Self-leveling sealant

Self-levelling sealant A sealant that is fluid enough to be poured into horizontal joints. It forms a smooth level surface without tooling also referred to as pouring-grade sealant . 

Polyurethane sealants are available in a non-sag formulation suitable for vertical joints and in a self-levelling formulation, useful for horizontal joints. The latter class of sealants flow into the joint giving a smooth level surface. They do not require tooling. 

Self-levelling polyurethane sealants are used to seal horizontal movement joints and construction joints in a variety of materials subject to light traffic such as concrete pavements (Figure 4.4), access roads, yards, parking areas, between rails and metal enclosures and around equipment and machinery. 

Figure 4.4 Application of self-levelling polyurethane sealant to a pavement joint. Reproduced with permission from Fosroc...

Table 7.9 Chemical-resistant polysulphide-sealant (specimen according to DIN 52 455, part 1, with acid-resistant clinker) (a) thixotropic (b) self-levelling. Source Morton International Ltd, Coventry, UK...

Polyester lighting sealants are self-levelling materials suitable for pouring into horizontal slots. They cure to form a tough resilient seal with a limited degree of movement. Salient features of polyester lighting sealants are as follows ... 

Colma SL Sealant Nemours Sika Chemical Co. propylene rubber — black color Self leveling, gray color 26.0 C... 

There are various uses requiring compounds with different flow characteristics. These range from a self-leveling material and one that must resist flow completely in vertical joints. A balance between fine and coarse fillers achieves the desired flow characteristics. Fine particle fillers build a network that result in thixotropic behavior. This must be balanced by the desired consistency and cost of the finished sealant. Care must be taken that the fillers are adequately dispersed to achieve the desired thixotropy. Specifically designed additives are available to impart thixotropy to a polysulfide sealant. These are listed in Table XI. 

Chem. Descrip. Silicone-modified polyester (51 1%) in solv. mixt. Uses Surf, wetting agent, flow aid, surf. tens, reducer for self-leveling epoxy coatings, sealants... 

Note (1) Sealant types are listed in order of increasing initial cost the list does not claim to be comprehensive. (2) Gun-grades are listed for joints in horizontal surfaces, the following self-levelling types are available (a) hot-poured bituminous and rubber/bitumen (b) cold-poured polysulphide and polyurethane. 

The sealants discussed so far are primarily supplied as gun-grades for application to joints on vertical building surfaces. A number of types (e.g. polysulphides) are also supplied as self-levelling or pourable grades for use in horizontal surfaces these sealants can be supplied with special properties, such as abrasion resistance for joints in trafficbearing surfaces. Bitumen and bitumen/rubber-based sealants are also supplied for these purposes both these types can withstand only limited movement. 

Manufacturers Comments Paste-like, self-levelling adhesive-sealant. RTV-1. Fast curing. High temperature resistance, good adhesion to ... 

Both the one-part and two-part sealants can be made in a range of viscosities and rheologies, from flowable and self-leveling to pastelike thixotropic compositions that will not sag significantly when applied to a vertical surface. 

In contrast, polyurethane sealants are widely used in many different applications. They are sold as two component and one-component gun-grade formulations, packaged in cartridges or in bulk. Pourable self levelling grades are also available. They compete directly with polysulfide and silicone sealants in many apphcations. 

The following paragraphs will describe the most important and most developed application areas for redispersible powders as they are ceramic tile adhesives/ tile grouts, thermal insulation systems (E.I.F.S.), self-leveling underlayments, patch and repair mortars, as well as water proof membranes (sealant slurries). 

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