A study on the applicability of the efficiency factor of supplementary cementitious materials to durability properties

Abstract

14Supplementary cementitious materials (SCMs), such as fly ash, pozzolan or blastfurnace slag, are 15 widely used to produce blended portland cements, since they lead to a significant reduction in CO2 16 emission in the production phase compared to portland cement. A practical and generally accepted 17 approach to evaluate the contribution of SCMs to the strength of the hardened concrete is through 18 the concept of the SCMs efficiency factor (i.e. k-value concept), which expresses the fraction of 19 portland cement that can be replaced by a SCM at unchanged strength. In the literature some studies 20 have also been focused on the use of the k-value approach also for the resistance against 21 carbonation and chloride penetration of blended portland systems. However, limitations of 22 applicability of SCMs efficiency factor to durability properties are not clear. In this paper the k-23 value of different SCMs, such as ground limestone, fly ash, natural pozzolan and ground granulated 24 blastfurnace slag, was investigated to detect firstly if it can be applied to carbonation-and chloride-25 related properties and, secondly, if strength can be considered as a proxy-criterion for durability 26 2 properties. Results showed k-values lower than 1 for all the SCMs with respect to compressive 1 strength and that these values were valid also for resistance to penetration of carbonation. As far as 2 the resistance to chloride penetration is concerned, k-values derived from strength tests were not 3 applicable and specific k-values should be evaluated; values higher than 1 were calculated for fly 4 ash and ground granulated blastfurnace slag, whilst values lower than 1 were obtained for ground 5 limestone and natural pozzolan. 6 7 Highlight 8 Efficiency factor k is often used as a practical approach for determination of the role of SCMs on 9 concrete strength. 10The applicability of k-values to durability-related properties is questionable. 11Strength -derived k-values showed to be appropriate as a proxy-criterion only for carbonation 12 resistance. 13Specific k-values are needed for chloride-resistance performance. 14 These k-values were around 1.5 for fly ash and slag and lower than 1 for ground limestone and 15 pozzolan. 16 17

Metakaolin as an Active Pozzolan for Cement That Improves Its Properties and Reduces Its Pollution Hazard

“…Generally they are mainly amorphous siliceous or siliceous and aluminous by-products after many industrial manufacturing processes, [3] [4] [5]. The most common of these are fly ash (FA), silica fume (SF), aluminous scraps, iron and steel industry slag, and metakaolin (MK).…”

Efficiency Concepts and Models that Evaluates the Strength of Concretes Containing Different Supplementary Cementitious Materials

“…Lollini et al in 2016 [55] evaluated the efficiency factor of SCM with respect to compressive strength. The author utilized the Smiths model to assess the k value valid for strength.…”

Contribution of Recycled Alumina Waste to Cement Strength and Microstructure Development

“…Durability of concrete has been a major concern of civil engineering professionals. Also, it has been of considerable scientific and technological interest over the last few decades, (Park et al, 1999;Nehdi & Hayek, 2005;Alessandra et al, 2016;Federica et al, 2016;Amer & El-Hoseny, 2017). silicate hydrate is known as C-S-H gel and results to significant strength gain.…”

“…In other words, cement concrete will be termed durable, when it keeps its form and shape within the allowable limits, while exposed to different environmental conditions, (Elena et al, 2016). Durability of concrete has been a major concern of civil engineering professionals.…”

“…The hydrous calcium aluminium sulfate, ettringite (AFt), is the usual hydrated product in the early ages of the hydration. The reaction of calcium silicate phases (C 3 S and β-C 2 S) predominates from about the time of initial set onward forming calcium silicate hydrates and Ca(OH) 2 , (Park, Sun, Lee,& Shin, 1999;Nehdi & Hayek, 2005;Mobili, Belli, Giosuè, Bellezze & Tittarelli, 2016;Federica, Elena, & Luca, 2016;Amer & El-Hoseny, 2017). …”