Optimisation of GBFS, Fly Ash, and Nano-Silica Contents in Alkali-Activated Mortars

Abstract

Although free-cement-based alkali-activated paste, mortar, and concrete have been recognised as sustainable and environmental-friendly materials, a considerable amount of effort is still being channeled to ascertain the best binary or ternary binders that would satisfy the requirements of strength and durability as well as environmental aspects. In this study, the mechanical properties of alkali-activated mortar (AAM) made with binary binders, involving fly ash (FA) and granulated blast-furnace slag (GBFS) as well as bottle glass waste nano-silica powder (BGWNP), were opti-mised using both experimentally and optimisation modelling through three scenarios. In the first scenario, the addition of BGWNP varied from 5% to 20%, while FA and GBFS were kept constant (30:70). In the second and third scenarios, BGWNP (5–20%) was added as the partial replacement of FA and GBFS, separately. The results show that the combination of binary binders (FA and GBFS) and BGWNP increased AAM’s strength compared to that of the control mixture for all scenarios. In addition, the findings also demonstrated that the replacement of FA by BGWNP was the most significant, while the effect of GBFS replacement by BGWNP was less significant. In particular, the highest improvement in compressive strength was recorded when FA, GBFS, and BGWNP were 61.6%, 30%, and 8.4%, respectively. Furthermore, the results of ANOVA (p values < 0.0001 and high F-values) as well as several statistical validation methods (R > 0.9, RAE < 0.1, RSE < 0.013, and RRSE < 0.116) confirmed that all the models were robust, reliable, and significant. Similarly, the data variation was found to be less than 5%, and the difference between the predicted R2 and adj. R2 was very small (<0.2), thus confirming that the proposed non-linear quadratic equations had the capability to predict for further observation. In conclusion, the use of BGWNP in AAM could act as a beneficial and sustainable strategy, not only to address environmental issues (e.g., landfill) but to also enhance strength properties.

Strain Hardening of Polypropylene Microfiber Reinforced Composite Based on Alkali-Activated Slag Matrix

“…Development of new strain-hardening inorganic composite can be in mixture composition and in manufacturing technology. In study of mixture compositions the following results were obtained: the use of microfiber in the amount of 2% by volume or more [51][52][53][54][55]; the use of rheologically active mineral additives in cement matrices with a superplasticizer to ensure workability at low W/C ratio and at high microfiber amount [56,57]; the use of mineral additives that improve workability and setting time in alkali-activated slag matrices [58][59][60][61]; the use of quartz sand with a low fineness modulus as a fine aggregate to obtain a homogeneous matrix and ensure a dense and uniform contact of matrix with the microfiber surface [62][63][64][65][66][67][68]. Manufacturing technology takes into account: the sequence of addition of components into a mixture [69][70][71][72][73]; mixing modes [62,[74][75][76][77].…”

“…An increase in density can be achieved by reducing the water-to-cement ratio using a superplasticizer and rheologically active mineral additives. High filling with microfiber can be achieved by justifying the choice of the type of concrete mixer [68][69][70][71], the sequence of addition of components [72][73][74], and the speed and duration of mixing [62,[75][76][77]. A laboratory automatic mixer for mortars from Tinius Olsen was used to prepare the mixtures (Figure 2).…”

Systematic Experimental Assessment of POFA Concrete Incorporating Waste Tire Rubber Aggregate

“…For example, response surface methodology (RSM) was widely used to not only reduce the number of experimental designs, but also to assess the interaction and relationship between the affecting parameters, as well as to predict and optimize the output effectively [ 58 , 59 , 60 ]. For instance, Algaifi, Mustafa Mohamed [ 61 ] optimize the mechanical properties of alkali-activated mortar incorporating (granulated blast-furnace slag) GBFS, fly ash, and Nano-Silica using RSM. Based on the outcome, it was inferred that the quadratic model predicted quite accurate and reliable results with the highest correlation ( R 2 ) of 0.9.…”

Research on Compressive and Flexural Properties of Coal Gangue-Slag Geopolymer under Wetting-Drying Cycles and Analysis of Micro-Mechanism

“…Ground granulated blast furnace slag (GGBFS) is a highly active powder, and alkali-activated slag (AAS) is a new type of gelling agent with good mechanical properties and excellent chemical durability [ 14 ]. GGBFS can also form high-strength geopolymers after being excited by alkalis [ 15 , 16 , 17 ], but its price is relatively expensive, and the large-scale use of slag will increase the cost of geopolymer preparation. The geopolymer produced by the combination of coal gangue and GGBFS can produce high-strength geopolymer in a short time [ 18 , 19 ], and the use of coal gangue as the main material can reduce the cost of preparing geopolymers.…”