Code of practice for the use of sulphur-type chemical-resistant mortars
1980 Edition

Sulphur mortars should be stored in a dry environment to prevent moisture absorption and degradation. Surfaces and containers that come into contact with the mortar must be kept dry. Adequate ventilation is necessary, and care must be taken to avoid flammable or explosive gases in storage and melting areas. Operators should employ protective equipment and follow fire safety measures, including obtaining flame permits and having suitable fire extinguishing equipment nearby.

Melting should be done in a clean vessel filled to no more than 50% with dry sulphur mortar. Heat slowly to approximately 135°C, stirring frequently with a steel ladle. Temperatures below 130°C cause congealing, while temperatures above 135°C increase viscosity and degrade appearance. Operators must wear protective gear such as leather aprons, asbestos gloves and boots, goggles, and masks. Ensure dry contact surfaces, avoid water near molten mortar to prevent foaming, maintain ventilation, check for flammable gases, and obtain appropriate flame permits. Fire extinguishers and wet cloths should be accessible.

For floors, silicate mortar is applied 6 to 8 mm thick on the back and two sides of tiles or bricks, with joint thickness limited to 6 mm. Joint material is removed to a 20 mm depth before setting, cured with acid for at least 72 hours, and joints are fully filled with sulphur mortar. Spacer chips are used under tiles to prevent air pockets. For walls, similar mortar thickness is applied, but only one course is laid at a time to avoid sliding. Joints are cured with resin for a minimum of 72 hours and sealed with 25 mm wide gummed paper before filling with molten sulphur mortar. The paper is removed once the mortar hardens, and excess mortar is trimmed smoothly.

Sulphur mortars exhibit good resistance to most non-oxidizing acids such as hydrochloric, sulphuric (up to 70%), and nitric acid (up to 40%), as well as concentrated sodium carbonate and acidic salt solutions. They have limited or no resistance to concentrated oxidizing acids, higher concentrations of alkalis, and various organic solvents. Chemical resistance is typically evaluated through immersion tests where mortar specimens are exposed to chemicals at ambient temperatures, with observations made on weight, strength, and physical integrity changes. Testing procedures follow IS 4456 (Part II) - 1967.

To avoid air pockets during pouring, use a galvanized bucket equipped with a sharp pouring spout aimed directly at the joint. Pour the molten sulphur mortar slowly and evenly, ensuring steady flow. If air bubbles form, they should be removed immediately while the mortar remains hot by gently poking with a thin mild steel rod. It is critical to maintain dry mortar and avoid overheating, as moisture and excessive heat can cause foaming and entrapment of air.