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PRE-PECKED CONCRETE /PRE-PLACED AGGREGATE CONCRETE (PAC)
Pre-packed concrete is a special technique of placing concrete under water. When 'tremie method' or 'bottom dump bucket method' are not found feasible, this method is adopted. This method is used where placing conventional concrete is extremely difficult, such as where massive reinforcement steel and embedded items are present, in underwater repairs, concrete and masonry repairs, or where shrinkage of concrete must be kept to a minimum.
TREMIE METHOD Underwater concreting using tremie method is convenient for pouring large amount of high flowable concrete. The concrete is moved to the hopper by either pumping, belt conveyer or skips.
Pre-packed concrete, is also called 'grouted concrete' consists of placing the coarse aggregate only in the form and thoroughly compacting it to form a prepacked mass. This mass is then grouted with the cement mortar of the required proportions. Pre-packed aggregate concrete (PAC) is concrete that is made by forcing grout into the voids of a mass of clean , graded coarse aggregate densely prepacked in formwork.
Graded aggregates similar to the substrate concrete will be placed firstly in the formwork. After the placement of graded aggregates, cement grout will be injected into the formwork from THE BOTTOM. The resulting concrete will be in excellent quality in proper implication. For the purpose of this repair method, grout typically consist of sand, cement, pozzolana , plasticizer/super plasticizer and an air entraining agent (for anticipated freeze and thaw problem, if required).
Materials Fine aggregates Water Course aggregates Portland cement Silica fume Super plasticizer
Pre-Placed Aggregate Concrete Repair to Concrete Wall
https: //www. youtube. com/watch? v=T 9 r 6 Cwj 5 Ehs&t=89 s
Kaynak https: //link. springer. com/article/10. 1007/s 12046 -016 -0549 -9 https: //www. quora. com/What-is-pre-packed-concrete https: //www. sciencedirect. com/science/article/pii/S 0950061818308249