In the first week or so after concrete is poured, you must maintain the proper temperature and dampness for proper curing. Curing is easy to skip in the instant but that will have a major impact on the quality of your finished work.
While curing is important for all concrete, the problems that arise from not curing are most obvious with horizontal surfaces. An uncured slab, whether decorative or plain gray, is likely to develop a pattern of fine cracks (called crazing) and once it's in use the surface will have low strength that can result in a dusting surface that has little resistance to abrasion.
The entire curing period of concrete takes about a month, but your concrete will be ready for use sooner. Each project will vary slightly due to differences in the weather, concrete mix and placement and finishing techniques.
When most people think of curing, they think only of maintaining moisture on the surface of the concrete. But curing is more than that-it is giving the concrete what it needs to gain strength properly. Concrete strength depends on the growth of crystals within the matrix of the concrete. These crystals grow from a reaction between Portland cement and water-a reaction known as hydration. If there isn't enough water, the crystals can't grow and the concrete doesn't develop the strength it should. If there is enough water, the crystals grow out like tiny rock-hard fingers wrapping around the sand and gravel in the mix and intertwining with one another. Almost sounds like a horror movie-our concrete baby has turned into a monster!
The other important aspect of curing is temperature-the concrete can't be too cold or too hot. As fresh concrete gets cooler, the hydration reaction slows down. The temperature of the concrete is what's important here, not necessarily the air temperature. Below about 50 F, hydration slows down a lot; below about 40 F, it virtually stops.
Hot concrete has the opposite problem: the reaction goes too fast, and since the reaction is exothermic (produces heat), it can quickly cause temperature differentials within the concrete that can lead to cracking. And cement that reacts too quickly doesn't have time for the crystals to grow properly so it doesn't develop as much strength as it should.
So in the soon-to-be famous movie, the Cement Monster That Enveloped the World, all the puny earthlings need to do to save civilization is get the concrete too cold, too hot, or too dry and he turns into a weakling. Our objective, though, is to help him envelope the earth and to make him as strong as possible!
So the objective is to keep our young and impressionable concrete damp and at the right temperature (ideally between 50 and 85 F). The most frequently overlooked curing aspect is keeping exposed concrete surfaces moist while they are hydrating. Most concrete, especially most decorative concrete, will have plenty of water initially in the mix to completely hydrate the cement. The problem is that if the exposed surfaces dry out then the concrete can't hydrate and our young concrete ends up with very sensitive skin-easily scratched and sometimes actually dusty.
There are three phases of curing and the length of time each lasts depends on the concrete and the environmental conditions. Check out Figure 1.6 in ACI 308, Guide to Curing Concrete, to see how this works:
During initial set, the rate at which the bleed water evaporates depends on a combination of factors: air temperature and humidity, concrete temperature, and wind velocity. The classic, and still best way to estimate the rate of evaporation is the Menzel/NRMCA nomograph-an easy-to-use chart that combines all of these factors. You can get this nomongraph out of ACI 308 or it's also available in an excellent piece in the March 2007 Concrete International, "Estimating Evaporation Rates to Prevent Plastic Shrinkage Cracking." You can also estimate evaporation rates using a free online program developed by Luke Snell and Amir Munir.
So you use these methods to figure out how fast the bleed water is evaporating--if it's greater than 0.2 pounds per square foot per hour, then initial curing is necessary because the concrete will be drying out. In the next section we'll discuss how to do initial curing.
After initial set, the concrete surface still needs moisture and now there's no bleed water. This is when you really need to cure the concrete. You need to assume that your concrete needs to be cured-it does! You don't want your perfect baby concrete to turn into a juvenile delinquent, do you?
Now let's narrow this conversation down a bit. Let's talk only about horizontal concrete and only about the moisture part of curing. To learn more about working in temperature extremes get a copy of ACI 305, Hot Weather Concreting or ACI 306, Cold Weather Concreting.
Let's also narrow things down to curing of colored concrete. We'll define that as any concrete with color, whether integral or dry-shake, whether it is going to be stamped or not. First, and most importantly, colored concrete is not really different than any other concrete, it needs exactly the same treatment to end up with quality concrete. Some of the methods, though, need to be a bit different since appearance is so much more important than it is for an industrial slab.
There are three ways to cure concrete: either we add water to the surface to replace the water that is evaporating or we seal the concrete to prevent the water from evaporating in the first place or we do both. Note that adding water to the surface is NOT adding water that will be worked into the concrete mix--that would increase the water-cement ratio of the surface concrete and weaken it, ruining all our curing efforts.
You need to think about initial curing when the bleed water is evaporating too rapidly to keep the surface wet prior to initial set. Traditionally that has been specified at greater than 0.2 pounds per square foot per hour. Many mixes today bleed at much lower rates than this, so if there is less bleed water then the evaporation limit needs to be set lower-more like 0.05 to 0.1 pounds per square foot per hour. The best approach for decorative concrete is to try to alter conditions so you don't need to do initial curing: block the wind, keep the sun off the concrete, get cooler concrete. If that's not possible, fogging just enough to keep the surface damp is possible, but the simplest approach is to use evaporation retardant. This chemical can be sprayed on to form a thin membrane on the surface that prevents the water from evaporating. It completely dissipates during finishing operations. Keep some of this around for dry windy conditions.
Water curing can be done after the slab pour by building dams with soil around the house and flooding the slab. The enclosed area is continually flooded with water. Ideally, the slab could be water cured for 7 days.Some builders on a tight schedule water cure for 3 days as this achieves approximately 80% of the benefit of water curing for 7 days.
When it comes to beautiful hardscape projects like patios and walkways, its hard to beat the high-end look of pavers. But, over time, water can get underneath the pavers, and weeds and grass can grow through the cracks. This can leave your carefully laid pavers looking messy and uneven. To keep pavers in place, you need polymeric sand.
Polymeric sand is a material used to fill the paver joints, which are the empty spaces between each paver. Its sometimes called jointing sand, paver sand, or hardscape sand. Coated with a water-activated polymer, the grains of polymeric sand stick together when dampened, producing a seal that looks like grout and makes a stronger joint than standard filler sand. The result is a longer-lasting paver installation.
Before starting a patio paver project, understand that polymeric sand is used for joints (the spaces between pavers) that are 1 inch or smaller. The polymeric sand drops into these cracks easily and provides the protection necessary to resist water, grass, weeds, and insects.
For paver projects or fieldstone patios with larger joints, polymeric dust might be the way to go. While it might seem strange that a finer material would be better for a larger gap, the dust creates a stronger barrier once it settles and does a better job of sealing out the elements.
The most common adhesive, or polymer, used in polymeric sand is silica. The silica forms a flexible hold between the individual grains of sand and the pavers. When the ground shifts due to water or weed roots, the silica flexes and keeps pavers in place. Depending on the manufacturer, polymeric sand can be a blend of chemical binders and glues as well as silica.
Some polymeric sand manufacturers mix Portland cement into their sand recipes. While these sands are still high-quality and durable, they sometimes create hazing around the pavers. Hazing is a white or light gray film that can form around the joints. The haze left by cement isnt just an aesthetic concern; it can affect the quality of paver sealers.
Polymeric sand comes in different colors that will match or complement your pavers. Dry pigments are mixed into the sand to produce greens, whites, browns, blacks, tans, and grays. This added touch can go a long way toward making a basic patio or walkway stand out more than dull old beige sand or gray concrete. Just as colored grout can make tile pop inside, colored polymeric sand can add a designer touch to your paver project outside. Choose the color that goes best with your pavers.
Another benefit of polymeric sand is it dries for foot and vehicle traffic quickly. Unlike concrete and cement, life can go back to normal soon after applying sand to the joints of a paver project. Most polymeric sands are ready for foot traffic after 24 hours. If its a driveway, wait 48 hours before parking a vehicle on it. Note, these drying times assume youve got sunny weather. Check the forecast before installing polymeric sand; if it rains before the polymeric sand dries, it will wash out to the top of the pavers, and youll have a mess on your hands.
Whether its a patio, driveway, walkway, Dominators Joint Stabilizing polymeric sand is worth a look. This product comes in a 45-pound bucket that can cover up 80 square feet of paver surface, depending on the size of the joints. DOMINATORSs poly sand comes in several colors including natural hue, titanium, charcoal, taupe, and carmel.
DOMINATOR polymeric sand features the companys Solid-Flex formula, made from a fine sand and free of cement. This allows the sand to flex while remaining durable and water resistant. Should any cracks appear over the course of a winter, Solid-Flex self heals, keeping ants, grass, weeds, and other paver-busters from taking advantage.
Paver projects are expensive. For those looking to save a bit of money on the sand to lock them in place, Sakretes Paver Set might be the product to go with. This 40-pound bucket of sand provides up to 45 square feet of coverage for joints -inch wide on 2-inch thick pavers. This formula also works for joints as wide as 1 inches, which is rare for a polymeric sand.
Part of what makes this product so affordable is its formula contains Portland cement, and while that can cause hazing, it will lock pavers in place securely. This formula also resists water erosion, insects, and weed growth. This product is available in tan or gray.
Alliance Gator Maxx G2 Intelligent Polymeric Sand is a brand pros trust. But, with its easy installation process, it works just as well for DIYers. This 50-pound bag of polymeric sand covers up to 85 square feet. It works on tight joints as well as joints as wide as 4 inches. This polymeric sand comes in black and beige.
The G2 Intelligent Polymeric sand features a no-dust, haze-free formula thats strong, durable, and easy to install. The formula is also rain safe in as little as 15 minutes, allowing you to apply it to a patio, walkway, or driveway on less-than-ideal days.
If youre making a repair or working on a small patio or walkway, Dominators 13-pound jug of polymeric sand might be just the ticket. This bucket has enough coverage for up to 32 feet of small joints, and the screw-on lid lets you store unused portions for later use with no worries it will dry out.
This product contains Dominators Solid-Flex formula, which allows the poly sand to stay pliable while not breaking down. Should cracks occur, Dominator self-heals, stopping ants and weeds from pushing through the cracks. It comes in titanium, charcoal, natural, taupe, and carmel.
Buddingcos Polymeric Sand is worth considering for any paver installation, including patios, walkways, driveways, pathways, and parking spaces. One bucket of this polymeric sand can offer up to 40 square feet of coverage, depending on the joint width.
Buddingcos formula is suitable for joints up to 1 inches, which is about average for a polymeric sand. However, its able to set in temperatures as low as 32 degrees, which allows you to get a jump on some of your outdoor projects in the early seasons or seal driveways in the winter.
Polymeric sand is a mixture of sand, adhesive, and sometimes Portland cement. Once pushed into the joints, water activates the adhesive, making the grains of sand bond together, as well as to the pavers, to create a durable surface.
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After the embalmers removed the organs and re-stuffed the body, they laid the body down on a sloped board and covered it completely with natron powder. The Egyptians collected this powder, a mixture of sodium compounds, from the shores of Egyptian lakes in the desert west of the Nile Delta. Unlike the hot sand that dried the earliest Egyptian mummies, the salty natron absorbed moisture without severely darkening and hardening the skin.
The embalmers left the body in the powder for 35 to 40 days to allow enough time for the body to dry completely. During this waiting period, somebody had to stand guard, as the body's strong odor attracted desert scavengers. After the 40 days were finished, the body was brought to the Wabet, the "House of Purification." The embalmers removed the incense and other stuffing from the body cavity and refilled it with natron, resin-soaked linen and various other materials. In some eras, to make the desiccated body more lifelike, the embalmers also stuffed material under the skin in the arms, legs and head. When the body was fully stuffed, the embalmers sewed up the incisions and covered the skin with a resin layer in order to keep moisture out. The body was then ready for the wrapping, or bandaging, procedure.
Bandaging was a very involved process, and it typically took a week or two to complete. While the deceased was drying in the desert, his or her family gathered roughly 4,000 square feet (372 sq. meters) of linen and brought it in to the embalmers. The wealthy sometimes used material that had clothed sacred statues, while the lower classes collected old clothing and other household linen. When the linen was delivered, the embalmers selected the highest-quality material and stripped it into long "bandages" measuring 3 to 8 inches across.
The embalmers then wrapped the body in a shroud and began methodically winding the bandages around the different parts of the body. Typically, they started with the hands and feet, wrapping all of the fingers and toes individually, and then moved on to the head, arms, legs and torso. Once all the parts of the body were wrapped, the embalmers began wrapping the body as a whole. As they applied new layers, the embalmers coated the linen with hot resin material to glue the bandages in place. During this entire process, the embalmers uttered spells and laid protective amulets on the body (for protection in the next world), wrapping them up at different layers.
After the mummy was fully wrapped, the embalmers attached a rigid cartonnage cage to the body and affixed a funerary mask to the head. This new face, which was either a likeness of the deceased or a representation of an Egyptian god, played an important role in the passage to the afterlife. It helped the spirit of the deceased find the correct body among the many Egyptian tombs.
When the mummy was completed, it was housed in a suhet, a coffin decorated to look like a person. The suhet was brought to the tomb in a procession of mourners. At the tomb, the priest, dressed as the jackal god Anubis, performed the "ceremony of the mouth," a ritual in which sacred objects were touched to the suhet's face, giving the deceased the powers of speech, sight, touch, hearing and taste in the next world. The suhet was then leaned against the wall inside the tomb, where it was sealed up with all the food, furniture and supplies that the deceased would need in the next world.
The best preserved bodies are from the middle period of Egyptian mummification. In later years, Egypt was flooded with outsiders who also wanted to be mummified in the traditional way. With this high demand, and the desire to bring in some money, the Egyptian embalmers began to pay more attention to the mummy's outer appearance than its inner preservation. Most of these rushed mummies quickly decomposed inside their ornate tombs, but the customers were none the wiser.
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To reach gas that was previously thought to be unreachable, pressure is used to fracture rock formations deep underground to allow a better flow of gas through a well. When the pressure is removed, the fracture collapses, which dramatically diminishes its effectiveness. A special type of refined sand is used as a "proppant" to keep the well linings propped open after water-based slurry has been injected into the casing. Hydraulic fracturing, or "fracking," is a mining technique that greatly enhances oil and gas well productivity and is being aggressively deployed around the world, and North America in particular. The sand remains in the fracture when the pressure is removed, keeping the fracture propped open and allowing the gas to continue to flow through the well. Thanks to the Marcellus Shale Formation, the Northeast region has experienced a recent economic boom. This turnabout came after technological advancements were made in horizontal drilling and fracking. Although fracking was used by the oil industry in the 1860s with liquid nitroglycerin in shallow wells, it wasnt until the modern version of this old technique was developed, in which the extraction of deeper pockets of natural gas became a reality. Frac sand is a high-purity quartz sand with very durable, round grains, and is a crush-resistant material produced for use by the petroleum industry. The U.S. is the largest consumer and producer of frac sand, and according to Wall Street Daily, about 25-30 million metric tons of it are used to supply the 1.1 million active gas and oil wells in the U.S. The American Petroleum Institute (API) determines frac sand specifications that include grain size, sphericity, crush resistance, and solubility. Mining companies are therefore eager to sell only frac sand that meets these API specifications to their well operator customers. To ensure an acceptable quality of sand, mining companies wash and dry it to remove all possible impurities. Two types of industrial dryers are ideally engineered to meet the stringent requirements that sand mining companies must adhere to, in order to consistently provide the highest quality sand to their energy producing customers. These dryers are fluid bed and rotary. On the surface, a fluid bed dryer is similar to many other types of drying equipment. It processes granular, free-flowing material at product temperatures ranging from 140 to 300F, and suitable materials include sand, minerals, clays, organic salts, coal, and specialty chemicals. But the similarities end there. In a fluid bed, the material being dried is suspended and completely surrounded by the drying air or gas, causing that material to behave like a fluid. Besides keeping the material in a seemingly liquid state, the gas stream is the media for heat and mass exchange. As a result of the intimate gas-to-solids contact, very high rates of heat transfer are accomplished while the sand grains are gently handled. The bedplate allows the uniform distribution of the gas stream during operation, and supports the bed of material during shutdown. A fluid bed dryer provides lower capital equipment costs at installation and lower operating costs over the life of the machine, including reduced baghouse and scrubber costs, while also increasing productivity. Because there are no moving parts inside the fluid bed, maintenance costs are greatly reduced compared to other systems. In contrast, rotary dryers handle a much broader range of materials, regardless of their conveying and handling characteristics. Whether the process requires the drying of fine and dusty powders, lumpy solids, sticky semi-plastics, sludges, pellets, agglomerates, or even a mixture of all of the above, a rotary dryer will successfully accomplish its task. A rotary dryer is a rotating cylinder, or shell, that is slightly inclined to the horizontal, and its length can be four to ten times its diameter. Material is fed into one end of the cylinder and, by virtue of its rotation and slope as well as the head effect of the material, and it exits continuously from the opposite end. The interior of the shell is equipped with specially designed flights that advance the feed material into the shells active zone and efficiently expose the material to the heat source. An important determination is the usage of direct or indirect heat in the drying process. Rotary dryers use either direct convection heat transfer or indirect heat transfer, which depends upon hot surfaces within the dryer to provide heat by conduction and radiation. The determination of direct versus indirect heat is contingent upon the properties of the material to be dried, the process conditions and the desired end product. The optimal method of drying frac sand is with direct heat, with hot air entering the rotating shell at one end, passing through it and exiting at the other end. Flights welded to the internal shell walls lift and shower the wet sand, bringing it into direct contact with the hot air. The configuration of the flights depends on the characteristics of the material being processed, and the length and diameter of the shell depends on the drying capacity. Indirect heat drying is most frequently used for products with small particle sizes that could result in excessive dust generation. The frac sand industry utilizes both types of dryers. Rotary dryers are the more expensive of the two, but they are more forgiving and allow greater process turndown capability. Fluid bed dryers cost less, are more thermally efficient and have minimal maintenance due to fewer moving parts. When taking into account certain frac sand drying requirements that must remain consistent throughout the process, such as throughput, particle size and moisture content, then fluid bed drying is the optimal method. However, rotary dryers provide greater versatility, which allows the frac sand market to better adjust to the needs of its industry. David Phillips is marketing & communications manager, Heyl & Patterson Inc., Carnegie, PA. Founded in 1887 in Pittsburgh, Heyl & Patterson is an industry leader in the design and construction of bulk transfer and thermal processing equipment for customers in a wide range of industries, including chemical, steel, biomass, energy, ports, and mining & minerals. For more information, visit www.heylpatterson.com.
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The Vulcan Drying Systems Frac Sand Drying System is custom-designed and manufactured to suit a customer's individual project needs. Most customers have sand ranging from 5-8% in moisture content. These drying systems consist of a rotary drum dryer and a burner mounted on a breeching plate. Vulcan Drying Systems Frac Sand Drying Systems are designed specifically to dry frac sands, making the material easy to transport, separate and handle.
Frac sand is fed into the rotary dryer. After passing through the dryer, the dried product is discharged to a transfer conveyor for further sorting and separation. The vapor from the process is pulled through a baghouse which removes fine particulates from the vapor stream.
Looking for a complete system to process your material? Vulcan Drying Systems designs and manufactures cost-effective solutions for any possible process. Our experienced team will create a system that will produce your desired result.
For years now, specialized sands known asfrac sands have been utilized to augment the production ofnatural gas and oil from wells. The mining and processing of sand for hydraulic fracturing (fracking) has grown into a booming industry in the Midwest.
Frac sand is used in the fracking process to create fractures in the rock to allow the free flow of oil, natural gas or natural gas liquids. The demand for frac sand is incredibly high, as a single well can use several thousand tons of the material.
The hydraulic fracturing process begins with the drilling of a well into a rock formation. A high-pressure fracking fluid is injected into the well. This fluid, made up of water mixed with frac sand and a blend of chemicals, acts as a propping agent, or proppant. The proppant prevents the fracture from closing and permits gas to flow through the well.
To ensure that the quality of sand is acceptable, mining companies wash and dry the frac sand to rid it of all possible impurities. Rotary dryers are the most proven and preferred method to dry frac sand. Dryers can be utilized at both the beginning and the end of the fracking process. Prior to its transportation to and use at a job site, frac sand must be dried and treated. Vulcan Drying Systems can supply a full range of equipment to dry, sort and move frac sand.
Silica Sand Dryer Introduction: Silica Sand Dryer is also known asrotary drum sand dryer.For the drying of silica sand ,the rotary drum dryer is used widely, and usually it is single drum sand dryer and triple-pass drum sand dryer. As the moisture of silica sand is surface water, then in order toenhance the heat efficiency and processing capacity, we need to increase the contact area between silica sand and hot air as much as possible. Our triple-pass drumsilica sand dryer achieves this aim perfectly. For one time drying, the silica sand dryer can dry the silica sand to be belowmoisture 1% directly. Structure of Silica Sand Dryer : Drum, gear, ring, carrier roller, air pipe, high pressure draught fan, reducer machine,chimney, cyclone dust catcher, 40mm thickness heat insulating layer, feeder, electric control box, belt conveyor, etc. Silica Sand Dryer Working Principle: Firstly, use one belt conveyor or bucket elevator to send the wet silica sand into the drum of silica sand dryer. On the inner wall of the cilinder/drum, there are many lifting plates which is welded according to one specialmethods. When the Silica Sand Dryer's drumis rotating, these lifting plates makes the silica sand up and down to mix with the hot air completely. Durng this process, the moisture is evaporated. On the another side of the silica sand dryer, there is one high pressure draught fan which sucks out the steam, and then the steam goes into the cyclone dust separator. In the cyclone dust separator, the dust inside the steam falls down and goes outthrough the discharging hole of the cyclone dust separator.The steam goes into atmosphere directly through the chimney which is connected to the cyclone dust separator. Furnace for the silica sand dryer :Our company's new designhot air furnace is very suitable. We have produced wellthe hot air furnace at our factory, and laterwhen the user gets the hot air furnace, the user only need to connect the hot air furnace to the silica sand dryer directly by themselves. It will save the user much time and cost. Furnace Type: According to the different fuel, Sunco Machinery can design and supply the related suitable furnace for the customers. --- To use diesel, natural gas, or LPG as fuel, the furnace is as follows: --- To use coal, waste wood, firewood as fuel, the furnace is as follows: --- To use rice husk, small wood chips as fule, the furnace is as follows: After being dried by the silica sand dryer, the moisture content of the dry silica sand can be less than 3%, or as need. Wet Sand Input Dried Sand Output ForCustomized Silica Sand Dryer, please supply more information as follows: --- Input moisture content (%) of wet silica sand ? --- Output moisture content (%) of dry silica sand ? --- Input capacity (ton per hour) ? --- Prefered fuel such as waste wood, coal, diesel, or natural gas, etc ? --- Other special requirements if have ? For more detail and price of Silica SandDryer, please contact Sunco Machinery: Email:[email protected] Mobile/WhatsApp: Video:https://www.youtube.com/watch?v=z1knBGM-3TM https://www.youtube.com/watch?v=IMF2nE7eAes https://www.youtube.com/watch?v=u1dgBh-JktI https://www.youtube.com/watch?v=eQ-4iNnxekw https://www.youtube.com/watch?v=4RrghfR9PV4 https://www.youtube.com/watch?v=3OkF8nPLuoQ
Silica Sand Dryer is also known asrotary drum sand dryer.For the drying of silica sand ,the rotary drum dryer is used widely, and usually it is single drum sand dryer and triple-pass drum sand dryer.
As the moisture of silica sand is surface water, then in order toenhance the heat efficiency and processing capacity, we need to increase the contact area between silica sand and hot air as much as possible. Our triple-pass drumsilica sand dryer achieves this aim perfectly. For one time drying, the silica sand dryer can dry the silica sand to be belowmoisture 1% directly.
Drum, gear, ring, carrier roller, air pipe, high pressure draught fan, reducer machine,chimney, cyclone dust catcher, 40mm thickness heat insulating layer, feeder, electric control box, belt conveyor, etc.
On the inner wall of the cilinder/drum, there are many lifting plates which is welded according to one specialmethods. When the Silica Sand Dryer's drumis rotating, these lifting plates makes the silica sand up and down to mix with the hot air completely. Durng this process, the moisture is evaporated.
In the cyclone dust separator, the dust inside the steam falls down and goes outthrough the discharging hole of the cyclone dust separator.The steam goes into atmosphere directly through the chimney which is connected to the cyclone dust separator.
Furnace for the silica sand dryer :Our company's new designhot air furnace is very suitable. We have produced wellthe hot air furnace at our factory, and laterwhen the user gets the hot air furnace, the user only need to connect the hot air furnace to the silica sand dryer directly by themselves. It will save the user much time and cost.
An experimental study has been carried out to investigate the convective air-drying characteristics of a wet sand layer. The experimental setup allows dynamic measurements of both sand layer weight and temperature, with hot air flowing towards the sand layer surface to ensure a uniform drying of it. Experiments are conducted for a 4mm thick sand layer for three air temperatures of 45, 60 and 75C. The lumped parameter method is used to analyze the sand layer heat transfer. The results show that the sand layer temperature continuously increases throughout the drying process, which can be divided into three stages, i.e. the initial rapid, intermediate slow, and final rapid increase stages. There is no constant temperature stage that is often observed in water film evaporation experiment. The drying process can also be divided into three stages according to the sand layer drying rate variation, they are the increasing, constant, and decreasing rate stages, which roughly correspond to the three temperature rise stages. The lumped parameter analysis result supports that the convective heat from the hot air is used mainly for the water evaporation.
Comes with your choice of patterns in a stylish waterproof carry bag. Absorbent, soft, and lightweight; dries quickly. Sand free and antibacterial. Works as a cooling wrap, towel, or blanket. Easily fits in a purse.
A microfiber towel with a suede-like feel on the skin. Antibacterial and quick-drying with a hanging loop. Buyer gets a choice of sizes and colors. Folds up small; very absorbent.
Customers who are turned off by the feel of microfiber should consider this feminine towel. It feels softer on the skin than other microfiber towels and can double as a cover-up.
Sand proof and bacteria resistant. Feels softer than other microfiber towels. Includes hanging loop. Dries quickly, even in high humidity. Cool retro flower print in a choice of colors.
Reinforced sewn edges have an attractive finish. Built-in loops so towel can be hung to dry. Soft suede material repels sand and debris. Available in three colors and five patterns.
Sure, making sand castles at the beach is fun. But most of us could do without all the sand, especially when its on our nice, clean beach towel. Unfortunately, its almost impossible to keep sand off your towel. And with every wipe, you spread it more and more.
But what if you could remove it from your towel with a simple swipe? You can if you have a sand-proof beach towel. Through fabric choice or construction, sand-proof beach towels are designed so that any sand that lands on the surface is easy to remove. They come in a wide variety of sizes and colors, so youre sure to find one that will make you willing to part with your old one.
Absorbent: Its amazingly absorbent, for starters. This synthetic material can absorb seven times its weight in liquid. But it dries very quickly, so sand wont stick to it like it does cotton, which stays damp for hours.
Lightweight: Microfiber is usually constructed from a combination of nylon and polyester, which makes it lighter in weight than cotton. Youll find this feature especially attractive when youre lugging bags of gear from your vehicle to the beach.
Most people enjoy microfibers soft, silky touch, but its not for everyone. If youre not thrilled with the fabrics traditional texture, consider other styles. Some advertise an alternative suede-like feel. Others may have a waffle weave or other texturing. So dont give up if towels youve tried so far havent felt particularly luxurious you have options.
Microfiber towels come in a variety of sizes. All of them fold down to practically nothing, so even the most oversized mat-style towel wont fill your bag. Still, you want to consider the user theres no need for a small child to struggle with a towel larger than himself. Quality towels range from 12 x 24 inches (which is roughly the size of a hand towel) all the way up to 78 x 35 inches (nearly as big as a twin bed sheet). Smaller towels are best for use with smaller individuals or for use solely for drying. The largest towels can be used to dry but double as a sand-free mat for relaxation.
The thin, lightweight construction of sand-proof towels is a selling point but this puts them at risk for blowing away. Some manufacturers design towels with pockets at the corners, so you can fill them with sand or other materials to weigh them down. If your towels lack this feature, plan on placing your gear on top of them to keep them from blowing away or taking them out only when its time to dry off.
Another way to keep track of your towels is by hanging them from a beach umbrella or canopy. Many towels come with a loop to hang them from your sun shade or on a hook in your bathroom to facilitate faster drying.
Its easy for a towel this thin to get lost in a linen closet, so many sand-proof towels come with storage pouches. This makes it harder for them to get misplaced or mixed in with your other towels. It also makes them easier to find in an overloaded beach bag. Sand-proof towels that come in elegant bags make an ideal pre-cruise or vacation gift for a loved one who has everything.
Theres a lot to love about the beach, but a sterile environment isnt one of them. Luckily, your towel can help. Many sand-proof beach towels are manufactured with antibacterial treatments that help guard against any microscopic dangers.
Mid-range: Sand-proof beach towels of a little higher quality generally cost $10 to $20 and will be larger, measuring around 4 x 2 feet. Some may be solid, others may feature stripes or simple patterns. Most will have bags that make them easier to store or carry as well as hanging loops for drying on the beach or in the bathroom.
Expensive: For $20 to $30, youll find a towel that should measure at least 5 x 3 feet, if not longer. Beach towels in this price range should be available in many colours and feature intricate, attractive designs. Many have additional protective treatments as well as hanging loops and storage bags.
We love the upscale style and added convenience that Aysesas Sand-Free Turkish Beach Towel offers. With a built-in storage pocket, its great for keeping track of small, easy-to-lose items when youre lounging. Stylish striping and attractive fringe give it a hint of sophistication many brightly coloured towels lack. Stylish horizontal stripes set the Lytepark Microfiber Beach Towel apart from traditional vertical-stripe designs, making yours easy to find at the pool or beach. At 70 x 35 inches, its almost as large as a twin sheet, so its big enough for whatever you need but folds down smaller than a beach coverup in your bag.
Q. Why cant I find a sand-proof towel thats fluffy?A. Simply put, sand-proof beach towels are designed not to do all the things that fluffy towels do to attract sand. Sand-proof towels have a sleek, tight weave that lets sand slide off. Fluffy cotton fibers, in contrast, have a raised, grabby surface that easily traps sand. Sand-proof towels are thin, allowing them to dry rapidly, so any sand that sticks releases quickly as the towel dries.
Q. How do I wash a sand-proof beach towel?A. If your towel is made of microfiber, like the majority of sand-proof towels, wash your towel with mild detergent in water thats warm or hot. Avoid fabric softeners, which leave deposits on the towel and plug the open spaces in the microfiber, greatly reducing its absorbency. If you have several microfiber towels, wash them together. If you dont, you may mix your microfiber with other synthetics that dont shed lint. Air drying is best for microfiber, although some can go in the dryer on low heat or no heat/tumble settings. If you purchase a mesh or parachute fabric item, be sure to check your specific products instructions.
Q. Why do microfiber towels dry so quickly?A. Microfiber generally dries three times faster than cotton largely because of their thin fibrers. Microfibers are absorbent but incredibly thin dozens of times thinner than a human hair. These towels are made of countless thin fibres, which individually absorb a ton of water, but dry quickly due to their size. Cotton towels, on the other hand, are made of fewer thick fibres, which take longer to dry.
What do you need to put in a locomotive to make it work? They need either water and coal or diesel or electricity, oh! and sand. Most engine sheds had storage for coal, water and oil, they also had facilities to provide dry sand.
The development of steam sanding was influential on locomotive design. As the sand could now be blown horizontally and directly under the wheels, it was no longer blown away by cross-winds before it could be effective. This prompted a resurgence of interest in some older single-driver locomotive designs, that had previously been limited by their adhesion performance.
The development of Holt's steam sanding gear on the Midland Railway in 1886 prompted Johnson to design his successful 'Spinners' of 1887, twenty-one years after the last singles, and which would remain in production for a further sixteen years.
A means was needed to improve the grip of the wheels on the track and a simple solution was found in applying sand betweent the driving wheels and the rails. This became part of the firemans duties and they would climb down from the engine and apply sand directly to the rails. This was a slow process, the engine then only able to go at the speed of the fireman applying sand to each side of the locomotive for the length of the affected section. Very quickly this was automated so a driver could drop sand directly in front of the wheels via pipes from sandboxes mounted above the wheels. Gravity fed, the process depended on a supply of dry sand to pass freely through the pipes. Any sign of dampness and the sand would stick together and clog the pipes.
Gravity sanding had other problems too. Although tubes were angled towards the driving wheels, gravity was often not enough to shoot the sand under the wheels of a stationary locomotive. Any wind was also enough to deflect the flow of sand. The sand was also applied to the rails at the wrong point for a static engine trying to reverse.
One of the most frustrating things as a passenger on a wet and windy autumn day was when the announcement came over the tannoy that the trains were delayed because of leaves on the line. You looked at this monster locomotive in front of you and were in total disbelief that something as tiny as a leaf could stop it, just another British Rail excuse!
Remembering those science lessons you partly slept through at school however would have pointed you to the world of friction. Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
Ice on steel has a low coefficient of friction, while rubber on a pavement has a high coefficient of friction, so you don't slip over. One of our problems is that steel on steel has a low coefficient of friction too. This is overcome by the sheer weight of the engines, both steam, diesel and electric, which enables the engines to grip onto the track so they can pull loads of 1000 tons or more.
The friction is so low however that it can be lost when too much force is applied to the driving wheels. In cars you hear the screech on hard acceleration where the wheels spin, in locomotives the same thing can happen and it is called wheelslip. Friction can be overcome by lubricants however and wet leaves provide just enough lubrication to cause problems.
There is a well documented incident of wheelslip that occured to the Blue Peter locomotive. Multiple problems resulted in the driving wheels loosing traction and accelerating to a theoretical speed of 140 mph before the cylinders and connecting rods failed.
The provision of dry sand became an important function of all locomotive sheds and Barrow Hill was no exception. Our coal trains often contended with branch lines which were used infrequently and thus a build up of debris was common. Slippery gradients with a load of full coal trucks were a special problem.
The sand drying oven and its chimney have all but disappeared from Barrow Hill. It was located in the corner of the shed now adjacent to our platform. The wagons containing the damp sand, from the quarries at Leyton Buzzard, were pulled alongside the high level access and the sand was thrown in to the top of the oven. In simple terms, as the sand dried it fell away at the bottom to be collected, riddled to remove any stones, and taken in sand buckeds to fill the individual locomotive sand boxes.. The oven was fueled by coal or scrap wood. When the area became a smokeless zone in the 1960's this system could not be used and two internal drying stoves were used. The original oven chamber had a floor put in to accomodate these stoves but this system also only lasted a few years.
Diesel and electric locomotive still suffer from the same problems of loosing traction. Indeed with the vastly increased power that these locomotives can produce it is just as important that this power can be used effectively by the driving wheels.
In front of each wheel is a nozzle that uses compressed air to spray sand, which is stored in tanks on the locomotives. The sand dramatically increases the traction of the drive wheels. Modern engines have an electronic traction-control system that automatically starts the sand sprayers when the wheels slip or when the engineer makes an emergency stop. The system can also reduce the power of any traction motor whose wheels are slipping.
Sand drying equipment has also moved on away from its coal fired origin. Types of drying equipment are now plentiful, compact and varied in design. Here is an example, both outside and in, of a rotary sand dryer. Although small this can dry a vast amount of sand very quickly.
The blue tower, local nicknames either "the octopus" or "the spider", was a container for the dry sand in the diesel era. No longer did fireman have to carry bucket loads of coal from the sand oven to the individual engines. The locomotive would drive under the tower and the sand would be fed by gravity into the sand boxes.
In the UK, it was standard practice to fit the sandboxes near the running plate, sometimes attached to the wheel splashers. In America the practice was to add a sand dome to the top of the boiler, in an attempt to use the boiler heat to keep the sand dry.
Rotary drum dryers have long been the preferred industrial dryer for processing sand in a variety of applications. Tolerant of variation in feedstock, highly reliable, and rugged, rotary dryers offer high-capacity sand drying at its finest for a variety of applications, including:
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I put the washed sand into a sieve in small parts, then shake in a tray of water. the water makes it a lot easier to flow since its already wet. Washing the small rocks that are captured in the sieve as well.
I drained the water simply by slowly pouring it out the tray, then bake in the oven at its lowest setting. Its important to have it below the boiling point of water and to have the oven start cold with the sand in. This is so the small rocks don't heat up too quickly and too far. Some rocks can have water trapped in them, heating fast and above 100c could cause them to explode.
I moved the sand around to make sure it was dry all the way through, Then let cool off before storing it in the two containers. Overall oven time was about 2 hours at 80c and cooling time of about another hour.Get in Touch with Mechanic