Portland cement mortars and concretes

Grandet and Ollivier (G81) made XRD examinations of layers of paste at 

Wu el al. (W33) and Monteiro and co-workers (M116,MI15) observed that, within the interfacial zone, the content of ettringite increases as the aggregate surface is approached. 

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Lead is relatively easily corroded where acetic acid fumes are present and under such conditions it either should not be used or should be efficiently protected. Generally, any contact between lead and organic material containing or developing acids will cause corrosion for instance, unseasoned wood may be detrimental. Trouble from this cause may be prevented by using well-seasoned timber, by maintaining dry conditions, or by separating the lead from the timber by bitumen felt or paint. Lead is also subject to attack by lime and particularly by Portland cement, mortar and concrete, but can be protected by a heavy coat of bitumen. A lead damp-proof course laid without protection in the mortar joint of a brick wall may become severely corroded, especially where the brickwork is in an exposed condition and is excessively damp. 

It has been known since the 1950 s that the incorporation of various polymers into portland cement mortars and concretes can considerably improve many physical and chemical properties (American Chemical Society, 1973 American Concrete Institute, 1972, 1973a, 1975 Auskem and Horn, 1971 Coughlin et a/., 1970 Dikeou et a/., 1969,1971,1972 Dow Chemical... 

Fibres may also prevent the occurrence of large cracks, thus preventing percolation of water and contaminants into ceramic materials such as Portland cement mortars and concretes. So, corrosion of steel reinforcement or potential deterioration of concrete may be reduced with the addition of a variety of fibres to the Portland cement matrices. In addition, other enhanced... 

The reinforcement increases the composite material tensile strength if fibre reinforcement is sufficiently effective. The tensile strength of the matrix itself is low for instance, that of Portland cement mortars and concretes is approximately equal to 10-12% of their compressive strength. Much higher composite tensile strength is obtained thanks to various systems of reinforcement, including systems with two or more different fibres (hybrid reinforcement). 

Another version of Portland cement mortar or concrete is the replacement of some of the Portland cement with rice hull ash. This ash additive markedly improves the resistance of the mortar or concrete to food acids and similar chemicals. Flyash (pozzolanic admixture) meeting ASTM C618 has also been widely used to improve the properties and sulfate resistance of Portland cement... 

Cement mortars and concretes have been used extensively in their present form since the beginning of the nineteenth century. There is no need to set out here their history or to describe their properties and applied technologies, because nearly every year several excellent books are published on these subjects. However, there is perhaps at present a new phase of development of Portland cement-based materials, stimulated by the following factors ... 

S. Chandra and J. Aavik, Influence of proteins on some properties of portland cement mortar, Int. J. Cement Compos. Lightweight Concrete, 9, 91 94 (1987). 

Cement is a binder that sets and hardens by itself or binds other materials together. The most widely known application of cements is in construction a second one is the area of bone cements. Cements used in construction are characterized as hydraulic or nonhydraulic and mostly for the production of mortars and concrete. Hydraulic cements set and harden after combining with water. Most construction cements are hydraulic and based on Portland cement, which consists of calcium silicates (at least 2/3 by weight). Nonhydraulic cements include the use of nonhydraulic materials such as lime and gypsum plasters. Bone cements and bone cement composites refer to compounds that have a polymer matrix with a dispersed phase of particles. For instance, polymethylmethacrylate (PMMA) is reinforced with barium sulphate crystals (for radio-opacity) or with hydroxyapatite... 

Table 2.1 shows the ionic concentrations measured by different researchers in the pore solution of cement pastes, mortars and concretes, obtained both with Portland cements (OPC) and blended cements [4-14]. Measurements were carried out by chemical analysis of the liquid extracted under pressure, using specific pore-extraction devices. 

Table 2.1 Ionic concentration (in mmol/L) measured in the pore solution extracted from cement pastes, mortars and concrete made with ordinary Portland cement (OPC) and with additions of blast furnace slag (GGBS), fly ash (PFA) and silica fume (SF). n.a. = concentration not available [15]... 

Presenting the rules of Portland cements classification and derived from them others kind of hydraulic binders, it must be underlined that the basis of this classification are their useful properties. In relation to this that cement is an intermediate product—the raw material for concrete production, these properties will concern the corrverrtiorral rrricro-concrete or the mortar, sometimes paste, and now and again cemerrt itself for example phase composition. Some experts reckon the mortar to some kirrd of concrete, however, it is a subject of controversy. 

Bouzoubaa, N., Zhang, M.H., and Malhotra, V.M. (1998) Superplasticized Portland cement production and compressive strength of mortars and concrete. Cement and Concrete Research 28, 1783-1796. 

Kostogloudis, G.C. et al. (1998) Comparative investigation of corrosion resistance of steel reinforcement of alinite and Portland cement mortars. Cement and Concrete Research 28,995-1010. 

Polymer-modified cement mixes are produced by mixing together an inorganic cement (most commordy Portland cement), water, and a dispersion of an organic polymer. If concrete aggregate or sand is also added, polymer-modified concrete or mortar mixes are obtained. Compared with similar polymer-free mixes, the addition of water may be reduced or omitted entirely, as the polymeric dispersion supphes part or all of the water needed for hydration and for obtaining adequate rheology of the mix. 

When Portland cement is added to water, reactions take place to form calcium silicate hydrates and release calcium hydroxide. These hydrates act as the glue in mortars and concretes to hold the matrix together. 

Some standardized grades of Portland cement and their uses are listed in Table 3.2-3. Mortars and concretes are mixtures of cement with specified amounts of sand, gravel, or crushed stones with specified particle sizes. 

Mortars and concretes made with high alumina cement are resistant against sulphate attack and also are better at resisting CO2 from ordinary drinking or mineral water. In comparison, the resistance against alkalis is lower than that of Portland cements. 

Acid attack from air or water may produce the conversion of calcium in Portland cement paste into soluble salts. As a result, the binding capacity of hardened mortars and concretes is reduced. 

R. Cerny, J. Madera, J. Podebradska, et al. The effect of compressive stress on thermal and hygric properties of Portland cement mortar in wide temperature and moisture ranges. Cement and Concrete Research, 30, pp. 1267-1276,2000. 

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