Challenge: What are the benefits of reactive alumina and how do I select the appropriate reactive alumina to upgrade refractory performance?

Solution: Reactive aluminas are key components and performance enhancers for modern refractory formulations, both castables and bricks. They have a major impact on water demand and rheological properties of castables and on the strength, porosity, and slag and wear resistance of the refractories.

The name "reactive alumina" initially comes from the ceramic industry, where it refers to the sintering reactivity of alumina powders. In the meantime, reactive aluminas have proven their value for refractory applications too, and a broad range of products have been developed especially for them.

Reactive aluminas are fully ground powders, which are significantly finer than ground aggregate minerals. They are practically agglomerate free when compared to ground calcined aluminas and therefore do not absorb water. This reduces the liquid requirement of refractory formulations and results in enhanced performance. Reactive alumina is typically combined with ground aggregate fines (e.g. tabular alumina) to fill out the matrix particle distribution of a refractory formulation and achieve optimized particle packing. Almost all modern high performance alumina refractories contain significant amounts of reactive alumina.

In castable formulations reactive alumina requires effective dispersing additives such as dispersing aluminas to exploit their full performance: ADS/W for silica fume-free, and M-ADS/W for silica fume containing castables. Almatis? reactive aluminas are categorized as mono-modal, bi-modal, or multi-modal according to their particle size distribution.

Components 1
Mono-modal (CTC 20)
Components 2
Bi-modal (CL 370)
Components 3
Multi-modal (CTC 50)

Almatis offers a wide range of reactive alumina products for various applications. The alumina particle size distribution has a significant effect on the properties of refractory formulations. Almatis global reactive alumina products can be briefly described as follows:

RG 4000: Mono-modal reactive alumina with a high amount of submicron particles for enhanced thermal reactivity and improved mechanical strength in high performance castables, pre-cast monolithic shapes, and special dry pressed products.

CTC 20: Mono-modal semi reactive alumina specifically designed for silica fume containing castables.

CL 370: Versatile bi-modal reactive alumina for manifold applications in vibration and self flow castables, furthermore in special shaped products.

CTC 40: Mono-modal reactive alumina with high sintering reactivity. It is recommended for use in silica-free and clay-free gunning mixes, also for special vibration castables and runner mixes.

E-SY 1000 and E-SY 2000 (contains spinel): Newly developed and versatile reactive aluminas for vibration, self flow, and pumpable (shot-creting) mixes. E-SY aluminas contribute to low dilatancy and easy mixing behavior of the castables.

CTC 50 and CTC 55 (contains spinel): Multi-modal reactive alumina for excellent flow properties in high performance, low water demand self flow castables.

E-SY 2000 and CTC 55 contain spinel, which improves the thermo mechanical properties and slag resistance of alumina refractories.

T60/T64 -20MY: Product originally derived from the tabular alumina production route, however further processed like reactive alumina. It supplements matrix fines reactive aluminas in high performing vibration and self-flow castables and enables soft flow behavior due to its broad particle size distribution.

CT 10 SG: A special ground alumina product with high specific surface area. It has high water retaining properties and is ideal to add stickiness and plasticity to clay free high performance gunning or plastic mixes, often in combination with CTC 40.

If technical assistance is required to select an appropriate reactive alumina for a specific application, experienced Almatis technical support is available in each global region. Request Technical Assistance