The engineering properties of high strength mortars incorporating juniper seed ash calcined at different temperatures: Comparison with other SCMs

• Published in: Powder technology 2023-05, Vol.422, p.118474, Article 118474
• Main Authors: Çelik, Damla Nur, Demircan, Rüya Kılıç, Shi, Jinyan, Kaplan, Gökhan, Durmuş, Gökhan
• Format: Article
• Language: English
• Subjects: alkalinity; carbon footprint; compression strength; electrical resistance; Embodied environmental impact; Europe; fruits; High strength mortar; Juniper seed ash; microstructure; modulus of rupture; porosity; Supplementary cementitious material; Sustainability; technology; trees; water uptake
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2023.118474

The juniper tree is widely distributed in Europe, but its fruit (juniper seed ash, JSA) is not well utilized, and most of it is naturally degraded. This study provides an efficient way to recycle JSA by calcining it at different temperatures (350 and 500 °C) to obtain supplementary cementitious materials (SCMs). The feasibility of using JSA to modify mortar is discussed from technical, economic and environmental aspects, and it is compared with conventional SCMs. The results show that the incorporation of JSA significantly improves the flowability of the mixture and reduces the unit weight of the hardened sample compared to conventional SCMs. However, JSA-modified mortars exhibit higher apparent porosity and water absorption due to the low pozzolanic reactivity and high porosity of JSA, but JSA outperforms RHA for high-content (12.5%–17.5%) SCM-modified mortars. The incorporation of a small amount (7.5%) of JSA reduces the compressive strength of the mortar, but the compressive strength of the mortar mixed with JSA-350 calcined at 350 °C is slightly higher than or similar to that of the traditional SCM-modified mortar. Since the flexural strength is more sensitive to the microstructure, the incorporation of JSA makes it significantly lower. In addition, the low reactivity and high porosity of JSA also lead to an increase in the 91-d capillary water absorption and a decrease in the electrical resistivity of the mortar samples. Meanwhile, the pozzolanic reaction of traditional SCM consumes Ca2+ ions and OH− to increase the electrical resistance of the mortar, while the alkalinity of JSA increases the content of OH− and reduces the electrical resistance of the mortar. In addition, using JSA to modify high-strength mortar also reduces its cost and carbon footprint, which indicates that recycling juniper seeds in high-strength mortar is a sustainable strategy. [Display omitted] •JSA is used as supplementary cementitious material to produce high strength mortar.•The economic and environmental benefits of SCM-modified mortars are evaluated.•The physical-mechanical properties, durability and microstructure of SCM-modified mortars are systematically studied.