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This study uses metakaolin, sodium hydroxide, sodium metasilicate, and water content as the reaction variables in the application of the design of experiment (DOE) method. At the same time, the various component factors and their interactions were analyzed to understand how these factors affect the mechanical properties of a metakaolin-based geopolymer incorporated with SiC sludge (SCSGPs). The results of the statistical analysis showed that the compressive strength of SCSGPs was affected by the Na/Si molar ratio (NSR) (p-level = 0.000 <0.05), the Na/Al molar ratio (NAR) (p-level= 0.000 <0.05), and the interaction between the dissolution rate of Si (DRA). Within the design scope of this study, the maximum compressive strength of SCSGPs and the coefficients of the NSR, the NAR, and the DRA of SCSGPs was evaluated. The multiple regression analysis and the tested coefficient of r2 were also studied. The multiple regression analysis models provide an effective reference for the application of SCSGPs. [ABSTRACT FROM AUTHOR]

This study aimed to verify the role and feasibility of co-fired fly ash (CFA) as an alternative construction material. It also demonstrated the engineering properties of CFA mortar and compared them with those of pulverized coal fly ash (PCFA) mortar. Further, CFA-PCFA-cement mortar specimens were mixed to produce ternary eco-binder mortars and find the optimal application proportion. The results pointed out that the pozzolanic strength activity index of CFA was 76 %, with only a slight pozzolanic reaction. The sum of the chemical composition (SiO 2 +Al 2 O 3 +Fe 2 O 3) of CFA was insufficient to meet ASTM C618 requirements, and it was deduced that a small amount of CFA should be used as the substitute for cement or fine aggregates. Specimens with CFA replacing fine aggregates contributed to lower water absorption, improved sulfate resistance, and increased compressive strength; Specimens with CFA replacing cement reduced shrinkage and improved sulfate resistance but decreased compressive strength and increased absorption. Blended CFA-cement mortars consisting of 5 % CFA as a replacement material for cement and fine aggregates had excellent engineering properties. Ternary blended CFA-PCFA-cement mortar exhibits superior engineering properties. The optimum proportion is an economy-friendly binder composed of 10 % CFA (5 % as cement and 5 % as fine aggregates) and 10% PCFA (as a replacement for cement). • Development and application of ternary economic binders in this study. • Ternary eco-binder consists of co-fired fly ash (CFA), pulverized coal fly ash (PCFA) and cement. • CFA is classified as a low pozzolanic reactive material. • Eco-binder consists of 5 % CFA as cement, 5 % CFA as fine aggregates and 10 % PCFA as cement. [ABSTRACT FROM AUTHOR]

Geopolymer concretes can be a viable alternative to conventional Portland cement-based materials. In their design, it is important to maintain an appropriate liquid-to-solid ratio (L/S), which affects several properties, such as the compressive strength, water absorption, and frost resistance. The objective of this paper is to analyze the influence of the fly-ash and metakaolin precursor types for three different L/S ratios: 0.30, 0.35, and 0.45. The results of the physical and mechanical properties, including the apparent density and compressive strength, as well the durability parameters, including frost resistance and water penetration depth, are presented in this paper. It was found that as the L/S ratio decreased, the average compressive strength increased for all materials. After freeze–thaw cycles, decreases in the compressive strength properties were observed for all types of materials—metakaolin- and fly ash-based—irrespective of the L/S ratio. Moreover, the frost resistance of geopolymers increased with the increase in the L/S ratio. The printability of the mixes was also verified in order to confirm the application of the developed materials to additive manufacturing processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • We demonstrated the feasibility of using RUFA for the preparation of geopolymers. • We conducted in-depth analysis into the microstructure of RUFA geopolymers. • Sodium-hydroxide-activated geopolymer presented superior mechanical properties. • We produced RUFA geopolymer with compressive strength exceeding 97.6 MPa. This study used reactive ultra-fine fly ash (RUFA) as the primary raw materials in the preparation of a novel RUFA geopolymer. Note that the solution to binder weight ratio was maintained at the same level by varying the concentration of the NaOH solution. Extensive analysis was conducted to characterize the flowability and mechanical properties. X-ray diffraction (XRD), Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP), thermogravimetric (TG), and zeta potential analyses were used to examine the microstructure of RUFA geopolymers. Increasing the concentration of NaOH also led to an increase in compressive strength. A high NaOH concentration of 12 mol/L resulted in compressive strength of 97.6 MPa at 28 days. Finally, increasing the concentration of NaOH increased the formation of the primary reaction geopolymerization product, N-A-S-H gel, resulting in a denser microstructure with lower porosity. [ABSTRACT FROM AUTHOR]

• A new cementless binder is developed from CFA, ggbs and DG. • Innovative cementless mixtures can be used as a binder for pervious concrete. • Reasonable amount of DG content can effectively improve the strength. • Main hydration reactants of cementless binders are C-S-H and AFt crystals. • Cementless pervious concrete has a compressive strength of 12 MPa. In this study, alkali-free activator-type ternary cementless binders were developed using ground granulated blast-furnace slag (GGBS), co-fired fly ash (CFA), and desulfurization gypsum (DG). The properties of cementless binders were verified and used to investigate the feasibility of application to pervious concrete. The results indicated that including CFA in cementless binders increased the initial and final setting times. The addition of DG shortened the setting time and the addition exceeded 7 wt% resulting in a rapid setting, which did not meet the ASTM C150 specification. A binary cementless binder with a CFA-GGBS mix achieved a maximum compressive strength up to 54% of the cement group, and the optimum mixture was 70% GGBS with 30% CFA. DG increased the SO 3 content of the binder and promoted the production of ettringite (AFt), resulting in an effective increase in compressive strength up to 92% of the cement group. The optimum proportion of cementless binders to meet the setting times was 70% GGBS, 25% CFFA, and 5% FGDG, resulting in maximum compressive strength up to 79% of the cement group. During the hardening period of the cementless pastes, the generation of AFt affected the internal pore structures of the C-S-H colloids, resulting in higher capillary pores. DG also accelerated the production of AFt, causing an increase in capillary pores. In addition, the maximum compressive strength of cementless pervious concrete developed in this study reached 12 MPa, and the permeability coefficient was up to 0.156 cm/s. It can meet the requirements of the general pervious pavement specification in Taiwan. [ABSTRACT FROM AUTHOR]

Our objective in this study was to promote the recycling of industrial by-products by combining ground granulated blast-furnace slag (G) and circulating fluidized bed co-fired fly ash (FA). We then added sodium silicate as an alkali activator (A) to a combination of G and FA (GFA) to create a novel cement-free cementitious material (AGFA). One of our main research aims was to explore the influence of the activator on GFA in terms of working and mechanical properties and drying shrinkage behavior. Hydration products were analyzed using XRD and SEM-EDS. The setting time of GFA was longer than that of AGFA, and the water absorption and fluidity were both higher. Adding sodium silicate to the GFA was shown to greatly improve mechanical properties through the formation of hydration products containing C–S–H, C-A-S-H, and C–N-A-S-H gels, which intertwined to form a dense microstructure. Compared to AGFA, the GFA was less affected by dry shrinkage, due to the expansive formation of ettringite (from anhydride) during the hydration process. Note that the reaction of the alkaline agent in AGFA with the anhydride in FA reduced the amount of ettringite that formed. The alkaline agent also promoted the depolymerization of vitreous G and FA particles, resulting in the formation of large quantities of gel, the process of which consumed much of the free water, resulting in further shrinkage. Further, it provides a good feasibility and application prospect in environmentally friendly building material of GFA and AGFA cementless composites and is expected to replace traditional cement-based composites. • This study developed an environmentally-friendly cementless composite. • Co-fired fly ash and GGBS can be combined to act as a full replacement for cement. • A novel cement-free cementitious material without activators was presented. • Sodium-silicate activated composites presented better mechanical properties. • The compressive strength of activated composite could reach more than 70 MPa. [ABSTRACT FROM AUTHOR]

Basic oxygen furnace slag (BOFS) was ground to three levels of fineness as a replacement for cement at weight proportions of 10, 30, 50, and 70 wt.%. Fineness and weight proportion were shown to have significant effects on the flowability and setting time of the mortars. The expansion of BOFS mortars increased with an increase in the proportion of cement replaced, thereby exacerbating the effects of cracking. Optimal mechanical properties were achieved when 10 wt.% of the cement was replaced using BOFS with fineness of 10,000 cm2/g. The compressive strength of BOFS mortar is similar to that of ordinary Portland mortar, which makes BOFS suitable for the partial replacement of cement as a supplementary cementitious material. Scanning electron microscopy results revealed that the reaction of CaO with H2O results in the formation of C–S–H colloids, whereas the reaction of SiO2 with Al2O3 produces C–A–S–H colloids. The use of BOFS as a partial replacement for Portland cement could make a tremendous contribution to the steel industry and help to lower CO2 emissions. [ABSTRACT FROM AUTHOR]

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using water-quenched blast-furnace slag (BFS) and co-fired fly ash (CFFA) to replace cement. The objectives of this study were to gauge the feasibility of using a non-cement binder in pervious concrete and identify the optimal binder mix design in terms of compressive strength, permeability, and durability. For filled percentage of voids by cement paste (FPVs) of 70%, 80%, and 90%, which mixed with CFFA and BFS as the binder (40 + 60%, 50 + 50%, and 60 + 40%) to create pervious concrete with no cement. The results indicate that the complete (100%) replacement of cement with CFFA and BFS with no alkaline activator could induce hydration, setting, and hardening. After a curing period of 28 days, the compressive strength with different FPVs could reach approximately 90% that of the control cement specimens. The cementless pervious concrete specimens with BFS:CFFA = 7:3 and FPV = 90% presented better engineering properties and permeability. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of adding circulating fluidized bed combustion (CFBC) ash, desulfurization slag, air-cooled blast-furnace slag and coal bottom ash to the controlled low-strength material (CLSM). Test methods include slump flow test, ball drop test, water soluble chloride ion content measurement, compressive strength and length change measurement. The results show that (1) the use of CFBC hydration ash with desulfurization slag of slump flow is the best, and the use of CFBC hydration ash with coal bottom ash and slump flow is the worst; (2) CFBC hydration ash with desulfurization slag and chloride ion content is the highest; (3) 24 h ball drop test (diameter ≤ 76 mm), and test results are 70 mm to 76 mm; (4) CFBC hydration ash with desulfurization slag and compression strength is the highest, with the coal bottom ash being the lowest; increase of CFBC hydration ash can reduce compressive strength; and (5) the water-quenched blast furnace slag and CFBC hydration ash would expand, which results in length changes of CLSM specimens. [ABSTRACT FROM AUTHOR]

Residues of co-combustion are not addressed in Taiwan standards for fly ash use in concrete. This paper presents feasibility of re-utilizing CFB co-fired fly ash (CFFA) as an alkali activator for the eco-binder of CFFA and GGBS. The optimal mixture of the binder is specimen F3S7, which reaches 31.43 MPa that is 72.4% compressive strength of OPM at 56 days. XRD and SEM showed that CFFA activated the GGBS to generate CaO, which reacted with H 2 O, SiO 2 , and Al 2 O 3 to form C–S–H and C–A–S–H pastes. Compressive strength reduction trend for F4S6 to F7S3 started after 28 days because high SO 3 content. [ABSTRACT FROM AUTHOR]