Microstructure and Durability of Ground Granulated Blast Furnace Slag Cement Mortars

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RESEARCH PAPER

Microstructure and Durability of Ground Granulated Blast Furnace Slag Cement Mortars Mohammed A. Saafan1 · Zeinab A. Etman1,2   · Doaa M. El lakany3 Received: 30 September 2019 / Accepted: 26 October 2020 © Shiraz University 2020

Abstract Ground granulated blast furnace slag is an eco-friendly material with regard to its production process and usage. In this study, slag cement (SC) is used to prepare different slag cement mortar (SCM) mixes to study mortar microstructure perspectives, physiochemical properties, mechanical properties and durability performance. The tests also included the evaluation of SC setting time and slag activity index. Test results showed that the used slag cement had a high activity index and prolonged initial setting time. SCM demonstrated positive synergistic effects on late compressive strength, enhanced durability against sulfates and acid attacks. Also, SCMs seem to produce a more stable structure at elevated temperatures. Strength and durability improvement was correlated with an improved microstructure as indicated by scanning electron microscope and X-ray diffraction analyses. Keywords  GGBFS · Durability · SEM · XRD · Heat of hydration

1 Introduction Recently, researches have been concerned with the implementation of environment-friendly construction materials. For instance, cement industry produces large emissions C ­ O2, which is seriously harmful. The use of by-products such as fly ash, silica fume and furnace slag has been studied for years. Their use comprises both environmental and economic benefits, such as conservation of resources, reduced greenhouse gas emissions and energy savings. Ground granulated blast furnace slag (GGBFS) is a by-product that processes both cementitious and pozzolanic properties. It has been used as a supplementary cementitious material for more than 100 years (Samad and A. Shah 2017). GGBFS performs more effectively than other supplementary cementitious materials as it can be used at high replacement ratios to produce slag cement (American Concrete Institute 2003).

* Zeinab A. Etman [email protected] 1



Civil Engineering Department, Faculty of Engineering, Menoufia University, Menoufia, Egypt

2



Higher Institute of Engineering and Technology, Menoufia, Egypt

3

Menoufia University, Menoufia, Egypt



Blast furnace slag has been used as a successful replacement material at ratios up to 80% by weight of Portland cement. The use of SC aims to improve concrete durability and to produce high strength and high-performance concrete (Taylor et al. 2010; Bougara et al. 2010). Ground granulated blast furnace slag can be obtained by quenching molten iron slag from blast furnaces. Its chemical composition is similar to that of Portland cement. Rapid water-quenching results in the formation of a glassy granulate product with an amorphous structure. The product is dried and ground into a fine powder. The grinding process continues until a specified surface area is obtained to ensure hydraulic activity (Bellmann and Stark 2009). T