This paper provides information about the synthesis and mechanical properties of geopolymers based on 12 fluid catalytic cracking catalyst residue (FCC). FCC was alkali activated with solutions containing 13 different SiO 2 /Na 2 O ratios. The microstructure and mechanical properties were analysed by using several 14 instrumental techniques. FCC geopolymers are mechanically stable, yielding compressive strength about 15 68MPa when mortars are cured at 65ºC during three days. The results confirm the viability of producing 16 geopolymers based on FCC.

Reuse of industrial and agricultural wastes as supplementary cementitious materials (SCM) in concrete and mortar productions contribute to sustainable development. In this context, Fluid catalytic cracking catalyst residue (spent FCC), a byproduct from the petroleum industry and petrol refineries, have been studied as SCM in blended Portland cement in the last years. Nevertheless, others environmental friendly alternative has been conducted in order to produce alternative binders with low CO 2 emissions. The use of aluminosilicate materials in the production of Alkali-Activated Materials (AAM) is an ongoing research topic which can present low CO 2 emissions associated. Hence, this paper studies some variables that can influence the production of AAM based on spent FCC. Specifically, the influence of SiO 2 /Na 2 O molar ratio and the H 2 O/spent FCC mass ratio on the mechanical strength and microstructure are assessed.Some instrumental techniques, such as SEM, XRD, pH and electrical conductivity measurements, and MIP are performed in order to assess the microstructure of formed alkali-activated binder. Alkali activated mortars with compressive strength up to 80 MPa can be formed after curing for three days at 65 ºC. The research demonstrates the potential of spent FCC to produce alkali-activated cements and the importance of SiO 2 /Na 2 O molar ratio and the H 2 O/spent FCC mass ratio in optimising properties and microstructure.

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A. Pereira; Akasaki, JL.; J.L.P.Melges; Mitsuuchi Tashima, M.; Soriano Martinez, L.; Borrachero Rosado, MV.; Monzó Balbuena, JM.... (2015). Effect of sugarcane bagasse ash (SBA) added to alkali-activated blast furnace salg (BFS) AbstractSugarcane bagasse is an agricultural waste which can be transformed, for cementing purposes, into an interesting material by combustion. Specifically, the ash (SBA) obtained by autocombustion was used for preparing alkali-activated cements by blending blast furnace slag (BFS). SBA had a large amount of quartz; however, it reacted in high alkaline medium. Mixtures of BFS/SBA have been used for preparing alkali-activated mortars, by using NaOH (8M solution), sodium silicate (8M solution in Na + and SiO 2 /Na 2 O molar ratio of 0.5) and KOH (8M solution) as activating reagents. Replacements of 25, 33 and 50% of BFS by SBA were carried out and compressive strengths in the range 16-51 MPa were obtained after 90 curing days. Microstructural studies demonstrated that the hydration products formed in the activation of BFS are not significantly affected by the presence of SBA in the mixture. The durability of alkaliactivated mortars was compared to ordinary Portland cement (OPC) mortar in the following media: hydrochloric acid, acetic acid, ammonium chloride, sodium sulphate and magnesium sulphate. The behaviour of alkali-activated mortars with BFS and BFS/SBA was better than that found for plain OPC mortars, especially in ammonium chloride, acetic acid and sodium sulphate media. After 200 days of testing in ammonium chloride solution, the compressive strength loss for Portland cement mortar was about 83.3%. For the same test conditions, alkali-activated mortars presented a maximum reduction of 48.4%. The presence of SBA in alkali-activated BFS mortars did not produce any serious problems in durability. As a general conclusion, sugarcane bagasse ash (SBA) obtained by autocombustion showed good cementing properties as a mineral precursor blended with blast furnace slag (BFS) in alkali-activated systems.

Blast furnace slag (BFS)/sugar cane bagasse ash (SCBA) blends were assessed for the production of alkali-activated pastes and mortars. SCBA was collected from a lagoon in which wastes from a sugar cane industry were poured. After previous dry and grinding processes, SCBA was chemically characterized: it had a large percentage of organic matter (ca. 25%). Solutions of sodium hydroxide and sodium silicate were used as activating reagents. Different BFS/SCBA mixtures were studied, replacing part of the BFS by SCBA from 0 to 40% by weight. The mechanical strength of mortar was measured, obtaining values about 60 MPa of compressive strength for BFS/SCBA systems after 270 days of curing at 20 °C. Also, microstructural properties were assessed by means of SEM, TGA, XRD, pH, electrical conductivity, FTIR spectroscopy and MIP. Results showed a good stability of matrices developed by means of alkali-activation. It was demonstrated that sugar cane bagasse ash is an interesting source for preparing alkali-activated binders.

This paper explored reported the effect of sewage sludge ash (SSA) on the mechanical and microstructural properties of geopolymers based on metakaolin (MK) involving two different SiO2/Na2O molar ratios (0.8 and 1.6), two temperature curing conditions (25°C and 65°C) and various ages of curing (1, 3, 7, 14, 28, 90 or 180 days). The geopolymers tests were characterized performed using different techniques: as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and compressive strength of mortars. Tests were performed for both high (65°C) and room (25°C) temperature curing conditions lasting for 1, 3, 7, 14, 28, 90 or 180 days. The geopolymeric samples were activated using sodium hydroxide and sodium silicate solutions using two different SiO2/Na2O molar ratios (0.8 and 1.6). The compressive strength tests showed that the replacement of MK by SSA in 10 wt.% when cured at 25 °C with the highest SiO2/Na2O molar ratio reaches similar compressive strengths after 14 days of curing compared to the samples with only MK, which reached a maximum compressive strength of 50.8 MPa at 180 days. The FTIR analyses carried out in the geopolymer pastes with SSA (10 wt.% of SSA and 90 wt.% of MK) showed a formation of N-A-S-H gels in the samples cured at 25 °C. The microstructural studies by XRD, TGA and SEM pointed out the formation of a crystalline phase as Na P-type zeolite in MK/SSA based-geopolymer pastes cured at 65 °C, which explained the loss of compressive strength of the samples cured at high temperature. However, the SSA retarded the crystallization process in the MK basedgeopolymer.

Biomass waste from rice straw has many management problems, including field firing causing severe air pollution and natural organic decomposition resulting in methane emission. The conversion of this waste to ashes may offer the possibility of reusing them in cementing systems. For the first time ashes from different parts of the rice plant (Oryza sativa) were characterised from the chemical composition point of view: rice leaf ash (RLA), rice leaf sheath ash (RlsA) and rice stem ash (RsA). Microscopic studies on ashes revealed heterogeneity in the distribution of chemical elements in the remaining cellular structure (spodograms). The highest concentration of SiO 2 was found in dumbbell-shaped phytoliths (%SiO 2 > 78%). In the global chemical composition of ashes, SiO 2 was also the main oxide present. According to Vassilev's classification of chemical composition, RLA belongs to the K-MA zone (medium acid), RlsA to the K-zone (low acid) and RsA to the S-zone (high acid). Calcination temperatures ≥550 • C completely removed organic matter from the straw and ashes underwent significant sinterisation by calcining at 650 • C due to the presence of potassium chloride. Here, ashes from global straw (rice straw ash, RSA) are characterised (via X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetry) and tested from a reactivity point of view (reaction towards calcium hydroxide) in order to assess the possibility for its reuse in cementing systems. Results from pastes made by mixing RSA and calcium hydroxide showed that the pozzolanic reactivity of the ashes is important (hydrated lime fixation of 82% for 7 days and 87% for 28 days in RSA:hydrated lime paste) and cementing C S H gel is formed after 7 and 28 days at room temperature. Compressive strength development of Portland cement mortars with 10% and 25% replacements by RSA yielded 107% and 98% of the strength of control mortar after 28 days of curing. Frattini test confirmed the pozzolanicity of the RSA blended cements. These reactivity results are very promising in terms of the potential reuse of ashes in cementing systems.

In the context of world concern with the environment, this study aims to characterize an auto-combustion produced bamboo leaf ash (BLA) by its pozzolanic behaviour, reactivity and its influence in the total porosity, pore size distribution, tortuosity and mechanical behaviour of cementitious matrices. The chemical and physical characterization of the BLA was carried using X-ray fluorescence, determination of amorphous silica content, X-ray diffraction, Fourier Transform Infrared Spectrophotometry (FTIR), laser granulometry and field emission scanning electron microscopy (FESEM). The assessed BLA is a siliceous material (74.23%) with an amorphous nature due to the amorphous silica content, which represents 92.33% of the total silica. The BLA was classified as highly reactive by assessing its pH and conductivity in a saturated calcium hydroxide (CH) medium for different proportions and temperatures. Frattini analysis, the study of CH:BLA pastes (Thermogravimetric analysis and FTIR) and Portland cement (OPC) /pozzolan pastes (Thermogravimetric analysis and FESEM) are in agreement with this classification. The replacement of OPC by BLA improved the mechanical behaviour of the cementitious matrices, as well their durability. All the mortars containing BLA presented very similar compressive strength to a control mortar (100% OPC) after only 3 days of curing and at the following tested curing ages: 7, 28 and 90 days. In the mercury intrusion porosimetry analysis, the pastes with 20 and 30% BLA content presented higher tortuosity or fewer connected pores than the control paste. Thus, the auto-combustion method proved to be successful and BLA is a suitable alternative for sustainable highperformance matrices.