STRIKING economies in building pro- duction are being achieved in Britain by the use of the vertical battery system of precasting concrete units.
First used for floors and internal structural walls, the system has since been extended to cladding panels, and the Building Research Station of the British Ministry of Public Building and Works has now developed it to the point where nearly all the major com- ponents of a modern building can be made on site and lifted into place by
crane.
By integrating the production and assembly stages, the system greatly reduces the amount of handling re- quired, so lessening the risk of damage to the parts themselves. It also enables far more panels to be handled from one crane position.
With more conventional methods of industralization, components are made in a factory, loaded for transport and then unloaded and stored in racks ready for assembly. Battery vertical casting is very simple by comparison. Instead of being poured into a factory mould, the panels are merely cast be- tween two other leaves of concrete set up on end in 'toast-rack' formation. The first pair of units made by conventional methods are placed vertically with their true faces inwards. The units cast between them then ob- tain true faces on both sides. Each group of three units can be spaced apart to allow the pouring of two further units. A whole battery is thus generated from two panels.
Speed and economy
from improved battery
from the beginning, they occupy the least possible space. The centrally- placed crane can lift them straight into position in the building. Being fair- faced from the beginning on both sides, they need hand-trowelling only on the upper edge, whereas panels produced in horizontal moulds are fair-faced on one side only.
Ten of the new panels can be made in the space used by one horizontal mould. A further refinement is to sink the batteries into the ground, so sim- plifying the delivery of concrete from the mixer.
Three Factors
It might well be asked why a method with such clear advantages was not adopted earlier. In fact, it has been made possible only by the kind of fundamental technical study for which the Building Research Station, UK, exists. Success in the casting of con- crete against concrete has been found to depend on three factors the design As the panels are stacked on edge of suitable mixes for the purpose, the
Batteries for curved cladding panels on a site in north London.
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use of suitable mould oils as release agents, and adequate vibration of the
concrete.
Preliminary research produced a solution to each problem in turn. It was discovered which mixes were most suitable for each kind of panel, and which mould oils made the best release agents. In each case the pre-conditions of successful use were exactly deter- mined. The study of vibration require- ments led to the design of an automatic vibrating rig which could be suspended from the concreting gantry above the toast-rack.
Poker vibrators are designed to operate one or two feet below the level of the concrete. The rig can be controlled accurately by a single opera- tor, and it largely eliminates the factor of human error from the vibrating process.
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It was of course necessary to carry out research into many other aspects of the moulding process for instance, a study of temperatures within the battery moulds during concrete curing. Many practical techniques were de- veloped also: such as the gantry equip- ment already mentioned, lifting devices for panels of varying shape, and the moveable frameworks which hold the mould units correctly in position.
Vertical battery casting on site was first used some years ago in the con- struction of a 17-storey block of flats, Angel House, Edmonton, North Lon- don, where it provided floors and internal structural walls. After that first highly successful demonstration, the Building Research Station pursued two further objectives the increased automation of the whole building pro- cess with consequent cost-saving and the extension of the battery casting method to deal with many other types of large concrete building components.
By the constant elaboration of minor techniques it has been possible to produce panels of widely varying shape. There is no reason why this method should not place at the build- er's command almost the whole range
Far East BUILDER, March 1969
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