Cement 1 #

CEMENT

OVERVIEW  A cement is a binder, a binder, a  a substance that sets and hardens as the cement dries and also reacts with carbon dioxide in the air dependently, and can bind other materials together. The word "cement" traces to the Romans, the Romans, who  who used the term opus caementicium to describe masonry describe masonry resembling modern concrete modern concrete that was made from crushed rock with burnt lime burnt lime as binder. The volcanic The volcanic ash and pulverized brick pulverized brickadditives additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum , cäment , and cement . Cements used in construction can be characterized as being either hydraulic ornon-hydraulic, depending upon the ability of the cement to be used in the presence of water (see  hydraulic and non-hydraulic lime plaster). plaster). Non-hydraulic cement will not set in wet conditions or underwater, and is attacked by some aggressive chemicals after setting. Hydraulic cement is made by replacing some of the cement in a concrete mix with activated aluminium silcates, pozzolanas, silcates, pozzolanas, such  such as fly ash, to activate cement setting in wet condition or underwater and further protects hardened concrete from chemical attack. (e.g., Portland cement) hardening cement) hardening because of  hydration.  hydration. The chemical process for hydraulic cement found by ancient Romans used volcanic ash (activated aluminium silicates), to activate cement hardening between theanhydrous theanhydrous cement powder and water or plaster and water instead of relying on water drying out and simultaneously reacting with airborn carbon dioxode. Presently cheaper, pollution free fly ash from power stations or other waste or by products are used as pozzolanas with plain cement to produce hydraulic cement. Pozzolanas can replace up to 40% of Portland cement. Thus, cement can harden underwater or when constantly exposed to wet weather. The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water and from chemical attack. Non-hydraulic cements and plasters do not harden in wet conditions. The most important uses of cement are as an ingredient in the production of  mortar of  mortar in masonry, and of  concrete, a  concrete, a combination of cement and an aggregate an  aggregate to form a strong building material. Types of cement and its uses 1. Ordinary Portland Cement

It is used in general construction works. All other varieties of Cement are derived from this Cement.

White Cement

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OPC with with pure white color color produced with white chalk or clay free from iron oxide.

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Instead of coal, oil fuel is used for burning.

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Much more costlier than OPC.

Colored Cement

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Suitable pigments used to impart desired color.

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Pigments used should be chemically inert and durable under light, sun or weather.

2. Modified Portland Cement

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This cement on setting develops less heat of generation than OPC.

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It is best suited in hot climate for civil works construction.

3. Rapid Hardening or High Early Strength Cement (Type III) Gains strength faster than OPC. In 3 days develops 7 days strength of OPC with same water cement

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ratio. 

After 24 hours – not less than 160 kg/cm2

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After 72 hours – not less than 275 kg/cm2

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Initial and final setting times are same as OPC.

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Contains more tri-calcium silicate (C3S) and finely ground.

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Emits more heat during setting, therefore unsuitable for mass concreting.

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Lighter and costlier than OPC. Short curing period makes it economical.

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Used for structures where immediate loading is required e.g. repair works.

4. Quick Setting Cement

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Sets faster than OPC.

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Initial setting time is 5 minutes.

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Final setting time is 30 minutes.

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Used for concreting underwater and in running water.

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Mixing and placing has to be faster to avoid initial setting prior to laying.

5. Low Heat Cement Low percentage (5%) of tri-calcium aluminates (C3A) and silicate (C3S) and high (46%) of di-calcium

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silicate (C2S) to keep heat generation low. 

It has low lime content and less compressive strength.

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Initial and final setting times nearly same as OPC.

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Very slow rate of developing strength.

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Not suitable for ordinary structures. 

Shuttering required for long duration so cost will increase.

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Prolonged curing is required.

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Structure utilization will be delayed.

6. Sulphate Resistant Portland Cement

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Percentage of tri-calcium Aluminate (C3A) is kept below 5% resulting in increase in resisting power against sulphates.

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Heat developed is almost same as Low Heat Cement.

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Theoretically ideal cement. Costly manufacturing because of stringent composition requirements.

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Used for structures likely to be damaged by severe alkaline conditions like bridges, culverts, canal lining, siphons, etc.

7. Water Repellent Portland Cement

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It contains a small percentage of water-proofing material with the cement and is manufactured under the name “Aqua-crete”.

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The cement is prepared with ordinary or rapid hardening cement and white cement.

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It is used in to check moisture penetration in basements etc.

8. Water Proof Portland cement

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It is prepared by mixing ordinary or rapid hardening cement and some percentage of some metal stearate ( Ca, Al etc).

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It is resistant to water and oil penetration.

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It is also resistant to acids, alkaline and salt discharged by industrial water.

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It is used for water retaining structure like tanks, reservoir, retaining walls, pool, dam etc

9. High Alumina Cement

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Black chocolate color cement produced by fusing bauxite and limestone in correct proportion, at high temperature.

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Resists attack of chemicals, Sulphates, seawater, frost action and also fire. Useful in chemical plants and furnaces.

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Ultimate strength is much higher than OPC.

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Initial setting time is 2 hours, followed soon by final setting.

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Most of the heat is emitted in first 10 hrs. Good for freezing temperatures in cold regions (below 18°C).

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Develops strength rapidly, useful during wartime emergency.

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Unsuitable for mass concrete as it emits large heat on setting.

10. Portland Slag Cement

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Produced by mixing Portland cement clinker, gypsum and granulated blast furnace slag.

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Cheaper than OPC, blackish grey in color.

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Lesser heat of hydration. Initial setting in 1 hr and final setting 10 hrs.

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Better resistance to soil agents, sulphates of alkali metals, alumina, iron and acidic waters.

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Suitable for marine works, mass concreting.

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Due to low early strength, not suitable for RCC.

11. Air Entraining Cement

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OPC with small quantity of air entraining materials (resins, oils, fats, fatty acids) ground together.

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Air is entrained in the form of tiny air bubbles during chemical reaction.

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Concrete is more plastic, more workable, more resistant to freezing.

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Strength of concrete reduces to some degree.

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Quantity of air entrained should not be more than 5% to prevent excess strength loss.

12. Portland Pozzolana Cement

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OPC clinker and Pozzolana (Calcined Clay, Surkhi and Fly ash) ground together.

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Properties same as OPC.

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Produces less heat of hydration and offers great resistance to attacks of Sulphates and acidic waters.

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Used in marine works and mass concreting.

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Ultimate strength is more than OPC but setting timings are same as OPC.

13. Supersulphated Cement

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Initially, not less than 70 per cent finely ground blast furnace slag, Calcium Sulphate and a small quantity of ordinary Portland cement or Portland cement clinker.

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It is finer than ordinary Portland cement.

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Its physical and other properties are almost same as are of ordinary Portland cement except the heat of hydration which is considerably lower.

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It is a slag cement and is resistant to majority of chemicals found in construction industry. It is also resistant to Sulphate attack.

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It is used in:

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Marine Structures.

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Mass concrete works subjected to aggressive waters.

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Reinforced concrete pipes in ground water.

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Concrete construction in Sulphate bearing soils.

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In factories where concrete is exposed to highly concentrated Sulphates.

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Construction of concrete sewers carrying industrial effluents.

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Underside of railway bridges.

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Under tropical conditions, its use is recommended only below 40`C.

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Can be used as a general purpose cement with adequate precautions.

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It should never be used for casting „steam cured concrete‟ products.

14. Masonry Cement

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Unlike ordinary cement, it is more plastic.

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Made by mixing hydrated lime, crushed stone, granulated slag or highly colloidal clays are mixed with it.

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Addition of above mentioned materials reduces the strength of cement.

15. Expansive or Expanding Cement

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The main difference in this cement is the increase in volume that occurs when it settles.

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Used to neutralize shrinkage of concrete made from ordinary cement so as to eliminate cracks. A small percentage of this cement with concrete will not let it crack. It is specially desirable for hydraulic structures.

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In repair work, it is essential that the new concrete should be tight fitting in the old concrete. This can be done by using this cement

16. Other Varieties

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High Alumina Cement  –  alumina cement is an inorganic material that form a dense texture when it reacts with water. It has excellent refractoriness, quick hardening and resistance to chemical attacks. Our high alumina cement is widely used for the production of high quality refractory castables and other special materials. It is made from bauxite and limestone with high temperature fusion process

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Blast Furnace Slag Cement - is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder.

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Hydrophobic Cement - other filler together with an air-entraining agent or a water-repellent additive. Waterproof cement is the name given to a portland cement to which a water-repellent agent has been added. Hydrophobic cement is obtained by grinding portland cement clinker with a film-forming substance such as oleic acid in order to reduce the rate of deterioration when the cement is stored under

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Oil-well Cement - Oil-well cements are used for cementing work in the drilling of oil wells where they are subject to high temperatures and pressures. They usually consist of portland or pozzolanic cement

HOW CEMENT IS MADE, MACHINE USED, MATERIALS

https://www.youtube.com/watch?v=woaUs5XnjUo - PROCESS dump truck- is a truck used for transporting loose material (such as sand, gravel, or  dirt) forconstruction. A typical dump truck is equipped with an open-box bed, which is hinged at the rear and equipped with hydraulic pistons to lift the front, allowing the material in the bed to be deposited ("dumped") on the ground behind the truck at the site of delivery. crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust SECONDARY CRUSHER PROPORTIONING EQUIPMENTGRINDING MILL

SLINKER COOLER

PROPORTIONING EQUIPMENT AND FINISH GRINDING MILL CEMENT STORAGE

SHIPPING

CEMENT PRODUCERS TOP 20 IN THE WORLD Rank

Company/Group

Country

Capacity (Mt/yr)

No. of plants

1

Lafarge

France

225

166

2

Holcim

Switzerland

217

149

3

CNBM

China

200

69

4

Anhui Conch

China

180

34

5

HeidelbergCement

Germany

118

71

6

Jidong

China

100

100

7

Cemex

Mexico

96

61

8

China Resources

China

89

16

9

Sinoma

China

87

24

10

Shanshui

China

84

13

11

Italcementi

Italy

74

55

12

Taiwan Cement

Taiwan

70

-

13

Votorantim*

Brazil

57

37

14

CRH**

Ireland

56

11

15

UltraTech

India

53

12

16

Huaxin

China

52

51

17

Buzzi

Italy

45

39

18

Eurocement

Russia

40

16

19

Tianrui

China

35

11

20

Jaypee***

India

34

16

IN THE PHILS 1. LAFARGE (MAKATI CITY) 2. CEMENTAID PHILIPPINES INC. (BICUTAN) 3. KINGSTONE STUCCO 4. PACIFIC CEMENT PHILIPPINES INCORPORATED (MAKATI CITY) 5. TAIHEIYO CEMENT PHILIPPINES INC. (CEBU) HISTORY OF CEMENT

Throughout history, cementing materials have played a vital role. They were used widely in the ancient world. The Egyptians used calcined gypsum as a cement. The Greeks and Romans used lime made by heating limestone and added sand to make mortar, with coarser stones for concrete.

The Romans found that a cement could be made which set under water and this was used for the construction of harbours. The cement was made by adding crushed volcanic ash to lime and was later called a "pozzolanic" cement, named after the village of Pozzuoli near Vesuvius. In places such as Britain, where volcanic ash was scarce, crushed brick or tile was used instead. The Romans were therefore probably the first to manipulate the properties of cementitious materials for specific applications and situations.

Hadrian's Wall, England, a few miles east of Housesteads.

Marcus Vitruvius Pollio, a Roman architect and engineer in the 1st century BC wrote his "Ten books of  Architecture" - a revealing historical insight into ancient technology. Writing about concrete floors, for example: "First I shall begin with the concrete flooring, which is the most important of the polished finishings, observing that great pains and the utmost precaution must be taken to ensure its durability". "On this, lay the nucleus, consisting of pounded tile mixed with lime in the proportions of three parts to one, and forming a layer not less than six digits thick." 

 And on pozzolana: "There is also a kind of powder from which natural causes produces astonishing results. This substance, when mixed with lime and rubble, not only lends strength to buildings of other kinds, but even when piers are constructed of it in the sea, they set hard under water." 

(Vitruvius, "The Ten Books of Architecture," Dover Publications, 1960.) His "Ten books of Architecture" are a real historical gem bringing together history and technology. Anyone wishing to follow his instructions might first need to find a thousand or so slaves to dig, saw, pound and polish...  After the Romans, there was a general loss in building skills in Europe, particularly with regard to cement. Mortars hardened mainly by carbonation of lime, a slow process. The use of pozzolana was rediscovered in the late Middle Ages. The great mediaeval cathedrals, such as Durham, Lincoln and Rochester in England and Chartres and Rheims in France, were clearly built by highly skilled masons. Despite this, it would probably be fair to say they did not have the technology to manipulate the properties of cementitious materials in the way the Romans had done a thousand years earlier. The Renaissance and Age of Enlightenment brought new ways of thinking, which for better or worse, led to the industrial revolution. In eighteenth century Britain, the interests of industry and empire coincided,

with the need to build lighthouses on exposed rocks to prevent shipping losses. The constant loss of merchant ships and warships drove cement technology forwards. Smeaton, building the third Eddystone lighthouse (1759) off the coast of Cornwall in Southwestern England, found that a mix of lime, clay and crushed slag from iron-making produced a mortar which hardened under water. Joseph Aspdin took out a patent in 1824 for "Portland Cement," a material he produced by firing finely-ground clay and limestone until the limestone was calcined. He called it Portland Cement because the concrete made from it looked like Portland stone, a widely-used building stone in England. While Aspdin is usually regarded as the inventor of Portland cement, Aspdin's cement was not produced at a high-enough temperature to be the real forerunner of modern Portland Cement. Nevertheless, his was a major innovation and subsequent progress could be viewed as mere development.  A ship carrying barrels of Aspdin's cem ent sank off the Isle of Sheppey in Kent, England, and the barrels of set cement, minus the wooden staves, were later incorporated into a pub in Sheerness and are still there now.  A few years later, in 1845, Isaac Johnson made the first modern Portland Cement by firing a mixture of chalk and clay at much higher temperatures, similar to those used today. At these temperatures (1400C1500C), clinkering occurs and minerals form which are very reactive and more strongly cementitious. While Johnson used the same materials to make Portland cement as we use now, three important developments in the manufacturing process lead to modern Portland cement: - Development of rotary kilns - Addition of gypsum to control setting - Use of ball mills to grind clinker and raw materials Rotary kilns gradually replaced the original vertical shaft kilns used for making lime from the 1890s. Rotary kilns heat the clinker mainly by radiative heat transfer and this is more efficient at higher temperatures, enabling higher burning temperatures to be achieved. Also, because the clinker is constantly moving within the kiln, a fairly uniform clinkering temperature is achieved in the hottest part of the kiln, the burning zone. The two other principal technical developments, gypsum addition to control setting and the use of ball mills to grind the clinker, were also introduced at around the end of the 19th century.

SIGNIFICANCE OF PRODUCT TESTING IN CEMENTS There are many ways and methods for the testing of cement. Some of them need a proper laboratory setup while other can be conducted at field itself. For the sake of convenience we will divide the methods under following two categories as (i) Tests in Field and (ii) Tests in Laboratory. Tests in Field Field tests are convenient way of primary inspection of cement when it is used in small scale works or when decision has to be made during purchase process. These are some of the steps that can ensure you good quality cement while inspection at site-

a) First cement bags should be open a little wide for visible inspection. There should not be any lumps formation inside the bag. b) Put your hand inside the bag and ensure additionally that there are not any hidden lumps. Also this activity should give u a feel of cool sensation on your hands. c) Take a sample of cement in your hand and rub it in between your fingers. It should be smooth in nature. d) Take another handful sample of cement and throw it in the bucket full of water. Particles of cement should float a while before sinking down. Tests in Laboratory Field tests only indicate that cement is not bad and can be used for small scale works. Thus Laboratory tests are necessary to confirm that cement is good in nature and can even be used for important works too. Following tests are necessary to be conducted on cement in laboratorya)

Fineness Test-The fineness of cement can be defined as the measure of size of particles of cement or in simple form “Specific Surface of Cement”. This test is usually carried out using IS sieve no.9 or 90 microns. b) Setting Time Test- Cement when mixed with water triggers a process which results in a hardened mass of mixture wherein hardness gradually increases with time. There are two setting times for cementInitial Setting Time (IST) or Final Setting Time (FST).It is tested using Vicat‟s Apparatus. Eg. For Portland Cement IST is around 30 mins and FST is around 600 mins. 2

c) Strength Test- The strength of cement is defined in MPa or N/mm . For grade 33 Portland cement, strength should be around 33MPa in 28 days. Compression test is carried out to check the strength of cement. d) Soundness Test- Soundness of cement can be defined as a process in which cement does not show any considerable change in volume after setting. Autoclave tests and Le Chateleir tests care carried out to check the soundness of cement. e) Heat of Hydration Test- The heat of hydration can be defined as heat from cement paste liberated as a reaction of water with cement. This test is usually carried out in thermos flask. f) Chemical Composition Test- A test is carried out on cement that tests the ratio of chemicals in the cement. Different standards and codes specify different value of such ratios.  A standard oxide and chemical composition of Portland cement is as given belowChemical Compound

Percentage

Lime, Cao

60-66

Silica, Sio2 

17-25

 Alumina,Al2O3 

3-8

Iron Oxide, Fe2O3 

0.5-6

Magnesia, MgO

0.5-4

Sulphur trioxide, SO3 

1-2

 Alkalis

0.5-1.3

Four main compounds that are present in cement and percentage of which decides (one of the parameter) the quality of cement are as follows1.

Tricalcium Silcate

2.

Dicalcium Silicate

3.

Trialcium Aluminate

4.

Tetracalcium Alumino Ferrite

News for the cement industry

Lafarge Republic launches ash-based cement Wednesday 14 May 2014

Philippines:  Lafarge Republic and the Global Business Power Corporation (GBPC) has launched an

initiative aimed to lower the costs of rehabilitation projects, such as the rebuilding efforts for Yolanda and the Bohol earthquake-affected areas, through the introduction of a ash-based cement called called KapitBalay cement. Kapit-Balay cement is a result of the Total Ash management partnership between Lafarge Republic and GBPC. Under this collaboration, Lafarge uses the fly ash from GBPC's power generation processes to produce blended cement. Under the partnership, the two companies worked on optimising the cost of producing the ash-cement, which enables them to contribute in lowering the overall cost of rebuilding with the additional support from Lafarge's packaging partner and a direct sales distribution model to rehabilitation projects

Post-typhoon rebuilding drives Philippines cement sales in Q1 Wednesday 30 April 2014

Philippines:  Cement sales rose by 8.6% in the first quarter of 2014. The surge was largely driven by

rebuilding following the destruction wrought by typhoon Haiyan in November 2013, according to the Cement Manufacturers Association of the Philippines (CEMAP). Cement producers sold 5.2Mt of cement in the first quarter of 2014 compared to 4.8Mt in the same period in 2013. "The increase was primarily due to reconstruction efforts following super-typhoon Haiyan," said CEMAP president Ernesto Ordoñez in a phone interview with local media. He added that rebuilding is likely to drive cement sales for 'more than a year' and that private sector confidence was also helping sales. Following typhoon Haiyan the government of the Philippines raised its budget for infrastructure in 2014 by 37% to US$9bn from US$6.6bn in 2013 to provide for rehabilitation and reconstruction in areas affected by the typhoon. In 2013 sales by the local cement industry grew by 6% to 19.4Mt/yr from 18.4Mt/yr in 2012

Some safety practices The risk assessments should contain the following: x The location of the plant or equipment x The work to be done x List of the hazards identified x List of the precautions taken x Personal Protective Equipment that should be worn x Issuer of Permit and length of time permit is valid for Cembureau, BIBM, ERMCO, FIEC, December 2002 x The producers should clearly indicate the potential risk and the means of protection against cement dermatitis by appropriate labeling and Material Safety Data Sheets. x The contractors (employers) should provide adequate information and related operational instructions to workers about potential risks when dealing with cement preparations. x The contractors (employers) should provide adequate protective equipment (e.g. special Chromium VI-free gloves, boots etc.) x The workers should effectively follow the instructions received and use the protective equipment correctly NOTE: SAFETY PRECAUTIONS OF SOME COMPANIES WOULD BE INSERTED HERE. SOURCE IS FROM A HANDOUT FROM THIS LINK http://www.wbcsdcement.org/pdf/HAS/tf3_guidelines.pdf  pg 51-onwards LINKS LINKS/SOURCE Cement overview en.wikipedia.org/wiki/Cement General reference http://webcache.googleusercontent.com/search?q=cache:http://www.epa.gov/osw/nonhaz/industrial/ special/ckd/rtc/chap-2.pdf Types of cement http://cescientist.com/types-of-cement/ http://webcache.googleusercontent.com/search?q=cache:http://www.horizonrefractories.com/highalumina-cement.html http://en.wikipedia.org/wiki/Ground_granulated_blast-furnace_slag http://www.britannica.com/EBchecked/topic/278977/hydrophobic-cement http://www.britannica.com/EBchecked/topic/426264/oil-well-cement HOW IS IT MADE http://en.wikipedia.org/wiki/Dump_truck http://en.wikipedia.org/wiki/Crusher HISTORY http://www.understanding-cement.com/history.html TRIVIA http://www.globalcement.com/magazine/articles/741-top-20-global-cement-companies http://panpages.ph/categories/ph10218-cement-suppliers-manufacturers/listings

news http://www.globalcement.com/news/itemlist/tag/Philippines safety http://www.wbcsdcement.org/pdf/HAS/tf3_guidelines.pdf pg 51-onwards Images/ video source http://www.travisperkins.co.uk/webimage/300000/380000/381000/381491-800.jpg http://www.steelmanreef.co.uk/images/stories/cement2.jpg http://www.scg-trading.com/upload/images/product/white_cement.jpg http://precast.org/wp-content/uploads/2011/05/Precast-Pigments.jpg http://www.sitcoindia.com/wp-content/uploads/2013/08/cement.jpg http://www.aso-cement.jp/en/products/img/pict_product_early02.jpg http://3.bp.blogspot.com/-XCXZPqnhqfE/TyvSTrYGJ-I/AAAAAAAAAEE/wXquKgh6Pzc/s1600/ultra-highearly-strength-sulfoaluminate-CSA-cement-4784_image.jpg http://www.mastour.com/blog/wp-content/uploads/2012/12/Quick-setting-cements.jpg http://spgroup.ie/media/catalog/product/cache/4/image/400x300/9df78eab33525d08d6e5fb8d27136e95/f/i/f  ile_44_4_2.jpg http://img.diytrade.com/cdimg/108044/24628397/0/1329126208/Lowheating_Portland_Cement_for_volume_concrete_HBC.jpg http://www.cementaustralia.com.au/wps/wcm/connect/website/packagedproducts/resources/7571a38045a02de0b39dbf6685a73cbc/Low-Heat-Cement.png http://www.cementaustralia.com.au/wps/wcm/connect/website/packagedproducts/resources/695f3a0045a04576b3c3bf6685a73cbc/Sulfate-Resisting-Cement.png http://2.imimg.com/data2/QJ/JX/IMFCP-1896254/sulphate-resistant-cement-815925-250x250.jpg http://3.imimg.com/data3/QQ/RY/MY-2842757/water-proof-repellent-cement-250x250.jpg http://2.imimg.com/data2/XY/UU/IMFCP-3353370/sikagard-water-repellent-coating-250x250.jpg http://www.ukroofingsupplies.co.uk/19-68-large/flexible-damp-proofer-and-waterproofer.jpg http://3.imimg.com/data3/TD/GS/MY-6530119/waterproof-coatings-250x250.jpg http://2.imimg.com/data2/KP/EN/MY-3609678/high-alumina-cement-250x250.jpg http://2.imimg.com/data2/YQ/PN/MY-2329187/portland-slag-cement-250x250.jpg http://www.cement.org/images/default-source/contech/construction/air_entrained.jpg?sfvrsn=2 http://sakthicements.com/img/psc.jpg http://2.imimg.com/data2/KY/QI/OLFCP-4171687/1136_2011-09-24_161-250x250.jpg http://www.ibk.ethz.ch/fo/research/FireSafety/Klingsch2/Betonabplatzen http://www.sakrete.com/uploads/products/Type_S_masonry_cement3.jpg http://2.imimg.com/data2/AA/UN/MY-2397283/cement-250x250.jpg http://i01.i.aliimg.com/img/pb/373/458/500/500458373_628.jpg http://image.made-in-china.com/43f34j00TvJaSqwILBpC/High-Alumina-Cement-325-Mesh-CA50-G7-.jpg http://sunriseassociatesindia.com/customer/images/big/BM-07.jpg http://2.imimg.com/data2/VR/IR/MY-3370100/cement-250x250.jpg http://www.my.all.biz/img/my/catalog/24344.jpeg HOW CEMENT IS MADE http://d-build.org/blog/wp-content/uploads/2010/11/cement-making460x333.gif https://www.youtube.com/watch?v=woaUs5XnjUo