TECHNICAL RULES TO BE ABIDED BEFORE AND AFTER DUMPING CONCRETE

• If the concrete is going to be dumped on earth then the ground must be compressed beforehand.
• In order to prevent the water of concrete to be absorbed by the ground or the filling, the base must be moisturised for a depth of 15 cm (without generating mud)
• Before dumping concrete on a rocky base the loose parts must be cleaned (without leaving any water)  
• In concrete dumping after construction joint, the prior concrete layer should be cleaned and in order to prevent the collection of dirt in the formwork a discharge place should be left at the very bottom,  
• Construction joint must be fixed beforehand,
• The concrete formworks must be impermeable and strong,
• The surfaces of the formworks that are going to be in touch with concrete must be cleaned before concrete dumping,
• The places apt to absorb water should be moisturised,
• Concrete cover should be used in the concrete formworks and field concretes,  
• Sufficient manpower and equipment should be ready before dumping concrete,
• The concrete dumping employees should be educated,
• Necessary measures should be taken if dumping is going to be materialised in cold or hot weathers,
• Concrete should be dumped without harming or moving the equipment of the formworks,
• Especially a spare concrete vibrator should be made available,
• Concrete must always be vertically dumped in the centre of the formworks,
• In columns and partitions, concrete should not be dumped from high above (Max. 1.5 m.)
• During pumping concrete should not strike the equipment and the formworks,
• In high column and partition concretes, concrete should be dumped upwards from the bottom with the help of an additional pipe or hose,
• In concrete dumping vibrator should be used according to the book,
• Vibrator should be held on the surface at a vertical state and in order to prevent segregation it should not be used overtime in concrete,
• Equipment should not be rocked during vibrator usage,
• In clean surfaces, after levelling process the surface has to lose its blaze before wooden trowel coating,
• To prevent surface cracks trowel coating has to be repeated for the second time,
• Concrete must be protected from heat, cold, desication, heavy rain, flood, vibrations and quakes that would endanger construction until it reaches sufficient hardness,
• Concrete must be cured at least 7 days with water or chemical curing material.

PLACING FRESH CONCRETE AND THE ISSUES TO MIND

The fresh concrete that has been produced as ready mixed concrete and transported to the construction site has to be placed at the following stage. Although the components have been blended at the required ratios and shuffled and transported perfectly it would be impossible to reach to the expected quality if placing of the fresh concrete at the construction site is not carried our properly.    

The main issues to follow in the placing process of concrete at the construction are as follows :

• Taking into consideration the features of the construction, such as  the type and position of the construction, the shape of the formwork and its dimensions, the most sufficient equipment and manpower must have been selected and should be ready for the placing process be ready,  
• Before starting the placing process the necessary preparations at the construction site must have been completed and the right planning should be done for a smooth operation,
• Application of placing process of fresh concrete in its proper place without disturbing the homogenuousity feature of concrete.  

Concretes that are in use today are produced as ready mixed concrete and transported to the construction site by transmixers and are placed in the proper place as fresh concrete mostly with the help of pumps according to the features of the construction.  


RULES FOR FRESH CONCRETE PLACING PROCESS:  

The most important target in placing the fresh concrete in its place is to preserve the homogenuousity of concrete and placement without any segregation.

• The placing process of concrete into the formworks should be made downwards, in a vertical position. The dumped concrete should not be piled up in a place then spread in all directions.
• Placing fresh concrete should be materialised by horizontal layers of certain thickness and each layer should not exceed 60 cm and vibration stressing process should be applied to each layer. The new layer should be placed on prior layer before the bottom layer reaches the final hardness.  
• Fresh concrete should not be placed in a free fall style from high distances.
• In fresh concrete dumping to narrow and deep formworks necessary6 measures should be taken so as not to give way for segregations and the application has to be conducted accordingly.  When placing concrete into narrow and deep formworks concrete pumps should be used and if needed additional pipes or hoses should be added to the pump lines to prevent segregation. In placing concrete into the curve shapes formworks (tunnel cincture concrete etc.) hoses or formwork windows on side surfaces should be utilised.  
• The density of the fresh concrete to be placed in the bottom layer of the deep formwork should be identical with the density of the fresh concrete to be placed on top.  
• The placing process of fresh concrete should start from the corners of the formworks. In inclined surfaces, placing should start from the lowest level.  
• Fresh concrete should not be placed under heavy rain. In such cases the concrete becomes more wet which results in reduction in resistance and durability especially in the concrete surface.