This standard outlines the specifications for chemically setting silicate-based mortars designed for acid-resistant masonry bonding. It is critical for professionals managing structures subjected to harsh acidic conditions, detailing the mortar's formulation, physical and chemical resistance properties, testing protocols, and packaging requirements to guarantee effectiveness against acids like nitric, chromic, sulphuric, and hydrochloric acids.
Overview
This standard outlines the specifications for chemically setting silicate-based mortars designed for acid-resistant masonry bonding. It is critical for professionals managing structures subjected to harsh acidic conditions, detailing the mortar's formulation, physical and chemical resistance properties, testing protocols, and packaging requirements to guarantee effectiveness against acids like nitric, chromic, sulphuric, and hydrochloric acids.
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Frequently Asked
Silicate mortars exhibit resistance to a range of acids including nitric, chromic, sulphuric, and hydrochloric acids, with potassium silicate mortars particularly recommended for sulphuric acid and its mixtures. They are not resistant to hydrofluoric acid, concentrated ortho-phosphoric acid, alkalies of any concentration, boiling water, or steam. Prolonged water exposure also causes degradation. Typical applications include jointing acid-proof masonry units and lining chemical tanks and floors.
Key differences include that sodium silicate mortars have a working time of at least 15 minutes, flexural strength of 35 kg/cm², and compressive strength of 100 kg/cm² after seven days. Potassium silicate mortars provide a longer working time of 20 minutes, higher flexural strength at 40 kg/cm², and compressive strength up to 150 kg/cm². Both have equal bond strength and toluene absorption limits. Potassium silicate mortars are preferred for enhanced sulphuric acid resistance.
The working time for sodium silicate mortars must be at least 15 minutes and for potassium silicate mortars at least 20 minutes, measured at 27 ± 2°C. Strength tests include flexural, compressive, and bond strength conducted after seven days of curing, following IS 4456 Part I testing methods. Mortars must meet or exceed specified minimum values for these properties to be accepted.
Silicate mortars are not suitable for environments containing alkalis of any concentration, as these cause deterioration. They also lack resistance to boiling water and steam. Frequent or prolonged exposure to water leads to degradation of the mortar's properties, limiting their use in such conditions.
Silicate solutions must be stored in airtight, sealed containers to prevent contamination and quality loss, while dry mixes should be packaged to avoid moisture ingress. Each package should be labeled with the manufacturer’s name, manufacturing date or batch number, net volume or weight, storage instructions, shelf life, and expiration date. Sampling of at least 10% of containers per lot is required for quality control purposes.
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