What makes a good concrete for refractory industry

May 31st, 2023

Furnace construction involves the implementation of a concrete safety sublayer under the fused-cast paving. Essential for sealing the back-up and insulation brick layers, the proper choice of concrete can also avoid potential glass infiltration between the joints of the fused cast paving tiles.
Overlooking quality and composition of the sublayer could result in severe furnace damage. This could lead to potential glass leaks, production stops, financial loss and above all, risks to employee safety.

Homogeneity and mechanical performance

Although chemical composition has an impact on how concrete behaves, a high-performance concrete safety sublayer offers two key features: the crystallography of the grains and the grain size distribution.

Depending on manufacturing process, grains can have either a beneficial or a detrimental impact on the furnace bottom’s performance. Grains are produced using a fused-cast process. They offer high density, leading to higher corrosion resistance in case of glass infiltration into the sublayer.

Even so, a high-performance concrete doesn’t rely solely on its crystallographic properties. The primary function of the concrete sublayer is to act as a protective barrier against glass infiltration. A porous or cracked concrete sublayer will suffer severe damage if there are glass infiltrations. A sublayer with well distributed grains within the concrete significantly increases resistance to glass infiltration. When tightly packed together, they will significantly reduce porosity and cracking occurrence.


Glass furnaces: impact of the concrete

When used together, high-quality dense grains and homogeneous grain distribution contribute to furnace performance and longevity. 

Glass infiltration between the paving tiles joints, then between the paving tiles and the sublayer concrete, is known to potentially cause severe upwards corrosion as well as potential glass defects. Dense grains and enhanced grain distribution, combined with tight chemistry and low levels of impurities, will reduce both glass infiltrations and upward drilling corrosion, thus preventing subsequent damage to the furnace bottom and reduced glass quality.

The bottom layer expands when the furnace is heated up to glass melting temperature. Close control over the thermal expansion of the concrete layer beneath the tiles is an absolute requirement to avoid cracks and glass infiltration. This is made possible by both the grain crystallographic structure and optimal distribution across the concrete layer, which will prevent early shrinkage of the concrete layer and cracks. 

Optimal grain size distribution is also closely linked to a concrete layer’s mechanical performance. Poorly distributed grains increase the risk of concrete delamination, which is when the concrete layer separates from the bottom layer. Optimal grain distribution within the concrete layer will lower the risk of delamination and thus prevent glass infiltrations and a reduced furnace lifespan.


The strength of expertise

The first step to avoid problems is to thoroughly select refractory concretes during the furnace design phase, and to optimize furnace performance and lifespan.

SEFPRO ensures that installing its concrete is as easy as possible for glassmakers, contractors and operators. Additives in the concrete enhance the rheology behaviors, ensuring that concrete reaches all relevant furnace areas, including remote ones. It pays close attention to concrete formulation and manufacturing its own grains.

For more information about our complete range of concrete solutions for glass furnaces, use our contact form and make sure to check our latest video on refractory concretes.