Laboratory work №9 Theme lessons: Research influence of fineness grinding siliceous component on water demand of molded masses and the physical and mechanical properties of cellular concrete

The purpose of lessons: illustrate the effect of undergraduates subtleties silica component grinding on some technological parameters of production of thermal insulating cellular concrete and their main properties.

This work may be performed by a team of undergraduates in full or more teams, performing its separate parts, followed by a generalization of the results as a group (subgroup). Possible tasks to perform work on cellular concrete are shown in Table 1.

Table 1 - Task Options

№ subgroups	№ Brigade	Kind of cellular concrete	The desired average density, kg / m3	Type silica component	Fineness silica component, cm2 / g
I	1	gas silicate	450	Sand Mountain	Rough milling (1500)
	2	gas silicate	450	Sand Mountain	Medium milling (2000)
	3	gas silicate	450	Sand Mountain	Fine grinding (2500)
	4	Foam on the mixed binder	400	River sand	Rough milling (1500)
II	5	Foam on the mixed binder	400	River sand	Medium milling (2000)
	6	Foam on the mixed binder	400	River sand	Fine grinding (2500)

Equipment, tools and technical means: foam concrete mixer capacity of 10-15 liters; mixing bowl (spherical) with a spatula; shaped sample cube size 7х7х7sm and 10x10x10 cm; Suttarda viscometer; laboratory autoclave; laboratory steaming chamber; an oven, press the SGP; VLG scales; measuring glassware; desiccator for storage of lime, quicklime; PSC-K.

The order of performance of works in the audience:

1. Undergraduates detect changes in water demand in the molding compositions according to the fineness of grinding silica component

2. Graduate sets the influence of this factor on the technological strength of the finished products

Working process

After receiving a task and raw materials, each team makes the following definitions.

1. By the method described in laboratory work №6, determines the specific surface teacher issued silica component, using existing laboratory PSC-K.

2. Using the procedure set forth in the laboratory work №8, the instrument Suttarda set the water demand of the molding composition for the composition of cellular concrete (concrete mix is ​​taken based on the results of laboratory work №8 or pre-selected).

3. Foam concrete or aerated concrete mixture is prepared and formed by three sample-twin (a method for preparing molding compositions and molding samples all teams use the same subgroup given one).

4. After the heat and humidity treatment produce test samples, determining their average density and the average tensile strength.

According to the results of undergraduates builds each subgroup common plots:

a) the specific surface area of ​​silica component (abscissa axis) -vodopotrebnost molding mass (ordinate);

b) the specific surface area of ​​silica component (abscissa) -limit compressive strength of samples (y-axis).

After the end of each graduate student is a report on the carried out research with the general conclusions and technical and economic considerations.

Record results from a team, it is recommended in the following form:

Kind of cellular concrete	Type of sand	Specific surface sand g/cm2	The desired average density of concrete in kg / m3	The actual average density of concrete in kg / m3	Water demand moldable mixture,%			Compressive strength, MPa
					1	2	3	1	2	3

1. 382 с.