Cement replacement materials

This interpretation was devised empirically from salt-induced corrosion of cast-in-place bridge decks in the United States. Also offsets are seen for different types of concrete (precast or containing cement replacement materials). 

Additives and cement replacement materials such as pulverized fuel ash (fly ash), ground granulated blast furnace slag, silica fume (micro silica) and other materials can reduce the pore size and block pores enhancing durability further. However, proper curing may be vital to get the required performance with these blended cements. 

Brooks J.J. and A. Neville. 1992. Creep and shrinkage of concrete affected by admixtures and cement replacement materials, ACI SP-135. Creep and Shrinkage of Concrete Effect of Materials and Environment. Detroit, MI American Concrete Institute. 

These materials are known by various names. The European concrete standards refer to them as additions.I The ASTM classifies them as mineral admixtures. In the literature, they are also described as supplementary cementing materials, cement replacement materials, or... 

Swamy, R. N., (ed ). Cement Replacement Materials, p. 259, Surrey University Press, Glasgow (1986)... 

Resin cements or polymer cements have been reviewed by Chandra, Justnes, and Ohama [343]. Polymer cements are materials made by replacing the cement at least partly with polymers. Cements can be modified by latex, dispersions, polymer powders, water-soluble polymers, liquid resins, and monomers. 

It is explained that the remaining uses of white asbestos (asbestos cement, friction materials, seals and gaskets, textiles and composites) are likely to become prohibited in the UK in the near future. This article examines in detail the choices available for its replacement. 

Biodentine is a specific proprietary brand of calcium silicate cement that has been available to the profession since 2009 [20], It is manufactured by Septodont, St Maur des Faussds, France. The material is formulated to set more rapidly than MTA or similar calcium silicate cements, and is produced as a dentine replacement material. It is recommended for pulp capping, and also for various aspects of endodontic repair, including root perforations, apexification and retrograde filling [20],... 

The typical chemical composition of pozzolanic materials such as pulverised fuel ash (PFA) and ground granulated blast furnace slag (GGBS) is well understood and their use as cement replacements is well-established in construction and concrete technology. Figure 15 compares the chemical composition of the waste materials used in this project and commonly used cementitious materials (OPC, GGBS and PFA). 

Canpolat et al. [33] have suggested the usage of zeolite, coal bottom ash and fly ash as replacement materials for production of the cement. It has been opined that the inclusion of zeolites, up to 15 %, results in an increase in the compressive strength of the cement, at early ages, whereas a decrease in compressive strength is observed when zeolites are used in combination with the fly ash. However, the setting time is found to decrease due to the replacement of clinker by the zeolite. This has been attributed to presence of adsorbed water (the excess water remained unused after the hydration process in the cement) on the zeolite surface. 

Shotcreting Using a modification of normal shotcreting techniques, it has been found possible to produce steel and polypropylene fibre shotcretes, for use particularly for lining of tunnels, and for stabilization of rock slopes. With this method, too, relatively high volumes of fibres can be added to the mix. Pulp type processes For asbestos cement replacements (cellulose or other fibres are used as a replacement for the asbestos), the fibres are dispersed in a cement slurry, which is then dewatered to produce thin sheet materials. These can be built up to the required thickness by layering. This process yields fibre contents of typically from 9% to over 20% by volume. 

Chemical Resistance. Table 2 shows the chemical resistance of PVA fiber (40). The fiber exhibits markedly high resistance to organic solvents, oils, salts, and alkaU. In particular, the fiber has unique resistance to alkaU, and is hence widely used in the form of a paper principally comprising it and as reinforcing material for cement as a replacement of asbestos. 

Fiber-Reinforced Cementitious Material. Use of asbestos (qv) has been legally restricted in Europe and the United States as being ha2ardous to health. In asbestos cement, which had consumed 70—80% of total asbestos, PVA fiber has been used in large amount as a replacement for asbestos. PVA fiber has a strength of at least 0.88 N/tex (9 gf/dtex) and can therefore provide the necessary reinforcement for cement the fiber has excellent adhesiveness to cement (qv) and alkaU resistance, and is not a health ha2ard. 

Based on the technology developed for using PVA fiber as a replacement for asbestos in cement products, Kuraray has been developing thick fibers for reinforcing concrete (42). Super-thick fibers with a thickness of 39 tex (350 den) (200 p.m in diameter) to 444 tex (4000 den) (660 p.m in diameter) are now available the 39 tex material is used for reinforcing various mortar-based cement products and the 444 tex material for reinforcing concrete in civil engineering works such as tuimels, roads, harbors, and bays. 

The materials used in a total joint replacement ate designed to enable the joint to function normally. The artificial components ate generally composed of a metal piece that fits closely into bone tissue. The metals ate varied and include stainless steel or alloys of cobalt, chrome, and titanium. The plastic material used in implants is a polyethylene that is extremely durable and wear-resistant. Also, a bone cement, a methacrylate, is often used to anchor the artificial joint materials into the bone. Cementiess joint replacements have mote tecentiy been developed. In these replacements, the prosthesis and the bone ate made to fit together without the need for bone cement. The implants ate press-fit into the bone. 

Sulfur as an Additive for Asphalt. Sulfur-extended asphalt (SEA) binders are formulated by replacing some of the asphalt cement (AC) in conventional binders with sulfur. Binders that have sulfur asphalt weight ratios as high as 50 50 have been used, but most binders contain about 30 wt % sulfur. Greater latitude in design is possible for SEA paving materials, which are three-component systems, whereas conventional asphalt paving materials are two-component systems. Introduction of sulfur can provide some substantial benefits. At temperatures above 130°C, SEA binders have lower viscosities than conventional asphalt. The lower viscosity enables the plant to produce and compact the mix at lower temperatures than with conventional... 

PVA fibers have found wide spread industrial use in cement as replacement for asbestos in cement products, reinforcement of mbber material such as conveyor belts and hydraulic mbber hoses used in cars, ropes, fishing nets, etc. Only a small amount of fibers is used in the production of textiles. 

Considerable effort has been devoted to finding alternative fibers or minerals to replace asbestos fibers ia their appHcations. Such efforts have been motivated by various reasons, typically, avadabihty and cost, and more recendy, health concerns. During Wodd War I, some countries lost access to asbestos fiber suppHes and had to develop substitute materials. Also, ia the production of fiber reiaforced cement products, many developiug countries focused on alternatives to asbestos fibers, ia particular on cellulose fibers readily available locally at minimal cost. Siace the 1980s however, systematic research has been pursued ia several iudustrialized countries to replace asbestos fibers ia all of their current appHcations because of perceived health risks. 

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