IL42471A - Method for curing concrete - Google Patents

Description

A CURING This invention called Direct Electric Curing relates to a curing method for either reinforced or Such concrete must set in the moulds into which the has until it has hardened to such a degree that it can be removed fom the mould or the mould dismantled without detriment to the resulting beam concrete or structure o The hitherto knovn methods for curing concrete are One of the characteristic parameters is the the Curing temperature of the concrete of precast concrete slabs for at an ambient of it takes about 24 hours for the concrete to the According to knovn method heat brought from an external applied wither to mould or to the concrete surface For that purpose mostly is used which is brought either through a pipe ooil arranged within the or steam which is introduced directly into the Instead of heated oil can be circulated i the or electric heating coils placed in the mould to raise its All o these methods supply heat to the from the Although methods shorten time of curing generally to about hours in the case of concrete slabs of the usual the outlay for the steam generation is considerable as are the heat losses in the system and As a matter of the overall thermal of the steam heating method does not exceed it is usually is the of the present to considerably shorten the curin time of either factory produced or poured in situ by an efficient and comparatively The method according to the invention relates to procaet concrete of conventional 6 20 but not exclude oit cr concrete slabs of larger sizes or other precast or alternating According to the invention current is passed a is through of the induced within the concrete and its steel this way heat is generated within the concrete can be zed at a efficiency of Although there ore methods by which an electric curpent passing through the is used to produce heat within the the present invention basically on two accountst reinforcement used as the comparatively low resistance of steel necessitates the application of very low voltages less than even for elements of considerable such as electric This in turn means a large current for a certain requiring excessively heavy and costly With the present current is carried by the having a speci resistance roughly x 10 times that of even for short paths of a few such as across the thickness of a slab or appreciably higher voltages are roughly from 20V up to 230V extreme When current is supplied by induction the heat by a coil transfer to the effected ovor the circumerence of the presenting a rather restricted required A the power levels are high temperature gradients would be around the reinforcing detrimental both to concrete and eventually to the iteol This faot restricts the use of the method to long con Direct Electric heat generated over the whole sectional area of the configuration dicular to the direction of the current oase of a that the actual surface length x heat expands instead of being as the former Powers from 2 to 20 per concreto can that on an average 50 times higher values than with the amperage and frequency to be used for the electric current within the concrete mass varies according to the and shape of the elements to be While an voltage exact rule for using a suitable current and frequency could not yet be established by the experiments carried number of combinations is appears that of the the square amperage used in inverse relation to the time needed for setting the In other wordst the shorter the time for may be envisaged that when curing slabs of greater heat losses at the marginal portions remote from the electric current source may occur and therefore lengthen somewhat the time for was It observed that the optimum temperature to be created by electric current within the concrete approximately the maximum temperature shall not exceed The invention will no be by way of examples and l is a perspective view of a concrete slab standing on a wooden 2 shows in perspective another slab enoased in wooden On a wooden base 1 stands a concrete slab 2 encased wooden planks The current flows the direction of the arrow and the led into the interior as indicated at The wooden planks are kept apart by wooden spacers According to 2 an elongated slab encased in C wooden planks 2 stands on rollers the 4 flows the directions induced in the conorete from the outside as indicated by the Examples The general conditions for both experiments were as Concrete usedi 200 poured in between mild steel plates of 8 mm thickness in a vertical with mesh reinforcement of 4 mm 20 cm The plates were insulated from vach wooden producing slabs of 6 i 54x22 cm 24 hours crushing strength tests carried cm out on cubes cut from the The samples were not watered a er removal from the The experiments were carried out under normal working conditions in the with an ambient temperature of about on moderately of two typical experimentβι Slab thickness 6 cm voltage applied and frequenoy 52 50 Herts maximum curing current during the varying with time 31 T maximum temperature max Aotual curing time 20 minutes Energy consumption 71 Example g Slab thioknees cm 58 V Hertz max T 9 max Aotual curing time 53 minutes Energy consumption 103 103 stonelike slabs were of appearance and supporting on removal from the when they carried their own without any apparent The crushing strength of the slabs immediately after 2 curing was found to be in the neighborhood of Similar data were obtained with larger slabs or x 100 x x 100 x at decreasing k t values of specific energy with increased slab of additional advantages achieved by the method according to the present invention ie that the equipment needed for carrying it out ie comparatively simple and requires minimum trans control equipment and Fo the may be replaced insufficientOCRQuality

Claims (1)

1. 7 C M A method for curing either reinforced or characterised n that an alternating current passed through the thickness of the of the concret when the concrete the the mperage and frequency to be chosen in accordance with thickness of the mass of concrete to be cured and with the time designated for A method for curing reinforced concrete substantially as is induced claimed in claim wherein the the of concrete by a conventional coil arrangement surrounding the concrete A method for curing concrete as olaimed in Claims 1 or wherein amperage and frequency for the electric tne range of ourrent are so that to 95 C is created within the concrete mix A method as claimed i claims 1 or 2 whenever employed fo precast slabs A method for curing precast concrete slabs as claimed Claims 1 or substantially as described hereinbefore and illustrated In the June insufficientOCRQuality