Binders in Refractory Concretes - Comparison (Cement Industry Focus)
Part 1: Overview of Binders in Refractory Concretes
Part 2: QuikTurn Vs. Rescobond Vs. EZ Est
Part 3: Laboratory Results of QuikTurn Vs. Rescobond Vs. EZ Est
Refractory concretes (castables and gun mixes) are overwhelming favorites for maintenance of refractory linings in North American cement plant preheaters and coolers. Refractory concretes provide high quality, durable linings that can reduce installation time especially when large volumes of refractory need to be installed.
Since their employment in the construction and maintenance of preheater linings dating back to the 1970’s, refractory concretes have traditionally contained calcium-aluminate cements as the binder. Similar to Portland cement, alumina cements are activated with water. These concretes typically feature good strength development within 24 hours of
installation, however, great care needs to be taken in drying out these linings, and frequently dry-outs for linings can extend several days.
It is often desirable to dress an existing lining during a maintenance outage by application of a refractory veneer using dry-gunite methods. Typically calcium aluminate-bonded concretes do not adhere well to existing linings, and veneer materials will more likely use a chemical binder, as chemically set refractories tend to have much greater adherence. Chemically-bonded monolithic refractories have an additional advantage of shorter drying times than alumina cement-bonded mixes.
A third technology has emerged for refractory concretes utilizing nano-particle sized colloidal silica (C/S) as a binder. This binder reduces the drying time for the refractory body as well as allows the potential for bonding to existing refractory.
The Nature of the Refractory Bonds
In the year 2000, the QUIKTURN™ series of products were developed and brought to the market. QUIKTURN technology incorporated a variety of novel features including a very low cement content to permit the refractory body to sustain a quicker initial dry-out using process-generated heat. Typically QUIKTURN products have been employed to both reduce dry-out time and allow safe dry-outs in vessels where controlling a dry-out schedule is difficult.
The aluminum ortho-phosphate bond is strong, can be alkali resistant and is considered a non-crystalline bond. In practicality, chemically-bonded refractories show little susceptibility to dry-out issues. Resco’s series of chemically-bonded monolithic products bears the trade name RESCOBOND®