Physical–microstructural evaluation and sulfate resistance of no‐cement mortar developed from a ternary binder of industrial by‐products

Abstract

The present research evaluates the physical properties and microstructure of no‐cement mrtar specimens, which were developed using three waste materials, rice husk ash (RHA), ground granulated blast furnace slag (GGBFS), and circulating fluidized bed combustion fly ash (CFA), as binders. Various weight ratios of GGBFS/RHA were used (100/0, 15/85, 30/70, and 45/55), and CFA was added at ratios of 10, 15, and 20% of total binder weight. Slump flow and unit weight were used to evaluate the fresh properties of the no‐cement mortar samples, while hardened properties of the mortar samples were evaluated through compressive strength (CS) and drying shrinkage tests. In addition, scanning electron microscopy/energy dispersive spectrometer and X‐ray diffraction patterns were used to analyze the microstructure of the samples, while visual examination and loss CS tests were used to estimate sulfate resistance. As a result, the inclusion of RHA required a higher amount of superplasticizer in order to achieve a similar flowability with RHA‐free mortar and remarkably reduced the fresh unit weight of the mortar mixture. In addition, the partial replacement of GGBFS with RHA up to 30% improved the 120‐day CS of mortar specimens with 10, 15, and 20% CFA content by 8.8, 10.4, and 10.1%, respectively. Moreover, the developed no‐cement mortars exhibited excellent performance against sulfate attack. Higher CFA content in the mixtures also generated higher volumes of hydration products and ettringite gel, which further increased mortar strength.

Development of a cementless eco-binder as an alternative to traditional Portland cement in construction activities

“…5, the increase in strengths at 91-day testing compared to 28-day strength for eco-binder samples ranged from 24-28% while the increment in the corresponding reference OPC100 sample was only 3%. The further strength increase in paste samples containing SCMs can be attributed to the continuous formation of C-S-H/C-A-S-H gels and AFt during the pozzolanic reaction process as mentioned in previous research [12].…”

“…5, the increase in strengths at 91day testing compared to 28-day strength for eco-binder samples ranged from 24-28% while the increment in the corresponding reference OPC100 sample was only 3%. The further strength increase in paste samples containing SCMs can be attributed to the continuous formation of C-S-H/C-A-S-H gels and AFt during the pozzolanic reaction process as mentioned in previous research [12]. In addition, the compressive strength development of all samples increased with hydration periods, and especially the rate of strength increment was significant at the later period of the eco-binders in contrast to the low strength development in the reference sample.…”

“…On the other hand, increasing RHA content was associated with incorporating less slag in the paste samples. As a result, there was a reduction in both amounts of portlandite and alumina, which contributed to the formation of C-S-H/C-A-S-H during the hydration process [12]. Therefore, the more slag replacement level by RHA content uses, the more strength reduction occurs as clearly seen in Fig.…”

“…Additionally, self-cementitious properties of CFA are possibly the most useful for the synthesis of a hydraulic binder and it is also identified that the optimum utilization of CFA in the blended binder of slag and CFA was in a range of 15-25% [10]. In previous work, the authors studied the engineering and durability properties of eco-friendly mortar developed from slag, CFA, and RHA, in which CFA acted as an activator [11,12]. However, the leaching potential of heavy metals from these waste materials in Vietnam and the characterization of hydration products contributing to strength development and its properties of eco-binder still have not been yet examined and verified.…”

Life-Cycle Assessment of Alkali-Activated Materials Incorporating Industrial Byproducts

“…Moreover, efficient industrial waste management and reducing the consumption of non-renewable natural resources are vital for sustainable development and cleaner ecosystems. Since the disposal of industrial waste materials is often associated with adverse environmental impact, a wide range of so-called “green” concrete and mortar mixtures incorporating industrial byproducts has been developed [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Since OPC is the primary concrete constituent responsible for CO 2 emissions and embodied energy (EE), efforts have been made to fully or partially replace it with supplementary cementitious materials (SCMs).…”