From mountains to microns. (1959)

[Music] this is the story of Portland cement the most useful and most widely used of all the world's building materials oddly enough unless you watch a construction job closely or our do-it-yourself builder around the house you rarely see Portland cement by itself but concrete which cement is the essential ingredient has so many different and important uses in such a variety of shapes and sizes that this fine powdery material is part of your life and is working for you every day for example you may live in an attractive house built of concrete block or a tall apartment building when you travel from one place to another you ride over miles of concrete highways under dozens of concrete overpasses and sometimes over high bridges spanning gorges between mountains at night you stay either at a multi-story hotel or in one of the hundreds of motels along the route either of which may be built of concrete wherever you look you see fire safe concrete protecting children in schools patients in great hospitals and worshipers in chapels churches and synagogues concrete houses industry banks and offices stores and shopping centers underneath our cities thousands of miles of concrete pipeline carry domestic and industrial wastes dangerous racing rivers are harnessed by locks and dams converting them into deep water ways for ocean-going ships huge concrete tetrapods weighing up to 31 tons each locked together to protect eroding shorelines from waves of great height and violence great dams protect thousands of square miles from floods the stored water is used in making electricity for home and industry or provides a steady source of precious water for irrigation irrigation facilities feeding floors silos and buildings of concrete have cut farm losses and reduced the drudgery of farm labor a thin slab of concrete takes you from your home to the corner store the biggest Jets take off or land on long heavy-duty concrete runways and now when you shake off the earth and head for outer space you blast off from a massive concrete launching pad what is this concrete that has so many forms and uses and why do so many people everywhere use it in the first place it is made of a few simple inexpensive materials gravel or crushed rock sand and water all of which you recognize as the most abundant materials on the face of the earth and Portland cement a manufactured product made of the commonest elements found in the Earth's crust when these materials are properly proportioned and mixed they form an easily workable mass which can be molded into any shape or form useful in construction [Music] when concrete cures it forms a mass harder and more durable than any of the materials that went into it it took a million pounds of pressure developed by this huge compression machine to break this concrete cylinder and you will notice that the breaks occurred right through the rocks and not around what happens when concrete cures and become so hard nothing much has happened to the stone and the sand except that they are rather evenly distributed but where is the water in the cement some of the water is evaporated but lots of it has combined with the cement to form a new substance called cement water paste which entirely surrounds every stone and every grain of sand and binds them together so Portland cement is the essential ingredient of concrete it is the only difference between water packed dry soil and solid concrete the most noticeable characteristic of Portland cement is that it's a very fine fluffy powder it may be various shades of grey and for special uses such as making paints and color products it may be pure white but the notable characteristic is still its finest I can truthfully say that cement is finer than the most expensive face powder and that several thousand particles of cement would not be overcrowded on the head of a pin but the fact is no one ever saw a particle of cement until the electron microscope came along to make it possible to magnify microns up to visibility for a particle of Portland cement is measured in microns 125 thousandths of an inch and this spoon contains millions of them this fineness is important because in concrete the cement water paste must entirely surround every stone and every grain of sand in order to bind together the mass of granular materials and obtaining this fineness is one of the major processes in making Portland cement the two principal elements combined in Portland cement are calcium and silica these are obtained from raw materials limestone beds of marl shale clay chalk and old oyster beds all of which must be extracted from thick deposits in mountains hills ledges underground mines or from the bottom of the ocean it takes 3,200 pounds of these raw materials to make a single ton of cement so the manufacture of Portland cement is literally a job of reducing mountains to micron sized particles making Portland cement is a precise chemical process which follows four basic steps gathering the raw materials crushing and grinding them to powder burning them and then grinding the burned materials to a superfine powder this process is employed the world over for Portland cement is not a brand name but a type of cement it was given that name by its inventor Joseph's husband in 1824 because he thought that the concrete made from his new cement resembled a natural building stone quarried on the Isle of Portland off the coast of England most cement plants are located near their supply of raw materials which may be open faced quarries deep mines beds of clay or Mauro or old shale deposits some Mills purchase rock from more distant quarries or shale from commercial dredges these are brought to the plant by rail and by barge most frequent sources of raw materials are open-faced quarries and thick deposits of limestone and shale that have lain in the earth for millions of years these materials must be loosened from their ledges by boring vertical shafts from the top and charging them with explosive each multiple blast drops thousands of tons of rock onto the quarry floor in size is suitable for transporting to the raw material storage areas large heavy-duty trucks loaded by great shovels are commonly used to move loose rock to the plan fleets of these trucks operate continuously until the quarry floor is cleared for the next blast rock from the quarry is usually dumped directly into primary crushers which reduce the material to sizes suitable for storage and handling primary crushers smash boulders the size of pianos into pieces the size of baseballs these are then fed into a secondary crusher which reduces all raw materials to a size not exceeding 3/4 of an inch the crushed rock is now moved into a large storage area where each kind of raw material to be used in making cement is stored separately a plant usually keeps from several days to several weeks apply on hand to assure continuous operation plant chemists continuously analyze each of the raw materials entering the mill thus whatever the materials may be they know the proper proportion of limestone shale marl shale slag or silica sand that must be combined to enter the next critical step in manufacture which is raw grinding or preparation of the materials for burning there are two methods of preparing the raw materials for Berney one is called the dry process the other the wet process some cement mills use one process on the other but the purpose of both is the same to grind the materials to a fine powder and to blend the various kinds of materials to be used so that they're thoroughly mixed a properly proportioned mixture is essential to affect the desired chemical changes in the kill in the dry process raw materials are taken from storage loaded into hoppers in previously determined proportions and charged into a rotating ball mill in this mill hundreds of steel balls carried up the side of the cylinder fall back into the constantly turning raw materials this action accomplishes preliminary grinding the material then passes into other rotating mills called tube mills where thousands of smaller steel balls grind the material to the finest required for the burning process in many plants ball and two mills are combined in so-called compartment mills the fine ground raw materials from which samples have been taken for testing are now pumped or carried by conveyors to a battery of huge storage silos here supply sufficient for several days of mill operation are always kept on hand in the wet process raw materials are charged into a ball mill but now water is added in the ratio of 35% water to 65% dry materials to form a creamy mixture called slurry the slurry passes through two bore compartment mills for fine grinding and is then pumped into a series of mixing tanks here samples are taken for laboratory analysis [Music] agitate er is thoroughly mixed the slurry aided by air blown in from the bottom of the tank now predetermined amounts of slurry from various mixing tanks are pumped into blending tanks the color-coded pipelines indicate the number of different slurry mixes that may need to be combined to produce the desired chemical combination the blended slurry is then pumped into large storage tanks to await burning the third and we'll spectacular process in making cement from this point on the wet and dry processes are identical the dry powder or the slurry has been carefully analyzed in the plant laboratory and the materials are ready to be fed into the kiln made of steel and lined with firebrick to withstand the intense heat the rotary kiln is the largest piece of moving machinery used in any industry some kilns are over 500 feet long longer than a 40-story building is high the kiln slopes downward from the feed intake toward the end where the hot product is discharged dropping about half an inch for every foot of its length it rotates about once a minute thus exposing all of the raw materials evenly to flames that reach temperatures of 2700 degrees every few minutes enough coal oil or natural gas is consumed in each kiln to heat an average home for several days operation of the kiln is carefully controlled through every minute of its 24 hour per day operation a panel of 20 or more instruments indicate temperature at various areas in the kiln speed of kiln rotation rate of fuel consumption draft production rate and other vital information the operator may also visually check the progress of materials through the kiln by means of a specially constructed port near the hot end during heating the materials passed through a spectacular range of color changes from glowing violent to red to white-hot incandescent here is where the chemical transformation of raw materials into new useful compounds takes place during the four hours required to pass through the kiln the calcium silicates illuminates and other compounds are formed that give Portland cement its binding ability and strength when the heated material emerges from the end of the kiln it appears in the form of red hot marble sized glass hard balls called clinker the next step is to cool the clinker by passing it through one of several types of cooling devices heat given off by cooling the clinker is returned to the kiln to save fuel and improve burning efficiency outside the kilns at the stacks additional complex equipment plays a silent but important role here giant electrostatic precipitators remove dust and fumes from the waste heat releasing cleaned exhaust heat into the air around the plant when cooled the clinker may be removed to storage shipped to another plant for grinding or passed directly into the fourth and final stage of cement making fine grinding the final stage in the manufacture of Portland cement is the fine grinding that reduces the clinker to a powder made up of particles the size of microns this process employs some of the same massive moving equipment that has been used in previous processing steps before final grinding a small quantity of gypsum is added to the clinker this aids in regulating the setting time when the cement is used in making concrete now the clinker is charged in two rotating ball and tube mills where thousands of steel balls grind the material to the superfine powder that is Portland cement in some Mills the ground material is passed through separators in which air is used to carry away the fine material returning coarser particles for additional grinding the cement is now so fine that it will pass easily through a sieve with 40,000 openings per square inch throughout the final process the freshly ground cement is tested every 60 minutes to assure a product that will make concrete of uniform strength and durability when mixed according to applicable specifications from the grinding mills the cement is pumped into batteries of tall silos very distorted awaiting shipment at the base of each silo is a tract on which a mobile cement pump can be moved from silo to silo giving the manufacturer easy access to all the cement in storage this pump sends the cement to the packing and loading area where it is prepared for shipment by various means of transportation much the mat is put into bags for shipping this is done by semi-automatic machines which fill and seal a 94 pound bag of cement in three seconds each bag of cement is one cubic foot a convenient measure later on when properly mixing cement sand gravel and water to make concrete the heavy paper bags have self sealing valves which are closed by the weight of the cement as the bag drops away from the machine large quantities of cement are shipped by railroad much of it in bulk in a specially designed hopper bottomed cars this car loader can fill a cement car in a few minutes any dust resulting is removed by a special device and returned to the storage silo increasing amounts of bulk cement are now being shipped directly to job sites by transport trucks these are loaded at the storage silos by overhead equipment similar to that used in railcar loading where plants are located near waterways large quantities of cement are transported by ship or barge every day all over the United States and Canada more than 175 mills and plants carry on these processes of blasting crushing burning grinding and shipping Portland cement although these mills vary in size from one kiln to a dozen or more and use different raw materials the methods are nearly identical therefore the finished product Portland cement is of a consistently high quality no matter where it is made this is because cement is made to meet rigid specifications which are recognized and carefully followed by all manufacturers of Portland cement more than 90% of these cement mills are members of the Portland cement association established in 1916 as an unincorporated nonprofit organization joined and voluntarily supported by its members its purpose is to improve both the quality of Portland cement and its use in concrete and other cement using products among the many important activities of the Association is the planning and directing of a cement plant safety program that has over the years made the cement industry the safest of all heavy industries scores of plants have outstanding longtime safety records and every mill is proud of its continuing record of accident-free days the Portland cement Association operates the largest and most modern research and development laboratories devoted to cement and concrete its staff of trained research engineers and scientists carry on a never-ending program of basic and applied research within these specially built and equipped laboratories and supervised such far-flung field projects as this longtime study of the effects of time and weather on the durability of thousands of different concrete specimens a continuous study of the effects of salt water and tide action on concrete piles and piers and this caravan which carries a fully equipped laboratory to the job or the project to conduct field tests the association's general office in Chicago is a clearinghouse for the latest technical information concerned with Portland cement and concrete here our staff provides engineering and educational services highly trained engineers writers and artists and photographers translate technical information into bulletins manuals publications and films for public use and finally the Association maintains six regional offices and 33 widely scattered district offices men by more than 400 specially trained engineers who work with architects engineers and contractors on problems involving the use of concrete and cement in construction this combined activity in research engineering and educational services and technical assistance in the field has not only assured better and safer highways more beautiful and economical buildings and more durable bridges and dams but has encouraged the design and construction of the many new and exciting shapes and forms and architectural and engineering structures that are fast changing the face of America all this has been made possible by the process that tears down mountains and turns them into the fine micron sized particles of the most useful of all building materials Portland cement [Music]