Do-it-yourself molds for concrete rings

The scope of reinforced concrete rings is quite extensive. If you need to save money, you can make them yourself. But this requires molds for concrete rings. The purchase of such equipment is an expensive pleasure, for private use it will not justify itself. But the forms can also be made independently. 

What are concrete rings for?

Most often, concrete rings are needed to build a well, but they are also used to build an autonomous sewage system – they make septic tanks or filtration wells. Another area of ​​application is manholes in the construction of a storm and drainage system. Even cellars are made of concrete rings. And there are different options – vertical, horizontal. In general, the scope is wide.

There are rings of different sizes for different needs, they also have different wall thicknesses, they can be with or without reinforcement. Despite such an abundance of choice, many are thinking about making reinforced concrete rings with their own hands. The thing is that when arranging a site, you may need more than one ring, and not even ten. For some, it takes more than a dozen just to make a well. The cost of manufacturing reinforced concrete products is much lower than their retail price. Even taking into account the fact that you have to make molds for concrete rings. And if you also take into account the cost of delivery, then the savings are very solid.

Varieties and sizes of concrete rings for wells

Industrially manufactured concrete and reinforced concrete rings must meet the standards prescribed in GOST 8020-90. Their dimensions can be taken from the table, as well as the approximate weight and price (indicated with delivery in Moscow).

For the manufacture of products of each type, there must be two parts of the formwork – external and internal. The distance between them is prescribed in GOST, depends on the size of the ring. For reinforced rings for a well with a diameter of 70 cm or 100 cm, these are 7 cm and 8 cm, respectively; when making rings without laying reinforcement, the wall thickness is much larger – 12 cm and 14 cm.

In addition to different sizes, there is also a different profile of the end part of the rings – even and with a lock. The lock is a protrusion of the comb-groove type. Such rings are called tongue-and-groove or castle rings. Placed on top of each other, they adhere well, it is difficult to move them under lateral loads, which is very important when constructing wells for any purpose. The disadvantage of this option is more complex shapes for concrete rings – it is necessary to form the corresponding steps at the ends.

Manufacturing technology of concrete and reinforced concrete well rings

For the manufacture of concrete rings in production, a hard solution with a small amount of water is used; after pouring, it is necessarily subjected to vibration. Without this process, it is impossible to achieve uniformity and high strength. In production, vibrators are built into the walls of molds; in private production, submersible vibrators for concrete can be used. These are relatively small devices, the body of which is held in the hands, and the vibrator head is lowered into concrete. The length of this nozzle should be sufficient to reach almost to the bottom of the ring.

What kind of concrete to use

Concrete for well rings in terms of soot strength is used not lower than B15 (class M200). The composition of rigid concrete, which is used in production:

• cement PC500Д0 — 230 kg:
• sand of medium grain size (size modulus 1,5-2,3) – 900 kg;
• crushed stone fraction 5-10 mm – 1100 kg;
• plasticizer C-3 — 1,6 kg;
• water – 120 liters.

The output is a cubic meter of concrete. The amount of water is indicated for sand with a moisture content of 4%. If the sand is wet, the amount of water is greatly reduced.

What must be said is that in an ordinary household pear-type concrete mixer you cannot mix such dry concrete. For kneading, you must use a forced-type mixer. If not, make more fluid concrete. The disadvantage of this solution is that it is necessary to keep the concrete in the formwork for some time (from 4 to 7 days, depending on the temperature). With one mold for concrete rings, the production of a dozen concrete rings can take months. The way out is to make the mortar as rigid as possible and have more than one pair of formwork.

Reinforcement of concrete rings

It is possible, according to all the rules, to tie a reinforcing ring from a ribbed bar with a thickness of 8-10 mm – circles interconnected by vertical segments of reinforcement. The number of reinforcement rings depends on the height of the ring. The optimal distance between them is 20-30 cm. With a well ring height of 90-100 cm, three or four reinforcement belts are made. Vertical segments are set in increments of 30-40 cm. They are tied with a special knitting wire.

Loops can be tied to the upper reinforcement belt, for which it will be possible to turn over the concrete ring using lifting equipment.

When installing a reinforcing belt, remember one detail: the reinforcement must be located in the thickness of the concrete. There should be at least 3-4 cm from the metal to the edge of the product. Therefore, the figure above shows that the reinforcement belts are not on the surface, but much lower. Approximately so and it is necessary to have armature.

Home-made concrete rings are often reinforced with a finished steel mesh – the thickness of the bar is at least 4 mm, the step is 20 cm. It is cut off at a tedious height and length, bent into a ring, and the edges are tied with wire. Such reinforcement is somewhat worse than the standard one, but it is quite enough to give greater strength.

What gives vibration

The vibrating process increases the strength of concrete by several classes (without changing the recipe). When processing concrete, it “sits down” before our eyes, air bubbles come out of it, aggregate and cement are more evenly distributed. It will not be possible to do without this procedure – the walls will be loose, they will leak and quickly collapse.

However, you can not overdo it – stratification can occur. Stop processing when the shrinkage of the mortar stops, the surface becomes smooth and cement milk appears on top.

Manufacturing process

The outer (outer) part of the formwork is installed on a flat platform or sheet of iron. If a tongue-and-groove ring is being made, the groove shaper is laid down. At a distance of 3-4 cm from the edge of the formwork, a reinforcing mesh is set. The inner part of the formwork is placed, fixed with screws to the protruding parts of the outer formwork (pins).

Concrete is thrown into the established form with shovels or some kind of device. After the ring is filled, vibrating is carried out (in ready-made forms, this takes 1-2 minutes). If necessary (look at shrinkage), concrete is added. After the end of the vibration, the surface of the ring is smoothed with a trowel. If necessary, install and press in the ridge ring.

In industrial conditions, demoulding is immediately carried out – for this, hard concrete is used so that you can immediately use the kit for the manufacture of the next ring. To do this, remove the fingers, take out the formwork. Forming the lower groove, the void former remains until the concrete sets.

How and from what to make molds for concrete rings

Factory forms are made of sheet metal, reinforced with stiffeners. The thickness of the metal is 3-8 mm, depending on the dimensions of the ring.

From barrels with thick walls

At home, bending sheet metal with the required radius of curvature is not at all easy. It is much easier to find two thick-walled barrels with different diameters. The diameters should differ by 14-16 mm. In this case, the wall thickness will be 7-8 mm. For a well ring with reinforcement – what is required.

The bottom of the barrels is cut off, the inside is made about 10 cm higher – it’s more convenient. To be able to remove the formwork from the finished ring, the barrels are sawn lengthwise into two parts. The halves must be securely connected. You can do this in different ways:

• having welded corners with drilled holes, tighten with bolts;
• make “ears” into which to drive wedges.

To prevent the inner part from leading, several spacers must be welded to each half, which will keep the walls from curvature.

Having inserted one part of the formwork into another, they are set at the same distance one relative to the other (measuring the gap in a circle). Holes are drilled in several places – under the studs with which they will be fixed. Studs are pieces of bar on both sides of which a thread is cut. The holes are arranged one opposite the other so that the formwork parts can be securely fixed.

Studs are inserted into the drilled holes, tightened with nuts. With a not very large wall thickness of the mold for concrete rings, most likely, you will have to put large washers or plates cut out of metal with a hole under the nuts so that the mold does not bend when pouring concrete.

sheet metal

If desired, you can make forms for concrete rings and from strips of sheet metal and wooden blocks, which will give rigidity to the formwork. Cut off a strip of the desired length – along the circumference + 10 cm per connection. The width of the strip is equal to the height of the ring + 10 cm. Bend the sides 5 cm at the bottom and top, make the same side along the edge of the strip. Drill holes in the side rail for the tie bolts. Cut the upper side every 20-25 cm (less if the diameter of the ring is small). Now the strip can be bent – get a ring. But it is very unstable – “plays”. Rigidity can be given with a wooden frame.

From the bar cut into pieces of 20-25 cm long. Fasten them under the side, drill a hole in the metal, screw pieces of bars onto the screws. With a length of bars of 20-25 cm, the shape will not be round, but multifaceted. If this is critical for you, you can make cuts more often, cut the bars shorter. You also need to strengthen the height. For this, bars are also used. They need to be fastened more often – so that the walls do not sag.

If you know how to use welding, you can go the other way. In addition to sheet metal, you will need a profiled square pipe. Fits 15*15mm or 20*20mm. First you need to bend four identical half-arcs from a profile pipe. Four large ones are for the outer formwork and four smaller ones are for the inner formwork. Weld cut strips of metal to the arcs.

From wooden boards or bars

If it is easier for you to work with wood, you can assemble molds for reinforced concrete rings made of wood. They are assembled from narrow planks, fixed at the bottom and top with a ring. The ring can be made of metal, for example, from a bent profiled pipe. It can be bent on a pipe bender with the required radius of curvature.

If cooperage is your forte, you can also make arcs from wood. The material is not so important. The strength and rigidity of the resulting form is important. Please note that the side is attached outside the larger formwork and inside the smaller one.

Important! In order for the formwork to be removed easily, it is necessary to lubricate the molds before pouring. If you plan to use concrete rings for a well with drinking water, you can use sunflower oil. If some kind of technical structure is supposed, it is possible to use mining mixed with engine oil or diesel fuel (or pure engine oil) as a lubricant.