Physics testing (forged and grinding resistance) and chemical tests (such as chlorides, fire losses) are performed at the Cementos Barrero SA Laboratory.
The Physical laboratory is responsible for carrying out mechanical strength, setting and volume stability tests to check the quality of the cement produced and further research tests are also conducted carrying out milling in the Bond grinding mill.
- Mechanical resistance: To produce the mixed mortar samples one part cement and three parts normalized sand are mixed in a kneading machine, in mass and with a water / cement ratio of 0.50.
- The mortar is prepared by mechanical kneading and compacted in a mold using a standard roller.
The mold is kept in a humid atmosphere for 24 hours and when it is demolded, the test tubes are immediately immersed in buckets filled with water in a moist chamber at a temperature of 20 ° C ± 1 ° C and relative humidity not below 90% until the moment of strength tests.
The specimens are removed from their wet conservation means and are broken at 1, 2, 7 and 28 days to study the hardening curve (according to standard, cements we manufacture break at 2 and 28 days).
It is taken to the breaking machine and specimens are broken at the bending zone into two halves and each part is subjected to compression tests in the compression zone obtaining the resistance value of each cement study measured in MPa.
- Hardening: This test determines the initial and end setting time of a paste made with Portland cement. The test involves filling a cement mold, the surface is smoothed and placed in a device with features previously defined in the UNE-EN 196-3 and the penetration of the probe into the mold is measured, where the test is considered valid when penetration is of (6 ± 1) mm and thus know the normal consistency of the cement. To determine the start of setting the mold is filled with the above paste, taken to the humidity chamber, the Vicat apparatus is calibrated and the penetration test is repeated until the needle is introduced (4 ± 1) mm.
And to determine the end of the setting the previous mold is reversed on its base plate and time is recorded with an accuracy of 15 minutes, it records the time from time zero and when the needle only penetrates 0.5 mm in the pulp. The value obtained is the end of the setting time.
- Volume stability: is determined by observing the volumetric expansion of the standard consistency cement paste, indicated by the relative displacement of two needles.
- Grindings: raw materials such as clinker, fly ash and slag, etc. are studied and cement is manufactured in a Bond mill we have in the laboratory to study the mechanical properties, the setting of manufactured cement and chemical composition to assess whether it is suitable or not for use in production.
The chemical laboratory is responsible for carrying out a series of checks on raw materials (clinker, limestone and gypsum), the intermediate product (process) and the finished product (bulk bag) to ensure it meets quality standards set by Cementos Barrero to satisfy all its customers and in turn meet the standards for the manufacture of Portland cement.
- Control of raw materials: these components must be keept track of, as they have a decisive influence on the quality of the final product. Reception control is carried out as well as monitoring the quality of our suppliers. A summary of studies carried out on raw materials and their frequency are shown in the table below:
Humidity Fire Losses RX Free lime Sulfates Methylene blue Clinker (*) (*) (*) (*) —– —– Limestone 1/day 1/day 1/day —— —– 1/week Gypsum 1/day —— 1/day —— 1/week —–
(*) Every day.
- Process control:
Fineness RX Resistance Every two hours in production Every day Every day
- Control of the finished product: a summary of all the tests performed on finished products as is standard are shown in the following table:
Property Testing methods Frequency normal period Initial resistance (2d) EN 196-1 2 trials/ week Normal Resistance (28d) EN 196-1 2 trials/ week First setting EN 196-3 2 trials/ week Final setting EN 196-3 2 trials/ week Volume stability EN 196-3 2 trials/ week Content on SO3 EN 196-2 2 trials/ week Content on chlorides EN 196-21 1 trials/ week Composition UNE 80216:1991 1 trials/ week Chrome UNE-EN 196-10 2 trials/ week
To reduce any feedstock we have a jaw crusher which supports particle sizes up to 90mm.
In the laboratory, there is a muffle furnace (reaches a temperature up to 1200° C) for calcining the samples and obtaining fire losses.
We have a RX fluorescence spectrometer that measures up to 11 elements and is calibrated for all raw materials and cement, thus you can know the composition of the sample more quickly than if we test via analytica.
Weekly it is verified by employers if the equipment has altered and also monthly analytical analysis of raw materials and cement are made to verify that the equipment is measuring correctly.
The fineness of the cements is determined in the laboratory by Permeability Blaine. We have two, one manual and other automatic. The fineness of cement is measured as specific surface, by observing the time it takes a fixed amount of air to pass through a compact layer of cement with specified dimensions and porosity.
In the control room we have a particle size analyzer, it lets us know the size distribution of the sample in question, in the range 0020-2000 microns.
We have also acquired a UV spectrophotometer for the determination of chromium (VI), which can cause allergic reactions in certain circumstances when human skin is in direct and prolonged contact with the cement, so the cement is analyzed daily to check that the levels of chromium are less than 2 ppm.