Silica Bricks

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Introduction of Silica Bricks

Silica bricks (also called silica refractory bricks or silicate fire bricks) are made of silica sand material, and the content of SiO2 is more than 94%. And Al2O3 is lower than 1.0%, apparent porosity is under 22%. Silica bricks belong to acid refractory bricks, which have the excellent ability to resist acid slag and acid erosion. Silica bricks have good strength in high temperatures, high refractoriness under a load of about 1640-1680℃, and a high softening point with temperature. and, silica bricks are also featured with highly dense characteristics and good heat conduction. The refractoriness can reach the most 1730°C. they are ideal high-temperature furnace construction materials. They are normally used in the iron & steel industry, and the super grade will be the necessary refractories in the glass industry. The silica refractories are manufactured as multiple asymmetric shapes, which are normally keyed or interlocked with each other by means of tongues and grooves. Silica bricks are widely used in the bottom and walls of coke ovens.

Features of Silica Bricks

Silica refractories consist mainly of silicon dioxide (SiO2). Silica refractories also contain calcium compounds formed from calcium hydroxide which is used as a bonding agent.

The fired silica bricks contain the crystalline SiO2 modifications cristobalite, tridymite, and some residual quartz. During the firing process, the lime reacts with the finest quartzite components to form wollastonite (CaO.SiO2). The matrix also contains very small quantities of calcium ferrite, hematite, magnetite, calcium olivine, and hedenbergite [calcium ferrous silicate, CaFe(SiO3)2], which are formed from impurities. These crystalline phases are the reason for the discoloration and spot formation on the fired bricks.

The transformed coarse grain generally consists of cristobalite, a proportion of residual quartz corresponding to the degree of transformation, and very little tridymite, whereas the fine-grained matrix is enriched with tridymite, glass, and wollastonite.

The density of fired silica bricks is lowest when the degree of transformation is farthest advanced and attains the value of 2.33 g/cm3 with a complete transformation.

Properties of Silica Bricks

1. Good corrosion resistance of acid slag.

2. The refractoriness of silica bricks is not quite high, about 1600-1730℃

3. Good stability under high temperatures.

4. Poor thermal resistance performance.

5. Good air tightness.

6. True density 2.35g/cm³.

7. Total volume expansion 1.5~2.2% at the temperature of 1450℃.

Characteristics of Silica Bricks

The mortar required for providing plaster on calcium silicate bricks is very less.

The color and texture of these bricks are uniform.

The compressive strength of sand lime bricks is about 10N/mm2. So, they are well-suitable for multi-storied buildings.

For constructions in clay soils, these bricks are preferable.

The trouble of Efflorescence does not arise in the case of sand lime bricks.

Not only bricks, blocks, and tiles can also be made using calcium silicate.

Sand lime bricks provide more comfort and accessibility for architects to attain desired shapes and designs.

These bricks have accurate shapes and sizes with straight edges.

Solar heat effect is reduced on exposed walls made of calcium silicate bricks.

Colored sand lime bricks do not need any finish to the wall, so, the cost reduces.

These bricks have great fire resistance and water-repellant properties.

Calcium silicate brick walls resist noise from outside.

The cost of construction gets reduced by about 40% of the total cost due to the following factors.

Application of Silica Bricks

For lay coking chamber of coke oven and partition wall of the combustor, kiln crown and wall of glass furnace and calcining kiln of silicate product.

Use highly dense silica fire brick to lay a Large-scale coke oven, which can thin the wall of the coking chamber and combustor to improve the production capacity.

Used in flow aluminum tanks, and aluminum gates, and is suitable for the upper wall of a furnace for masonry of low alkali borosilicate glass.

Physical Parameters

Item / Model		XHJSIB94	XHJSIB96	XHJSIB98
Chemical Composition	SiO₂	≥94	≥96	≥98
	Al₂O₃	≤1.0	≤1.0	≤0.5
	Fe₂O₃	≤1.3	≤1.0	≤0.5
Apparent porosity	%	≤22(24)	≤22(24)	≤22(24)
Cold crushing strength	Mpa	≥45(35)	≥45(35)	≥45(35)
Refractoriness under load	0.2Mpa ºC	≥1650	≥1680	≥1710
Remaining quarts	%	≤1.0	≤0.8	≤0.8
Compressive Creep	%	≤0.8	≤0.8	≤0.8
Thermal expansion coefficient	1000ºC, %	≤1.28	≤1.25	≤1.23
Apparent density	g/cm³	≤2.32	≤2.32	≤2.32