Self-leveling

The calcium sulfate [7778-18-9] discharged from the furnace can also be recovered. This is less the practice in the United States where natural gypsum is plentiful and inexpensive than in Europe, where CaSO recovery for use in cement (qv) and self-leveling floors is common. Some CaSO is recovered in the United States, primarily for lower end uses such as road aggregate. 

As fibers in the feed mat pass between the feed toU and feed plate, they ate separated by metallic wine teeth on the lickerin toU and carried to an air venturi where they ate stripped and tumbled until they strike a moving, perforated collection surface. At the collection surface, the airborne fibers foUow paths of least resistance and accumulate in a self-leveling manner while the air passes through perforations. Fiber orientation in the web is isotropic in layers corresponding to the number of fibers transferred from the wine teeth to the air-transportation 2one, the intensity of the air, and the speed of the collection surface. 

Self-leveling epoxy, polyester or reactive acrylic resin systems 9/105... 

Thin coating Trowelled coatings Self-leveling screeds... 

Self-leveling These are generally based on solvent-free epoxy and there are a number of proprietary products available. Generally, they are 3-8 mm thick, but if the base floor is too rough, it is advisable to first level this with a cement/resin screed. 

This group includes dyes that react with the fibre at 100 °C or above, without alkali present. Dyes in this group have self-levelling properties so there is no need to exercise control by means of dyeing auxiliaries. Good results can be obtained by controlling the rate of temperature rise. 

Cohesiveness, mobility, and self-leveling characteristics are increased. 

These polymers are thermoplastic materials usually supplied as redispersible powders. They are widely used in proprietary prepackaged products such as tile grouts, self-leveling underlay and patching materials. 

LMC is used in underwater concrete for both new construction and repair. The important requirements to obtain antiwashout capability, such as segregation resistance, flowability, self-leveling characteristics and lower bleeding are provided by the addition of viscosity-enhancing polymeric admixtures at polymer-cement ratios of 0.2-2.0%. These admixtures are water-soluble polymers, and classified under two groups, viz., cellulose types such as methyl cellulose and hydroxy ethyl cellulose and polyacrylamide types such as polyacrylamide and polyacrylamide-sodium acrylate [101]. 

With the advent of high-performance concrete and the development of third-generation (mostly acrylic polymer-based) superplasticizers which provide significantly higher water reduction at flowable consistencies, this demarcation has blurred. Through the use of a mixture of admixtures it is now possible to obtain highly durable low water-cement ratio concretes that are nearly self-leveling and yet quite cohesive. 

Flow and self-leveling characteristics of these products are governed by the rheological behavior of the slurrylike materials. At the low water-cement ratios required to ensure proper suspension of the solids, most selfleveling compositions are characterized by a yield stress and thixotropic behavior [75]. To obtain self-leveling properties, the yield stress has to be reduced and this is achieved by the selection and combination of suitable mix ingredients at... 

Fig. 7.24 Self-leveling underlayment placed by pumping (courtesy Monica Martyn).

The pivotal role that superplasticizers play in the formulation of self-leveling mortars is due to the dramatic effects they produce on flow behavior. Such effects are believed to be derived by the adsorption of the admixture on the surfaces of cement grains, thereby providing surfaces of a similar or zero charge which are mutually repulsive. They thus fully disperse cement particles, freeing more water for lubrication and reducing interparticle attraction. Both yield stress and plastic viscosity are decreased and the decrease is greater for yield stress it may be completely eliminated if sufficient admixture is added so that Newtonian behavior is observed (Fig. 7.25) [75, 76]. 

Often it is difficult to adjust the mixture proportions to achieve desired design parameters for all properties of concrete. Consequently the properties of colloidal underwater concrete are controlled by the addition of three chemical admixtures. Minimum water-cement ratios range from 0.36 to 0.40. Cement and fine-aggregate contents are usually higher than corresponding mixes placed on land, and silica fume may be used in conjunction with a superplasticizer or conventional water reducers to reduce segregation. The key to a non-dispersible concrete with self-leveling characteristics is the successful optimization of the VEA with the superplasticizer used to increase the slump. 

Concretes containing VEAs have consistencies that are structured while static but become highly flowable, with self-leveling characteristics, when work is imparted to it. Data presented in Fig. 7.28 show that medium-strength concretes with equal slumps perform very differently in the washout test. This indicates that the slump test does not correlate to washout... 

These are used to produce prepackaged products such as decorative wall coatings, ceramic tile adhesives, self-leveling floor overlays and patching mortars for concrete structures. On site, addition of the product manufacturers specified amount of water produces a material with the desired properties. During the wet mixing, the... 

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