrete Gas concrete Strength Foam concrete range, 0.7-7 7-17 17- 41 MPa Fig. 1 Classification of lightweight concrete Density range, 250-800 800-1350 1350-1850 1 kg/m3 Assistant Professor, N S S College of Engineering, Palakkad, 678 008
CHEMICAL ADMIXTURES FOR CONCRETEG B Vamadev*FOSROCIntroductionConcrete is the most widely used construction material in the world. Its consumption is around20 billion tonnes annually which comes to around two tonnes per every living person. Thereasons for such widespread use of concrete are its adaptability, durability, strength, availabilityand economy. Concrete is the only material which can be used everywhere; literally, frompavements to roofs.But the most sought after properties of concrete, viz., workability in the fresh state and strengthand durability in the hardened state, cannot always be realised with its regular constituents. Insuch cases, chemical admixtures become essential requirements for concrete.AdmixtureAn admixture is defined as the material added during the mixing process of concrete in aquantity not exceeding 5% by mass of the cement content of the concrete to modify theproperties of the mix in the fresh and/or hardened state. Both chemical and mineral admixturesare widely used. Silica fume and fly ash are the most widely used mineral admixtures.Chemical AdmixturesAs mentioned above, the purpose of using chemical admixtures is to modify certain properties ofconcrete. The ACI committee has listed the properties mentioned below.In the fresh state, admixtures perform the following functions :1. Increase workability2. Accelerate or retard the setting time of concrete3. Reduce or prevent settlement or to create slight expansion4. Modify the rate and/or capacity for bleeding5. Reduce segregation6. Improve pumpability7. Reduce slump loss* G B Vamadev – Business Manager –Concrete Industries, Fosroc Chemicals (India) Pvt.Limited, Bangalore
BEHAVIOUR OF CONCRETE EXPOSED TO FIRE Dr. George Mathew, Reader School of Engineering Cochin University of Science and Technology, Kochi-22The behaviour of various physical properties of concrete that has influence on the overallbehaviour of concrete when exposed to fire has been discussed in this paper. The possibledamage to reinforced concrete structural members when exposed to fire and the methodof reinstatement of fire damaged RCC members are also discussed in this paper.Concrete is the most widely used 6. Creep Deformation andmaterial in construction. In general, the 7. Strengthuse of concrete in construction can begrouped in to two, viz. As concrete is made of different materials, its behaviour with temperature1. Used as structural concrete- Used depends on several factors and as such a to construct structural members such general remark can only be made with as Reinforced Cement Concrete ( respect to the various properties. RCC) and Pre-Stressed Concrete (PSC) members and Thermal Expansion of Concrete2. Used as a protection material to structural steel against fire – Thermal expansion of materials is one of Primarily Plain Cement Concrete ( the important properties as far as fire PCC) safety is concerned. In structures, members restrained from expansion byThe structural behaviour of a building the surrounding elements or thesubjected to fire depends primarily on development of differential expansion ofthe variations developed in the different materials leads to the failure ofproperties of individual materials which members in a structure, which mayare exposed to fire. The material ultimately lead to even itsproperties which are of importance when collapse.Thermal expansion of concretea structure is exposed to fire are: is influenced by different parameters such as the type of cement1. Thermal Expansion - type of aggregate2. Thermal Diffusivity - water content at the time of3. Modulus of Elasticity temperature change and4. Poisson’s Ratio - age of concrete5. Stress-Strain Relationship
QUALITY CONTROL OF CONCRETE George Mathew Reader, Cochin UniversityOne of the most important requirements in good concrete construction is that the qualityof concrete used in the structure should conform to that specified in the design.There are several tests that can be made with both plastic and hardened concrete, but thestrength test is widely used in specifying, controlling, and evaluating concrete quality.Quality concrete must be able to 1)carry loads imposed upon it; 2) resist deterioration;and 3) be dimensionally stable. Although the strength test is not a direct measure ofconcrete durability or dimensional stability, it provides an indication of the water-cementratio of the concrete. The water-cement ratio, in turn, directly influences the strength;durability; wear resistance; dimensional stability; and other desirable properties ofconcrete. The strength test is also used to measure the variability of concrete. VARIABILITY OF CONCRETEConcrete is subject to numerous factors that affect its strength and other properties. Thesemay include variations in the manufacturer of cement; preparation of aggregates;batching, mixing, and curing of concrete; and finally in the preparation, handling, andtesting of the sample specimens. The major sources of variation in the strength test resultsare listed in Table 1. Table 1 – Principal sources of variations in strength test results Variations in properties of concrete Discrepancies in testing methods Changes in water-cement ratio Improper sampling procedures Poor control of water Excessive variation of moisture in aggregate Variations in water requirement Variations due to fabrication techniques Aggregate grading, absorption, Molding of specimen particle shape. Poor quality molds Cement and admixture properties Handling and curing of newly made Air Content specimen Delivery time and temperature Variations in characteristics and Changes in curing proportions of ingredients Temperature variation Aggregates Variable moisture Cement Delays in bringing specimens to Admixtures the laboratory Variations in batching, mixing, Poor testing procedures transporting, placing and compaction Care of specimen, transportation Improper placement in testing Variations in temperature and curing machine Testing machine platens out of specifications. Incorrect speed of testing.
Cement• Trends in India• Special Concrete• Cement Manufacturing Procedure• Types of Cement• Major Compounds in Cement• Physical Quality Parameters• Chemical Quality Parameters• Cement Plants & Products• Packaging
CEMENTM.A. JosephAditya Birla• Trends in India• Manufacturing Procedure• Special Types of Concrete• Types of Cement• Major Compounds in Cement• Physical Quality Parameters• Chemical Quality Parameters• Cement Plants & Products• Packaging
Effect of Supplementary Cementing Materials on Chemical Durability of Concrete. Nazeer M Faculty in Civil Engineering TKM College of Engineering Kollam – 691 005. Kerala. ABSTRACTIncreasingly greater attention has been paid in recent years to the problem of structuraldurability of plain and reinforced concrete structures. The extensive application of thesebuilding materials and their limited life in various media has necessitated a growingvolume of repair and restoration of reinforced concrete structures. Considering thedifficulties of such repairs, it is imperative to provide an adequate and guaranteed servicelife of reinforced concrete right at the time of designing and erecting the building orstructure.Recently, High Performance Concretes incorporating various mineral admixtures areused to combat the adverse effects of chemically aggressive environment. Thesupplementary cementing materials used for improving the performance of concrete aresilicafume, flyash, ground granulated blast furnace slag, and metakaolin. These materialsare either added as admixtures (mineral admixtures) or as a partial replacement ofcement. A concrete with these materials, prepared from lower w/c ratio and withchemical admixtures, shows reduced permeability and enhanced strength.This report discusses the effects of supplementary cementing materials against thechemical deterioration of concrete.INTRODUCTIONDurability of hydraulic-cement concrete is defined as its ability to resist weathering action,chemical attack, abrasion, or any other process of deterioration. Durable concrete will retain itsoriginal form, quality, and serviceability when exposed to its environment. Major causes ofconcrete deterioration are freezing and thawing, aggressive chemical exposure, abrasion,corrosion of metals, and chemical reactions of aggregates.Freezing and ThawingWhen water begins to freeze in a capillary cavity, the increase in volume accompanying thefreezing of water requires a dilation of the cavity equal to 9% of the amount of excess water outthrough the boundaries of the specimen or some of both effects. During this process, hydraulicpressure is generated and the magnitude of that pressure depends on the distance to an escapeboundary, the permeability of the intervening material and the rate at which ice is formed.Experience shows that disruptive pressures will be developed in an saturated specimen of pasteunless every capillary cavity in the paste is not farther than three or four thousandths of an inchfrom the nearest escape boundary. Air entrainment has proved to be an effective means ofreducing the risk of damage to concrete freezing and thawing.Causes of deterioration of the hardened concrete by freeze-thaw action can be related to thecomplex microstructure of the material, and also the specific environmental conditions.
Fracture Mechanics of Concrete Structures Palivela Subba Rao Associate Professor Department of Civil Engineering JNTU College of Engineering Kakinada 1 RUDIMENTS OFFRACTURE MECHANICS Palivela Subba Rao, Associate Professor Department of Civil engineering JNTU College of engineering Kakinada, (AP) 1
Rudiments of Fracture Mechanics11.1 Introduction In general, material/ structural component fails either due to any of the following ortheir combinations. i) Yielding ii) Buckling iii) Fatigue iv) Impact v) Fracture etc. Thereforea component is designed so as to avoid the yielding of the maximum loaded point. This isconsidered as the basic requirement of design and is taught in all courses on strength ofmaterials at under graduate level. Over the ages, man has been under an impression that strength of material is materialproperty and strength is the criterion for failure of material / structural components under aninfluence of external loads. Contrary to this, the incidents that occurred in the past during theSecond World War times taught man lesions: There is some other criterion for failure ofmaterial, beyond strength criterion. Failure of Liberty ships during the world war-II has givena way to think in a different way from conventional way of understanding of material failure. Crack occurrence in a structural component either during its construction/manufacturing or during its life time is inevitable. Performance of a cracked structuralcomponent under mechanical loading is very much different from that of the samecomponent without crack. The study of performance of a cracked body under the externalloading is called as ‘Fracture Mechanics”. Therefore “Fracture mechanics” is based on theimplicit assumption that there exists a crack in the structural component. The crack may beman made such as a hole, a notch, a slot, etc. For a long time man had some idea about the role of a crack or notch. While cutting atree, he would make a notch with an axe at its trunk and then pull it down with a rope. Whilebreaking a stick he would make a small notch with a knife before bending. Leonardo daVinci (1452-1519) was the first person to make a set up to measure the strength of a wire. Hefound that strength of a wire depends on its length. It was his argument that longer wire waslikely to have more number of cracks.1.2 Strength of materials Approach (Strength criterion) The basic assumption in strength of materials approach is that stress is uniform throughout the net cross-sectional area, if there is a hole or crack in structural component. Suppose arectangular plate is under a uniform tension as shown in fig.1 If the strength of the plateis σ y , its width, B and thickness, t ; then the failure load, Py = Btσ y . This is based on theassumption that stress is uniform through out the width. For example, if the same plate has anelliptical hole as shown in fig.1, then its failure load, Py = (B − 2a )tσ y , according to strengthof materials criterion. But the actual failure load, from experiments, has been found to beentirely different from the calculated load, Py = (B − 2a )tσ y , which is much lessthan Py = (B − 2a )tσ y . The plate with an elliptical hole under uniform tension is analyzedMr. P.Subba Rao, Associate Professor,Department of Civil Engineering , JNTU College of Engineering, Kakinada, (AP).
Repair and Rehabilitation of Concrete Structures Using Special Materials Dr. Prasad Varma Thampan C.K.*Introduction:Reinforced concrete (RC) is the most extensively used material for construction ofdifferent types of structures such as bridges, tanks, chimneys, dams, buildings, harborsetc. Maintenance and repair of such structures is presently one of the most significantchallenges facing the concrete building industry. The distress to concrete can be causedfrom various sources. The required degree of high standard is not always achieved duringoriginal construction in the case of materials and required degree of quality control is notachieved in practice and as a result of this the structure is seriously affected which in turnrequires early repair and renovation work. It is reported that the expenses incurred inRussia on repair and restoration of industrial structure over a normal period of four to fiveyears reach the total cost of the structure. In USA, the total annual loss due to concretedeterioration is reported to be 3% of the annual construction expenditure. Even in India,where the per capita consumption of cement/concrete is much less than global average,the annual loss due to deterioration of steel and concrete structure is estimated to be of theorder of Rs 300-500 crores. The circumstances leading to inadequate quality control areworse in our country, where concrete is still a material ‘made at site’ rather than in readymix-plants in most of the constructions. In addition to faulty construction and naturalaging, man made explosions as well as natural hazards like earthquake, cyclone, etc. alsocan cause serious distress to structures.The distress in concrete can be observed in the form of cracks. Cracks in concrete are themanifestation of some disorder; structural, physical, chemical or even biological disordersin the body of concrete, which shows up as cracks, which further aggravate thedeterioration process of concrete with time. Hence timely analysis of the causes ofdistress, correct selection of repair materials and implementation of most suitable repairmethodology are required for an effective, economical and early rehabilitation of theaffected structure.Assessment of damages in concrete structures:The distress and damages in concrete shall be examined in detail and be assessed todetermine (1) the cause of damage (2) the type and extent of damage. Table 1 shows thesymptoms of damage as cracks, spalling, discoloration etc and the probable cause of such* Assistant Professor of Civil Engineering, N.S.S. College of Engineering, Palakkad-8.
constructive solutions Dr. V. SYAM PRAKASH ProfessorCollege of Engineering Trivandrum
Dr. V. SYAM PRAKASH Professor College of Engineering TrivandrumREADY MIXED CONCRETE FOR QUALITY CONSTRUCTION Dr. V. SYAM PRAKASH Professor College of Engineering Trivandrum