Cement
Production
Types of cement
Properties and test
   Fineness
   Soundness
   Consistency
   Compressive strenght
   Setting time
   Heat of hydration
   Specific gravity
   Loss on ignition
Specimens preparation


Cement
The cement is an inorganic material largely used in the construction industry, both on site and during the production of semi-manufactured products.
When melted with water, the cement becomes like a paste characterized by adhesive properties: for this reason it is considered an hydraulic binder and properly defined as hydraulic cement.
The paste of cement and water is generally used as a binder together with solid inert materials such as sand, gravel and small rocks to form the mortar and prepare different types of concrete (light, reinforced, pre-stressed…).

There are also many types of cement which may differ for composition and properties and therefore used for different purposes. When planning a building, engineers have to specify the kind of cement that must be utilized in order to meet the technical requirements and assure the best performances. Matest offers a wide range of cement testing equipments in compliance with the International Standards in force. We invite you to enter “Cement-Mortar” section.

Production Types of cements Properties and test Cement specimens preparation

Production
The cement is obtained from the extraction of raw materials such as limestone and clay. After being mined, the raw materials undergo a crushing treatment in order to reduce their dimensions and therefore ease the transfer to the production centres. The first production phase is dedicated to the grinding and desiccation processes: the raw materials are dosed or eventually combined with other components, then turned into thin powder and transferred to the storage. Afterwards this mixture is heated in a cement kiln, a huge slowly rotating and sloped cylinder, with temperatures increasing over the length of the cylinder up to 1450°C: the resulting material is the clinker, characterized by hydraulic properties.

The cement production is the result of a next mixing process where the clinker is combined with other components (such as gypsum) - in quantities that may vary in accordance with the required technical specifications - and then grinded until a thin and homogeneous powder is obtained.

Types of cement
There are different typologies of cement which may differ for composition and class of compressive strength and therefore may be used for different purposes. The technological improvements applied to the construction industry and the use of both artificial materials and natural ones have led to a continuous development of new typologies. The most common cements are Portland cement, special Portland cements, blended cements, quick-setting cement and aluminous cement.

The Portland cement is the most common type of cement in general usage and it is the basic ingredient of concrete, mortar and plaster. Invented in 1824 by the mason Joseph Aspdin, it resembles the rock of Portland in properties, which is an island in the Dorset county (England). It is obtained from the clinker grinding, combined with gypsum or anhydride to regulate the setting time. When mixed with water, it solidifies in few hours (6-12 hours) and hardens progressively during the next weeks. The cement lime mortar is made of Portland cement and it is particularly used as plaster to cover the building’s external surfaces.

Besides the common Portland cement, there are also many special Portland cements made of Portland cement plus other components in different percentage quantities. The most famous ones are the iron Portland cement and the white cements.

The pozzolan cement and the blast furnace cement are defined as blended cements: the first one is obtained by adding Pozzolan (fly ash), while the second one includes blast furnace slag such as coal ash, foundry slag and residuals taken from the quartz heating.

Another kind of cement largely used in the construction industry is the quick-setting cement, also known as Roman cement. It is produced by heating the Portland cement at lower temperatures; when mixed with water it sets and hardens very quickly and therefore it is suitable for small fixing jobs and reparations.

The aluminous cement results from the bauxite. It is well known as fused cement due to the components’ fusion that may occur during the heating phase, where the temperature can reach up to 1600°C. After this phase, the cement is poured into moulds to form ingots which are subsequently cooled with water and finally grinded to obtain the final product. This special kind of cement has a neutral nature, while the common Portland cement has a basic one, due to the mortar presence.

Properties and test
The cement properties come from a complex interaction of physical and chemical factors that come into action immediately after the mixing with water. To a first phase of "setting", that takes some hours, a second phase of "hardening" follows, starting quickly for the first twenty-eight days and becoming slower in the next weeks. During both the phases, remarkable thermal effects as well as a reduction of volume are shown.

Matest “Cement-Mortar” section offers you a complete and wide range of material testing equipments to carry out all kind of test on mortar and cement in order to check whether their properties are in compliance with the technical specifications fixed during the planning phase. The most important properties to be tested are as follows:

• Fineness
• Soundness
• Consistency
• Compressive strength
• Setting time
• Heat of hydration
• Specific gravity
• Loss on ignition

Fineness
The cement fineness notably affects the hydration speed and therefore the starting time of the setting and hardening phases. It is measured by means of the Blaine air permeability apparatus (EN 196-6), offered by Matest in the standard version as well as in the automatic one. This property can also be tested using the Water flowing sieve device described by D.M.3/6/68 Standard.

Soundness
The test of soundness are important to check the expansion phenomena that may occur due to the presence of free calcium oxide and/or crystalline magnesium oxide. Le Chatelier moulds are used to determine the cement expansion either in cold and boiling water. With respect to this kind of test, Matest Le Chatelier water bath is made with stainless steel inside chamber and can hold up to twelve Le Chatelier moulds in the removable rack. The appliance is supplied with a special device that keeps the bath temperature at the boiling point, by avoiding the water evaporation and therefore assuring that the moulds are kept covered by the water during the test.

Soundness test on cement specimens can also be performed by means of the Autoclave which allows the operator to establish if the magnesium oxide value is higher than the one approved by the law. After having prepared the prism moulds by means of the relevant moulds, the operator have to put them into the autoclave for the curing process. This test is suitable for the determination of the possible expansive ability of the specimen in a short time, due to the accelerated curing process.

Consistency
Mortar and cement consistency is an important property for their workability. As a matter of fact, according to the cement/sand used in the construction process, different consistencies may be obtained on equal water/cement ratio and vice versa. The consistency test can be performed by means of the following Matest cement testing equipments: Flow tables , Dropping ball apparatus , Plunger penetration apparatus and Mortar workability apparatus.

Compressive strength
The most common cements used in the civil engineering are classified in two categories: “normal cements” and “high-resistance cements”. To test the compressive strength of the cements and classify them into one of the three established classes (32.5 – 42.5 – 52.5), Matest offers a wide and complete range of compression machines both manual and servo-controlled for compression test on cement, mortar, rocks and refractory materials.

The versatility and flexibility of Matest production allows the operator to combine a cement compression/flexural frame with another one. Matest “Cement-Mortar” section also includes compression machines with two measuring ranges both with one testing chamber and with a double one (“High performance”).

Setting time
The starting and the final setting time of a hydraulic binder is measured with the Vicat apparatus whose automatic version, known as Vicatronic, has become one of the most popular Matest products. Vicatronic has been designed and manufactured using the most recent and sophisticated technologies and it has been conceived to perform the test automatically, assuring precise and repeatable results. Matest “Cement-Mortar” section also includes other two useful testing solutions for the setting time determination: the Gillmore apparatus and the Automatic recording penetrometer “Italcementi model”.

Heat of hydration
The heat of hydration released by the hydrate cement during the interaction with water can be measured by applying the solution method and using the Calorimeter. The resulted value is particularly useful when a great concrete casting is required, in order to reduce the undesired effects that may be caused by high heat values or temperatures.

Specific gravity
The specific gravity of a hydraulic cement and mortar can be measured with the Le Chatelier flask and the Bulk density apparatus which is composed by a sieve funnel with tripod, a one litre unit weight measure, a spatula, a straight edge and an aluminium scoop.

Loss on ignition
Lime and cement loss on ignition is the percentage loss in weight that these materials undergo when they are heated at 950°C. The test allows the operator to check if the cement has been mixed with cheap elements or if water and carbon dioxide have been absorbed by the cement during the storing phase. The Muffle furnace 1200°C has been conceived to determine the loss on ignition of building lime and cements as well as to measure the content of chloride, carbon dioxide and alkali.

Cement specimens preparation
The preparation and the maintenance of the cement and mortar specimens must follow the procedures described by the International Standards. An appropriate preparation of the specimens represents a fundamental step of the whole material testing process. Here below you will find some equipments offered by Matest for your sampling preparation:

• Two or Three gang prism moulds of different dimensions for soundness and shrinkage test
• Jolting Apparatus to compact cement mortar prisms
• Manual and Automatic Mortar Mixers and Computerized Mortar Mixer “Mixmatic”
• Water Baths for cement curing
• Large capacity curing cabinet