SUPPLEMENTARY CEMENTITIOUS MATERIALS FROM RECYCLED CEMENT PASTE

Abstract

Method for producing a supplementary cementitious material from concrete waste and similar materials, supplementary cementitious material obtainable by the method, use of the supplementary cementitious material for making hydraulic building materials and alkali activated binders, method for manufacturing alkali activated binders, composite binders and alkali activated binders comprising the supplementary cementitious material, and use of the composite binder for making hydraulic building materials.

Claims

1. A method for producing a supplementary cementitious material comprising Ca, Si, Mg, Al, Fe, wherein the an X-ray amorphous proportion is at least 60% by weight based on the a total weight of the supplementary cementitious material and having a mass ratio $\frac{m\left(\mathrm{CaO}\right)+m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)}<0.9$ determined from the amounts of the oxides measured by X-ray fluorescence (XRF), comprising the steps: i) providing a starting material comprising hydrated cement ii) melting the starting material provided in step i) in a furnace at a temperature between 1000 C. to 1800 C. obtaining a melted mixture, iii) subsequent rapid cooling of the melted mixture obtained in step ii) adjusting an X-ray amorphous proportion of at least 60% by weight based on the total weight of the supplementary cementitious material to provide the supplementary cementitious material.

2. The method according to claim 1, wherein the starting material comprising hydrated cement is obtained from waste concrete or waste material, which has an analogous chemical/mineralogical composition.

3. The method according to claim 1, wherein the starting material comprises one or more of the following based on the total weight of the starting material: 10 to 30% by weight CaO, 0 to 10% by weight MgO, 20 to 60% by weight SiO.sub.2, 3 to 10% by weight Al.sub.2O.sub.3, and/or 1 to 5% by weight Fe.sub.2O.sub.3.

4. The method according to claim 1, wherein the supplementary cementitious material has pozzolanic properties comprising 90 to 100% by weight pozzolanic phases based on the total weight of the supplementary cementitious material.

5. A supplementary cementitious material comprising Ca, Si, Mg, Al, Fe, having an X-ray amorphous proportion of at least 60% by weight based on a total weight of the supplementary cementitious material, wherein an amount of CaO ranges from 20 to 45% by weight based on the total weight of the supplementary cementitious material, and having a mass ratio $0.45<\frac{m\left(\mathrm{CaO}\right)+m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)}<0.9$ determined from amounts of the oxides measured by X ray fluorescence (XRF), obtained by the method according to claim 1 comprising the steps i) providing a starting material comprising hydrated cement ii) melting the starting material provided in step i) in a furnace at a temperature between 1000 C. to 1800 C. obtaining a melted mixture, iii) subsequent rapid cooling of the melted mixture obtained in step ii) by direct contact with water adjusting an X-ray amorphous proportion of at least 60% by weight based on the total weight of the supplementary cementitious material to provide the supplementary cementitious material.

6. The supplementary cementitious material according to claim 5 having a particle size distribution with a D.sub.90 from 5 m to 500 m measured by laser diffraction.

7. The supplementary cementitious material according to claim 5 having a Rosin Rammler slope n in a range from 0.6 to 1.4.

8. A method for manufacturing an alkali activated binder wherein a supplementary cementitious material obtained by the method defined in claim 1 is provided and mixed with an alkali silicate having a modulus 3.0 as alkaline activator to provide the alkali activated binder.

9. (canceled)

10. An alkali activated binder comprising the supplementary cementitious material obtained by the method defined in claim 1 and an alkali silicate having a modulus 3.0 as alkaline activator.

11. The alkali activated binder according to claim 10, wherein the alkaline activator is selected from sodium silicate, potassium silicate and mixtures thereof.

12. The alkali activated binder according to claim 10 comprising, based on a combined dry weight of the supplementary cementitious material and alkaline activator, 1 to 40% by weight alkaline activator.

13. (canceled)

14. A hydraulic binder comprising the supplementary cementitious material obtained by the method defined in claim 1 and a cement.

15. The hydraulic binder according to claim 14, wherein the cement is selected from the group consisting of Portland cement, calcium sulfoaluminate cement and calcium aluminate cement.

16. The hydraulic binder according to claim 14 comprising, based on the total weight of the hydraulic binder, 1 to 88% by weight supplementary cementitious material and 22 to 99% by weight cement.

17. (canceled)

18. The supplementary cementitious material according to claim 5, comprising from 90 to 100% by weight pozzolanic phases and having a particle size distribution with a D.sub.90 from 10 m to 200 m, measured by laser diffraction, and/or a Rosin Rammler slope n in the range from 0.7 to 1.2.

19. The supplementary cementitious material according to claim 5, wherein the starting material comprises one or more of the following based on the total weight of the starting material: 10 to 30% by weight CaO, 0 to 10% by weight MgO, 20 to 60% by weight SiO.sub.2, 3 to 10% by weight Al.sub.2O.sub.3, and/or 1 to 5% by weight Fe.sub.2O.sub.3.

20. The alkali activated binder according to claim 11, comprising, based on the combined dry weight of the supplementary cementitious material and alkaline activator, 5 to 35% by weight alkaline activator.

21. The alkali activated binder according to claim 10, wherein the alkaline activator is potassium silicate in an amount, based on the combined dry weight of the supplementary cementitious material and alkaline activator, from 10 to 30% by weight.

22. The hydraulic binder according to claim 14, wherein the supplementary cementitious material comprises from 90 to 100% by weight pozzolanic phases and has a particle size distribution with a D.sub.90 from 25 m to 200 m, measured by laser diffraction, and/or a Rosin Rammler slope n in the range from 0.7 to 1.2.

23. The hydraulic binder according to claim 15, comprising, based on the total weight of the hydraulic binder, 1 to 88% by weight supplementary cementitious material and 22 to 99% by weight cement.

Description

[0098] The term substantially free means that a particular material is not purposefully added to a composition, and is only present in trace amounts or as an impurity. As used herein, unless indicated otherwise, the term free from means that a composition does not comprise a particular material, i.e. the composition comprises 0 weight percent of such material.

[0099] FIG. 1: Particle size distribution of GRCP 1 and GRCP 2.

Example 1

[0100] Two industrial RCPs (RCP 1 and RCP 2) were obtained from concrete demolition waste and used for glass preparation. The chemical compositions (in % by weight) of RCP 1 and RCP 2 determined by XRF (X ray fluorescence) and stated as oxides are listed in table 1 and 2. The loss on ignition (LOI) is reported as well. About 5 kg of each RCP was melted in graphite crucibles in an induction furnace at 1800 C.50 C. and held constant for 30 min at the targeted temperature. In order to produce vitreous structure molten glasses were rapidly quenched in a water ice bath. Afterwards, magnetic particles were removed using a magnet. The compositions (in % by weight) of the resulting SCMs (glass compositions GRCP 1 and GRCP 2) are listed in table 3a, table 3b lists the Blaine surface and basicities. The SCMs (GRCP 1 and GRCP 2) were ground in a laboratory ball mill to Blaine fineness of about 4000 cm.sup.2/g.

TABLE-US-00001 TABLE 1 Chemical composition of RCPs RCP 1 RCP 2 LOI at 1050 C. 22.6 18.5 SiO.sub.2 43.0 43.5 Al.sub.2O.sub.3 4.7 6.6 TiO.sub.2 0.3 0.4 MnO 0.1 0.1 Fe.sub.2O.sub.3 2.2 2.2 CaO 23.2 23.0 MgO 1.1 2.6 K.sub.2O 0.9 1.0 Na.sub.2O 0.4 0.5 SO.sub.3 0.9 1.5 P.sub.2O.sub.5 0.1 0.1 Total 99.5 99.9

TABLE-US-00002 TABLE 2 RCP 1 RCP 2 Quartz 33 29 Calcite 32 11 Amorphous 21 39 Other 13 21 Total 100 100

TABLE-US-00003 TABLE 3a Resulting chemical compositions of GRCPs: GRCP 1 GRCP 2 LOI at 1050 C. 0 0 SiO.sub.2 58.8 54.8 Al.sub.2O.sub.3 6.0 9.0 TiO.sub.2 0.4 0.5 MnO 0.1 0.1 Fe.sub.2O.sub.3 0.7 0.8 CaO 30.3 30.0 MgO 1.0 3.0 K.sub.2O 1.0 1.3 Na.sub.2O 0.5 0.6 SO.sub.3 0.5 0.5 P.sub.2O.sub.5 0.02 0.02 Total 100.5 100 Amorphous content 98.7 99.8

TABLE-US-00004 TABLE 3b Blaine surface and basicities of GRCPs: GRCP 1 GRCP 2 Blaine 4270 cm.sup.2/g 4180 cm.sup.2/g B0 0.51 0.55 B1 0.53 0.60 B2 0.48 0.52 B3 42.80 38.56

[0101] Cements were prepared from 57.3% by weight ground industrial Portland clinker, 38.2% by weight ground glasses as SCM (GRCP 1 and GRCP 2) and 4.5% by weight ground anhydrite. Limestone-containing cement was also prepared as reference. The cement clinker and limestone were each ground to 4000 cm.sup.2/g Blaine fineness in a laboratory ball mill. Finally, materials were homogenized using the same device.

[0102] Compressive strength was measured in mortars after 1, 2, 7 and 28 days. The mortars were prepared from the cements, quartz sand with a D.sub.50 of 0.4 mm and water in weight ratios 2:3:1.1, i.e. at water-to-cement ratio of 0.55, and mixed according to DIN EN 196-1. The mortars were cast into steel moulds to produce cubes 2 cm2 cm2 cm. These cubes were tested for compressive strength according to DIN EN 196-1, with same load rate in stress per seconds as in the norm. For each testing date, 5 cubes were tested and the result reported below is an average. The properties of the final cement compositions (stated as oxides in % by weight) are listed in table 4a. The measured strengths are listed in table 4b.

TABLE-US-00005 TABLE 4a CEM-L CEM-GRCP 1 CEM-GRCP 2 LOI at 1050 C. 16.8 0.2 0.1 SiO.sub.2 12.3 33.7 32.1 Al.sub.2O.sub.3 3.4 5.7 6.5 TiO.sub.2 0.2 0.3 0.3 MnO 0.03 0.1 0.1 Fe.sub.2O.sub.3 2.2 2.4 2.4 CaO 59.2 50.1 50.1 MgO 1.3 1.6 2.3 K.sub.2O 0.8 1.3 1.3 Na.sub.2O 0.1 0.3 0.4 SO.sub.3 3.1 3.4 3.4 P.sub.2O.sub.5 0.1 0.1 0.1 Total 99.5 99.1 99.2

TABLE-US-00006 TABLE 4a CEM-L CEM-GRCP 1 CEM-GRCP 2 compressive strength 10.3 9.7 9.6 1 d [MPa] compressive strength 19.9 19.7 19.7 2 d [MPa] compressive strength 29.4 29.3 30.1 7 d [MPa] compressive strength 35.0 50.0 51.7 28 d [MPa]

Example 2

[0103] Alkali activated binders were made from melted recycled concrete paste as supplementary cementitous material and four different alkaline activators. The recycled concrete paste paste had the composition as shown in table 5.

TABLE-US-00007 TABLE 5 XRF RCP LOI 1050 C. 18.5 SiO.sub.2 43.5 Al.sub.2O.sub.3 6.6 TiO.sub.2 0.4 MnO 0.1 Fe.sub.2O.sub.3 2.2 CaO 23.0 MgO 2.6 K.sub.2O 1.0 Na.sub.2O 0.5 SO.sub.3 1.5 P.sub.2O.sub.5 0.1 Total 99.9 quartz 26.5 calcite 10.0 amorphous 34.5 albite 4.2 microcline 3.3 clinker phases 1.0 others 15.8

[0104] The tested activators were potassium silicate solution with a modulus of 1.5, sodium silicate solution with a modulus of 3.2, a dry sodium carbonate, and a sodium hydroxide solution with a concentration of 10 mol/l. For preparation of the samples, the supplementary cementitious material (or binder) was mixed 30 seconds with the aggregate (sand), then 1 minute with the activator (or water) at a water/binder ratio of 0.375 (0.4 for sodium silicate due to poor workability), and the obtained paste was poured into a plastic cup as mould. The dry activator was mixed with the source material in such an amount that 10% by weight sodium carbonate with respect to the binder were present. Instead of mixing with the activator, those samples were mixed with water. Each sample contained 3 g of binder and 4.5 g of aggregate. The samples were stored 24 hours at 20 C. and 65% relative humidity. Then, the samples were assessed by pressing them with a spatula and trying to remove them from the cup. Only the sample made with potassium silicate having a modulus below 3.0 could be demoulded. The other samples were still wet and could not be demoulded. Further tests with sodium silicate having a modulus from 1.0 to 2.0 provided samples with appreciable strength which could be demoulded.