when the steel tao unit is not used the natural cracking of the concrete is uncontrolled temperature changes increase the cracking destroying the overall strength of the concrete because the slabs are not tied together the pressure of heavy the inner structure of the highway begins to deteriorate and eventually to crumble and fall apart because they are light and compact they can be assembled either right on the job just ahead of the pavers or it more convenient that they can track your stockpile the steel plate fit snugly and the oblique slap to keep it from floating in the wet concrete used in this combination the unit becomes a contraction jo another important use of the dolly and it is in an expansion joint concrete naturally expands and contracts with changes in temperature also solid material sometimes gets down into the joints and takes up space in time if nothing is done about it the slabs will buckle by inserting a cargo fiber seller instead of the steel plate i mean just provided to absorb the pressure and the highway remains intact with the fiber seller in place that our unit is ready for its job in an expansion joint the cellar allows for the expansion of the concrete due to temperature changes as well as its growth as it ages it also prevents foreign material from entering the joint when the dal unit is placed in position a temporary cap is installed over it this is to protect against the first rush of concrete in pouring the capital be removed before the concrete h in addition short planks of tubing i slipped over one end of each day out alternating between one side of the joint and the other thus working spaces provided within the concrete for the longitudinal movement of the slabs thermal changes affecting the concrete cause it to expand and thereby exert pressure on the filler which forces the sealing compound slightly above the joint when the pressure is relieved the compound retracts to fill the void thus maintaining it sealing properly country paving today is a highly organized assembly line operation the dry ingredients sandstone and cement are carefully measured elsewhere and brought to the job by a fleet of trucks each batch is dumped into the door grump a very which is really a mixer on wheels capable of handling up to seventy two batches per hour and single lane paving the teamwork of man and machines up to an average of three thousand feet up finished paving in an eight hour day the maker has to drop this design enables the paving operation to proceed without delay because while one batch is being mixed another is being transferred to the bucket this way of working is called a strike off method of taping which means that the first course of concrete is roughly leveled off at the proper height for laying in the reinforcing steel which is in the form of steel mats this hinge type is a product of bethlehem steel company the steel matter fabricated a number of that claims plants and mill depots the special hinge makes it possible to handle the extra wide mats easily because they fall to eight foot when they can be loaded compact clay and shipped on trucks or railroad cars they require a minimum of field storage space and when folded for shipment clip is preventing the cracking of the mat the procedure following the second course of concrete is the same as for the first the same machinery is used and all operation i repeated except of course the spreader is raised to the new lead in doubl slabs may be thought as wide as twenty four feet most highway steel products are designed to fit either paving method but in double lane paving single buyers or reinforcing steel are used in place of hotbox these buyers provide a cent tie between the two halves of the wide slab in double layer and the center joint is formed by cutting after the concrete is poured this gives the double lane slab the appearance of tooling naturally a double went sleigh and requires twice as many steel mats as a single lane in both types of paving the hinged mats are simply unfolded and laid out side by side just a simple arrangement of steel rods crisscrossing the bed but when the final course of concrete is put in place on top of them this strong measure of steel locks the whole thing together this is highway steel in one of its simplest but most effective forms the sp now goes to work on the concrete mass this action serves not only to distribute the concrete evenly between the farms but also agitated so as to maintain the proper distribution of the ingredients whether the road builders are using the double lane method or paving one lane at a time the basic procedure from here on is the same following along behind the spreader is a battery of finishing machine each machine has two hours on aiding members called screens which scrape off the concrete at the level of the paving fawns this operation is repeated by a second question which closely follows the first the action of this grades not only establishes the final grade level of the finished highway but also to date and improve the structure of the concrete near the surface the last machine in the line is the longitudinal floater but before this goes to work the temporary and starting caps over the doll units are spotted in remo thus the concrete surface is smoothed out in both directions then the right highway is ready for the rear guard of hand craftsman to follow the road building machinery craftsman before the final finish on the road surface any slight wrinkles left in the wet concrete are smoothed out by the hand slope finish or other men follow with strips of burlap on a wooden frame giving the surface the proper texture for traffic finish the edges along the paving forms and smooth out the concrete along the joints there are several ways of curing concrete in this instance burlap is placed over the fresh paving and kept moistened until a concrete is s or cured this prevents the concrete from drying out too fast when the pavement is completely dry the joints are sealed which helps to prevent moisture from getting down into the subgrade and is the final step of the paving process this section of finished highway with its backbone of steel will be utilized by numberless trucks and passenger cars during its lifetime it is therefore not surprising that the same type of construction is being used in airport runways which today need to be more durable than ever before planes are bigger than they used to be they try faster and they carry a heavier load concrete has been found to best withstand the effect of impact and the terrific hate generated by fields such as are used in jet planes and and steel products that make today's highways possible also serve today's airways by strengthening the airport runway no highway is really completed until it's equipped for s whenever there's a current rail or other dangerous spot along the road there is a need for protection safety beam guardrail is a strong and effective highway guard the steel posts to which the beam is attached arrive on the job  punched a special post driving equipment mounted on a truck drives them to uniform depth safety beam guardrail is called form from strips steel and then punched and shared to specified length simultaneously the channel construction gives an unusual strength after that formed and punched the guard rails are finished by being cleaned and given their protective coat of paint safety beam guardrail gives ample protection because the continuous steel beam tends to absorb impact and distribute it over a wide area a finish coat of white paint completely installation making the safety being visible night and day the safety being guardrail adds to the streamlined appearance of the highway another highway safety guide adaptable for use with words of concrete or steel posts is the cable guardrail the shape and depth of the offset bracket gives this guide rail exceptional shock absorbing qualities the anchor rod is attached to a concrete block buried in the ground turn buckles maintain tension in the cables this is still another packaged unit of the steel plant the addition of right away sensing gives further protection to the motorist and to the property owner its ins joint construction contributes to its flexibility which is used as well as it installation there is a protective web of steel hung on it supporting south fast in a post a finishing touches deal for the modern highway and so your highway is completed and steel has entered into every phase of this building steel equipment protection to the traveler in all parts of the country highways that are so important and necessary to our civilization are being built today with highways that was there and for many years to come they must be strong and