Use of ancient copper slags in portalnd cement and alkali activated cement matrices

Some Chilean copper slag dumps from the nineteenth century still remain, without a proposed use that encourages recycling and reduces environmental impact. In this paper, the copper slag abandoned in landfills is proposed as a new building material. The slags studied were taken from Playa Negra and Púquios dumps, both located in the region of Atacama in northern Chile. Pozzolanic activity in lime and Portland cement systems, as well as the alkali activation in pastes with copper slag cured at different temperatures, was studied. The reactivity of the slag was measured using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), electrical conductivity and pH in aqueous suspension and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, copper slag-Portland cement mortars with the substitution of 25% (by weight) of cement by copper slag and alkali-activated slag mortars cured at 20 and 65 C were made, to determine the compressive strength. The results indicate that the ancient copper slags studied have interesting binding properties for the construction sector.Nazer, A.; Paya Bernabeu, JJ.; Borrachero Rosado, MV.; Monzó Balbuena, JM. (2016). Use of ancient copper slags in portalnd cement and alkali activated cement matrices. Journal of Environmental Management. 167:115-123. doi:10.1016/j.jenvman.2015.11.024S11512316

Use of residual diatomaceous earth as a silica source in geopolymer production

The use of binders as an alternative to Portland cement has gained importance in recent years. Among them, geopolymeric binders, developed by the reaction between an aluminosilicate precursor and a high alkalinity solution, have become one of the most promising alternatives. The activating solution generally comprises waterglass and sodium hydroxide. Since waterglass is the most expensive material and has a high environmental impact, using alternative silica sources will lead to more sustainable binders. Previous studies have successfully used rice husk ash (RHA) as a silica source. This research aims to assess the possibility of using diatomaceous earth (or diatomite) as an alternative silica source, like the previous studies with RHA. Diatomite is a sedimentary rock with a high amorphous silica content formed by fossilized diatom remains. In this work, the geopolymer was obtained using a fluid cracking catalyst residue as the precursor and six different activating solution types prepared with commercial products, residual diatomite (from beer and wine industries) and RHA. The results open a new possible route for the reuse and recovery of diatomaceous earth residue, although the compressive strength results of the mortars were slightly lower than those for mortars prepared with RHA or commercial reagents

Reutilisation of hazardous spent fluorescent lamps glass waste as supplementary cementitious material

Spent fluorescent lamps glass (SFLG) waste, manually and mechanically processed in a lamps waste treatment plant, was used to partially replace up to 50 wt% Portland cement (PC). Both waste types exhibited similar pozzolanic activity. The mortars containing up to 35 wt% SFLG met the specifications for other pozzolanic materials (e.g. fly ash) and, after 90 curing days, their compressive strength values were similar to or higher than those of the 100% PC sample (58.8 MPa). Our results provide an alternative reutilization process for this hazardous waste to reuse SFLG as-received (no washing to reduce mercury) and contributes to less PC use.Funding for open access charge: CRUE-Universitat Jaume

Durability of glass fiber reinforced cement (GRC) containing a high proportion of pozzolans

[EN] Glass fiber reinforced cement (GRC) is an excellent composite for architects and engineers because it can be molded to produce laminar panels or to create complicated designs. GRC is a fine concrete reinforced with alkali-resistant glass fibers at 3¿5% per mass. However, fiber durability is limited because of the aggressiveness of the alkaline medium produced during Portland cement hydration (effect of portlandite). The objective of this study is to assess GRC with high Portland cement replacement with pozzolans (ground fly ash or a mixture of ground fly ash and sonicated silica fume) in order to reduce the corrosion of the fibers. The selected high-content pozzolan (60% replacement) composites were tested under different conditions: aging, drying¿wetting, freezing¿thawing, and chemical attack (ammonium chloride and sulfuric acid). The modulus of rupture and toughness were determined. Composite behavior showed that the samples with pozzolans not only better resisted aging, but also physical and chemical attacks, and specimens presented a better modulus of rupture and toughness than the samples prepared with 100% Portland cement (control specimens). Due to the good behavior in durability terms, the high pozzolan content GRC products are suitable in potential corrosive environments for sunscreens, drainage channels, cable trays, sound barriers, or pavements.This research was funded by Spanish Ministry of Education and Science and FEDER funds (Project BIA 2004-00520)Lalinde, LF.; Mellado Romero, AM.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Paya Bernabeu, JJ. (2022). Durability of glass fiber reinforced cement (GRC) containing a high proportion of pozzolans. Applied Sciences. 12(7). https://doi.org/10.3390/app1207369612

Air-void system characterization of new eco- cellular concretes

[EN] Cellular concrete is an alternative to conventional concrete as a low-density and high-insulating building material. The eco-cellular concretes (ECCs) based on geopolymer technology have been recently introduced by the scientific community. A form of ECC was studied, in which the fluid catalytic cracking residue and the blast furnace slag were employed as precursors, the rice husk ash was utilized as an alternative silica source in the activator, and the aerating reagent was replaced with recycled aluminum foil. Field emission scanning electron microscopy, optical microscopy, and ImageJ version 1.48 software (National Institutes of Health) were employed to characterize the void distribution. Bulk density and porosity were determined by hydric tests. The results revealed that lowest densities without strength loss were obtained when the cementing matrix had a homogeneous void system: similar spacing between pores, narrow size ranges, and nonconnected pores. A relationship was established between open and closed porosity with density and thermal conductivity.The authors acknowledge the financial support from the Universitat Politecnica de Valencia (UPV) through internal project GEOCELPLUS. The authors are especially grateful to Dr. Josefa L. Rosello Caselles for the recycled aluminum foil, and also to the Electronic Microscopy Service of the UPV. Thanks also go to DACSA, BP Oil, and Cementval for supplying the raw materials.Font-Pérez, A.; Borrachero Rosado, MV.; Soriano Martinez, L.; Monzó Balbuena, JM.; Paya Bernabeu, JJ. (2021). Air-void system characterization of new eco- cellular concretes. Journal of Materials in Civil Engineering. 33(5):1-10. https://doi.org/10.1061/(ASCE)MT.1943-5533.0003692S11033

Geopolymer eco-cellular concrete (GECC) based on fluid catalytic cracking catalyst residue (FCC) with addition of recycled aluminium foil powder

[EN] This study presents a new cellular concrete design focused on the energy eco-efficiency and the sustainability concept: geopolymer eco-cellular concrete (GECC). Geopolymer systems made from alkali-activated fluid cracking catalyst residue (FCC) aerated by recycled aluminium foil powders (R) were designed. Commercial aluminium powder (A) was also used as an aerating agent in GECC matrix and its effect was compared with traditional cellular concrete (TCC) made with ordinary Portland cement (OPC). The more alkaline medium of the GECC system improved the hydrogen reaction rate and consequently a higher efficiency in the pore matrix development can be found. Aluminium powder addition of 0.2% by mass of the precursor (FCC) was enough to yield cellular concrete with a natural density significantly lower than that found for TCC. The replacement of A by R made it possible to produce an alternative GECC in which the recycling of the waste aluminium has an important eco-efficiency role because its low cost and its energy saving function. Ground R has less aeration effectiveness than A. However, when comilling of FCC þ R was carried out, advantageous performance GECC was attained. Very interesting properties were obtained for this material: good pore size and its proper distribution in the matrix, low natural density (600e700 kg/m3), relatively high compressive strength (2.5e3.5 MPa), low open/closed porosity ratio (1.15) and the lowest thermal conductivity (0.581 W/mK). This opens an interesting way of reusing both FCC as precursor and aluminium foil waste as an aerating agent in the preparation of new geopolymer eco-cellular concrete (GECC).This work was developed within the scope of the project Geocelplus (internal project, Universitat Politècnica de València).The authors give special grateful to Dra. Mrs. Josefa L. Roselló Caselles for kindly support and recycled aluminium foil supply. The authors also thank the Electron Microscopy Service of the Universitat Politècnica de València (Spain).Font-Pérez, A.; Borrachero Rosado, MV.; Soriano Martinez, L.; Monzó Balbuena, JM.; Paya Bernabeu, JJ. (2017). Geopolymer eco-cellular concrete (GECC) based on fluid catalytic cracking catalyst residue (FCC) with addition of recycled aluminium foil powder. Journal of Cleaner Production. 168:1120-1131. doi:10.1016/j.jclepro.2017.09.110S1120113116

Evaluation of rice straw ash as a pozzolanic addition in cementitious mixtures

[EN] Rice husk ash is one of the most widely studied biomass ashes used in pozzolanic addition. Given its lower silica content, rice straw ash (RSA) has been explored less often, despite the fact that, according to the United Nations Food and Agriculture Organization (FAO), rice straw (RS) production is estimated at 600 million tons/year. In this work, RSA was physically and chemically characterized, and its pozzolanic properties were assessed. A controlled conditioning, burning, homogenization and grinding procedure was carried out to obtain RSA from RS. Chemical composition, insoluble residue, reactive silica, chloride content and particle size distribution were assessed for ash characterization. To determine RSA pozzolanicity, Frattini, electrical conductivity and pH measurements in an aqueous suspension of hydrated CH/RSA mixtures were obtained. Portland cement (PC) mortars with 15% and 30% RSA substitutions evaluated. The mechanical tests showed specimens with a strength activity index up to 90% and 80% with 15% and 30% RSA, respectively, after 3 days, and these values grew to 107¿109% after 90 curing daysThis research was funded by the Spanish Government and FEDER funds (MINECO/FEDER-Project RTI2018-09612-B-C21).Hidalgo, S.; Soriano Martinez, L.; Monzó Balbuena, JM.; Paya Bernabeu, JJ.; Font, A.; Borrachero Rosado, MV. (2021). Evaluation of rice straw ash as a pozzolanic addition in cementitious mixtures. Applied Sciences. 11(2):1-17. https://doi.org/10.3390/app11020773S11711

Compressive strength and microstructure of alkali-activated mortars with high ceramic waste content

[EN] The present work investigated alkali-activated mortars with high ceramic waste contents. Tile ceramic waste (TCW) was used as both a recycled aggregate (TCWA) and a precursor (TCWP) to obtain a binding matrix by the alkali-activation process. Mortars with natural siliceous (quartz) and calcareous (limestone) aggregates, and with other ceramic waste materials (red clay brick RCB and ceramic sanitaryware CSW waste), were also prepared for comparison purposes. Given the lower density and higher water absorption values of the ceramic aggregates, compared to the natural ones, it was necessary to adapt the preparation process of the recycled mortars by presaturating the aggregate with water before mixing with the TCWP alkali-activated paste. Aggregate type considerably determined the mechanical behaviour of the samples cured at 65 °C for 3 days. The mortars prepared with the siliceous aggregate presented poor mechanical properties, even when cured at 65 °C. The behaviour of the limestone aggregate mortars depended heavily on the applied curing temperature and, although they presented the best mechanical properties of all those cured at room temperature, their compressive strength reached a maximum when cured at 65 °C, and then decreased. The mechanical properties of the mortars prepared with TCWA progressively increased with curing time (53 MPa at 65 °C for 28 days). An optimum 50 wt% proportion was observed for the limestone/TCWA mortars (¿43 MPa, 3 days at 65 °C), whereas the mechanical properties of that prepared with siliceous particles (10 MPa) progressively increased with the TCWA content, up to 100 wt% substitution (23 MPa). Limestone particles interacted with the binding matrix, and played an interesting beneficial role at the 20 °C curing temperature, with a slight reduction when cured long term (28 days) at 65 °C. The results demonstrated a potential added value for these ceramic waste materials.The authors would like to thank the Spanish Ministry of Science and Innovation and the Spanish Ministry of Economy and Competitiveness for supporting this study through Projects GEOCEDEM BIA 2011-26947 and BIA2015 70107-R, respectively. They also thank FEDER funding.Reig, L.; Sanz, M.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Soriano Martínez, L.; Paya Bernabeu, JJ. (2017). Compressive strength and microstructure of alkali-activated mortars with high ceramic waste content. Ceramics International. 43(16):16322-16334. https://doi.org/10.1016/j.ceramint.2017.07.072S1632216334431

Stabilization of soil by means alternative alkali-activated cement prepared with spent FCC catalyst

[EN] Alkali-activated cements are widely studied as alternative and sustainable binder in soil stabilization. In this research work, a mold was designed and constructed, which allowed small cubic specimens to be made (40 x 40 x 40 mm(3)). With the newly designed mold, cubic samples of soil stabilized with portland cement (OPC) and alternative AAC (based on spent fluid catalytic cracking catalyst FCC) were prepared from which compressive strength was obtained. Cylindrical specimens were also prepared using the same binders as in the previous case to obtain their compressive strength. The results obtained in both cases were compared. Greater resistances for cubic samples were achieved. The cubic specimens were selected for being better in terms of standard deviation of compressive strength for AAC stabilized soil. The obtained compressive strength and standard deviation results were compared between the soil specimens stabilized with different stabilizers cured at 7, 14, 28, and 90 days. The method allows small-sized cubic specimens to be prepared. It improves ergonomics. It also facilitates a large number of specimens being obtained with a small amount of sample. Soil stabilized with AAC yielded higher compressive strength after 90 days compared to that with OPC.Spanish Ministry of Economy and Competitiveness, Grant/Award Number: BIA2015 70107-R.Cosa-Martínez, J.; Soriano Martinez, L.; Borrachero Rosado, MV.; Paya Bernabeu, JJ.; Monzó Balbuena, JM. (2020). Stabilization of soil by means alternative alkali-activated cement prepared with spent FCC catalyst. 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Compressive strength and microstructure of alkali-activated blast furnace slag/sewage sludge ash (GGBS/SSA) blends cured at room temperature

In the present work, ground granulated blast furnace slag (GGBS) and sewage sludge ash (SSA) blends were assessed for the production of alkali-activated pastes and mortars. Percentages of SSA to substitute GGBS ranged from 0–30 wt.% and sodium concentrations of 6–10 mol.kg-1 were used for the activating solutions. Pastes and mortars were cured at 20 ºC for up to 90 days. Raw materials were characterised by granulometric analysis, XRF, XRD, FTIR and SEM techniques. The replacement percentage of GGBS by SSA and the sodium hydroxide concentration of the alkaline activator were optimised to produce mortar with compressive strengths close to 30 MPa after 28 curing days at room temperature. Best results were obtained in samples blended with 20 wt.% SSA activated with 6 mol.kg-1 NaOH solutions which, according to the XRD, FTIR and microscopic results, contained higher amounts of (N,C)-A-S-H gel. The potential use of SSA for the development of alternative cementitious materials at room temperature has been demonstrated