ASTM C617 PDF

It is highly important for engineers to know how strong concrete is, and so construction materials testing companies send their field technicians to various construction sites to make cylindrical samples out of the same concrete that is being poured read ASTM C31 to learn how cylinders are made. Back at the lab, these samples are cured in a temperature-controlled moisture room with a constant fog spray, and on certain days a couple of samples from that set are loaded to their breaking point with a hydraulic press machine. There is usually a 7 day break and a 28 day break, and if something fails to meet strength a spare sample is set aside for a 56 day break. This way, you have a record of how the concrete gained strength over that period of time, and you may be able to pinpoint problems in the making or curing of the concrete or in the mix itself. Concrete strength is highly variable and can change with many factors, including the size and shape and condition of the cylinder, the way it was batched and mixed and transported from the concrete plant to the job site, the way it was molded in the field, and the temperature and moisture conditions during the curing process. Lightweight concrete will differ in mix design and strength compared to regular concrete, and smaller samples may be able to handle less load than larger ones.

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It is highly important for engineers to know how strong concrete is, and so construction materials testing companies send their field technicians to various construction sites to make cylindrical samples out of the same concrete that is being poured read ASTM C31 to learn how cylinders are made.

Back at the lab, these samples are cured in a temperature-controlled moisture room with a constant fog spray, and on certain days a couple of samples from that set are loaded to their breaking point with a hydraulic press machine. There is usually a 7 day break and a 28 day break, and if something fails to meet strength a spare sample is set aside for a 56 day break. This way, you have a record of how the concrete gained strength over that period of time, and you may be able to pinpoint problems in the making or curing of the concrete or in the mix itself.

Concrete strength is highly variable and can change with many factors, including the size and shape and condition of the cylinder, the way it was batched and mixed and transported from the concrete plant to the job site, the way it was molded in the field, and the temperature and moisture conditions during the curing process. Lightweight concrete will differ in mix design and strength compared to regular concrete, and smaller samples may be able to handle less load than larger ones.

These results are their quality control for the whole process of pouring concrete from batching to placement. Strength test information can also help them figure out if admixtures put into the concrete mix at the job site are effective. Technicians who test these cylinders must be appropriately trained and certified. ASTM C requires that an examiner not related to your company must see you demonstrate this test in order to be qualified to do it.

Equipment for Concrete Strength Testing To break cylinders, you will need several pieces of equipment. Testing Machine - The testing machine is powered by hydraulic fluid, and uses a piston to lift the lower bearing block and push the cylinder into the upper bearing block, loading the cylinder with increasing weight until it ruptures. It is typically operated by a lever or several buttons to retract, hold, or advance the lower bearing block, and its results may be reported by a dial gauge or a digital readout.

This is a sensitive piece of equipment and it must regularly be calibrated and maintained. Calipers or Ruler - Measuring the diameter of each cylinder is vital to the test results, as you will need to calculate the area of the cylinder to find the strength.

Keeping a daily record of your cylinder diameters is recommended. It helps to get one that comes with a bubble level. You put the straightedge across the end of the cylinder, and poke the nail at it to see if it goes underneath. Cylinder Wraps - This is safety equipment, and also helps to keep the testing machine and its surrounding area clean. They are rectangular pieces of canvas with velcro on the ends that wrap around the cylinder and keep concrete fragments contained, protecting the machine operator from sudden ruptures shooting concrete everywhere.

Retaining Rings - If you are using unbonded caps, these contain neoprene pads that help absorb the shock on the cylinder as it breaks, and go over the ends of the cylinder.

Make sure they are level when you place them on. Sulfur capping equipment - This equipment consists of sulfur mortar, a sulfur pot apparatus to melt the mortar in, capping plates, spoons, and various other items.

Spacers - Break machines are typically built to break 6x12 cylinders, so if you have smaller samples you will need to put something in there for them to sit on, kind of like a booster seat for a small child.

Typically these are made of steel or some other strong material, and are cylindrical in shape, but a little wider than the diameter of the cylinders that sit on them. Brush and dustpan - Keeping the bearing surface of the testing machine clean and clear of debris is very important, because it needs to be plane and level for each cylinder to break properly. It is recommended that you sweep it clean after each break.

Wheelbarrow - A wheelbarrow can be used to hold broken samples to throw them away after you are done testing. Safety goggles - Wear eye protection, as this can get messy!

Bring the cylinders out of the moisture room, keeping them covered with wet burlap to keep them moist. Check the cylinders over for defects holes, cracks, crumbliness as you set them on the table, use your straight edge and nail to check for planeness, and set the ones with ends that are not plane aside to be saw cut. You will want to look at the perpendicularity of the cylinder as well, to make sure it does not depart from a vertical axis by more than half a degree. If you want to break cylinders uncapped, they must be plane within 0.

Measure the diameter of each cylinder twice, in the center of each cylinder at 90 degree angles. Make sure that your two diameters are not off from each other by more than two percent, or a test on that cylinder would be considered invalid. Make sure that the bearing surfaces of the machine are clean and free of debris, and if you are using unbonded caps, check the cleanliness of your neoprene caps. You should have a record at your break station of the number of cylinders that have been broken on those particular caps.

Discard the caps and put new one in the retaining rings if there are large cracks or gouges in them, or if you have broken over cylinders on those caps. It is also recommended that you flip the caps at 50 cylinders. Put the neoprene caps on the ends of your cylinder, and check to make sure they fit right and are plane and level. Place the specimen on the lower bearing block or on a centered spacer, if breaking a 4x8 cylinder and align it with the upper bearing block, using the rings on the bottom block to center it.

A good spot is around lbs for a 6x12 cylinder breaking at psi. Remember that psi is load divided by the area, so you could calculate this for any size cylinder and any specified strength. If everything is good, proceed to the next step, but if the cylinder is off center, remove the load and readjust the position of the cylinder. You can now apply load to the cylinder.

The cylinder will hit a peak, then drop. If it drops slightly, the load may begin to increase again, so let it go until the load is decreasing steadily and you can see clear evidence of a forming fracture pattern, and then turn the lever back to the off position. Pull the cylinder out of the machine, and then remove the caps. Carry it over to your wheelbarrow and remove the wrap, letting the pieces fall into the wheelbarrow.

Determine the type of fracture and then write down the load and the type of fracture.

ECIL NOTIFICATION 2012 PDF

ASTM Standard Test Method C39: Compressive Strength of Concrete Cylinders

Ganos Retarders may be used to extend working time, but their effects on required water-cement ratio and strength must be determined. NOTE 7—Low-strength molding plaster, plaster of paris, or mixtures of plaster of paris and portland cement are unsuitable for capping. Parte 1 de 2 Designation: Make caps as thin as practicable. Originally approved in A very slight twisting motion may be required to extrude excess paste and minimize air voids in the paste.

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ASTM C617: Capping Concrete Cylinders With Sulfur Mortar

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CONEXION DE TRANSFORMADORES MONOFASICOS PDF

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EN FORET BOZZA PDF

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