US 4,226,542 A · Cement slurry reclamation system and method

Abstract

A slurry reclamation system for use with a concrete ready-mix plant which enables 100% reclamation of the constituents of concrete mix returned to the plant site by vehicles. Returned concrete mix is dumped into an inlet hopper having a screw classifier for removing aggregate and coarse sand, and a weired channel enabling gravity flow of the water, cement fines and sand fines constituents into a slurry vessel. The slurry in the vessel naturally separates into clarified water and concentrated slurry, and agitators are provided for periodically stirring up the slurry to maintain the cement fines active. The slurry vessel is sized in such a manner as to guarantee complete consumption of slurry returned during a day's production by the end of the following production day, the volumetric capacity of the vessel being related to the total average volume of water used to produce fresh concrete during a representative production day. An autochangeover unit automatically switches the water supply to truck washout stations and the screw classifier between normal plant supply water and the clarified water in the vessel, depending upon the level of the latter. The system enables substitution of slurry for cement fines alone, sand alone, water alone, or any combination of these concrete constituents in accordance with the percent activity of the cement fines in the slurry and production demand.

Claims61

Dependent claims

In a method of manufacturing concrete in which a slurry is formed by mixing returned concrete and water in a vessel and wherein said slurry is selectively added to fresh concrete mix, the improvement comprising the steps of:

(a) providing a slurry vessel having a volume sufficiently great to accomodate a predetermined fractional portion of the total average volume of water used to produce fresh concrete during a predetermined production period, said fractional portion being less than unity;
(b) depositing aggregate-less returned concrete in said vessel during a production period;
(c) determining the specific gravity of said slurry during the next succeeding production period;
and
(d) withdrawing said slurry from said vessel for admixture to fresh concrete mix at a rate selected in accordance with said specific gravity so that substantially all of the slurry is consumed within said next succeeding production period.

2 more elements

A system for reclaiming returned concrete mix for use in the production of fresh concrete in a ready-mix plant, said system comprising:

an unloading station for receiving returned concrete mix;
means coupled to said unloading station for separating aggregate from said returned concrete mix;
a slurry vessel coupled to said separating means for receiving the resulting slurry remaining after aggregate separation, said slurry vessel having a volumetric capacity sufficiently great to accomodate a predetermined fractional portion of the total average volume of water used to produce fresh concrete during a predetermined production period, said fractional portion being in the range from about one-fifth to about one-half;
means for supplying water to said unloading station and said aggregate separating means;
a source of water coupled to said water supply means;
means for alternating the source of the water supplied to said unloading station and said aggregate separating means between said water source and said vessel, said alternating means including means for sensing the level of the fluid in said slurry vessel, and means responsive to said sensing means for coupling said water source to said unloading station and said aggregate separating means when said fluid level falls below a predetermined level and for coupling clarified water from said slurry vessel to said unloading station and said aggregate separating means when said fluid level is equal to or greater than a higher predetermined level;
means coupled to said slurry vessel for sensing the density of said slurry;
means for supplying slurry from said vessel to said ready-mix plant at a rate determined by said density so that substantially all of the slurry is consumed within a predetermined time period no greater than the slurry curing time;
and
means for periodically agitating said slurry for a predetermined duration.

7 more elements

Dependencies are inferred from the claim text.

Cement slurry reclamation system and method

Life of this patent

Cement slurry reclamation system and method

Life of this patent

Abstract

Claims61