Dr Chenmeng Zhang

One-part alkali-activated materials (AAMs) with fly ash and ground granulated blast furnace slag (GGBS) offer mechanical performance similar to conventional concrete and improved environmental sustainability. This paper examines the fresh and mechanical properties of 27 AAM mixes with varying mix proportions. Key design parameters include activator/binder ratio (A/B) from 0.05-0.15, binder content from 460-1050 kg/m³, and fly ash/GGBS ratio from 50/50-10/90. Flow table and setting time evaluated the workability, and compressive and flexural tests assessed the mechanical properties. Carbon emission and cost assessments were also performed. One-part AAMs achieved compressive strengths of 66 MPa at 7 days and 76 MPa at 28 days. Mixes with low binder content (460 kg/m³) showed 4-28% lower compressive strength at 84 days compared to 28 days. Higher binder content (650-1050 kg/m³) and A/B (0.1-0.15) had increased compressive strength by 6-21% at 84 days than at 28 days. The mix with 0.15 A/B, 650 kg/m³ binder, and 30/70 fly ash/GGBS ratio performed best in a multi-criteria assessment that considers mechanical properties, embodied carbon, and cost.

One-part alkali-activated materials (AAMs) with fly ash and ground granulated blast furnace slag (GGBS) offer mechanical performance similar to conventional concrete and improved environmental sustainability. This paper examines the fresh and mechanical properties of 27 AAM mixes with varying mix proportions. Key design parameters include activator/binder ratio (A/B) from 0.05-0.15, binder content from 460-1050 kg/m³, and fly ash/GGBS ratio from 50/50-10/90. Flow table and setting time evaluated the workability, and compressive and flexural tests assessed the mechanical properties. Carbon emission and cost assessments were also performed. One-part AAMs achieved compressive strengths of 66 MPa at 7 days and 76 MPa at 28 days. Mixes with low binder content (460 kg/m³) showed 4-28% lower compressive strength at 84 days compared to 28 days. Higher binder content (650-1050 kg/m³) and A/B (0.1-0.15) had increased compressive strength by 6-21% at 84 days than at 28 days. The mix with 0.15 A/B, 650 kg/m³ binder, and 30/70 fly ash/GGBS ratio performed best in a multi-criteria assessment that considers mechanical properties, embodied carbon, and cost.

This presentation mainly focuses on geopolymer in self-sensing applications. At the beginning, it introduced the principle of self-sensing materials and the motivation of using geopolymer. Then, the fresh and hardened performance as well as the carbon emission of both geopolymer and cement-based materials were exhibited. Some representitive results about the geopolymer with different electrode and conductive fillers were shown as well. Finally, the results of self-sensing performance of representive geopolymer and cement-based samples with and without graphite and steel fibres were shown. In conclusion, geopolymer had better conductivity as matrix compared with cement-based materials. The mixes with graphite had worse performance in mechanical and fresh properties but better distribution of conductive particles. The mixes with steel fibres had better conductivities and mechanical performance, but depends on the percentage of the fillers.

This study investigates the effect of metakaolin (MK) as a partial replacement of cement (CEM I) in high-workability mortars, with emphasis on fresh-state behaviour, mechanical properties, microstructural development, and carbon footprint implications. Mortars were produced with MK replacement levels ranging from 0 to 50% by mass of binder, under a constant water-to-binder ratio and fixed superplasticiser amount. Fresh-state results showed that increasing MK content reduced flowability due to its high fineness; however, high workability was maintained for replacement levels up to 20%. At 28 days, MK replacement up to 10% retains approximately 90–95% of the control compressive and flexural strength, whereas higher replacement levels lead to gradual strength reductions (to ~55–60% at 50% MK), despite comparable early-age strength gains across all mixes. Durability-related indicators demonstrated reduced water absorption and capillary uptake at moderate MK contents (approximately 20–30%), indicating refined pore structure and reduced pore connectivity. Microstructural analyses using SEM, TGA, and XRD confirmed effective portlandite consumption and the formation of dense C–A–S–H-type hydration products at moderate MK replacement levels, whereas excessive MK contents resulted in unreacted MK. A comparative carbon footprint assessment showed that MK incorporation leads to proportional reductions in embodied CO2 emissions, with replacement levels of 10–20% providing the most favourable balance between mechanical performance, durability, and environmental benefit. Therefore, the results demonstrate that MK can be used as a supplementary cementitious material for producing low-carbon, high-workability mortars.

This paper presents a statistical assessment of the relationship between compressive strength and embodied carbon for a database of 100 geopolymer mortar mixes, with comparison to conventional cement mortars. The geopolymer dataset covers a wide range of formulations and curing conditions, with 28-day compressive strengths between approximately 5 and 80 MPa and cradle-to-gate embodied carbon values ranging from 29 to 501 kgCO₂eq/m³. Linear regression and distribution-based analyses were used to quantify trends and variability in strength-carbon relationships. The results indicate a positive correlation between compressive strength and embodied carbon for geopolymer mortars, although with substantial scatter reLlecting differences in precursor chemistry and activator composition. At a compressive strength of approximately 20 MPa, the mean embodied carbon of geopolymers was approximately 170 kgCO₂eq/m³. This represents a reduction of around 60-65% compared with typical embodied carbon values for cement-based mortars, which is approximately 460 kgCO₂eq/m³. The lowest carbon geopolymer mix showed carbon reductions of more than 90% relative to cement-based mortars. The Lindings demonstrate the potential of geopolymer mortars to deliver substantial embodied carbon reductions at equivalent strength. Keywords. Geopolymer mortars; Embodied carbon; Compressive strength; Life cycle assessment (LCA); Low-carbon construction materials