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This paper studied the durability, microstructure, and fire behavior of lightweight mortars based on cement, metakaolin (MK), ultrafine ground granulated blast furnace slag (UGGBFS), ceramic waste powder (CWP), and clay brick waste powder (CBWP). Two sets of mixes were prepared with two types of lightweight aggregate including lightweight expanded clay aggregate (LECA) and pumice aggregate. Regarding the durability assessment, the electrical resistivity and water absorption of the mortars were measured. The UGGBFS-based alkali-activated mortar with pumice aggregate exhibited the highest electrical resistivity and lowest water absorption, while CBWP-based geopolymer mortar with LECA showed the lowest electrical resistivity, and the water absorption of this mortar was 62% higher than that of the equivalent cement mortar. In addition, scanning electron microscopy (SEM) images showed that UGGBFS-based mortar developed a dense matrix with few pores; whereas, incomplete geopolymerization and voids were detected in CWP- and CBWP-based mortars. Furthermore, the effect of elevated temperatures ranging from 23 to 800 °C on the compressive strength of specimens was investigated. According to the results, CWP- and CBWP-based mortars showed the best performance and retained about 54% and 49% of their original strength at 800 °C, respectively. Furthermore, a statistical study was carried out on the fire test results to quantify the contribution of different parameters using analysis of variance (ANOVA) method. It was shown that temperature was the most influential parameter.

Alkali-activated materials (AAMs) and geopolymers are identified as potential alternatives to conventional Portland cement due to their ability to convert wastes into useful materials and reducing the CO2 emissions. Furthermore, they offer a higher strength-to-weight ratio than comparable Portland cement binders, which makes them a suitable material for lightweight concrete/mortar applications. The present study aimed to examine the effect of precursor and lightweight aggregate type on workability, compressive strength, flexural strength as well as the environmental impact of lightweight mortars. For this purpose, precursors derived from waste aluminosilicate sources including ground granulated blast furnace slag (GGBFS), metakaolin (MK), waste ceramic powder (WCP), and waste clay brick powder (WCBP) were used for the synthesis of alkali-activated and geopolymer mortars. In addition, an equivalent Portland cement mortar was prepared for comparison purposes. Pumice and lightweight expanded clay aggregate (LECA) were used as the lightweight aggregates. Based on the test results, the WCP- and WCBP-based geopolymer mortars exhibited a higher workability than other mortar mixes. Generally, mortars prepared with pumice aggregate showed lower workability and higher mechanical strength than LECA incorporated mixes due to the higher density of pumice and its better bonding with paste. Alkali-activated and geopolymer mortars presented a higher initial strength and reached about 80% of their 28-day compressive strength in 1 day, whereas that of the cement mortar was only 33%. The maximum 28-day compressive strength (82.5 MPa) and flexural strength (9.28 MPa) were obtained for the GGBFS-based and MK-based mortars, respectively, which were about 29% and 41% higher than that of the counterpart Portland cement mortar. From an ecological point of view, geopolymer and alkali-activated mortars exhibited about 50% (on average) less carbon footprint and were 25% (on average) lower in energy demands. The findings highlight the superiority of alkali-activated and geopolymer mortars over Portland cement counterparts for lightweight applications due to their better workability, higher initial strength, and lower environmental impact.

In this paper, durability and mechanical properties of self-compacting mortars containing various percentage of natural zeolite and nano-silica were assessed experimentally using compressive and flexural strength, water absorption, electrical resistivity and rapid chloride permeability tests. The results showed that the mechanical properties of self-compacting mortars would be increased by increasing the replacement levels of natural zeolite and nano-silica. Addition of natural zeolite and nano-silica increased the electrical resistivity of self-compacting mortars and consequently decreased the permeability of the self-compacting mortars. The chloride ion penetration into self-compacting mortars were decreased by increasing natural zeolite and nano-silica contents. It was also observed that the presence of the pozzolan and nano material has a positive influence on the microstructural properties and hydration process of self-compacting mortars. Additionally, the artificial neural network modeling could efficiently predict the durability mechanical properties of self-compacting mortars.

In this paper, the effects of using Cr2O3 and ZnO2 nanoparticles on the mechanical properties and durability of self-compacting mortars are investigated. A fraction of Portland cement was replaced with 1, 2, 3, 4 or 5 wt.% of either Cr2O3 or ZnO2 nanoparticles, and 25 wt.% fly ash. The rheological properties of these mortars were determined through the mini-slump flow diameter and V-funnel flow time tests. The mechanical and durability characteristics were evaluated by compressive and flexural strength, water absorption, electrical resistivity and rapid chloride permeability tests. The microstructure of the mortars was assessed through the use of scanning electron microscopy. The inclusion of 2 wt.% Cr2O3 or 4 wt.% ZnO2 nanoparticles had the best result in compressive and flexural strength tests. Also, mixtures containing either 3 wt.% of Cr2O3 or 5 wt.% of ZnO2 nanoparticles obtained the best result in terms of durability. It can be deduced that the properties of these mixtures are significantly improved by the addition of Cr2O3 and ZnO2 nanoparticles.