Abstract
Calcined hwangtoh is a pozzolanic material that is increasingly being used as a mineral admixture in the concrete industry. This study shows a hydration model for cement–hwangtoh blends and evaluates the various properties of hwangtoh-blended concrete using reaction degrees of binders. First, a kinetic reaction model is proposed for analyzing the pozzolanic reaction of hwangtoh. The reaction of hwangtoh includes three processes: the initial dormant period, boundary reaction process, and diffusion process. The mutual interactions between the binary reactions of cement and hwangtoh are thought to be in line with the items in capillary water and calcium hydroxide. Second, the reaction degrees of cement and hwangtoh are determined based on a blended hydration model. Furthermore, the chemical (chemically combined water and calcium hydroxide contents), mechanical (compressive strength), thermal (hydration heat), and durability aspects (carbonation depth) of hwangtoh-blended concrete are systematically predicted. The results show good agreement with experimental results.
Highlights
Hwangtoh is an environmentally friendly material and belongs to the family of clay
Because the hydration of binders essentially stops when relative humidity is less than 80%, further hydration of hwangtoh and cement in the carbonation test period was ignored in this study (Maekawa et al 2009)
4 Conclusions This research shows an integrated model that simulates the binary hydration of cement–hwangtoh blends and assesses the various properties of cement–hwangtoh blends
Summary
Hwangtoh is an environmentally friendly material and belongs to the family of clay. Hwangtoh can purify indoor air by absorption, and it is widely used in hospital buildings for reducing sick building syndrome, including sore throat and headaches. Calcined hwangtoh is increasingly used in the cement and concrete industry because of its unique environmentally friendly characteristics and chemical reactivity (Kim et al 2017). Many experimental investigations have been performed on the hydration, mechanical, durability, and thermal properties of hwangtoh-blended concrete. Go et al (2010, 2009) reported that the optimal temperature for thermal activation of hwangtoh is about 800 °C, thermally activated hwangtoh shows clear pozzolanic activity, and the hydration heat of hwangtoh-blended concrete is lower than that of control concrete. Koo et al (2015) presented a comparison with a plain environment, where mice in the hwangtoh-blended environment showed higher food and water intake, higher fertility rate, and healthier offspring.
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