Determine the normal consistency and setting timе of cement test

Laboratory work №1

Sieve Analysis

For the characterization of bulk goods of different forms and sizes, the knowledge of their particle size distributions is essential. The particle size distribution, i.e. the number of particles of different sizes, is responsible for important physical and chemical properties such as solubility, flowability and surface reaction. In many industries such as food, pharmaceutics and chemistry traditional sieve analysis is the standard for production and quality control of powders and granules. Advantages of the sieve analysis include easy handling, low investment costs, precise and reproducible results in a comparably short time and the possibility to separate the particle size fractions. Therefore, this method is an accepted alternative to analysis methods using laser light or image processing.

To guarantee a high degree of reproducibility and reliability, sieve shakers and accessories have to fulfill the requirements of national and international standards. This means that test sieves, sieve shakers and all other measurement instruments (e.g. scales) which are used for the characterization of particle distributions have to be calibrated and subjected to test agent monitoring as part of the quality management system. Apart from that, it is absolutely necessary to carry out the sample preparation with great care. Only then is it possible to achieve sieving results which allow a reliable characterization of a product.

Sieve Analysis in Quality Control

We all know the term “quality”. It is widely used to describe a product of particularly high value. However, the exact definition of quality is as follows: Quality is the compliance of defined properties with the detected properties of a product as determined by performing tests. A product can be described as high-quality if a test measurement ascertains that the desired properties lie within a given tolerance. If the measured values deviate too much, the quality is lower. Many materials, whether natural or artificial, occur in dispersed form (material which does not form a consistent unity but is divided into elements which can be separated from each other, e.g. a pile of sand). The particle sizes and their distribution within a material quantity - i.e. the fractions of particles of different sizes – have a crucial influence on physical and chemical properties.

A few examples of properties which can be influenced by the particle size distribution:

 ■ the strength of concrete

 ■ the taste of chocolate

■ the dissolution properties of tablets

■ the pourability and solubility of washing powders

 ■ the surface activity of filter materials These examples clearly show how important it is to know the particle size distribution, particularly within the context of quality assurance of bulk goods for production processes. If the particle size distribution changes during the production process, the quality of the product will change as well.

Sifting sand

A sand sieve is a tool for sifting sand or other particles in order to sort the particles according to size. It is usually a simple screen of metal or plastic, with openings of a set size, designed to allow particles of a certain size or smaller to pass through, while catching any larger particles. These sieves can be small, hand-held tools used by gardeners or scientists or large, industrial devices used in the production of quarry products like sand and gravel.

An analytical technique called sand sieve analysis is often used to determine the relative composition of sand or composite sediment according to particle size. Sand sieves of gradually decreasing size from top to bottom are arranged in a column, sometimes held by a frame or other apparatus. The sediment sample is weighed and poured into the top sieve, and this sieve is shaken for a set amount of time. As the sediment passes through the sieves, they are each shaken for the same amount of time. The individual sizes of sediment particles are then weighed, allowing for classification of the sample.

Gardeners and hobbyists sometimes use a sand sieve to separate sand and other soil particles. Bonsai enthusiasts often employ them for this purpose, to allow them to more precisely formulate the specialized soil mixtures used for growing dwarf trees. Archaeologists and paleontologists sometimes employ sand sieves to sift sand or other sediment for very small artifacts or bits of bone and teeth.

In industry, sand sieves are often used for producing sand of a particular uniformity of particle size for things like children's play areas, pool filters, sandblasting applications, concrete and mortar mixes. Industrial sand sieves may be very large, capable of handling many thousands of tons of sand per day, and are often fed by conveyor belts. By changing the number of sieves or mesh sizes of a series of sand sieves, nearly any combination of particle sizes can be produced.

Sand sieves are sold in standard sizes and are designated by a number that usually refers to the number of holes per inch. Taking into account the standard diameter of wire used to make a sand sieve, the maximum particle size can be calculated from the mesh number of the sieve. To calculate this figure in inches, divide 0.6 by the sieve number. To calculate this figure in millimeters, divide 15 by the sieve number.

Procedure:

For sand:

1. Take more than 2000 grams of sand.

2. Dry the sand to constant weight.

3. Sieve the sand through sieves with round holes 2.5 mm in diameter and with nets of 1.25; 0.63; 0.315 and 0.16. (sift until the sieve passes more than 0.1% of sand in 1 minute)

4. Weigh the sand on each sieve.

5. Calculate the sieve residues by the formula (for each sieve):

 

a_i = (m_i/m)*100,

 

a_i - sieve residues;

m_i - mass of sand on a sieve;

 m - total mass of sand.

 

Table 1. Test log (weigh of sieve residues)

Name of bulk material	Number of sieve

Conclusion

bulk modulus

Control questions

1. Sieve analysis is used for what materials?

2. If you sift 2 kg of sand and 20 kg of sand, which results will be more accurate?

3. Is it necessary to sift the sand for the concrete mix? Why?

4. Is it possible to sift materials with water?

5. What parameters are determine by sieving?

ГОСТ 8735-88. Песок для строительных работ. Методы испытаний

Laboratory work №2

Determine  the  normal consistency and setting timе of  cement test

 

Importance:

· Test for Setting Time:

This test is carried out to find whether a cement sets at a rate suitable for a particular work. There is no necessary relationship between the time of setting and that of hardening or attaining the maximum strength. A slow setting cement may harden more rapidly than a quick setting one, and vice versa. The hardening of cement is actually a continuation of the chemical action which began with setting. If the cement is placed in the mould. After initial setting time the cement mould can be detached and after final setting time the Vicatt’s apparatus plunger gives no impression..

The initial setting time can be defined as “time taken by paste to stiffen to such an extent that the Vicatt’s needle is not permitted to move down through the paste through 25 mm.”.

The final setting time can be defined as “ it is the time after which the paste becomes so hard that Vicatt’s 5mm needle doesn’t sinks visibly and leave no impression”.

With Portland cement and rapid hardening cement the normal initial setting time should not be less than 30 minutes and the final setting time should not be more than 10 hours. With quick setting cement the initial setting time should not be less than 5 minutes and the final setting time should not be more than 30 minutes.

· Test for Consistency:

This test is carried out to find the consistency of cement. For normal consistency of cement the maximum amount of water to be added is 30%. In this test the room and water temperature is also noted at the time of making the paste. The standard needle penetration is 10 mm.

Apparatus and Samples:

i) The apparatus used for these tests is Vicatt’s Apparatus.

It consists of a frame, bearing a movable rod, weighing 300 gram, and having either:

· A removable needle, 1mm in diameter, for finding out the initial setting time, or

· A needle, 5mm in diameter for determining the final setting time, or

· A plunger, 10mm in diameter for determining the normal consistency.

· The rod has an indicator which moves under a scale (graduated in mm.) attached to the frame.

ii) A paste of neat cement, which is prepared to the to the normal consistency, is held in a conical hard rubber ring, 8mm in diameter and 4 cm high. The percentage of water mixed to form a paste of normal consistency should be carefully noted.

iii) Triple beam balance.

iv) 300 gram sample of cement.

v) Trowel.

vi) Conical hard rubber ring.

vii) Water.

viii) Graduated cylinder.

 

Fig. 1. Vicat apparatus

 

Scale - шкала

normal consistency - plunger on the dissolution of the plate 5-7 mm

needle on the dissolution of the plate 1-2 mm

needle plunged into the test 1-2 mm

 

Procedure:

· Take the triple beam balance and set the reading of the scale to zero.

· Take a pan and measure its weight.

· Measure 400 gram sample of cement.

· Take the cylinder and measure 80 ml. of water.

· Now start making the paste of cement. It should be taken care that the time of making paste doesn’t exceed 1 minute. Also note the time of making paste.

· Now put the paste in the rubber ring from the wider side i.e. from down side, and make both the upper and lower surface smooth by dragging it on a smooth surface.

Now the two tests will be conducted separately by different procedures as:

Procedure for Normal Consistency Test:

· Take the Vicatt’s apparatus and place the rubber mould beneath the rod.

· Set the 10 mm. diameter plunger on the lower side of rod. Place the lower end of plunger just above the surface of paste.

· Now release the rod and note down the penetration of plunger in the paste.

· For cement to be of normal cons i stence the penetration should be 10 mm according to ASTM standard on room temperature.

· If it’s not so then the water and cement ratio will not be standard.

Procedure for Initial Setting Time Test:

· For determining the initial setting time of cement paste, set the 1mm. diameter needle on the lower end of the rod.

· Now release the rod for 30 seconds and note the time at which the needle was released, record this in the table along with the penetration of needle in the paste.

· After periodic time again release the rod for 30 seconds note the penetration of the needle in paste.

· Repeat the above step until the penetration becomes just 25 mm. which is ASTM standard. Calculate the total time up to this step, which will be the initial setting time of the cement. Compare it with the standard time and give comments.

Procedure for Final Setting Time Test:

· For determining the final setting time of cement paste, set the 5 mm diameter needle on the lower end of the rod.

· Now again repeat the above steps for noting the final setting time of cement.

· The final setting time will be noted when the needle if released doesn’t sink visibly and leaves no impression on the surface of the paste.

· Then compare it with the ASTM standard time. The final setting time can be found by the formula:

· Final setting time = 90 + 1.2 (initial setting time)

 

Table 2. Test log

№	Сomposition			Initial Setting Time	Final Setting Time
1
2
3

 

 

Control questions

1. What apparatus is needed to determine the normal consistency of the cement test?

2. What apparatus is needed to determine the timing of setting the cement test?

3. Show and name the details of the device to determine the normal consistency of the cement paste?

4. What is the standard normal consistency of the cement test?

5. Is it possible to change the setting time for cement?

 

Laboratory work №4