This document outlines the standardized techniques for assessing the unhydrated oxide content in building lime materials. It includes comprehensive guidelines on sample handling, drying, thermogravimetric testing, and chemical assays to measure unhydrated oxides and sulphur trioxide accurately, serving as a vital reference for quality assurance in construction lime applications.
Overview
This document outlines the standardized techniques for assessing the unhydrated oxide content in building lime materials. It includes comprehensive guidelines on sample handling, drying, thermogravimetric testing, and chemical assays to measure unhydrated oxides and sulphur trioxide accurately, serving as a vital reference for quality assurance in construction lime applications.
Audience
Contents
Structure
Overview of the testing methods applicable to building lime materials, including chemical and physical analysis techniques. Use of distilled or reagent-grade water as specified under IS 1070:1992 is mandated. The section also details the computational steps for determining lime constituents, accompanied by illustrative formulas and a flowchart to facilitate understanding.
Instructions for selecting and preparing lime samples according to IS 712-1973. Procedures include drying, grinding, slaking at controlled temperature to form a stiff putty, and vacuum drying to achieve constant mass. The chemical analysis protocol for sulphur trioxide determination is described, including reagent volumes and precipitation steps.
Details on the apparatus required such as autoclaves with specific pressure gauges, furnaces capable of high-temperature control, and thermobalances. The section outlines operational parameters and equipment features to maintain accuracy and safety during testing.
Stepwise methodology for preparing samples, conducting tests, and performing calculations. Emphasizes adherence to IS 712:1973 for sample handling and details formulas for calculating chemically combined water, calcium oxide equivalents, remaining combined water, and magnesium oxide equivalents.
Calculation approach for determining unhydrated oxide, accounting for adjustments based on carbon dioxide and sulphur trioxide contents. Includes formulas to calculate chemically combined water, calcium oxide equivalents from CO2 and SO3, water equivalents, and magnesium oxide equivalents.
Describes the chemical analysis process for SO3, including sample dissolution, filtration, precipitation with barium chloride, ignition of precipitate, and subsequent weight measurement. Provides the formula to convert barium sulphate weight to sulphur trioxide percentage.
Summarizes essential calculation formulas for chemically combined water and oxide equivalents with clear stepwise instructions. Includes conversion factors and multipliers needed for accurate chemical analysis in lime testing.
Instructions on documenting findings, applying correct rounding practices, and interpreting calculations for chemically combined water, calcium oxide, and magnesium oxide equivalents. Emphasizes use of distilled water and adherence to relevant IS standards.
Outlines safety precautions for conducting chemical analyses, including proper reagent use, equipment handling, and compliance with standard operating procedures to ensure safe and accurate testing environments.
Lists relevant Indian Standards related to lime testing, reagent water specifications, and rounding rules. Provides contact information for standardization authorities and cross-references to related testing protocols.
Frequently Asked
The preparation involves selecting samples as per IS 712-1973, slaking the lime at 25 ± 2°C to form a stiff putty, drying the slaked material in a vacuum until a constant weight is reached, accurately weighing 1 gram of this dried sample, autoclaving it at approximately 20.746 kg/cm² pressure for three hours followed by one hour holding, and finally drying again before thermogravimetric analysis.
The method entails weighing 1 gram of dried hydrated lime, autoclaving it under specified pressure conditions, then heating at a controlled rate below 200°C per hour up to 380°C. The sample is held at this temperature until mass stabilizes, then heating is resumed until constant weight is achieved. The mass loss between 280°C and 380°C corresponds to the decomposition of magnesium hydroxide, which is calculated to quantify unhydrated oxide content.
Testing requires precision analytical balances, sieves for particle size distribution, standard laboratory glassware such as beakers and pipettes, water baths for temperature control, pH measurement instruments, filtration assemblies, reagent-grade distilled water, and stirring devices. Additionally, specialized equipment like autoclaves, furnaces with temperature regulation, and thermobalances are essential for accurate testing.
Approximately 2.5 grams of the sample is mixed with cold water and dilute hydrochloric acid, heated until dissolved, then filtered. The filtrate is diluted to 250 ml, boiled, and treated with hot barium chloride to precipitate barium sulphate. After standing overnight, the precipitate is filtered, washed, ignited in a platinum crucible until constant mass, and weighed. The sulphur trioxide percentage is calculated by multiplying the precipitate weight by a factor of 0.343.
The autoclave pressure should be raised to approximately 20.746 kg/cm² within about three hours and maintained at this level for one hour. The steam corresponding to this pressure is approximately 212°C. After treatment, pressure should decrease from 21 kg/cm² to below 1 kg/cm² within 12 hours. The equipment must include safety valves, pressure gauges, and automatic pressure controls.
Ask AI about any clause, requirement, or provision in IS 6932 PART 5. Get instant, clause-cited responses powered by our indexed library.
Free tier includes 150 queries (50 AI + 100 Reference) · No credit card required