CA1315960C - Reclaiming of waste concrete - Google Patents
Reclaiming of waste concreteInfo
- Publication number
- CA1315960C CA1315960C CA 545153 CA545153A CA1315960C CA 1315960 C CA1315960 C CA 1315960C CA 545153 CA545153 CA 545153 CA 545153 A CA545153 A CA 545153A CA 1315960 C CA1315960 C CA 1315960C
- Authority
- CA
- Canada
- Prior art keywords
- acid
- concrete
- methylenephosphonic acid
- accelerator
- retarder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/16—Waste materials; Refuse from building or ceramic industry
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/10—Accelerators; Activators
- C04B2103/12—Set accelerators
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/20—Retarders
- C04B2103/22—Set retarders
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Civil Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Inorganic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
- On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
RECLAIMING OF WASTE CONCRETE
Abstract of the Disclosure A process for reclaiming mixed unused concrete comprising the steps of 1) before the concrete sets, adding a retarder in an amount sufficient to retard hydration for up to an additional 90 hours, 2) optionally, at the end of the desired retardation period, diluting the retarded concrete with fresh concrete, and 3) adding an accelerator to the retarded concrete to restore it to a settable state.
Abstract of the Disclosure A process for reclaiming mixed unused concrete comprising the steps of 1) before the concrete sets, adding a retarder in an amount sufficient to retard hydration for up to an additional 90 hours, 2) optionally, at the end of the desired retardation period, diluting the retarded concrete with fresh concrete, and 3) adding an accelerator to the retarded concrete to restore it to a settable state.
Description
- l - 15~-009O
1315~
This invention relates to concrete reclamation.
It is nowadays the usual practice that the concrete re~uired for major construction operations is not mixed on the job site, but is supplied in ready-mix trucks from a central mixing plant located close enough to the site that the concrete can be placed within about 90 minutes fran mixing. It often happens, particularly at the end of the day's work, that a ready-mix truck returns from the job site with an unused portion of concrete. Under present practice this concrete cannot be: u~ed, and is simply dumped into a disposal site before it sets. This practice i9 undesirable for both econanic and environmental reassns.
It has now been found that such excess concrete may be made usable by adding to the concrete sufficient retarder to prevent 15~ sett mg~overnight or ev~n over~a weekend, then on the ne~t working day mlxing the retarded concrete wi~h fresh concrete and adding an accelerator to counteract the effect a~ ~he retarder.
Indeed, with a suitable choice of rekarder it may be possible ` ~ to omit~the step of mixing with fresh concrete, whereby the entire batch oE retarded concrete is re-accelerated and is usable as if it were ~re~h concrete.
::
1 3 ~ 0 Accordingly, the present invention provides a process for reclaiming mixed unused concrete ccmprising the steps of 1) before the concrete sets, adding a retarder in an amount sufficient to retard hydration for up to an additional 90 hours, 2) optionally, at the end o~ the desired retardation period, diluting the retarded concrete with fresh concrete, and 3) adding an accelerator to the retarded concrete to restore it to a settable state.
Optionally, a water reducing strength enhancer may be added to the dlluted concrete tcgether with the accelerator~
m e retarders used in the process of the invention must, when used in apprupriate qyan,tities, be long-acting ~that is, capable o~
retarding hydration for more than 6 hours) and reversible in action, so that addition of an accelerator ca~ restore the concrete to essentially its original state.
The preferred retarders are phosphonic acid derivatives, more preferably those containing hydroxy and amino groups, which are capabIe of acting as oalcium chelating agents. Particularly preferred retarders of this type are compounds of the Dequest (R.T.M ) series, sold by Monsanto Co.(St. Louis, Mo.), in particular:
:
Dequest 2000: ami~otri(methylenepho~phonic acid) Dequest 2006: aminotri~methylenephospbonic acid), pentasodiu~ salt ~equest 2010: 1 hydroxyethylidene~ diphosphonic acid 5 D~qu~st 2016: l-hydr~gyethylidene~ diphosphonic acid, tetra~odi~m salt Dequest 2041: ethylenediaminetetra(methylenephosphonic acid) Dequest 2047: ethylenediaminetetra(methylenephosphonic acid~, calcium sodium salt 0 Dequest 2051: hexamethylenediaminetetra(methylenephosphonic acid) 131~9~
- 3 - 154-009~
Dequest 2054: hexamethylenediaminetetra(methylenephosphonic acid), potassium salt Dequest 2060: diethylenetriaminepenta(methylenephosphonic acid) Dequest 2066: diethylenetriaminepenta(methylenephosphonic acid), sodium salt.
Other suitable retarders include hydroxycarboxylic acids and their salts, including citric, gluconic, tartaric, fumaric, itaconic, malonic and glucoheptanoic acids; polycarboxylic acids and their salts, e.g. polylnaleic, polyfumaric, polyacrylic and polymethacrylic acids, preferably of low molecular weight: antioxidants e.g.
ascorbic acid and isoascorbic acid;
polymers e.g. sulphonic acid - acrylic acid copolymers, polyhydroxysilanes and polyacrylamide, preferably of lcw molecular weight; carbohydrates, e~g. sucrose and corn syrup; and lignosulphonates, e.g. calcium lignosulphonates. of these, the hydroxycarboxylic acids, polycarboxylic acids, isoascorbic acid, and polyhydroxysilanes are preferred.
More preferred retarders are mixtures of at least one retarder of the phosphonic acid type with at least one retarder of a different type. As many of the non-pbosphonic acid retarders also have water~reducing properties, these may also have the effect of increasing the compressive strength of the final set concrete.
Particularly preferred eetarders are mixtures of the Dequest series with citric acid, parti~ularly Dequest 2000 / citric acid.
Preferred ratios of Dequest to citeic acid are from 1:1 to 2:1.
.~
Preferred accelerators for adding in step 3 of the process of the invention are those classified in ASTM C 494 as Type C
admixtures. Preferred accelerator compositions are chloride-free and may contain for example calcium salts e.g. calcium nitrate and calcium formate, thiocyanates, triethanolamine and glycolurils e.g.
teimethyIolglycoluril. A particularly preferred accelerator of this type is that sold by Master Builders Inc. (Cleveland, Ghio~ under the trade mark Pozzolith 555 A.
~ 3 11 ~
1315~
This invention relates to concrete reclamation.
It is nowadays the usual practice that the concrete re~uired for major construction operations is not mixed on the job site, but is supplied in ready-mix trucks from a central mixing plant located close enough to the site that the concrete can be placed within about 90 minutes fran mixing. It often happens, particularly at the end of the day's work, that a ready-mix truck returns from the job site with an unused portion of concrete. Under present practice this concrete cannot be: u~ed, and is simply dumped into a disposal site before it sets. This practice i9 undesirable for both econanic and environmental reassns.
It has now been found that such excess concrete may be made usable by adding to the concrete sufficient retarder to prevent 15~ sett mg~overnight or ev~n over~a weekend, then on the ne~t working day mlxing the retarded concrete wi~h fresh concrete and adding an accelerator to counteract the effect a~ ~he retarder.
Indeed, with a suitable choice of rekarder it may be possible ` ~ to omit~the step of mixing with fresh concrete, whereby the entire batch oE retarded concrete is re-accelerated and is usable as if it were ~re~h concrete.
::
1 3 ~ 0 Accordingly, the present invention provides a process for reclaiming mixed unused concrete ccmprising the steps of 1) before the concrete sets, adding a retarder in an amount sufficient to retard hydration for up to an additional 90 hours, 2) optionally, at the end o~ the desired retardation period, diluting the retarded concrete with fresh concrete, and 3) adding an accelerator to the retarded concrete to restore it to a settable state.
Optionally, a water reducing strength enhancer may be added to the dlluted concrete tcgether with the accelerator~
m e retarders used in the process of the invention must, when used in apprupriate qyan,tities, be long-acting ~that is, capable o~
retarding hydration for more than 6 hours) and reversible in action, so that addition of an accelerator ca~ restore the concrete to essentially its original state.
The preferred retarders are phosphonic acid derivatives, more preferably those containing hydroxy and amino groups, which are capabIe of acting as oalcium chelating agents. Particularly preferred retarders of this type are compounds of the Dequest (R.T.M ) series, sold by Monsanto Co.(St. Louis, Mo.), in particular:
:
Dequest 2000: ami~otri(methylenepho~phonic acid) Dequest 2006: aminotri~methylenephospbonic acid), pentasodiu~ salt ~equest 2010: 1 hydroxyethylidene~ diphosphonic acid 5 D~qu~st 2016: l-hydr~gyethylidene~ diphosphonic acid, tetra~odi~m salt Dequest 2041: ethylenediaminetetra(methylenephosphonic acid) Dequest 2047: ethylenediaminetetra(methylenephosphonic acid~, calcium sodium salt 0 Dequest 2051: hexamethylenediaminetetra(methylenephosphonic acid) 131~9~
- 3 - 154-009~
Dequest 2054: hexamethylenediaminetetra(methylenephosphonic acid), potassium salt Dequest 2060: diethylenetriaminepenta(methylenephosphonic acid) Dequest 2066: diethylenetriaminepenta(methylenephosphonic acid), sodium salt.
Other suitable retarders include hydroxycarboxylic acids and their salts, including citric, gluconic, tartaric, fumaric, itaconic, malonic and glucoheptanoic acids; polycarboxylic acids and their salts, e.g. polylnaleic, polyfumaric, polyacrylic and polymethacrylic acids, preferably of low molecular weight: antioxidants e.g.
ascorbic acid and isoascorbic acid;
polymers e.g. sulphonic acid - acrylic acid copolymers, polyhydroxysilanes and polyacrylamide, preferably of lcw molecular weight; carbohydrates, e~g. sucrose and corn syrup; and lignosulphonates, e.g. calcium lignosulphonates. of these, the hydroxycarboxylic acids, polycarboxylic acids, isoascorbic acid, and polyhydroxysilanes are preferred.
More preferred retarders are mixtures of at least one retarder of the phosphonic acid type with at least one retarder of a different type. As many of the non-pbosphonic acid retarders also have water~reducing properties, these may also have the effect of increasing the compressive strength of the final set concrete.
Particularly preferred eetarders are mixtures of the Dequest series with citric acid, parti~ularly Dequest 2000 / citric acid.
Preferred ratios of Dequest to citeic acid are from 1:1 to 2:1.
.~
Preferred accelerators for adding in step 3 of the process of the invention are those classified in ASTM C 494 as Type C
admixtures. Preferred accelerator compositions are chloride-free and may contain for example calcium salts e.g. calcium nitrate and calcium formate, thiocyanates, triethanolamine and glycolurils e.g.
teimethyIolglycoluril. A particularly preferred accelerator of this type is that sold by Master Builders Inc. (Cleveland, Ghio~ under the trade mark Pozzolith 555 A.
~ 3 11 ~
Preferred water-reducing strength enhancers which may optionally be added together with the accelerator in step 3) are those classified in ASTM C 494 as Type A admixtures; that is, they are water reducing agents which of th~mselves have no substantial retarding or accelerating effect. A particularly preferred material is that sold by Master Builders Inc. under the trademark Pozzolith Polyheed.
It is also p~ssible, instead of using a combination of a Type C
admixture as accelerator and a Type A admixture as water-reducing agent, to use a single addition of a Typ0 E admixture, which is a water-reducing accelerato~. The combination of a Type C and a Type A
product is however preferred.
~ he quantities of retarder and of accelerator which must be added, as a percentage of the weight of the concrete, in the pr~cess Of the invention will vary according to a number of different factors, which will readily be appreciated by the man skilled in the art. These include:
1) The formulation of the retarder and accelerator used.
2) The length of time for which re~ardation is desired. This will nonmally be overnigh~ (12-18 hours~ or over a weekend (36-90 hours, preferably 60-72 hours).
3) The ASTM type of cement. While types I-IV can be used in the present process, types I and II are preferred. The degree of fly ash substitution in the cement will affect the quantity of accelerator to be added in step 3) of the process: in general more accelerator is required with increasing fly ash substitution.
4) The time of addition of the retarder to the concrete defined as the length of time between mixing the concrete and adding the retarder. The retarder may be added to the unused portion of the concrete as soon as the used portion ,, .
131 a960 _ 5 - 154-0090 has been placed, or may be added when the ready-mix truc~
returns to the mixing plant, or as long as the concrete maintains the required slump, air content and unit weiyht.
Preferably the retarding agent is added to the cement S within 1 to 4 hours after initial mixing. rihe longer the time of addition, the more retarder may be required.
It is also p~ssible, instead of using a combination of a Type C
admixture as accelerator and a Type A admixture as water-reducing agent, to use a single addition of a Typ0 E admixture, which is a water-reducing accelerato~. The combination of a Type C and a Type A
product is however preferred.
~ he quantities of retarder and of accelerator which must be added, as a percentage of the weight of the concrete, in the pr~cess Of the invention will vary according to a number of different factors, which will readily be appreciated by the man skilled in the art. These include:
1) The formulation of the retarder and accelerator used.
2) The length of time for which re~ardation is desired. This will nonmally be overnigh~ (12-18 hours~ or over a weekend (36-90 hours, preferably 60-72 hours).
3) The ASTM type of cement. While types I-IV can be used in the present process, types I and II are preferred. The degree of fly ash substitution in the cement will affect the quantity of accelerator to be added in step 3) of the process: in general more accelerator is required with increasing fly ash substitution.
4) The time of addition of the retarder to the concrete defined as the length of time between mixing the concrete and adding the retarder. The retarder may be added to the unused portion of the concrete as soon as the used portion ,, .
131 a960 _ 5 - 154-0090 has been placed, or may be added when the ready-mix truc~
returns to the mixing plant, or as long as the concrete maintains the required slump, air content and unit weiyht.
Preferably the retarding agent is added to the cement S within 1 to 4 hours after initial mixing. rihe longer the time of addition, the more retarder may be required.
5) The setting time of the original concrete. If the concrete has an intrinsically low rate o set, then less retarder and more accelerator will be required than for one with a higher rate of set.
6) The temperature of the concrete. The higher the temperature, the faster the setting time and thus the larger the quantity of retarder which will be required.
Because of the more rapid setting, it is preferred that for concrete temperatures above 20C ( 70F), the re~arder should be added within 3 hours of initial mixing.
Because of the more rapid setting, it is preferred that for concrete temperatures above 20C ( 70F), the re~arder should be added within 3 hours of initial mixing.
7) The volume of the concrete to be treated. A large volume of concrete at a given initial temperature will set more rapidly than a small volume at the same initial temperature. T~liS iS because the large volume cannot lose the heat of hydration so quickly and therefore gives a greater temperature rise and thus a higher rate o~ set.
Hence, for example, two cubic meters of concrete may require more than twice as much retarder as d oes one cubic 25 ~ ~ meter.
Hence, for example, two cubic meters of concrete may require more than twice as much retarder as d oes one cubic 25 ~ ~ meter.
8) The proportion o reclaimed~concrete to fresh concrete in the final mix. The old concrete may range from 5~ to 100%
of the total mix, preferably 10-50% by weight of the total. Clearly, the higher the proportion of reclaimed concrete, the more accelerator must be added.
:::
~ 3 ~
- 6 -- 154-O~9O
of the total mix, preferably 10-50% by weight of the total. Clearly, the higher the proportion of reclaimed concrete, the more accelerator must be added.
:::
~ 3 ~
- 6 -- 154-O~9O
9) The types and amounts of the admixtures in the original and in the freshly added cement.
In a preferred method of operating the process of the invention, when a ready-mix truck returns to the mixing plant with an S unused portion of concrete, the temperature of the load is measured with a probe, the volume of ths load is estimated, and on the basis of these data and of the kncwn characteristics of the concrete batch, the quan~ity of retarder necessary to keep the load usable unJcil the next w~rking day is oalculated. Advantageously, this may be dcne by a suitably programmed microcGmputer, and the required amcunt o~
retarder (preferably as an aqueous solution) may be automatically metered into the load.
.
The load is mixed for a short time, then left to stand without further mixing until the next working day. The reqyired amcunt of fresh concrete is then mixed into the reclaimed concrete, the temperature is again measured, and the required amount of accelerator (and, if required, of water reducing agent) is calculated. Again, addition may be carried out under automatic computer control.
The following Examples illu~trate the invention. All parts and perceAtages are by weight unless indicated otherwise.
~ -::: :
; , : :
_ 7 _ 1 3 ~ 154-0090 Examples Standard concrete formulation Component kg/m3 concrete Kaiser Cement Iype I/II 250 Fly ash (Jim Bridger, CF 46.5 517 @ 70F) Sand 864 ~tone 1008 Water 175 Retarder formulation R
An aqueous solution containing 12.8% aminotri(methylene-phosphonic acid) ~Deqyest 2000) and 8% citric acid.
Accelerator formulation C
Pozzolith 555 A (Master Builders), a calcium nitrate-based chloride free accelerator supplied as an aqueous solution containing 48.7~ active material.
~ter reducer fonmulation A
Pozzolith Polyheed (Master Builders), a low-ratardation lignosulphonate-based water reducer, supplied as an aquecus solution cont~ining 39% active materialO
In the following ~xamples, all additions of admixtures to the concrete are given as percentages by weight ~ased ~n the dry weight o~ cementitious material (i.e. cenent plu5 fly ash) in the concrete.
The percentages are of dry active material unless otherwise stated.
-- 8 _ 1 3 1 ~ 154-0~9~
Exam~le 1 Four samples of the standard concrete formulaticn are rnixed and left to stand in 5 ~allon (approx. 20 1) containers for two hours. To three of the containers aee added 5 % wt. of aqueous solutions of Dequest 2000, alone or with citric acid~ as sho~n in Table 1. To the fourth sample is added 5 % wt. water only, as reference. The concrete samples are mixed and allowed to stand overnight. After 24 hours, the three retarded samples are diluted with fresh concrete at a ratio of one part of the retarded concrete to five parts of fresh concrete, and reactiYated with 3.1% of accelerator formulation C and 0.3 ~ of water r~ducer formulation A. ~able I shows the measured compressive strength after 14 and 28 days.
Table I
No. % Dequest 2000 % citric acid Compressive strength (kg/cm2) 14 days 28 days 1 0.318 - 290 390 2 0.227 - 277 370 3 0.318 0.200 321 432 ~xample 2 ~Example 1 is repeated, using for each sample 0.318 % of a Dequest material plus 0.200% citric acid as retarder, added in 2 5~ -of aqueous solution. Reacti~ation is carried out as in E~ample 1.
2~ Table II shows the results in terms of ~ air content, rate of hardening to initial set (after re-activation~ and ~onpressive streAgth after 1 day and 7 day~.
", ... . .. . . .. .
g ~ 3 1 ~ 54 00go ble II
No. Dequest % air rate of hardening Compres3ive strength material thr) (kg/om2) 1 day 7 days 1 2000 2.0 4.0 153 443 2 2006 1.8 4.25 147 41B
3 2010 1.9 3.875 140 402 4 2016 1.~ 4.0 144 41~
2041 1.8 5.0 121 423 6 2~51 2.0 3.5 138 416 7 2054 1.9 3~25 144 ~16 8 2060 1.8 3.875 135 414 9 2066 2.2 3.75 156 none 0.7 5.5 86 256 ~
(reference) E~ample 3 Experiment has shown that suitable dosages of retarder formulation R (in litres of solution per 100 kg of cementitious material) for o~ernight and for weekend retardation, as a function of the concrete temperature and volume of concrete to be treated, is as given in Table III
Table III
Co,ncrete temp~rature Overnight dosage (%) Weekend dcsage %
F ~C for up to for more than (approx.) 1.5 m3 1.5 m3 _ . . . . .
90-99 ~ 30-35 3.4 : 4.4 9.0 80-~9 25-30 3.1 4.0 8.4 70~79 20-25 2.5 3.4 7.8 : ' 60-69 15-20 2.2 2.8 7.1 30~50-59 10-15 1.5 1~5 6.5 ~-49 5-10 1.2 1.2 S.9 32-39 0-5 ~.9 0.9 5.3 .. .. , , . _ _ , lo- 131 3 9 ~ 0 154-0090 The retarded concrete, after mixing with 5 parts of fresh concrete to 1 part of old retarded concrete, can ~e re-activated with the amounts of accelerator fonmulation C (in litres of solution per 100 kg cementitious material aC shown in Table rv Table rv Concrete temperature overnight retardation weekend retardation F C (approx) accelerator dosage (%) accelerator dosage .
80-89 25-30 1.9 5.3 107~-79 20-25 2.5 6.5 6C-69 15-20 3~1 7.1 50-59 10-15 3.7 7.5 4~-49 5-1~ 4.4 7.8 32-39 0-5 5.0 8.1 ~
.
:` :
~ . ~
~:
:
In a preferred method of operating the process of the invention, when a ready-mix truck returns to the mixing plant with an S unused portion of concrete, the temperature of the load is measured with a probe, the volume of ths load is estimated, and on the basis of these data and of the kncwn characteristics of the concrete batch, the quan~ity of retarder necessary to keep the load usable unJcil the next w~rking day is oalculated. Advantageously, this may be dcne by a suitably programmed microcGmputer, and the required amcunt o~
retarder (preferably as an aqueous solution) may be automatically metered into the load.
.
The load is mixed for a short time, then left to stand without further mixing until the next working day. The reqyired amcunt of fresh concrete is then mixed into the reclaimed concrete, the temperature is again measured, and the required amount of accelerator (and, if required, of water reducing agent) is calculated. Again, addition may be carried out under automatic computer control.
The following Examples illu~trate the invention. All parts and perceAtages are by weight unless indicated otherwise.
~ -::: :
; , : :
_ 7 _ 1 3 ~ 154-0090 Examples Standard concrete formulation Component kg/m3 concrete Kaiser Cement Iype I/II 250 Fly ash (Jim Bridger, CF 46.5 517 @ 70F) Sand 864 ~tone 1008 Water 175 Retarder formulation R
An aqueous solution containing 12.8% aminotri(methylene-phosphonic acid) ~Deqyest 2000) and 8% citric acid.
Accelerator formulation C
Pozzolith 555 A (Master Builders), a calcium nitrate-based chloride free accelerator supplied as an aqueous solution containing 48.7~ active material.
~ter reducer fonmulation A
Pozzolith Polyheed (Master Builders), a low-ratardation lignosulphonate-based water reducer, supplied as an aquecus solution cont~ining 39% active materialO
In the following ~xamples, all additions of admixtures to the concrete are given as percentages by weight ~ased ~n the dry weight o~ cementitious material (i.e. cenent plu5 fly ash) in the concrete.
The percentages are of dry active material unless otherwise stated.
-- 8 _ 1 3 1 ~ 154-0~9~
Exam~le 1 Four samples of the standard concrete formulaticn are rnixed and left to stand in 5 ~allon (approx. 20 1) containers for two hours. To three of the containers aee added 5 % wt. of aqueous solutions of Dequest 2000, alone or with citric acid~ as sho~n in Table 1. To the fourth sample is added 5 % wt. water only, as reference. The concrete samples are mixed and allowed to stand overnight. After 24 hours, the three retarded samples are diluted with fresh concrete at a ratio of one part of the retarded concrete to five parts of fresh concrete, and reactiYated with 3.1% of accelerator formulation C and 0.3 ~ of water r~ducer formulation A. ~able I shows the measured compressive strength after 14 and 28 days.
Table I
No. % Dequest 2000 % citric acid Compressive strength (kg/cm2) 14 days 28 days 1 0.318 - 290 390 2 0.227 - 277 370 3 0.318 0.200 321 432 ~xample 2 ~Example 1 is repeated, using for each sample 0.318 % of a Dequest material plus 0.200% citric acid as retarder, added in 2 5~ -of aqueous solution. Reacti~ation is carried out as in E~ample 1.
2~ Table II shows the results in terms of ~ air content, rate of hardening to initial set (after re-activation~ and ~onpressive streAgth after 1 day and 7 day~.
", ... . .. . . .. .
g ~ 3 1 ~ 54 00go ble II
No. Dequest % air rate of hardening Compres3ive strength material thr) (kg/om2) 1 day 7 days 1 2000 2.0 4.0 153 443 2 2006 1.8 4.25 147 41B
3 2010 1.9 3.875 140 402 4 2016 1.~ 4.0 144 41~
2041 1.8 5.0 121 423 6 2~51 2.0 3.5 138 416 7 2054 1.9 3~25 144 ~16 8 2060 1.8 3.875 135 414 9 2066 2.2 3.75 156 none 0.7 5.5 86 256 ~
(reference) E~ample 3 Experiment has shown that suitable dosages of retarder formulation R (in litres of solution per 100 kg of cementitious material) for o~ernight and for weekend retardation, as a function of the concrete temperature and volume of concrete to be treated, is as given in Table III
Table III
Co,ncrete temp~rature Overnight dosage (%) Weekend dcsage %
F ~C for up to for more than (approx.) 1.5 m3 1.5 m3 _ . . . . .
90-99 ~ 30-35 3.4 : 4.4 9.0 80-~9 25-30 3.1 4.0 8.4 70~79 20-25 2.5 3.4 7.8 : ' 60-69 15-20 2.2 2.8 7.1 30~50-59 10-15 1.5 1~5 6.5 ~-49 5-10 1.2 1.2 S.9 32-39 0-5 ~.9 0.9 5.3 .. .. , , . _ _ , lo- 131 3 9 ~ 0 154-0090 The retarded concrete, after mixing with 5 parts of fresh concrete to 1 part of old retarded concrete, can ~e re-activated with the amounts of accelerator fonmulation C (in litres of solution per 100 kg cementitious material aC shown in Table rv Table rv Concrete temperature overnight retardation weekend retardation F C (approx) accelerator dosage (%) accelerator dosage .
80-89 25-30 1.9 5.3 107~-79 20-25 2.5 6.5 6C-69 15-20 3~1 7.1 50-59 10-15 3.7 7.5 4~-49 5-1~ 4.4 7.8 32-39 0-5 5.0 8.1 ~
.
:` :
~ . ~
~:
:
Claims (17)
1. A method for reclaiming mixed unused concrete comprising the steps of 1) before the concrete sets, adding a retarder in an amount sufficient to retard hydration for up to an additional 90 hours;
2) at the end of the desired retardation period, adding an accelerator to the retarded concrete to restore it to a settable state.
2. A method according to Claim 1 in which the retarded concrete is diluted with fresh concrete before adding the accelerator.
2. A method according to Claim 1 in which the retarded concrete is diluted with fresh concrete before adding the accelerator.
3. A method according to Claim 1, in which the retarder comprises at least one phosphonic acid derivative.
4. A method according to Claim 3, in which said retarder comprises at least one compound selected from aminotri(methylenephosphonic acid); aminotri(methylenephosphonic acid), pentasodium salt 1-hydroxyethylidene-1,1-diphosphonic acid;
1-hydroxyethylidene-1,1-diphosphonic acid, tetrasodium salt;
ethylenediaminetetra(methylenephosphonic acid);
ethylenediaminetetra(methylenephosphonic acid); calcium sodium salt;
hexamethylenediaminetetra(methylenephosphonic acid);
hexamethylenediamunetetra(methylenephosphonic acid), potassium salt;
diethylenetriaminepenta(methylenephosphonic acid);
diethylenetriaminepenta(methylenephosphonic acid), sodium salt.
1-hydroxyethylidene-1,1-diphosphonic acid, tetrasodium salt;
ethylenediaminetetra(methylenephosphonic acid);
ethylenediaminetetra(methylenephosphonic acid); calcium sodium salt;
hexamethylenediaminetetra(methylenephosphonic acid);
hexamethylenediamunetetra(methylenephosphonic acid), potassium salt;
diethylenetriaminepenta(methylenephosphonic acid);
diethylenetriaminepenta(methylenephosphonic acid), sodium salt.
5. A method according to Claim 1 in which said retarder comprises at least one compound selected from hydroxycarboxylic or polycarboxylic acids and their salts; ascorbic and isoascorbic acids; sulphonic acid - acrylic acid copolymers; polyhydroxysilanes; polyacrylamide; carbohydrates and lignosulphonates.
6. A method according to Claim 5 in which said retarder comprises at least one compound selected from hydroxycarboxylic acids, polycarboxylic acids, isoascorbic acid and poly-hydroxysilanes.
7. A method according to Claim 1, in which said retarder comprises - at least one compound selected from the phosphonic acid derivatives and, - at least one compound selected from hydroxycarboxylic or polycarboxylic acids and their salts; ascorbic and isoascorbic acids;
sulphonic acid - acrylic acid copolymers;
polyhydroxysilanes; polyacrylamide carbohydrates; and lignosulfonates.
sulphonic acid - acrylic acid copolymers;
polyhydroxysilanes; polyacrylamide carbohydrates; and lignosulfonates.
8. A method according to Claim 7, in which said retarder comprises - at least one compound selected from aminotri(methylenephosphonic acid); aminotri(methylenephosphonic acid), pentasodium salt; 1-hydroxyethylidene-1,1-diphosphonic acid;
1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt;
ethylenediaminetetra(methylenephosphonic acid);
ethylenediaminetetra(methylenephosphonic acid); calcium sodium salt, hexamethylenediaminetetra(methylenephosphonic acid);
hexamethylenediaminetetra(methylenephosphonic acid), potassium salt;
diethylenetriaminepenta(methylenephosphonic acid);
diethylenetriaminepenta(methylenephosphonic acid), sodium salt; and - citric acid
1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt;
ethylenediaminetetra(methylenephosphonic acid);
ethylenediaminetetra(methylenephosphonic acid); calcium sodium salt, hexamethylenediaminetetra(methylenephosphonic acid);
hexamethylenediaminetetra(methylenephosphonic acid), potassium salt;
diethylenetriaminepenta(methylenephosphonic acid);
diethylenetriaminepenta(methylenephosphonic acid), sodium salt; and - citric acid
9. A method according to Claim 8, in which said retarder comprises of aminotri(methylenephosphonic acid) and citric acid.
10. A method according to Claim 9, in which the ratio of aminotri(methylenephosphonic acid) to citric acid is from 1:1 to 2:1.
11. A method according to Claim 1, in which said accelerator comprises at least one compound selected from calcium salts, thiocyanates, triethanolamine, and glycolurils.
12. A method according to Claim 11, in which said accelerator consists of a mixture of calcium nitrate, sodium thiocyanate, triethanolamine and trimethylolglycoluril.
13. A method according to Claim 1, in which a water reducing strength enhancer is added together with the accelerator.
14. A method according to Claim 13, in which said water reducing strength enhancer is a lignosulphonate derivative.
15. A method according to Claim 2 in which the reclaimed concrete ranges from 10% to 50% by weight of the total mix.
16. A method according to Claim 1, in which said retarder is added after about 1 to 4 hours from the initial mixing of the concrete.
17. A concrete which has been treated according to the method of Claim 1.
3700fPG/AY/FZ
3700fPG/AY/FZ
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US90048986A | 1986-08-26 | 1986-08-26 | |
| US900,489 | 1986-08-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1315960C true CA1315960C (en) | 1993-04-13 |
Family
ID=25412613
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 545153 Expired - Lifetime CA1315960C (en) | 1986-08-26 | 1987-08-24 | Reclaiming of waste concrete |
Country Status (16)
| Country | Link |
|---|---|
| JP (2) | JPS6360184A (en) |
| KR (1) | KR930006338B1 (en) |
| CN (1) | CN1023998C (en) |
| AT (1) | AT393501B (en) |
| AU (2) | AU591327B2 (en) |
| BE (1) | BE1002417A4 (en) |
| CA (1) | CA1315960C (en) |
| CH (1) | CH677788A5 (en) |
| DE (1) | DE3727907C2 (en) |
| ES (1) | ES2007402A6 (en) |
| FR (1) | FR2603275B1 (en) |
| GB (1) | GB2194528B (en) |
| HK (1) | HK86493A (en) |
| IT (1) | IT1211682B (en) |
| PH (1) | PH24105A (en) |
| SG (1) | SG34793G (en) |
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|---|---|---|---|---|
| IT1211682B (en) * | 1986-08-26 | 1989-11-03 | Sandoz Ag | WASTE CONCRETE RECOVERY PROCEDURE |
| MY110252A (en) * | 1988-01-14 | 1998-03-31 | Construction Research & Technology Gmbh | Method for stabilizing concrete residues. |
| US5203919A (en) * | 1988-01-14 | 1993-04-20 | Sandoz Ltd. | Method and compositions for stabilizing concrete residues |
| JPH03159944A (en) * | 1989-11-14 | 1991-07-09 | Fujita Corp | Application of hydraulic composite material |
| CH678526A5 (en) * | 1990-01-27 | 1991-09-30 | Sandoz Ag | |
| US4976316A (en) * | 1990-02-20 | 1990-12-11 | Atlantic Richfield Company | Method of accelerating set of cement by washover fluid containing alkanolamine |
| CH680730A5 (en) * | 1990-07-09 | 1992-10-30 | Sika Ag | |
| GB2248612B (en) * | 1990-10-10 | 1994-10-12 | Ciba Geigy Ag | Corrosion inhibition in concrete structures |
| FR2680130A1 (en) * | 1991-08-07 | 1993-02-12 | Kadim Ltd | Method of employing a hydraulic binder and device for applying said binder |
| FR2699915B1 (en) * | 1992-12-29 | 1995-03-10 | Prod Ind Cfpi Franc | Composition of materials improving the rheological properties of cement-based products. |
| FR2724648B1 (en) * | 1994-09-20 | 1997-09-05 | Sandoz Sa | CONTROL OF HYDRATION OF CEMENT-BASED SYSTEMS |
| DE19518469B4 (en) * | 1995-05-19 | 2007-05-03 | Construction Research & Technology Gmbh | Process for the recycling of residual concrete |
| GB9511700D0 (en) * | 1995-06-09 | 1995-08-02 | Sandoz Ltd | Improvements in or relating to organic compounds |
| DE19714632A1 (en) * | 1997-04-09 | 1998-10-15 | Quinting Gmbh | Impervious, setting retarded concrete composition |
| ES2183673B1 (en) * | 2000-02-03 | 2004-09-01 | Sic Lazaro, S.L. | PROCEDURE FOR THE MANUFACTURE OF HIGH DENSITY COUNTERWEIGHTS. |
| WO2002024425A1 (en) * | 2000-09-21 | 2002-03-28 | Rdc Holdings Pte Ltd | Production of concrete |
| JP2002226241A (en) * | 2001-01-30 | 2002-08-14 | Mitsui Constr Co Ltd | Method for recycling concrete material by vacuum freeze drying |
| DE602005002937T2 (en) * | 2004-03-19 | 2008-07-31 | James Hardie International Finance B.V. | MULTIMODE ACCELERATOR FOR CEMENT MATERIALS |
| DE102005015841B4 (en) * | 2005-04-06 | 2009-04-30 | Sto Ag | Device for processing building material |
| JP2007076976A (en) * | 2005-09-16 | 2007-03-29 | Esu Ea:Kk | Method for keeping fluidity of mortar already kneaded and method for adjusting setting of the same |
| JP2007293561A (en) * | 2006-04-25 | 2007-11-08 | Shoichi Nakamura | Personal authentication accessory |
| SE533961C2 (en) * | 2007-02-22 | 2011-03-15 | Saint Gobain Byggprodukter Ab | Delay composition, use of such composition and method of handling use |
| DE102007060455A1 (en) | 2007-12-12 | 2009-06-18 | Deutsche Amphibolin-Werke Von Robert Murjahn Stiftung & Co. Kg | Device for mixing construction material |
| PL2553188T3 (en) | 2010-12-20 | 2019-01-31 | Industrilås I Nässjö Ab | Handle assembly for double-walled door |
| US9725369B2 (en) | 2014-08-13 | 2017-08-08 | Crispycrete, Llc | Method of processing unhardened concrete |
| WO2018154890A1 (en) * | 2017-02-22 | 2018-08-30 | デンカ株式会社 | Hardening agent for ready-mix shipped rapid-hardening concrete, ready-mix shipped rapid-hardening concrete material, ready-mix shipped rapid-hardening concrete composition, and method for preparing same |
| CN108101410A (en) * | 2017-12-28 | 2018-06-01 | 湖北鑫统领万象科技有限公司 | A kind of house ornamentation cement additive and its application |
| CN114430710B (en) | 2019-08-01 | 2024-09-27 | Gcp应用技术有限公司 | Coordinating concrete delivery and placement |
| CN110436808B (en) * | 2019-09-10 | 2021-08-06 | 同济大学 | Recycling method of fresh waste concrete |
| CN110776297A (en) * | 2019-10-28 | 2020-02-11 | 安徽理工大学 | Sulphoaluminate cement-based concrete and preparation process thereof |
| CN115926067B (en) * | 2022-12-28 | 2024-09-03 | 科之杰新材料集团有限公司 | High-temperature-resistant hyperbranched retarder for concrete and preparation method thereof |
| EP4417587A1 (en) * | 2023-02-20 | 2024-08-21 | Sika Technology AG | Methods for the application in thick layer of cementitious compositions comprising kinetic regulator |
| CN118388168A (en) * | 2023-08-24 | 2024-07-26 | 宁波新力建材科技有限公司 | Concrete composite additive and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE754200A (en) * | 1969-08-01 | 1970-12-31 | W R Grace & Cy | PLASTER AND CEMENT COMPOSITIONS AND FLEXIBLE MANUFACTURED PRODUCTS MADE FROM THESE COMPOSITIONS |
| JPS5025623A (en) * | 1973-07-05 | 1975-03-18 | ||
| JPS5115856A (en) * | 1974-07-30 | 1976-02-07 | Jiro Ito | Ryutai funtai yobunriki |
| JPS535222A (en) * | 1976-07-02 | 1978-01-18 | Nippon Concrete Ind Co Ltd | Utilization method of cement contained waste water |
| GB1538103A (en) * | 1977-07-14 | 1979-01-10 | Ici Ltd | Set-promoting composition for calcium sulphate hemihydrate plaster |
| JPS55149153A (en) * | 1979-05-02 | 1980-11-20 | Kao Corp | Recycling method of concrete slag |
| DE2937835A1 (en) * | 1979-09-19 | 1981-04-02 | Ohsmann, Hans, 4796 Salzkotten | HYDRAULIC BINDERS FOR THE PRODUCTION OF DELAYED CLEANING OR WALL MORTARS OR. SUITABLE TRANSPORTMORTARS |
| CH646124A5 (en) * | 1980-01-25 | 1984-11-15 | Sika Ag | PLASTERING AND WALL MORTAR WITH EXTENDED SETTING TIME. |
| US4466834A (en) * | 1983-01-03 | 1984-08-21 | W. R. Grace & Co. | Corrosion inhibiting additive for cement compositions |
| JPS59195564A (en) * | 1983-04-20 | 1984-11-06 | 旭化成株式会社 | Cement setting control |
| US4466836A (en) * | 1983-04-28 | 1984-08-21 | The Dow Chemical Company | Set retarding compounds for use in cement slurries |
| JPS6140854A (en) * | 1984-07-31 | 1986-02-27 | 藤沢薬品工業株式会社 | Cure retarder for deep layer mixture treatment art |
| IT1211682B (en) * | 1986-08-26 | 1989-11-03 | Sandoz Ag | WASTE CONCRETE RECOVERY PROCEDURE |
-
1987
- 1987-07-28 IT IT4823687A patent/IT1211682B/en active
- 1987-08-21 DE DE3727907A patent/DE3727907C2/en not_active Expired - Lifetime
- 1987-08-24 CA CA 545153 patent/CA1315960C/en not_active Expired - Lifetime
- 1987-08-24 AU AU77347/87A patent/AU591327B2/en not_active Expired
- 1987-08-24 CH CH3231/87A patent/CH677788A5/de not_active IP Right Cessation
- 1987-08-24 BE BE8700940A patent/BE1002417A4/en not_active IP Right Cessation
- 1987-08-24 KR KR1019870009236A patent/KR930006338B1/en not_active IP Right Cessation
- 1987-08-24 FR FR8711878A patent/FR2603275B1/en not_active Expired - Lifetime
- 1987-08-24 GB GB8719953A patent/GB2194528B/en not_active Expired - Lifetime
- 1987-08-25 CN CN87105879A patent/CN1023998C/en not_active Expired - Lifetime
- 1987-08-25 PH PH35727A patent/PH24105A/en unknown
- 1987-08-25 AT AT2121/87A patent/AT393501B/en not_active IP Right Cessation
- 1987-08-25 JP JP62209413A patent/JPS6360184A/en active Granted
- 1987-08-26 ES ES8702476A patent/ES2007402A6/en not_active Expired
-
1991
- 1991-05-30 AU AU78017/91A patent/AU624316B3/en not_active Ceased
- 1991-09-12 JP JP3233084A patent/JP2694883B2/en not_active Expired - Lifetime
-
1993
- 1993-03-29 SG SG34793A patent/SG34793G/en unknown
- 1993-08-19 HK HK86493A patent/HK86493A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| GB2194528A (en) | 1988-03-09 |
| DE3727907A1 (en) | 1988-03-03 |
| FR2603275B1 (en) | 1991-11-22 |
| GB8719953D0 (en) | 1987-09-30 |
| IT8748236A0 (en) | 1987-07-28 |
| HK86493A (en) | 1993-08-27 |
| DE3727907C2 (en) | 1996-11-07 |
| GB2194528B (en) | 1990-07-25 |
| IT1211682B (en) | 1989-11-03 |
| ES2007402A6 (en) | 1989-06-16 |
| AU7734787A (en) | 1988-03-03 |
| AU591327B2 (en) | 1989-11-30 |
| KR930006338B1 (en) | 1993-07-14 |
| KR880002771A (en) | 1988-05-11 |
| AU624316B3 (en) | 1992-04-08 |
| JPH0517266A (en) | 1993-01-26 |
| JPS6360184A (en) | 1988-03-16 |
| AT393501B (en) | 1991-11-11 |
| ATA212187A (en) | 1991-04-15 |
| JPH0215519B2 (en) | 1990-04-12 |
| BE1002417A4 (en) | 1991-02-05 |
| PH24105A (en) | 1990-03-05 |
| SG34793G (en) | 1993-06-11 |
| FR2603275A1 (en) | 1988-03-04 |
| CH677788A5 (en) | 1991-06-28 |
| JP2694883B2 (en) | 1997-12-24 |
| CN87105879A (en) | 1988-03-16 |
| CN1023998C (en) | 1994-03-16 |
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