Cementing other types

Portland cement is classified as a hydrauHc cement, ie, it sets or cures in the presence of water. The term Portland comes from its inventor, Joseph Aspdin, who in 1824 obtained a patent for the combination of materials referred to today as Portland cement. He named it after a grayish colored, natural limestone quarried on the Isle of Portland, which his cured mixture resembled. Other types of hydrauHc cements based on calcium materials were known for many centuries before this, going back to Roman times. Portland cement is not an exact composition but rather a range of compositions, which obtain the desired final properties. The compounds that make up Portland cements are calcium siHcates, calcium aluminates, and calcium aluminoferrites (see ). 

Other Types of Portland Cements. White Portland cementis standard Type I or III Pordand cement with raw materials selected and controUed to have negligible amounts of Hon and manganese oxides, which impart the gray color. The white Pordand cement is used in decorative and architectural appHcations like precast curtain waUs, terra22o surfaces, stucco, tile grout, and decorative concrete. 

Cement. Portland cement, a mixture of calcium siUcate and calcium aluminate minerals, is produduced by the calcination of argillaceous limestone or mixtures of limestone and clay (see Cement). Although other clays can be used, ka olin is preferred because of its alumina and siUca content and low level of impurities. It is especially desirable in the manufacture of white cement and other types requiring careful control of chemical composition. Air-floated ka olin, because of its low cost, is usually used. 

Other types of cements include anhydrite, barite, pyrite, iron hydroxides haematite, albite and apatite and are subordinate. 

Because cement kilns are so good at destroying organic chemical wastes, emissions of dioxins - or any other type of products of incomplete combustion (PIC) - are so low they pose no danger to the environment. In the case where some of the hazardous waste fuels used contain toxic dioxin, the cement kiln temperatures of 1650°F will destroy dioxins in less than one second. Because cement kilns operate at much higher temperatures (at least 2450°F), and because the burning wastes have an average residence time in the kiln of at least two seconds, any dioxins are destroyed. However, dioxin waste is never accepted by Southdown for use in its cement kilns. 

The data presented in this section illustrate that, with the exception of those accelerating water-reducing admixtures containing calcium chloride, there is an abundance of evidence to support the conclusion that water-reducing admixtures of lignosulfonate chemical form certainly will not accelerate any kind of corrosion with reinforcement and, when used to reduce the water-cement ratio, will form a more permeable and durable protective cover for the reinforcement. In view of the chemical nature of the other types of materials such as the hydroxycarboxylic acids and hydroxylated polymers, it seems most likely that these materials too would have no deleterious effect in this respect. 

Examination of Sulphlex-233 mixtures with other types of aggregates generally have confirmed the results presented here. Sulphlex-233 mixtures can meet or exceed most Marshall design and compressive strength criteria at either equal volume or equal weight replacement of asphalt cement, but "optimum" mixtures are obtained at or near the equal volume replacement level. The Sulphlex-233 mixtures are in many cases susceptible to water damage, and the use of tall oil as an anti-strip additive has been recommended where indicated. 

The inorganic classification includes the metal pan type, consisting of a perforated metal pan with a sound-absorptive mineral wool pad the perforated cement-asbestos type, consiting of a perforated cement-asbestos sheet with a sound-absorptive mineral wool pad acoustical plasters and tile prepared from mixtures of inorganic or mineralized fibers with or without asbestos and other fillers. In general, acoustical products in this classification possess good fire and flame resistance, but are relatively expensive and difficult to manufacture and apply. 

Dry process cement production facilities often have several other types of manufacturing equipment designed to increase fuel efficiency. First, many dry process kilns add a preheater to the feed end of the kiln to begin heating of the feed prior to its entrance to the kiln. Two main types of preheaters exist, the suspension preheater and the traveling grate preheater both use hot, exiting kiln air to facilitate a more efficient heat transfer to the feed than could occur in the feed end of the kiln itself.1 This... 

Abnormal retardation of superplasticized mixes The factors responsible for extended retardation of superplasticized mixes are closely related to the Blaine surface area and to the chemical composition (mainly the C3A content) of the cement used to produce it it is also dependent upon the SP dosage, the prevailing ambient and concrete temperature. Low-C3A cements like Type V are susceptible to extension of their set even at dosages that are considered normal for other cements with higher C3A. contents [125, 137, 139]. 

Particulate composites are used in greater volume than any others because concrete is a particular composite. In many ways, concrete is the archetype of this class of composites. It consists of particles or aggregates of various sizes almost always of mineral materials, bonded together by a matrix of an inorganic cement originally mixed with and hardened by its chemical reaction to water. Many types of particles are employed, at least five different types of Portland cements and several other types of inorganic cements act as binders. 

The great majority of Portland cements made throughout the world are designed for general constructional use. The specifications with which such cements must comply are similar, but not identical, in all countries and various names are used to define the material, such as OPC (Ordinary Portland Cement) in the UK, or Type I Portland Cement in the USA. Throughout this book, we shall use the term ordinary Portland cements to distinguish such general purpose cements from other types of Portland cement, which are made in smaller quantities for special purposes. 

A knowledge of the relevant high-temperature phase equilibria is necessary for understanding the factors that govern acceptable bulk compositions for Portland cement clinker, the conditions under which the latter can be manufactured, and the phase composition and microstructure of the resulting material. This chapter deals with these equilibria and with the phases to which they relate, with the exception of the major clinker phases, which were described in Chapter I. Some anhydrous phases primarily of interest in relation to other types of cement are also considered here. Principles underlying the preparation of anhydrous silicate, aluminate and other high-temperature phases are outlined. 

Mineral additions may be broadly categorized as pozzolanic materials or latent hydraulic cements. Neither type reacts significantly with water at ordinary temperatures in the absence of other substances. Pozzolanic materials are high in Si02 and often also in AI2O3, and low in CaO they are sufficiently reactive that mixtures of them with water and CaO produce C-S-H at ordinary temperatures and thereby act as hydraulic cements. If they contain AI2O3, calcium aluminate or aluminate silicate hydrates are also formed. Because they are low in CaO, this component must be supplied in stoichiometric quantity. In a composite cement, it is provided by the Portland cement through decreased formation of CH and decreased Ca/Si... 

Other types of admixtures used with calcium aluminate cements include water reducers and superplasticizers (Section 11.4), which also act as retarders, and thickening agents, such as carboxymethylcellulose. Complex formulations may be used for special purposes for example, a ready-mix mortar for high-performance road repair might contain 55% Ciment Fondu and 45% sand, with glass fibre, aluminium powder, Li2C03, sodium gluconate and methyl ethyl cellulose (M93). 

All the cements considered in this book fall into the category of hydraulic cements they set and harden as a result of chemical reactions with water, and if mixed with water in appropriate proportions continue to harden even if stored under water after they have set. Much the most important is Portland cement. Chapters I to 4 of the present work deal mainly with the chemistry of manufacture of Portland cement and with the nature of the resulting product. Chapters 5 to 8 deal mainly with the processes that occur when this product is mixed with water and with the nature of the hardened material. Chapters 9 to 11 deal with the chemistry of other types of cement, of admixtures for concrete and of special uses of cements. Chapter 12 deals with chemical and microstructural aspects of concrete, including ones relevant to processes that affect its durability or limit its service life. 

Polymeric fibers are popular for reinforcing concrete matrices because of their low density (more number of fibers for a prescribed volume fraction), high tensile strength, ease of dispersion, relative resistance to chemicals, and relatively low cost compared to other kinds of fibers. Polypropylene and polyolefin fibers are typically hydrophobic, resulting in a relatively poor bond with concrete matrices compared to some other types of fibers. Treatment of polypropylene with an aqueous dispersion of colloidal alumina or silica and chlorinated polypropylene enhances the affinity of these fibers toward cement particles. Treatment of polypropylene fibers with a surface-active agent provides better dispersion of the fibers and a stronger bond between cement and fiber. The earlier attempts at surface treatments of polypropylene fibers have had only limited success and have not been commercially attractive. 

At least part of the reason for these observations must be that precipitation is severely inhibited by organics such as humic acids (Berner et ai, 1978). Mitterer and co-authors (e.g., Mitterer and Cunningham, 1985) have explored the possible role of organic matter in cement formation. These authors suggested that, whereas some types of organic matter inhibit precipitation, other types, particularly those rich in aspartic acid, favor precipitation by complexing calcium. Inhibition of precipitation, coupled with slow transfer of fresh supersaturated seawater into sediment pores, seems to account for the lack of extensive early cementation. 

The Navajo sandstone in the Black Mesa area is an aeolian quartz sandstone (Harsh-barger et al., 1957). Besides quartz, other types of sand grains include mostly plagio-clase and, to a lesser extent, orthoclase (Dulaney, 1989 Harshbarger et al., 1957). The sandstone is cemented by calcite and, to a lesser extent, by silica, and red iron oxide rims are common on the sand grains. 

Two other types of operations involve cement slurries. They are used to plug back a well from a deeper to a shallower depth for a number of reasons abandonment, whip stocking, lost circulation, or shutting olf water. Squeeze cementing consists of forcing a column of cement slurry... 

Masonry cement was developed to overcome the above problems. It is specified in ENV 413-1 [9.4]. Essentially it consists of Portland cement (at least 25 % in Type MC 5 and at least 40 % in the other Types) and an inorganic material (such as limestone), finely ground to more than 85 % passing 90 microns. Two of the four Types contain an air-entraining agent, while the other Types do not. The Standard specifies the characteristics of the cement, the fresh mortar and the compressive strengths. The limestone content of masonry cement can be over 70 % in Type MC 5 and over 55 % in the other Types. 

Most joint replacements utilize polymers to some extent. Finger joints usually are replaced with a poly(dimethylsiloxane) Insert and over h00,000 such replacements are made each year (l). More recently a poly(1, -hexadiene) polymer has been tried in this application (l). Many other parts of the hand, such as the bones, have also been replaced by silicone rubber. Other types of joints, such as the hip or the knee, often involve the contact of a metal ball or rider on a plastic surface which is usually made from high density, high molecular weight polyethylene. These metal and plastic parts are usually anchored in the body using a cement of poly(methyl methacrylate) which is polymerized in situ. Full and partial hip prostheses are implanted about... 

---