GB2333291A

GB2333291A - Making concrete; heating water

Info

Publication number: GB2333291A
Application number: GB9900670A
Authority: GB
Inventors: Roger Longley
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-01-14
Filing date: 1999-01-14
Publication date: 1999-07-21
Anticipated expiration: 2019-01-14
Also published as: GB9800623D0; GB2333291B

Abstract

A method of warming water for making concrete in batches comprises feeding the precise amount of water; and releasing that amount of of water from the tank by displacing it with the same precise amount of cold water. Apparatus for carrying out the method employs a tank 10 having an inlet at the bottom, an outlet at the top, at least one heater e.g. three thermostatically controlled electric immersion heaters 16, and means for feeding to the inlet the precise amount of water required for one batch. Inlet pipe 12 has a flow control valve 20 and the amount of water required for one batch is fed in by means comprising a water meter 44 controlled by computer 46.

Description

"Making Concrete" This invention relates to a method of and apparatus for making concrete in batches, particularly for the production of cast concrete articles.

Concrete cures by hydration, a chemical reaction between the water and cement included in the mix. Initial curing provides in the region of 60 per cent of ultimate strength and normally occurs in 24 to 72 hours. The mean temperature of the mix has a very significant effect on its initial curing time, for example: Under 2 degrees Celsius curing is very retarded or does not occur at all.

Between 2 and 7 degrees Celsius curing is retarded.

Between 7 and 15 degrees Celsius optimum rapid curing occurs.

Over 15 degrees Celsius curing results in poor quality concrete which is likely to have cracked.

Cast concrete articles affected by retarded curing are very detrimental to daily batch production, because one day after filling the mould the concrete is not strong enough to be removed therefrom. This problem is common in winter conditions. Various known methods of indirectly heating concrete newly-cast into moulds in order to overcome the problem have included curing the concrete within a heated building, providing covers beneath which warm air is blown or hot water pipes are disposed, passing an electric current through reinforcing bars in the concrete, and heating the moulds electrically. These known methods use mains gas, propane or electricity, and are expensive in installation, running and maintenance costs.

However, the fundamental problem is the lack of direct heat energy within the concrete itself. Once this is provided, curing will be initiated and sufficiently maintained. The chemical reaction tends to be selfsustaining by generating its own heat, though it is beneficial to minimise heat loss by insulating the mould from the atmosphere. The solution is to make the mix with water warmed to, say, 15 to 20 degrees Celsius whenever the problem arises due to cold weather, so as to eliminate the effect of frost on all of the individual constituents of the mix. There have been other prior attempts to employ this solution, involving tanks large enough to hold sufficient water for a whole day's production which was heated overnight. Not only were the tanks very bulky and costly, but the heating of such a large amount of water was not cost-effective.

The object of the present invention is to enable warmed water to be used in a concrete mix using a compact source which has low running and maintenance costs.

According to one aspect of the invention, a method of making concrete in batches includes the steps of feeding the precise amount of water required for one batch into a tank; heating to a predetermined temperature, at one time, only said amount of water; and releasing said amount of water from the tank by displacing it with the same precise amount of cold water.

The method may comprise the further steps of mixing the heated water with the amounts of cement and aggregate required for one batch; and allowing the mix to cure.

Alternatively, the method comprises the further steps of mixing the heated water with the amounts of cement and aggregate required for one batch; placing the mix in a mould for an article; allowing initial curing of the mix to occur; and removing the article from the mould.

Another aspect of the invention comprises concrete made in accordance with any one of the three preceding paragraphs.

According to a further aspect of the invention, in apparatus for carrying out the method set out in the fifth paragraph of this specification the tank has an inlet at the bottom and an outlet at the top, at least one heater is associated with the tank, and means are provided for feeding to the inlet the precise amount of water required for one batch.

Preferably, said means comprise a water meter controlled by a computer.

Preferably, also, a manually adjustable flow control valve is provided in the inlet in order to control the rate at which water is displaced from the outlet.

Preferably, manually adjustable thermostatic control means are provided for sensing the water temperature and regulating its upper limit.

Preferably, also, a master thermostat renders the or each heater inoperative in the event of failure of the thermostatic control means.

The or each heater is preferably an electric immersion heater.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, of which Figure 1 is a perspective view of a tank with part of its wall broken away for clarity; and Figure 2 shows electric circuitry for heating water in the tank.

Referring now to the drawings, a cylindrical tank 10 is fabricated from steel plate with a thickness of, say, 4 or 5 millimetres. The diameter and height of said tank are, say, 35 centimetres and 90 centimetres respectively.

This compact tank will hold about 50 litres of water which can be released in a minimum time of, say, 20 seconds to make about half a cubic metre of concrete mix. The precise amount of water required for one batch of concrete is determined by calculation and is fed into the tank 10 as required by means (not shown) comprising a water meter 44 controlled by a computer 46. The tank 10 has a maximum capacity of, say, twice the amount of water required per batch and a minimum capacity equal to said amount. The tank 10 has an inlet at the bottom through a pipe 12, and an outlet at the top through a pipe 14, said pipes being of steel and each having a diameter of, say, 25 millimetres.

Three electric immersion heaters 16 each having a power requirement of, say, 6 kilowatts at 240 volts extend from the top to the bottom of the tank. A manually adjustable flow control valve 20 is interposed in the inlet pipe 12 in order to control the rate at which water is displaced from the outlet. Each of the immersion heaters 16 conventionally includes a thermostat 21 with a manually adjustable switch 22 for sensing the water temperature and limiting heating of the water. A master thermostat 18 secured on top of the tank 10 cuts off the supply of electricity to all the immersion heaters 16 if one or more of the thermostats 21 should fail. As illustrated in Figure 2, additional electric circuitry enclosed in a metal cabinet 24 with a clear plastics front comprises three neon indicator lamps 26, three 32 ampere double pole contactors 28, one 240 volt indicator lamp 30, three 32 ampere miniature circuit breakers 34, one 2.5 ampere single pole miniature circuit breaker 36, and three 32 ampere double pole miniature circuit breakers/isolators 38, all wired together as shown. A three-phase power supply denoted by three live input wires 40 and one neutral wire 42 is required. A manually operable mains switch (?) is provided for turning on and off the supply of power to the immersion heaters 16.

The method of operation comprises calculating the precise amount of water required for one batch of mix and feeding it into the tank 10, heating to a predetermined temperature, at one time, only said amount of water, and releasing said amount of water from the tank when required by displacing it with the same precise amount of cold water at a rate determined by the setting of the flow control valve 20. The heated water is then promptly mixed with the amounts of cement and aggregate (which expression is herein intended to include sand) required for one batch of concrete, batches being produced at intervals of, say, three minutes. The mains switch (?) is normally left turned on so that power is permanently supplied to the immersion heaters 16 subject to their automatic thermostatic control.

Each batch of the mix is either placed in a mould for an article, left long enough to allow initial curing to occur, and then removed from the mould; or is simply placed in situ and allowed to cure completely.

In a modification, the water is heated by means of gas.

Thus direct heat energy is supplied to the concrete mix by heating to a predetermined temperature, at one time, only the precise amount of water required for one batch, permitting the use of compact, economically operating, low maintenance apparatus which is relatively inexpensive to install.

Claims

1. A method of making concrete in batches including the steps of feeding the precise amount of water required for one batch into a tank; heating to a predetermined temperature, at one time, only said amount of water; and releasing said amount of water from the tank by displacing it with the same precise amount of cold water.

2. A method according to claim 1, comprising the further steps of mixing the heated water with the amounts of cement and aggregate required for one batch; and allowing the mix to cure.

3. A method according to claim 1, comprising the further steps of mixing the heated water with the amounts of cement and aggregate required for one batch; placing the mix in a mould for an article; allowing initial curing of the mix to occur; and removing the article from the mould.

4. Concrete made in accordance with any one of the preceding claims.

5. Apparatus for carrying out the method set out in claim 1, wherein the tank has an inlet at the bottom and an outlet at the top, at least one heater is associated with the tank, and means are provided for feeding to the inlet the precise amount of water required for one batch.

6. Apparatus according to claim 5, wherein said means comprise a water meter controlled by a computer.

7. Apparatus according to claim 5 or claim 6, wherein a manually adjustable flow control valve is provided in the inlet in order to control the rate at which water is displaced from the outlet.

8. Apparatus according to any one of claims 5 to 7, wherein manually adjustable thermostatic control means are provided for sensing the water temperature and regulating its upper limit.

9. Apparatus according to claim 8, wherein a master thermostat renders the or each heater inoperative in the event of failure of the thermostatic control means.

10. Apparatus according to any one of claims 5 to 9, wherein the or each heater is an electric immersion heater.

11. A method of making concrete in batches substantially as hereinbefore described.

12. Apparatus for making concrete in batches, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and accompanied by, the accompanying drawings.