For Your Information
Information on Ready Mixed Concrete
Pouring Ready Mixed Concrete
Pouring ready mixed concrete is the process of laying, vibrating and surface finishing of concrete by pushing the concrete to its concrete form at the outlet of truck mixer or end of pump. The responsibility of producer ends from the time he/she delivers the concrete to the user at the outlet of truck mixer outlet or end of pump; all the processes to be applied thereafter are under the responsibility of user.
The user should pay attention to some important points to obtain high performance from the result of pouring the concrete.
Considerations before pouring the concrete;
- Measures should be taken for issues around the place of pouring such as vehicles, iron and sand piles, electricity and telephone wires etc. that would prevent the operation of ready mixed concrete equipment and a comfortable working area should be ensured. The ground on which the pumps and truck mixers will work should be sound enough against the danger of breaking down and sliding.
- All molding works should be completed. Concrete forms should be sound, without any gap that would avoid filtering light, with smooth surfaces, clean and lubricated with concrete form oil. Concrete form framework should be sound.
- All reinforcement works should be completed. Reinforcements should have been controlled and tied in a way to prevent from getting loose during pouring. Spacers should be stable and measures should be taken to avoid from damaging while pouring the concrete.
- Team and equipment of sufficient number of elements and quality should be ready for pouring. Especially vibrators that are obligatory to use according to the new Earthquake Regulations should be ready and in working condition with spares.
- You should be ready for maintenance (special treatment) after pouring the concrete (water, hose, covers, etc.).
- If ground concrete such as field, road and floor will be poured, then the ground should be firmly pressed and watered enough (up to 15 cm depth).
Considerations while pouring the concrete;
After all the preparations are completed, it is the time for the most important stage, namely pouring the concrete. Placing the concrete form may be as follows based on the position of building;
- Using concrete pump to every level required because of being rapid and easy,
- Direct from truck mixer with the help of guides,
- Using buckets if there is crane,
- Using sliding guides if concrete form is on a lower level.
We may list the points to consider while pouring and laying the concrete;
- The point where the concrete is poured should be the place where it will be laid. You should avoid as much as possible from carrying the concrete to the area it will be laid by pouring it on a point and dragging or transferring it. The concrete may be spread to maximum 3 meters far from the area it is poured.
- The concrete should be poured in horizontal layers as much as possible. Thickness of each layer should be between 15 and 30 cm. Layer thicknesses should be even and homogenous in every point.
- Concrete should be poured freely at maximum 1,5 m height. You should take measures when it is required to pour from a higher place (for instance, reentrants may be placed on columns or gradation guide may be used, etc.)
- Primary target while pouring the concrete should be protecting the homogeneity and avoiding from decomposition.
- The concrete should always be poured vertical to the concrete form.
- The concrete should be poured without interruption but continuous. Cold joints should be avoided. For this purpose, the speed of pouring should have been planned and applied very carefully.
- In case of any obligation to interrupt pouring and if there are joints, then the surface of joints should be cleaned and it should be made dry and contented to water.
- Physical impacts on the concrete forms and equipment should be avoiding during pouring.
- Vibration and surface finishing processes during the laying process should be consecutive in a specific harmony.
Vibration is the most important stage of pouring concrete as it affects the results. The purpose of vibration is as follows;
- Removing the air gaps in the concrete and forming a structure free of gaps and impervious,
- Ensuring the adherence between concrete and reinforcement fully,
- Spreading the concrete throughout every point of concrete form.
An ideal vibration is ensured only by means of vibrators. The use of vibrators has been obligatory according to the New Earthquake Regulations and it is an important device as absolute as the concrete itself.
There are three types of vibrators used for pressing the concrete.
1. Submersible Vibrators: It is the type of vibrator providing best result. It consists of a motor, a hose taking power from the motor and transferring to a metal pin on its end, and a metal pin that can form different areas of effect based on its diameter. Such metal pin operates by vibrating and ensures pressing with the effect of vibration when it is submersed in the concrete.
2. Concrete Form Vibrators: They are used in high elements with especially intense reinforcement where submersible vibrators cannot be used. Such vibrator is installed on the concrete form on its outer side; they operate with the principle of pressing by vibrating the concrete form and so the concrete inside through the transmission by concrete form. However, the concrete form should be sound enough.
3. Surface Vibrators: It is in the form of a template operating with vibration. The concrete is pressed from the surface to depths with the effect of vibration. This vibrator is mainly used in ground, field, pavement and road concrete and its effect thickness is maximum 20 cm.
We may list the points to consider in the pressing process ensured using submersible vibrators;
- Metal pin should be submersed in vertical position to the top surface of concrete to be pressed.
- If the concrete of an element having thick cross section is to be pressed, then the layer thicknesses should be between 30 and 70 cm.
- Submersing range should not exceed 40-60 cm depending on the effect radius of metal pin.
- Submersing should be very fast; it should be kept for 5-15 seconds inside based on the viscosity of concrete and pulled back slowly. Pulling speed should be approximately 8 cm/sec.
- The indicator for a successful pressing is the formation of a very thin grout layer on the surface.
- If the concrete is to be pressed in more than one layer, then the metal pin should be submersed to a depth as 1/3 of one-down layer from the top and both layers should be united.
- Metal pin should not be contacted to the concrete form surface. The distance between the concrete form surface and submersing point should be at least twice the pin diameter.
- Metal pin should not touch the equipments during the operation of metal pin.
- Submersing should start from the top point of concrete pile.
Surface Finishing Process
Surface finishing process is the last process to be applied while the concrete is still fresh.
Surface finishing process is important especially in pavement, road, field and other ground concrete in terms of technique and aesthetics. Such process is performed generally by using wooden or steel templates and then trowels. The purpose is to form a smooth surface without gaps. More special surfaces may be obtained by using propeller machines when required.
The surfaces of vertical elements such column, curtain, wall are generally finished with concrete form. Required surfaces are obtained through wooden and steel concrete forms. Surface quality of such elements may vary also with the effect of pressing.