METHOD FOR THE TREATMENT OF NON-HARDENED CEMENT COMPOSITIONS, ADMIXTURE TO BE USED IN SUCH METHOD, AND USE OF SOLID GRANULES PRODUCED BY SUCH METHOD

Abstract

Methods for the treatment of non-hardened cement compositions, especially returned concrete, and to admixtures suitable to be used in such methods. Admixtures included modified starch and a sugar. Further, solid granules obtained by such methods and fresh concrete or mortar utilizing solid granules thus obtained.

Claims

1. A method for the treatment of non-hardened cement compositions, the method comprising the steps of: a) providing a non-hardened cement compositions, b) providing an admixture which comprises a modified starch and a sugar, c) mixing the non-hardened cement compositions and the admixture to form a coagulated material, d) discharging the coagulated material obtained under c) into a storage facility, e) drying the coagulated material to form solid granules, and f) optionally separating the dried, solid granules into fractions of different particle size.

2. A method according to claim 1, wherein the admixture provided in step b) essentially consists of a modified starch and a sugar.

3. A method according to claim 1, wherein the admixture essentially consists of 70-80 w % of modified starch and 20-30 w % of a sugar.

4. A method according to claim 1, wherein the modified starch is a copolymer of starch grafted with acrylic acid and acrylamide.

5. A method according to claim 1, wherein the sugar is sucrose.

6. A method according to claim 1, additionally comprising a step of crushing and/or grinding the solid granules.

7. A method according to claim 6, wherein the crushing and/or grinding is done under an atmosphere of CO.sub.2.

8. A concrete or mortar mixture comprising at least one cement and aggregates, wherein at least 30 w % of the total weight of aggregates are solid granules obtained in a method as described in claim 1.

9. An admixture for a method for the treatment of non-hardened cement compositions, the admixture comprising a) a modified starch, and b) a sugar.

10. An admixture according to claim 9, wherein it essentially consists of a modified starch and a sugar.

11. An admixture according to claim 9, wherein it essentially consists of 70-80 w % of modified starch and 20-30 w % of a sugar.

12. An admixture according to claim 9, wherein the modified starch is a graft copolymer of starch with a copolymer of starch grafted with acrylic acid and acrylamide.

13. An admixture according to claim 9, wherein the sugar is sucrose.

14. An admixture according to claim 9, wherein it is a monocomponent admixture.

15. An admixture according to claim 9, wherein it is a multicomponent.

Description

FIGURES

[0085] FIG. 1 shows solid granules obtained in a method as described for example 1-2. Granules of this type could easily be crushed as described in Example 1. Result of crushing is shown to the left of FIG. 1. Results as shown in FIG. 1 are rated with 1 for compactness of granules and 1 for breakability of granules.

[0086] FIG. 2 shows solid granules obtained in a method as described for example 2-3. Granules of this type could be crushed as described in Example 1. Result of crushing is shown to the left of FIG. 2. Results as shown in FIG. 2 are rated with 2 for compactness of granules and 2 for breakability of granules.

[0087] FIG. 3 shows solid granules obtained in a method as described for example 3-7. Granules of this type could hardly be crushed as described in Example 1. Result of crushing is shown to the left of FIG. 3. Results as shown in FIG. 3 are rated with 3 for compactness of granules and 3 for breakability of granules.

[0088] FIG. 4 shows solid granules obtained in a method as described for example 2-4. Granules of this type could not be crushed as described in Example 1. Result of crushing is shown to the left of FIG. 4. Results as shown in FIG. 4 are rated with c for compactness of granules and not measurable for breakability of granules.

[0089] FIG. 5 shows a pile of solid granules discharged into a storage facility. Solid granules were prepared as described in example F1 (Capitol) of table 7.

[0090] The following examples will provide the skilled person with further embodiments of the present invention. They are not meant to limit the scope of this invention.

EXAMPLES

[0091] The following raw materials were used: [0092] Mod starch: modified starch; starch grafted with acrylic acid potassium salt and acrylamide (CAS 119131-19-0). [0093] Starch: potato starch, not modified [0094] Cellulose: Carboxymethyl cellulose (Mw 50,000 g/mol) [0095] Sucrose: Sigma Aldrich; >99.5% purity [0096] Glucose: D-(+)-glucose; Sigma-Aldrich; >99% purity [0097] Gluconate: sodium D-gluconate; Sigma-Aldrich; >99% purity [0098] Citric acid: Sigma Aldrich; >99.5% purity [0099] Rice husk: Pillowganic; Horticulture Garden

[0100] The following admixtures F1-F31 were prepared by mixing the ingredients in following table 1 until visually homogeneous powders were obtained.

TABLE-US-00001 TABLE 1 admixtures prepared (all numbers in g) A1 A2 A3 A4 A5 A6 A7 A8 A9 Mod Starch 100 70 70 75 80 Starch 70 Cellulose 75 77 Sucrose 100 30 30 25 20 25 23 Glucose 30 A10 A11 A12 A13 A14 A15 A16 A17 Mod Starch 75 75 75 75 Cellulose 75 67 75 75 Sucrose 18 18 Gluconate 25 25 Citric acid 25 33 SHMP 25 25 Rice husk 7 7

[0101] Portland cement Type I (ASTM 150-00) with the following compositions were used:

TABLE-US-00002 TABLE 2 phase composition of cements (in w % rel to dry cement weight) C3S C2S C3A C4AF Cement 0 Holcim USA n.m. n.m. n.m. n.m. Cement 1 LafargeHolcim, Whitehall 48 17 11 8 Cement 2 CalPortland, Mojave 57 15 4 11 Cement 3 Lehigh Cement, Nazareth 57 13 9 8 Cement 4 Capitol Cement 60 12 11 6 n.m .: not measured

Example 1

[0102] Mortars were prepared by mixing 441.6 g Portland cement Type I (type as indicated in table 3), 358.8 g concrete sand, and 1084.8 g sand #3 on a Hobart mixer for 1 minute. Then 1.73 mL polycarboxylate-based superplasticizer (Sikament 686 supplied by Sika Corp) and water were added to yield a weight ratio of water to cement of 0.5. Mixing on the Hobart mixer was then continued at speed #1 for 3 minutes. The mortars were then mixed by hand with a spatula for 30 seconds. The respective admixture type and amount as indicated in following table 3 was then added. Mixing was then continued at speed #1 for another 2 minutes. Formation of the granules was clearly visible.

[0103] Slump was measured on the mortar mixes before addition of the admixture according to standard ASTM C143/C143M using a mini-cone. Therefore, the mini-cone was placed on a non-absorptive base plate and then filled in two layers equal in volume of mortar. Each layer was rodded 25 times with a steel rod, then the top was striked off. The mini-cone was slowly lifted with 3-4 seconds and slump measured. The slump is an indicator for similar mixing quality of the mortars prepared. Compactness and breakability of granules was rated according to visual rating scheme (see FIGS. 1-4). The compactness was judged directly after formation of the solid granules at the end of mixing. For the breakability judgement, the formed block of granules was dried for 24 h at 20-23 C./10% r.h. and then intended to be broken up with a hammer in one stroke. A rating of 1 is very good, a rating of 2 is good, a rating of 3 is poor. A rating c means that the sample was cured and no granules were formed.

TABLE-US-00003 TABLE 3 examples 1-1 to 1-12 (examples 1-3, 1-4, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11 are not according to the present invention) Example 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 Admixture A5 A6 A8 A13 A7 A10 A11 A12 Cement 0 0 0 0 0 0 0 0 Dosage [kg/m.sup.3] 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Initial slump [cm] 10 9.5 9.5 10 n.a. n.a. n.a. n.a. Compactness* 3 1 3 c c 3 3 c Breakability** 2 1 2 3 3 2 2 n.m. Example 1-9 1-10 1-11 1-12 Admixture A1 A2 A3 A4 Cement 4 4 4 4 Dosage [kg/m.sup.3] 1.2 1.2 1.2 1.2 Initial slump [cm] 10.2 10.2 10.2 10.2 Compactness* c dnc c 3 Breakability** n.m. dnc 3 2 n.a.: not available n.m.: not measurable dnc: does not coagulate n.m.: not measurable

[0104] A low rating in compactness and breakability is desirable. It is thus apparent from table 3, that admixture A6 performs best.

Example 2

[0105] Concrete was prepared by mixing 22.23 kg sand, 29.8 kg gravel, and 9.23 kg of water on a Concrete Steel-Drum Electric Mixer for 45 seconds. Then, 10.26 kg Portland cement Type I (type as indicated in table 4), were added and mixing continued for 1 minute. Next, 40 mL polycarboxylate-based superplasticizer (Sikament 686 supplied by Sika Corp) and 1.03 kg of water were added to yield a weight ratio of water to cement of 0.5. Mixing was then continued for 3 minutes and 15 seconds. Next, the respective admixture type and amount as indicated in following table 4 was added. Mixing was then continued for another 2 minutes. Formation of the granules was clearly visible.

[0106] Slump, compactness, and breakability were measured as described in example 1.

TABLE-US-00004 TABLE 4 examples 2-1 to 2-5 (examples 2-3, 2-4, 2-5 are not according to the present invention) Example 2-1 2-2 2-3 2-4 2-5 Admixture A5 A6 A8 A13 A14 Cement Holcim Holcim Holcim Holcim Holcim Dosage [kg/m.sup.3] 1.2 1.2 1.2 1.2 1.2 Initial slump [cm] 19.7 19.7 20.3 19.7 19.1 Compactness* 3 2 2 c 3 Breakability n.m. 1 2 n.m. n.m. n.m .: not measurable

Example 3

[0107] Concrete in example 3 were prepared in the same way as in example 2. For example 3, Portland cement from different suppliers was tested. The Portland cement, type of admixture and admixture dosage is indicated in below tables 5-8. Results obtained are also indicated in below table 5-8.

TABLE-US-00005 TABLE 5 examples 3-1 to 3-3 (example 3-1 is not according to the present invention) Example 3-1 3-2 3-3 Additive A8 A6 A16 Cement 1 1 1 Dosage [kg/m.sup.3] 1.2 1.8 1.8 Initial slump [cm] 21 20.3 21 Compactness* 3 2 2 Breakability 2 2 2

TABLE-US-00006 TABLE 6 examples 3-4 to 3-6 (example 3-4 is not according to the present invention) Example 3-4 3-5 3-6 Additive A8 A6 A16 Cement 2 2 2 Dosage [kg/m.sup.3] 1.2 1.8 1.8 Initial slump [cm] 21 21 21 Compactness* 2 2 2 Breakability 2 2 2

TABLE-US-00007 TABLE 7 examples 3-7 to 3-9 (example 3-7 is not according to the present invention) Example 3-7 3-8 3-9 Additive A8 A6 A16 Cement 3 3 3 Dosage [kg/m.sup.3] 1.2 1.8 1.8 Initial slump [cm] 20.3 20.3 20.3 Compactness* 3 2 3 Breakability 3 1 3

TABLE-US-00008 TABLE 8 examples 3-10 to 3-13 (example 3-10 not according to the present invention) Example 3-10 3-11 3-12 3-13 Additive A8 A6 A16 A17 Cement 4 4 4 4 Dosage [kg/m.sup.3] 1.8 1.8 1.8 1.8 Initial slump [cm] 19.7 19.7 20.3 20.3 Compactness* c 1 2 3 Breakability 3 1 2 n.m.