What is a Sonotube?
A Sonotube is a type of concrete form that takes the shape of a cylindrical column. They are constructed from several layers of cardboard and waxed or laminated to make them waterproof.
Sonotubes are mainly used in casting columns and posts that are constructed with concrete. Sonotube also refers to a proprietary brand of SPC RESOURCES, INC. Some versions of these forms are made of fiber, plastic, or even composites to cater to small home jobs and large construction projects.
Their sizes range widely, from small versions available at hardware stores to large tubes several feet long and having a diameter of several feet.
In order to use Sonotubes for creating columns and support structures, first, the desired position has to be located. Once the position is found, the tube has to be secured in place before concreting.
Pouring of concrete is completed until the wax-coated Sonotube is filled. Once the concrete has set, the tube can be removed easily, leaving behind a strong column.
To accommodate differing requirements, Sonotubes come in various sizes, and the optimal size is selected based on the design of the structure, the regulations on construction, and the characteristics of the supporting soil.
Off-the-shelf Sonotubes are prone to splitting as a consequence of water exposure for more than 24 hours, but custom Sonotubes are able to endure moisture for 72 hours.
Types of Sonotubes
The introduction of Sonotubes changed the paradigm for many architects, contractors, and designers as it provided a versatile solution that enables the erecting of columns without having to manufacture complicated molds or forms.
These tubes serve as a solution for column forming and make the processes faster, easier, and more efficient.
As is further explained below, Sonotubes are offered in a myriad of sizes to suit a plethora of applications. These include the fabrication of column supports for buildings, patios, cabanas, etc.
It may be hard to believe that made from tightly wound paper, Sonotubes can withstand several cubic yards of concrete. This, along with being the most economical option available for constructional supporting structures, makes Sonotubes remarkable.
Every Sonotube type is developed with a specific use case in commercial construction. The variety of sizes offered increases the efficiency of construction projects by providing more options for various structural requirements.
Finish Free
Finish Free Sonotubes are used when the column must be perfect. Flawless in the sense there aren’t any seams, air bubbles, voids, or any imperfections resulting from some spiral mark removal.
These tubes have an interior coating to ensure a very smooth surface. Furthermore, they are equipped with a strip cord that enables fast formwork removal.
Unfortunately, finished free sonotubes come in a limited range of diameters between 12 inches and 36 inches. They also vary in volume, with concrete ranging from 0.349 cubic yards to 3.142 cubic yards.
Commercial Sonotubes
The fabrication of commercial Sonotubes relies on materials specified for commercial construction and all its persistent conditions.
The process begins with paper that is water-resistant with a maximum of 72 hours of rainfall. These tubes are made out of very strong tear resistant materials that can withstand very high bull pressure of 20 feet.
The external poly-woven layer of Sonotubes makes them highly superefficient in terms of longevity and durability. These commercial grade tubes are available in dimensions ranging from 6 to 60 inches in diameter, with lengths spanning between 12 to 20 feet.
Blasting Tubes
In the blasting industry, blasting Sonotubes are incorporated into the blast holes to maintain the shape of the hole, preventing any potential collapse from occuring.
These tubes are made of a specialized paperboard that incorporates a water resistant seal, making it extremely durable and offering additional support during water blasting.
This is achieved by drilling holes on the face of a rock, adding explosives within the holes, and blasting the explosives to break the rock for more drilling space.
In order for this to work, the holes must be maintained so that the following drilling process remains efficient.
DIY Builder’s Sonotubes
Unlike Commercial Sonotubes whose diameters are wider, these do it yourself Sonotubes come with comparatively smaller diameters, albeit with the same strength and durability.
They can conveniently have their size adjusted from 6 to 12 inches and are perfect for building decks, setting lamp and fence poles, mounting porch swing sets, and setting mailbox post.
Generally, hardware stores sell these Sonotubes at standard four feet lengths and DIY users can easily find these in most stores.
How Sonotubes Are Made?
Manufacturing Sonotubes is just as easy as creating tubing for other purposes, and their production process is exactly the same.
Constructed to withstand the pressure of poured concrete, Sonotubes boast superior strength and durability compared to other types of Sonotubes and this specific requirement partially dictates the use of special construction materials along with techniques.
The equipment used to manufacture Sonotubes is unique and these lower production portions require the same facilities in comparison to other types.
Given that Sonotubes can reach diameters of sixty inches, it requires a larger size of mandres to be used for the paper strips used to wind.
Making Sonotubes
Trimming Process
The first step in the processing of Sonotubes begins with the cutting of the cardboard sheets into strips.
These sheets come from a big roll of a cardboard and is fed into a cutting machine that cuts them into strips of appropriate height to wind around a mandrel. After the sheets have been processed, the strips are wound onto a reel.
Winding Process
The strips are first wound onto a heavy metal reel and then taken to a winding machine. Several strips are placed in parallel to one another to be wound around a mandrel which is a cylindrical rod whose outer diameter is equal to the inner diameter (ID) of the Sonotubes.
The ribbons are wound in a helical manner resulting in an angle of less than 90 degrees when a ribbon is applied on the mandrel. This helical winding improves the strength as well as the durability of the Sonotubes.
As the winding process continues further, cardboard ribbons are added to the Sonotubes and it is these ribbons which determine the thickness and the outside diameter (OD) of the Sonotube.
The required strength and durability of the Sonotubes are ensured through these multiple winding processes which guarantee that the Sonotubes meet the required thickness and performance specifications.
Foam Adhesive
The ribbons wound about the mandrel have a heavy-duty foam adhesive that is glue aplied so that the ribbons are together without any airflow pockets, bubbles or cavities that would disrupt the smoothness and the strength of the Sonotube.
A simplified form of the glue application process presented in the image below involves layer after layer of paper ribbons being wound.
Sonotubes are treated with proprietary coatings and adhesives which provide water, tear and exceptionally strength resistant properties. Those are needed in order to endure the poured concrete pressure and to comply with the required toughness criteria.
Pressure Roller
The most critical part of manufacturing Sonotubes is to ensure that the ribs of cardboard strips are interbonded and secured properly. The adhesive that is applied during the winding stage keeps the ribbons from moving.
Alongside this, a pressure roller is designed to press each ribbon layer firmly. This roller eliminates voids, air pockets, or bubbles from within the beneath the surface of the finished product.
The pressure provided by the roller is applied on the ribbons and also acts in such a way that the glue is spread uniformly within each strip. This serves to increase the structural strength and toughness of the Sonotube.
How are sonetubes used?
For construction tasks specifically, Sonotubes pose a fast and easy solution. Their material is durable yet lightweight, which allows for easy handling and installation.
As with any construction project, Sonotubes needs to be executed with a set of systematic steps to ensure maximum efficiency and the desired outcome.
Relative to other construction materials, Sonotubes are formidably strong, making them a popular choice among builders. In the past, it was labor intensive to construct the molds to pour concrete into, requiring a good deal of effort, planning, and time.
This method was also inefficient in the sense that there was a limit to how many columns could be molded in a given time frame and the equipment offered.
Unlike traditional methods, Sonotubes do not require external support during use. This allows for the construction of multiple columns at a given time, which drastically cuts the time and cost of construction.
Furthermore, Sonotubes are made of biodegradable paper that can be recycled, allowing them to be turned into new Sonotubes.
Purchasing Sonotubes is far more economical than buying other support structures, such as prefabricated concrete columns.
Companies can acquire multiple Sonotubes at a fraction of the cost it would take to buy a single set of pre-manufactured columns consisting of concrete, which also need additional expenses for delivery and storage.
Installation Location
In most cases, Sonotubes are embedded in the soil and supported by a footing form, which stabilizes the column and prevents it from dislocating. Footings are vital when the soil being supported is not ideal.
Since the concrete column is going to be submerged, it is important to check that the bottom of the hole is graded. Furthermore, the hole needs to be dry because liquid can interfere with the proper setting of the Sonotube.
Footing Base
The footing base, normally made out of plastic, can be shaped as a circle or a square. For the Sonotube to be placed, the top of the footing should be sawed to create a hole that is equal to the Sonotube’s width.
More expansive Sonotubes may need greater footings, which ought to be thick and well constructed. When the Sonotube is filled with concrete, the footing has to be snug to the Sonotube so that it is held in position.
It is important to make sure the Sonotube is leveled after it is placed and that it is properly plumbed.
As an alternative, footings may be pre-fabricated or constructed using wood forms and rebar where concrete is poured into the forms. Either option can have rebar footings placed into them or have them constructed around them in the hole.
Dirt Fill
Soil is required to be backfilled to the region around the base and foot of the Sonotube before concrete is poured. Care is required not to dislodge the Sonotube or alter its plumb alignment.
Properly compacting the volume of soil around the tube will help stabilize it and will allow for better placement of concrete.
Pouring Concrete
Sonotubes can accommodate several types of concrete, depending on the region where the construction is taking place, the type of column being constructed, and the load the columns are designed to support. The distinction between cement and concrete is critical, with the former serving as a binding material in the concrete composite.
Concrete was developed in the 1980s as an improvement over traditional cement by incorporating ingredients that increase the strength of the material by filling water filled pores. A mixture like this lowers the size of pores that are left filled with water after hydration, thus providing a stronger material.
To incorporate additional stability as needed, the Sonotube may require the use of rebar depending on what type of structure is being supported. Rebar strengthens the concrete mixture and must be placed before pouring so that it can be adequately encapsulated in the concrete.
By volume, concrete generally has 60% to 75% of sand, gravel, and rock, 15% to 20% of cement, and 15% to 20% of water. The water is used as a chemical solvent for cement that serves as a glue, crystallizing the concrete to ensure permanently bonded concrete comes to existence as a solid, unitary setup.
Concrete Curing
The time taken to cure concrete is subject to its composition and the surrounding weather. The full curing is said to take close to a month, however, it can be utilized much earlier. The most common curing is said to go through the following steps:
- 24 to 48 hours – removal of the forms is possible, along with completion of the initial set. For Sonotubes, they can be part of the cut-off.
- Partial curing is done in a duration of 7 days. • The concrete is expected to be fully cured by 30 days.
Keep in mind these approximations do change based on the site conditions or other surrounding factors. Curing has a notable impact on increasing the strength, toughness, water resistance, and abrasion resistance of concrete.
Crystals forming in the cement matrix are what give concrete its strength. These crystals are formed when a chemical reaction occurs between cement and water in other words, curing.
Advantages of Sonotubes
An eco-friendly and cost-effective approach for designing cylindrical column structures is Sonotubes. The footings are placed deeper in the ground, which saves labor.
These Sonotubes are also easy to dispose of as they can be cut with ease and do not require any additional tools or machinery.
Rounded Shape
Bending from the shaft provides cover for a variety of structures where Sonotubes are placed for support on erected components.
Also, construction projects involving Sonotubes are easier to smoothen owing to the absence of edges which may indent the surface.
Cost Efficiency
Sonotube forms are more economical than their metal or fiberglass counterparts. You can purchase multiple sonotubes at a lesser price than one fibreglass form.
They come in a variety of sizes such that you can buy all the sizes required for a project in a single purchase.
Lightweight Advantage
Lightness is one of the major advantages of Sonotubes. This makes handling easier and reduces the labor cost. Sonotubes are easier to transport, maneuver, place, and store.
After use, the Sonotubes can have their cardboard material repurposed, recycled, or reused, which adds to Sonotubes’ environmental friendliness.
Easy to Install
Installation ease is one of the most remarkable benefits of Sonotubes. There is no complex construction or the use of heavy equipment required.
The Sonotubes can be manually moved into their desired position. Proper supports can be added, and the concrete can be poured swiftly without complications.
Speeds Production
Projects with several columns work best with Sonotubes. You are not required to wait for one column to set so that the next can be placed.
There is the option to set multiple columns simultaneously which saves massive amounts of time when it comes to construction time. All columns can also be poured in one go.