Concrete batching facility and method
A concrete batch mixing system and method are disclosed that enable the batch master to measure and control both the water and cementitious ingredient feeds in relation to each other so as to be able to blend the two ingredients in a known, selected, adjustable and repeatable manner, and to agglomerate these ingredients in a counter-rotating twin screw mixing apparatus for use in the preparation of batches of mixed concrete in a concrete batching process.
1. A concrete batching system comprising:
(1) a pre-mixing system for pre-mixing a selected portion, but less than all, of a concrete batch, said premixing system further comprising:
(a) a cementitious ingredient supply system including a weigh batcher for apportioning weighed amounts of cementitious ingredients for concrete batches excluding stone and sand aggregate materials;
(b) a pre-mixer agglomerator for blending said cementitious ingredients and wetting agents excluding said aggregate materials to form a concrete pre-mix fraction of a concrete batch, said agglomerator having spaced inlet and discharge openings toward opposite ends thereof and including a twin screw mixing and conveying system having intermeshing screw conveyors for both mixing and conveying said ingredients, said screw conveyors being further characterized by a variable pitch that increases from inlet to discharge;
(c) a pre-feeder for metering said cementitious ingredients at a selected, controlled feed rate into said pre-mixer agglomerator;
(d) a liquid supply system for supplying a selected amount of wetting agents at a selected rate for blending with said cementitious ingredients in said pre-mixer agglomerator;
(e) a control system for controlling the amounts and rates in apportioning and mixing of cementitious ingredients and wetting agents in said concrete pre-mix;
(2) an aggregate supply system configured to supply aggregate ingredients only directly to a final mixing vessel bypassing said pre-mixing system; and
(3) a final mixing vessel for receiving premixed material from said pre-mixing system and aggregate from said aggregate supply system and conducting final mixing of ingredients.
2. A concrete batching system as in claim 1 wherein said control system further comprises metering devices to control the supply of wetting agents which measure both the total amount supplied and the supply rate and a shutoff valve for shutting off said supply of wetting agents when a selected total is reached.
3. A concrete batching system as in claim 2 wherein said prefeeder includes a variablespeed metering screw conveyor operable at a selected rate.
4. A concrete batching system as in claim 3 wherein said control system further comprises a central processing unit for receiving input information as to the feed rates of said cementitious ingredients and said wetting agents and generation outputs to coordinate blending thereof at selected ratios.
5. A concrete batching system as in claim 1 wherein said prefeeder includes a variable-speed metering screw conveyor operable at a selected rate.
6. A concrete batching system as in claim 1 wherein said control system further comprises a central processing unit for receiving input information as to the feed rates of said cementitious ingredients and said wetting agents and generation outputs to coordinate blending thereof at selected ratios.
7. A concrete batching system as in claim 1 wherein said liquid supply system includes a surge tank and associated pump.
8. A concrete batching system as in claim 1 wherein said liquid supply system further comprises a liquid supply source for measuring and applying said liquid wetting agents to said mixing chamber from a plurality of spaced locations in said mixing section.
9. A concrete batching system as in claim 8 wherein said twin screw mixing and conveying system has counter-rotating screws and said counter-rotation directs material away from said liquid supply system inlets.
10. A concrete batching system as in claim 1 wherein said pre-mixer agglomerator further comprises an additional inlet opening above said discharge opening to selectively allow material to pass directly through said mixing chamber unmixed.
11. A concrete batching apparatus comprising:
(1) a pre-mixing system for pre-mixing a selected portion of a concrete batch, said pre-mixing system further comprising:
(a) a cementitious ingredient supply system including a weigh batcher for apportioning weighed amounts of cementitious ingredients excluding aggregate materials for concrete batches;
(b) a pre-mixer agglomerator for blending said cementitious ingredients and said wetting agents to form a concrete pre-mix, said agglomerator being further characterized by a twin screw mixing and conveying system wherein said twin screw mixing and conveying system is characterized by intermeshing screw conveyors which both mix and convey said ingredients, said mixing and conveying system having an inlet metering section featuring a narrow pitch, a mixing section having a pitch greater than that of the inlet metering section and a discharge section having a pitch greater than that of the mixing section;
(c) a prefeeder for metering each weighed amount of cementitious ingredients at a selected, controlled feed rate into said pre-mixer agglomerator;
(d) a liquid supply system for supplying a selected amount of wetting agents at a selected rate for blending with said cementitious ingredients in said pre-mixer agglomerator;
(e) a control system for controlling the amounts and rates in apportioning and mixing of cementitious ingredients and wetting agents in said concrete pre-mix;
(2) an aggregate supply system configured to supply aggregate ingredients directly to a final mixing vessel bypassing said pre-mixing system; and
(3) a final mixing vessel for receiving premixed material from said pre-mixing system and aggregate from said aggregate supply system and conducting final mixing of ingredients.
12. An apparatus as in claim 11 wherein said inlet metering section of said intermeshing mixing screw conveyors are characterized by a pitch equal to about one-half pitch or less.
13. An apparatus as in claim 12 wherein said inlet metering section of said intermeshing mixing screw conveyors are characterized by a pitch equal to about one-quarter pitch.
14. An apparatus as in claim 11 wherein said mixing section of said intermeshing mixing screw conveyors are characterized by a pitch equal to about one full pitch or less.
15. An apparatus as in claim 14 wherein said mixing section of said intermeshing mixing screw conveyors are characterized by a pitch from about one-half to about two-thirds pitch.
16. An apparatus as in claim 11 wherein said discharge section of said intermeshing mixing screw conveyors are characterized by scoops or paddles.