Bio-Based Admixture (Black Tea Extraction) for Better Performance of Metakaolin Blended Cement Mortars

Abstract

With high pozzolanic reactivity, metakaolin (MK) is a popular supplementary cementitious material (SCM), which can be used to partially replace Portland cement in concretes. Due to its small particle size, however, MK can agglomerate, resulting in a nonuniform matrix and underperformance of the produced concrete. To address this issue, this paper exploits a low-cost, bio-based admixture—black tea extract (BTE)—to replace the traditional petroleum-based chemical admixture to enhance the dispersion and workability of MK blended cement mortars. Major biomolecules in the BTE such as caffeine, catechin, theanine, and theaflavin are rich in polyphenol, hydroxyl, and carboxylic acid groups, which can interact with cement particles and have profound effects on the hydration process and microstructure of the hydration products. Experimental studies showed that BTE does improve the workability of the MK blended cement mortar. More importantly, the BTE introduces significant change on the microstructure of the hardened pastes. Both the pores with size less than 50 nm and the total porosity of the hardened paste were significantly reduced, leading to a significant improvement in the micro- and macro-mechanical properties of the hardened paste. Experimental results suggest that up to 35% greater improvement in the compressive strength at 28 days was achieved using the proposed bio-admixture. Economic and environmental advantages of using the BTE as a renewable admixture were also illustrated through analyzing the cost–benefit, embodied carbon, and eco-efficiency of the MK blended mortars.

Investigation the effect of nanocarbon tube prepared from tea waste on microstructure and properties of cement mortar

“…From the results obtained, it can be seen that the workability increased by 16% and 10% at higher percentages of replacement of 3% and 4%, respectively. These results are consistent with those of previous studies in which a decrease in slump was demonstrated (Jakhrani et al 2019;Fang et al 2022). According to (Fang et al 2022) the primary results of previous studies showed that the workability of mortar containing tea waste as a cement substitute was increased due to the high neness of tea waste and the treatment process for tea waste before use compared to owing mortar without tea waste.…”

The Effects of Nano-Based Bio-Carbonates in Superhydrophobic Concrete—A Review

“…Minimal surface energy material called nP is employed. SiO 2 nanoparticles have a 25 nm size distribution [78]. Different chemical substances such as deionized water and potassium hydroxide are examples of analytical reagent (AR) grades.…”

Assessment of Pozzolanic Activity of Ground Scoria Rocks under Low- and High-Pressure (Autoclave) Steam Curing

“…Taftan natural pozzolan was combined with inorganic activators such as sodium hydroxide and sodium silicate to develop an inorganic polymeric binder [10]. Several studies on conventional and nonconventional wastes as pozzolanic materials have been published to show the pozzolanic properties from different perspectives [11,12]. However, when compared to other methods, there are fewer studies that cover autoclave curing of cementitious materials (Alawad et al, 2015 [13]).…”