Polymer-impregnated materials concrete

The third part, Chapters 10-12, examines the properties of composites, where one component is usually nonpoly meric. Two broad classes of composites are treated polymer-impregnated materials, such as wood or concrete, and fiber- and particle-reinforced plastics and elastomers. The approach throughout draws upon basic chemistry, materials science, and engineering. The phases discussed here tend to be large and well-defined, but the interactions at the phase interfaces remain crucial in determining properties. 

Ethyl silicate (tetraethoxysilane) is often used without modification as a water-repellent material for concrete and masonry in general. All, or nearly all. the ethoxyl groups are hydrolyzed by the moisture of the air to form cross-linked watcr-rcpcllcnt polymers. The material is applied in desirable thickness, dissolved in some volatile solvent which soon evaporates. Silicone resins which arc partially condensed before application, or even fully condensed, can also be used here. In the latter case, hardness is achieved on evaporation of the solvent. Certain silicone resins arc useful as hydrophobic agents for the impregnation of paper and fabrics. 

As mentioned in Introduction, recently polymer-impregnated mortar and concrete have hardly been used as construction materials except for a few applications. At present, their precast products such as permanent forms are manufactured to order at Materras Oume Co., Ltd. in Japan, which is their only manufacturer in the world. However, a recent great interest has been oriented toward the durability improvement of reinforced concrete structures by the concrete surface impregnation techniques using alkyl alkoxy silane-based barrier (or surface) penetrants, similar to the field polymer impregnation techniques [85]... 

E. Tazawa and S. Kobayashi Properties and applications of polymer impregnated cementitious materials, in Polymers in Concrete, SP-40, American Concrete Institute, Detroit (1973), pp.57-92. 

W. G. Smoak Polymer impregnation and polymer concrete repairs at Grand Coulee Dam. in Polymer Concrete, Uses, Materials, and Properties, SP-89, American Concrete Institute, Detroit (1985), pp.43-49. 

Polymers. The purpose of adding polymers to the concrete matrix is to improve the characteristics of the fresh concrete (such as workability) and also to enhance the hardened properties such as flexural strength, modulus of elasticity and adhesive performance [8]. The incorporation of polymers into concrete may be in the form of polymer modified concrete (PMC), polymer impregnated concrete (PIC) or as polymer concrete (PC) [9], For this project, the objective was to develop an ultra-lightweight concrete material using Portland cement as the main binder modified with a suitable polymer - thus a PMC application. The polymer modifiers selected for the development of the ultra-lightweight thin filmed material were a commercially available SBR latex as well as a readily available acrylic polymer. 

This chapter will be devoted to the consideration of nascent research undertakings, possible new materials, and as yet unanswered research questions. First, an effort will be made to codify and classify composite materials and polyblends with respect to topological considerations. We will examine what other ways may possibly exist to make new combinations of two types of polymeric molecules. How many ways exist to mix two kinds of polymer molecules What relationships can be developed among such diverse materials as particulate and fiber-reinforced plastics, polymer-impregnated concrete, and foams, paint films, etc. ... 

In polymer-impregnated cementitious materials the prehardened cement paste, mortar or concrete is impregnated with a low molecular weight, low-viscosity polymer precursor, which, after having filled the existing pore space, is brought to polymerization. The resultant material is a hardened cementitious body, in which the original pores are filled with the polymer. 

Polymer-impregnated concrete and mortar elements are being employed in applications where an exceptionally high performance of the material is required, such as in highly corrosive environments. 

By changing the c-s-f on both atom-molecular and micro levels, PI(PCC) is obtained. Change of c-s-f on atom-molecular level is done by nature of bond and that on micro level is done by polymer impregnation. Such material with a compressive strength over 100 MPa is as brittle as an ordinary concrete mortar with strength of 30 - 40 MPa(5). 

There are less exotic ways of increasing the strength of cement and concrete. One is to impregnate it with a polymer, which fills the pores and increases the fracture toughness a little. Another is by fibre reinforcement (Chapter 25). Steel-reinforced concrete is a sort of fibre-reinforced composite the reinforcement carries tensile loads and, if prestressed, keeps the concrete in compression. Cement can be reinforced with fine steel wire, or with glass fibres. But these refinements, though simple, greatly increase the cost and mean that they are only viable in special applications. Plain Portland cement is probably the world s cheapest and most successful material. 

The technology of concrete impregnation with organic polymers is the most commonly known [173]. The sulphur impregnated concrete was also studied, however, the durability of this material was poor, because of the instability of sulphur in the highly basic cement matrix. 

The impregnation of hardened concrete or mortar with polymers increases the strength of the material signifieantly forrrfold increases are not rmcommoa At the same time the material attains a more brittle character. The creep of the material is also reduced... 

Polymer concrete is a composite material formed by polymerising a monomer and aggregate mixture. There is no other cementitious material present in it. PPCC (or LMC) is a Portland cement concrete produced usually by replacing a specified portion of the mixing water with a latex (polymer emulsion). It can also be produced by adding a monomer to fresh concrete with subsequent in situ curing and polymerisation. PIC is a hardened Portland cement concrete with impregnated monomer which is polymerised in situ. 

The use of fiber-reinforced polymer (FRP) composite materials in the reinforcement of concrete structures has shown important results. These interventions are based on the application of carbon fiber, glass, or aramid impregnated with thermosetting polymers. The effectiveness of these interventions is demonstrated both by extensive research in the laboratory and by applications to existing structures. 

Yu Fei-xiong and Huang Yiun-yuan, Mechanical properties of PIC impregnated and polymerized under high pressure. Polymer Concrete, Uses, Materials and Properties, SP-89 ACI Committee 548, 1983, pp. 161-176. 

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