Engineering materials concrete

The payoff to society from greater attention to the surface and interfacial engineering of concrete is potentially immense high-tech concretes that will prolong the life of public works and reduce their maintenance costs as well as dramatic new applications for this old reliable material. 

Concrete is no longer a rationalized mixture of cement, sand and stone, but has matured to an engineered material containing a mixture of admixtures. Admixtures modify the structure-property relationship of normal concrete by chemically altering the rate of cement hydration and or, the nature of the hydration products. The last decade has seen a wide interest in many aspects of admixtures and research on the chemistry of the aqueous phase of the cement-water-admixture system has demonstrated that admixtures can control the type of products formed so that many properties can be designed into concrete. The correct combination of admixtures can produce concrete that is custom-made for the particular job at hand. 

Figure 5.54 Compressive strength of concrete as it develops with time. Reprinted, by permission, from S. Somayaji, Civil Engineering Materials, 2nd ed., p. 127. Copyright 2001 by Prentice-Hall, Inc.

It is almost paradoxical that in the history of mankind composite materials were earlier used than their "homogeneous" rivals. The earliest "engineering materials" were bone, wood and clay. Wood is a composite of matrix lignin and a cellulosic reinforcement bone is a natural composite where fibres of hydroxyapatite reinforce the collagen matrix and the oldest building material was adobe clay as a matrix, reinforced by vegetable fibres. After the industrial revolution other composites were added reinforced rubber, reinforced concrete, reinforced asphalt, etc. 

Hanks AJ, Magni ER (1989) The use of bituminous and concrete material in granular base and earth. Materials Information Report MI-137, Engineering Materials Office, Ontario Ministry of Transportation, Downsview, Ontario, Canada, p 472... 

PIC must be considered a new complex material with specific characteristics, which place it in a position, firom the viewpoint of quality and cost, between traditional concrete and other groups of engineering materials such as metals and ceramics. 

The concept of composite materials is ancient to combine different materials to produce a new material with performance and efficiency imattainable by the individual constituents. An example is adding straw to mud for building stronger mud walls. Some more recent examples, but before engineered materials became prominent, are steel rods in concrete, cement and asphalt mixed with sand, fiberglass in resin, etc. In nature, examples abound a palm leaf, cellulose fibers in a lignin matrix (wood), collagen fibers in an apatite matrix (bone), etc. 

Moriya H, Manthei G, Mochizuki S, Asanuma H, Niitsuma H, Jones R, Ei-senblatter J (2002) Collapsing method for delineation of structures inside AE cloud associated with compression test of salt rock specimen. In 16 Int. Acoustic Emission Symposium, November 12-15 2002, Tokushima, Japan Ohtsu M (1998) Basics of acoustic emission and apllications to concrete engineering. Materials Science Research International 4(3) 131-140... 

Recommendations for Design and Construction of Concrete Structures using Continous Fibre Reinforcing Materials, Concrete Engineering Series 23, Ed., A. Machida, Japan Society of Civil Engineers, Tokyo, Japan, 1997. 

Steel fibres continue to have a wide range of apphcations in civil engineering materials. There are some structural applications where they have been used in concrete without any conventional reinforcing bars. These have been short span, elevated slabs, for example a parking garage at Heathrow Airport... 

Advanced fibre-reinforced polymer (FRP) composite materials in bridge engineering materials, properties and applications in bridge enclosures, reinforced and prestressed concrete beams and columns... 

ISIS Design mannal No. 4 - Strengthening reinforced concrete stractnres with externally bonded fibre reinforced polymers. ISIS, Canada, 2001. JSCE Recommendations for design and constraction of concrete stractnres nsing continnons fibre reinforcing materials. Concrete Engineering Series 31, Japan Society of Civil Engineers, Japan, 1998. 

A large variety of materials, ranging from steel to concrete, is used by the engineer to construct bridges, roadways, tunnels, etc. The corrosion engineer is primarily interested in the chemical properties (corrosion resistance) of materials, but he or she must have knowledge of mechanical, physical, and other properties to assure desired performance. The properties of engineering materials depend upon their physical structure and basic chemical composition. 

A widely respected author. Dr. Chen has authored and coauthored more than 20 engineering books and 500 technical papers. His books include several classical works such as Limit Analysis and Soil Plasticity (Elsevier, 1975), the two-volume Theory of Beam-Columns (McGraw-Hill, 1976 and 1977), Plasticity in Reinforced Concrete (McGraw-Hill, 1982), and the two-volume Constitutive Equations for Engineering Materials (Elsevier, 1994). He currently serves on the editorial boards of more than 15 technical journals. 

Jackson, N. and R. K. Dhir, eds. 1996. Civil Engineering Materials, 5th ed. Basingstoke, U.K. Macmillan. Good basic introduction to materials used regularly by civil engineers. Covers metals, concrete, timber, bitumen, soils, polymers, and bricks and block work. Aimed at a student audience. 

Such tests, as exemplified for concrete and natural stone, should also be conceived for many other materials. However, it is necessary to know the damage mechanisms, and such facilities have to be constructed according to each individual case. Teamwork, including experts of different disciplines, e.g., mechanical engineers, materials scientists, electrochemists, as well as microbiologists, is indispensable. If all difficulties are overcome and the simulation system is functional, the user has a valuable tool to discover unknown interactions between the living environment and the technical mate-... 

Usually, creep models for engineering materials are based on the use of the strain-time response of the material. Other quantities, such as deflection and creep modulus, can be obtained using the corresponding relationships. Figure 4.4 shows the general strain versus time response of rPET polymer concrete subjected to constant stress and temperature. 

Almost no engineering material is safe from or immune to microbial corrosion. In Chapter 8 the vulnerability and susceptibility of copper and cupronickels, duplex stainless steels and concrete will be discussed in a brief and informative manner. I had my reasons for picking these materials copper and its alloys have the reputation of being poisonous to micro-organisms, duplex stainless steels are known for their high resistance to corrosion thanks to their duplex microstructures of ferrite and austenite, and concrete is widely used in both the marine and water industries because of its good performance and cost effectiveness. 

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