Standard for determining trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar in Vietnam

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1. General regulations on trực tiếp bóng đá k+procedure for determining trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar

TCVN 7572-21:2018has trực tiếp bóng đá k+ following definition: "A quantity that characterizes trực tiếp bóng đá k+ level of methylene blue adsorption of aggregates containing clay and is calculated by trực tiếp bóng đá k+ number of grams of methylene blue adsorbed per kg of aggregate."

General regulations on trực tiếp bóng đá k+ procedure for determining trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar according toTCVN 7572-21:2018are as follows:

- Water used in analysis according to TCVN 4851 (ISO 3696) or water of equivalent purity (hereinafter referred to as “water”).

- trực tiếp bóng đá k+ percentage concentration of a diluted solution is expressed as trực tiếp bóng đá k+ number of grams of solute in 100 mL of water. For example, for methylene blue, a 0.5% solution is a solution of 0.5 g of methylene blue dissolved in 100 mL of water.

- Analytical criteria are carried out in parallel on two weighings of trực tiếp bóng đá k+ test sample.

trực tiếp bóng đá k+ absolute value difference between two parallel determination results must not exceed trực tiếp bóng đá k+ allowable limit. If it exceeds trực tiếp bóng đá k+ allowable limit, reanalysis must be performed.

- Determine constant volume

Determine trực tiếp bóng đá k+ constant mass by: heating or drying trực tiếp bóng đá k+ sample to a specified temperature and keeping it at that temperature for 15 minutes; cooling trực tiếp bóng đá k+ sample in a desiccator to room temperature; and weighing. trực tiếp bóng đá k+ process is repeated until trực tiếp bóng đá k+ difference between two consecutive stops does not exceed 0.1% of trực tiếp bóng đá k+ mass of trực tiếp bóng đá k+ test sample.

- Indicates mass, volume and results

+ Mass in grams (g);

+ Volume in milliliters (mL);

+ trực tiếp bóng đá k+ final result in grams per kilogram (g/kg), is trực tiếp bóng đá k+ average of two analytical results conducted in parallel, resulting in three significant figures.

2. Standards for chemicals and reagents to determine trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar

- Crystalline methylene blue (C16H18CIN3S.nH2O, n = 3, chemical purity ≥ 98.5 %).

- Methylene blue standard solution, 5 g/L.

Dissolve [(100+W)/20] g methylene blue to trực tiếp bóng đá k+ nearest 0.0001 g (equivalent to 5 g methylene blue dried at 100 °C ± 5 °C) in 500 mL to 700 mL warm water (water does not exceed 40 °C). Gently stir trực tiếp bóng đá k+ methylene blue solution for about 45 minutes until trực tiếp bóng đá k+ solution completely dissolves, then cool to room temperature. Transfer to a 1000-mL volumetric flask, add water to trực tiếp bóng đá k+ mark, and shake well. trực tiếp bóng đá k+ solution can be used for four weeks, stored in a dark glass bottle.

W is trực tiếp bóng đá k+ moisture content determined in Appendix A.

- Kaolinite

Kaolinite is finely ground to a particle size that passes through a 0.063 mm sieve, dried at a temperature of (105 ± 5) °C to a constant weight, and cooled in a desiccator to room temperature before weighing for testing.

3. Equipment and tools used to determine trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar in Vietnam

Equipment and tools used to determine trực tiếp bóng đá k+ methylene blue index of aggregates for concrete and mortar are specified inTCVN 7572-21:2018, including:

Common glassware used in trực tiếp bóng đá k+ laboratory and:

- Analytical balance, accurate to 0.0001 g.

- Technical scale, accurate to 0.01g.

- Drying oven, capable of adjusting temperature and controlling temperature within (105 ± 5) °C.

- Sieves of all types, with hole size of 2 mm; 0.25 mm; 0.1 mm and 0.063 mm.

- Agate mortar and pestle.

- Glass cup or polyethylene plastic cup, capacity 1000 mL, 2000 ml.

- Volumetric flask, made of glass, with a capacity of 1000 mL.

- Erlenmeyer flask, made of glass, with a capacity of 500 mL.

- Glass chopstick, length 300 mm, diameter 8 mm.

- Stirrer, capable of controlling trực tiếp bóng đá k+ stirring speed to (600 ± 60) r/min with 3 or 4 stirring blades with a diameter of (75 ± 10) mm, magnetic stirrer with a diameter of over 10 mm.

- Stopwatch, accurate to 0.1 s.

- Thermometer monitors temperature, with graduations accurate to 0.1 °C.

- Desiccator, containing silica gel beads.

- Burette, capacity 5, 25, 50 mL.

- Filter paper, medium flow, ash-free quantitative (average pore diameter of about 7 μm).

Best regards!

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