Laboratory work №5 Theme lessons: Determination of moisture in raw materials

The purpose of lessons: Moisture determination of raw materials

The plan of lessons

1. Introduction to the methods of drying materials

Running time of work – 3 hours

Brief theoretical information

The thermal conductivity of heat-insulating materials increases dramatically when moistened. Effect of humidity pas thermal conductivity material because the thermal conductivity of air and water differ from each other by about 20 times, so the determination of moisture content of heat-insulating materials and structures is a fundamental test.

Humidity characterizes the wetting material and is usually expressed as a percentage by weight or volume.

Humidity - the ratio of the mass of water contained in the material, the weight of the material in a dry state:

Wa = (m - m1) / m1 * 100

where: т - mass of the sample before drying, kg (g);

        т1- mass of the sample dried to constant weight, kg (g).

There are several ways to determine the moisture of thermal insulation materials. These methods are based pas heating (drying) material in an oven, rapid methods and indirect methods of determining the moisture content, for example, based on a change of electrical conductivity of materials according to their moisture. The last group of methods not widely used thermal insulation materials in the test due to the lack of reliable sensors for humidity.

Equipment, tools and technical means: raw materials; shaker; a set of screens; drying cabinet; wet storage cabinet; libra.

The order of performance of works in the audience:

1. Master students familiarize with the methods of drying materials.

2. After studying the necessary information undergraduates determine the mass fraction of moisture.

Working process

Typically the humidity of a heat insulating material is determined by the evaporation of water in the laboratory ovens. Methods of determining this is as follows.

The collected sample material is placed in a sealed container and weighed to the nearest 0.1 g of the sample vessel was then placed in an oven, remove the lid and the sample material is dried to constant weight at a temperature of 105-110 ° C. The moisture content of the material is calculated by the formula:

W = (m₁ - m) / (m - m₂) * 100

where: m₁ - mass of the cup with the sample of wet material;

         m - mass of the cup with the dried material; g;

         m₂ - mass of the empty cup with a lid of

Sampling and the establishment of an average lot of material moisture produced as follows.

1. Loose heat-insulating materials (mineral and glass wool, expanded perlite and vermiculite, and so on. N.) The total sample should be not less than 30 g and consist of three batches of not less than 10 g each, taken from selected trials for any three of packages.

2. To determine the moisture content of flexible material (such as rockwool) total sample should be not less than 15 g and consist of three batches of 5 g each, taken from three different locations selected for the test cloth (product). Humidity such a sample taken as the average moisture content of the product, and the party humidity is calculated as the arithmetic mean value of the results of tests of three selected for this product.

3. To determine the moisture content of rigid thermal insulation materials (products made of cellular concrete, ceramic, lime-siliceous, fibrolite products, etc.) the total sample shall be not less than 20 g and consist of two batches of 10 g each, taken from each product selected for testing. High humidity Party is calculated as the arithmetic mean value of the results of tests of three selected for this product.

Rapid methods. These methods are based on the use of radiation heat flux. They differ from the conventional method in that the drying of the material produced are not in an oven, and infrared rays. Under these drying methods the duration of sample material does not exceed 15 minutes.

Control questions

1. What is the moisture content of raw materials?

2. How is the determination of the mass fraction of moisture of raw materials?

3. The method of drying materials?

Safety requirements

1. Laboratory premises in which work is performed to determine the chemical composition of cement and cement production materials should be equipped with ventilation systems in accordance with GOST 12.4.021.

2. When operation of electric installations and electric appliances used in the process analysis must be performed by electrical safety regulations in accordance with GOST 12.1.019.

3. When working with acids and alkalis, observe the safety regulations in force in chemical laboratories.

4. When operating the units with sources of ionizing radiation (X-ray apparatus) should be guided by the requirements of the radiation safety standards NRB-76/87 and the basic sanitary rules OSP-72/87.

5. When working with flammable and explosive substances must be complied with safety requirements according to GOST 12.1.010.

6. When working with hazardous and noxious substances is necessary to use protective equipment according to GOST 12.4.004, personal protective equipment (respirators in accordance with GOST 12.4.011 GOST 12.4.028 or rubber gloves according to GOST 12.4.103, clothing according to GOST 27654 and GOST 29058).

List of used literature:

Main literature

1. Жакипбаев Б.Е., Альжанова А.Ж. Композиционные силикатные материалы. Учебник для магистрантов. Изд-во ЮКГУ, 2016. – 186 с.

2. Bibol Ye. Zhakipbayev Composite silicate materials. Textbook for master students. SKSU published, 2016. – 180 P.

3. Худякова Т.М., Жакипбаев Б.Е. Технология вяжущих и композиционных материалов. Учебник для магистрантов. Изд-во ЮКГУ, 2015. – 226 с.

Additional literature

1. Горлов Ю.П. и др. Технология теплоизоляционных материалов. – М.: 1980. - 399 с.

2. Горлов Ю.П. Технология теплоизоляционных и акустических материалов и изделий. – М.: 1989. - 384 с.

3. Горлов Ю.П. Лабораторный практикум по технологии теплоизоляционных материалов. – М.: ВШ. 1982. – 239 с.

4. А.Г.Комар Строительные материалы и изделия. – М.: 1988. - 527 с.

5. Китайцев В.А. Технология теплоизоляционных материалов. – М: 1970. – 382 с.