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Ferrisilicate was considered a crystalline zeolite containing iron (III) and silicon in the zeolite lattice positions. The aim of this work is to study the influence of Fe2O3/SiO2 molar ratios contained in the Fe-silica on the properties of geopolymer materials derived from waste fired clay brick and metakaolin. Fe-silica with various Fe2O3/SiO2 molar ratios of 0.2, 0.4, 0.6, 0.8 and 1.0 were synthesised using rice husk ash and hematite. 0 and 10 wt. % of each type of aluminosilicate is added to each type of Fe-silica. A commercial sodium silicate solution with a SiO2/Na2O molar ratio of 1.6 is used as a hardener. X-ray diffractometry and Fourier Transform Infrared spectroscopy are used for the characterisation of the Fe-silica and the geopolymers. In addition to these analyses, the compressive strengths of the geopolymer materials have been measured and the fragments obtained have been examined using a scanning electron microscope. The results show that the compressive strengths of metakaolin-based geopolymers increase from 53.34 to 69.08 MPa when the Fe2O3/SiO2 molar ratios contained in the Fe-silica are incremented from 0 to 0.8. When the Fe2O3/SiO2 molar ratio is increased from 0.8 to 1.0, they are reduced from 69.08 to 63.22 MPa. In contrast, those of geopolymer materials derived from waste fired clay brick decrease from 45.42 to 21.15 MPa when their Fe2O3/SiO2 molar ratios rise from 0 to 0.6 increases from 21.15 to 24.11 MPa beyond 0.6. The micrograph of the geopolymer material from the mixture of metakaolin and Fe-silica with a molar ratio of Fe2O3/SiO2 equal to 0.8 is more compact, homogeneous and partially smooth compared to other geopolymers. The presence of hematite and cristobalite, which act as fillers, is evident from the X-ray patterns of geopolymer materials after the addition of Fe-silica. This work shows that the addition of metakaolin to multi-molar of Fe-silica significantly improves the compressive strength of geopolymer materials. On the other hand, this addition leads to a reduction in the compressive strength when waste fired clay brick is used. [ABSTRACT FROM AUTHOR]

To reduce the impact on global warming, many countries and regions are advocating the use of low‐carbon and green supplementary cementitious materials (SCMs) to improve the cement industry. This study investigates the shear behavior of reinforced concrete (RC) beams made with a novel green concrete, limestone, calcined clay, and cement clinker (LC3). Full‐scale shear tests were conducted on RC and LC3‐RC beams to evaluate their fundamental behavior for structural applications. The shear resistance of LC3 concrete beams was evaluated using Chinese, American, and Eurocode codes, while carbon emission and environmental impact were analyzed by life cycle assessment (LCA). Results showed that LC3‐RC and RC beams exhibited similar shear behavior in terms of crack initiation, propagation, and development. The increase in concrete strength improved the stiffness of LC3‐RC specimens, while RC specimens remained unchanged. The ductility of RC specimens was inversely proportional to concrete strength, while LC3‐RC beams exhibited optimal ductility. The increase in stirrup ratio significantly improved the shear resistance of both LC3‐RC and RC beams. With increased shear‐span ratio, the failure mode of LC3 specimens improved, changing from diagonal‐compression to shear compression or diagonal tension failure. The shear resistance of both LC3‐RC and RC beams was underestimated by GB 50010‐2010, ACI 318‐19, and Eurocode 2. LC3 concrete significantly reduced energy consumption and carbon emissions and achieved favorable environmental benefits in terms of GWP, PMFP, POFP, TAP, and TETP. Increasing usage of limestone in LC3 may further decrease environmental potential without sacrificing mechanical properties. The findings of this study contribute to the development of sustainable and environmentally friendly structures in engineering. [ABSTRACT FROM AUTHOR]

Limestone calcined clay cement (LC3) holds promise as a new type of sustainable cement-based material, but the mechanisms underpinning its engineering performance are still poorly understood. Here, a metal intrusion-enhanced imaging approach was employed to quantitatively analyze and link the pore structure development of LC3 to its hydration process, i.e. solid-phase development, and mechanical performance. We found that the early age microstructural development in LC3 is inhomogeneous, with the perimeter of limestone particles displaying higher porosity relative to that surrounding calcined clay and clinker. At later ages, the formation of carboaluminates and calcium-aluminate-silicate-hydrates homogenized the overall microstructure of LC3, thereby delivering improved mechanical performance. Overall, our analysis suggested a more efficient particle packing in LC3 mixes, which decreases the volume/connectivity of micro-pores and can account for LC3's notable flexural strength. These findings can assist the development of improved LC3 binder formulations alongside other ternary binders with possibly higher limestone additions. [ABSTRACT FROM AUTHOR]

The combined use of calcined clay and limestone (LC2) with slag cement can ease the promotion of a clay-type binder and elongate the use of traditionally used slag. Results showed that addition of 22–39% LC2 can enhance the compressive strength of slag cement concrete by 26, 86, 39 and 24% at 3, 7, 28 and 90 days, respectively. Quantitative X-ray radiation diffractometry (QXRD), thermogravimetry analysis (TGA), calorimetry and thermodynamic modelling have been used to reveal the individual role of each constituent in the quaternary blend. Results showed that the degree of hydration of slag cement can be increased by LC2, and calcined clay was understood to be the main contributing factor owing to the pozzolanic reactivity and filler effect. Limestone can increase the reaction degree of slag owing to the generation of hydrated mono-/hemi-carboaluminate (Mc/Hc). A synergistic effect of slag and limestone can contribute to the later performance in quaternary LC2–slag cement. [ABSTRACT FROM AUTHOR]