The pH of Cement-based Materials: A Review
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908 DOI
https: //doi. org/10.1007/s11595-020-2337-y
The pH of Cement-based Materials: A Review Sumra Yousuf1,2, Payam Shafigh3,4*, Zainah Ibrahim1*
(1.Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; 2.Department of Building and Architectural Engineering, Faculty of Engineering & Technology, Bahauddin Zakariya University, Multan 60000, Pakistan; 3.Department of Building Surveying, Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia; 4.Center for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia)
Abstract: Cement-based materials (CBMs), such as paste, mortar and concrete, are highly alkaline with an initial high pH of approximately 12.0 to 13.8. CBMs have a high pH due to the existing oxide mineral portlandite and alkali metal contents in Portland cement. The high pH of concrete provides excellent protection and reinforces the steel bars against corrosion. The pH of concrete does not remain constant due to ageing and other defect-causing factors, such as chloride ingress, alkali leaching, carbonation, corrosion, acid attack, moisture and biodegradation process. Reducing the concrete pH has negative impact on the strength, durability and service life of concrete buildings. However, the high pH of concrete may also cause concrete structure deterioration, such as alkali silica reaction, porosity and moisture related damages in concrete structures. The pH of CBMs can be influenced by high temperatures. For instance, the extremely high volume (85%-100%) of slag-blended cement pastes shows considerable pH reduction from 12.80 to 11.34 at 800 ℃. As many concrete structure deterioration are related to concrete pH, using an accurate and reliable method to measure pH and analyse the durability of reinforced concrete structure based on pH values is extremely important. This study is a comprehensive review of the pH of CBM in terms of measurement, limitations and varying values for different CBM types. Key words: pH; cementitious materials; concrete; portlandite; durability; corrosion; alkali
1 Introduction Cement-based materials (CBMs), such as concrete and mortar, are the most important construction materials for all types of constructional works[1]. Concrete is used in the construction of approximately two thirds of the world’s buildings and other infrastructures[2]. The supreme importance and valuable utilisation of cement in the current construction industry is due to its high stability, high strength, versatility, economy, and capacity to be moulded into any desired shape and size[3,4]. Approximately 1 ton of concrete must be produced per
© Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature 2020 (Received: Apr. 29, 2019; Accepted: May 18, 2020) SUMRA Yousuf: Ph D student: Assistant Prof.; E-mail: sumra. [email protected] *Corresponding author: PAYAM Shafigh: Senior Lecturer; Ph D; E-mail: [email protected]
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