Properties, Types, Tests, and Benefits of Acid-Resistant Bricks

Acid-resistant bricks are made of clay or shale with low lime and iron content and are vitrified in ceramic kilns at high temperatures.

To prevent surface deterioration by acids, acid-resistant bricks are used to construct floorings vulnerable to acid attack, the lining of chambers and towers in chemical plants, the lining of sewers carrying industrial effluents, and so on.

Standard Properties of Acid-Resistant Bricks

Dimensions

Acid-resistant bricks must have standard dimensions of 230 x 114 x 64 mm. Tolerances on dimensions are allowed as shown in the table below:

	Dimensions in mm	Tolerances in mm
Length	230	±3.5
Width	114	±2.0
Depth	64	±1.0

2. Finish

When fractured, the finished brick must have a fine-grained texture that is dense and homogeneous. The brick must be true to shape, sound, flat, and free of flaws and other manufacturing flaws that would impair its utility.

Types of Acid-Resistant Bricks

There will be two types of acid-resistant bricks manufactured:

1. Class I Bricks

These acid-resistant bricks are recommended for severe corrosive environments, such as pickling tanks, storage tanks, and heavy-duty floors that come into contact with corrosive liquids on a regular basis.

2. Class II Bricks

These acid-resistant bricks are recommended for working areas and floors exposed to fumes, acids, and chemicals on a regular basis in fertilizer silos. These are also used to line and skirt silos.

Test for Acid-Resistant Bricks

The acid-resistant brick tests are as follows:

• Absorption of water
• Flexural power
• Compressive power
• Resistance to acid

The first three tests must be performed in the same manner as those for regular bricks. The following are the links to the tests:

Test for Acid Resistance

1. Preparation of Test Specimen

The acid resistance test specimen must be made from individual bricks, and a minimum of five bricks must be tested. In a stoneware mortar, each brick is crushed to powder.

Each brick's sample powder is taken and passed through an 850-micron sieve before being retained on a 600-micron sieve. The powdered sample must be dust-free washed as follows:

• A 30 g specimen is placed in a porcelain basin and 150 ml of distilled water is added.

• Place the basin on a sand bath and heat the mixture in it until it begins to boil.

• Care must be taken to avoid specimen loss due to spurting while boiling, and heating must be maintained for one hour.

• Remove the particles and rinse them with cold, distilled water.

• Dry the material to a constant weight by placing it in an oven set to 110°C.

2. Reagents

The following reagents must be used in the test:

1. Nitric acid concentration
2. Concentrated Sulphuric Acid

3. Test Procedure

1. A prepared specimen weighing 25 g is weighed and placed in a porcelain basin.
2. The specimen is treated with a solution of 13 mL sulphuric acid, 7 mL nitric acid, and 65 mL distilled water.
3. The basin and its contents are carefully placed on a sand bath and heated until all nitric acid has evaporated and sulphuric acid begins to fume profusely.
4. The basin and its contents are cooled to 27 2°C before adding 10 ml of nitric acid and 90 ml of distilled water.
5. The heating process is repeated until the sulphuric acid begins to fume strongly once more.
6. The basin and its contents are cooled, and the acid is carefully decanted. 150 ml of cold distilled water is added and brought to a boil.
7. The cycle of freshwater addition, boiling, and decantation must be repeated until the decanted liquid is found to be free of sulphuric acid when tested with barium chloride solution. During the process, no particle shall be lost.
8. After the final decantation, dry the sample to constant weight in an oven set to 110°C.

4. Calculation and Report

Criteria for Conformity for Performance Requirement of Acid-Resistant Bricks

Sl No	Requirement	Class I Bricks	Class II Bricks
1	Water Absorption	≤ 2%	4%
2	Flexural Strength	≥ 100kg/cm2	70 kg/cm2
3	Compressive Strength	≤ 700kg/cm2	500 kg/cm2
4	Resistant to Acid	≤ 1.5%	4%

Advantages of Acid-Resistant Bricks

The following are the benefits of acid-resistant bricks:

1. It has a high acid resistance, a low water absorption rate, is not easily oxidized at room temperature, and is not easily contaminated.
2. It's used in the chemical industry for things like ditch puzzle acid, acid wells, acid storage libraries, and acid impacted ground.
3. When special metals and alloys become uneconomical due to chemical attacks at high temperatures, it is a cost-saving material.
4. By allowing the use of less expensive alloys, these acid-proof brick liners can reduce concentration and temperature levels.

FAQs

What is the standard dimension of acid-resistant bricks?

Acid-resistant bricks must have standard dimensions of 230 x 114 x 64 mm.

What is the required finish of acid-resistant bricks?

When fractured, the finished brick must have a fine-grained texture that is dense and homogeneous. The brick must be true to shape, sound, flat, and free of flaws and other manufacturing flaws that would impair its utility.

Which are the types of acid-resistant bricks, and what are their applications?

The acid-resistant bricks shall be manufactured in two classes:

1. Class I Bricks

These acid-resistant bricks are recommended for severe corrosive environments, such as pickling tanks, storage tanks, and heavy-duty floors that come into contact with corrosive liquids on a regular basis.

2. Class II Bricks

These acid-resistant bricks are recommended for work areas and floors exposed to fumes, acids, and contact with pith dry chemicals in fertilizer silos. These are also used to line and skirt silos.

Which are the reagents used for the acid resistance test?

The following reagents are used in the acid resistance test: 

1. Concentrated Nitric Acid

2. Sulphuric Acid Concentrate