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Abstract
A lot of reinforced concrete (RC) structures in Syria went out of service after a few years of construction. This was mainly due to reinforcement corrosion or chemical attack on concrete. The use of blended cements is growing rapidly in the construction industry due to economical, ecological and technical benefits. Syria is relatively rich in scoria. In the study, mortar/concrete specimens were produced with seven types of cement: one plain Portland cement (control) and six blended cements with replacement levels ranging from 10 to 35 %. Rapid chloride penetration test was carried in accordance with ASTM C 1202 after two curing times of 28 and 90 days. The effect on the resistance of concrete against damage caused by corrosion of the embedded steel has been investigated using an accelerated corrosion test by impressing a constant anodic potential. The variation of current with time and time to failure of RC specimens were determined at 28 and 90 days curing. In addition, effects of aggressive acidic environments on mortars were investigated through 100 days of exposure to 5 % H2SO4, 10 % HCl, 5 % HNO3 and 10 % CH3COOH solutions. Evaluation of sulfate resistance of mortars was also performed by immersing in 5 % Na2SO4 solution for 52 weeks. Test results reveal that the resistance to chloride penetration of concrete improves substantially with the increase of replacement level, and the concretes containing scoria based-blended cements, especially CEM II/B-P, exhibited corrosion initiation periods several times longer than the control mix. Further, an increase in scoria addition improves the acid resistance of mortar, especially in the early days of exposure, whereas after a long period of continuous exposure all specimens show the same behavior against the acid attack. According to results of sulfate resistance, CEM II/B-P can be used instead of SRPC in sulfate-bearing environments.
Highlights
Use of natural pozzolan in production of blended Portland cements makes important effects on physical, chemical, mechanical and durability properties of mortar and concrete depending on its substitution ratio and its fineness (Al-Chaar et al 2013; Senhadji et al 2012; Hossain 2009; Ghrici et al 2006; Cavdar and Yetgin 2007; Turanli et al 2005; Colak 2003; Rodriguez-Camacho and Uribe-Afif 2002)
The objective of this paper is to report a part of this ongoing research on the effect of different amount of scoria when adding as cement replacement on some durability-related properties
At 90 days curing, the compressive strengths of blended cement concretes are comparable to those of plain cement concrete. – The chloride penetrability of scoria-based concrete mixes is much lower than that of plain concrete, especially at high replacement levels of scoria. – According to the results of accelerated corrosion test, concretes produced with scoria-based binders decelerated rebar corrosion
Summary
Use of natural pozzolan in production of blended Portland cements makes important effects on physical, chemical, mechanical and durability properties of mortar and concrete depending on its substitution ratio and its fineness (Al-Chaar et al 2013; Senhadji et al 2012; Hossain 2009; Ghrici et al 2006; Cavdar and Yetgin 2007; Turanli et al 2005; Colak 2003; Rodriguez-Camacho and Uribe-Afif 2002) Since these materials enter the cement production after kiln process, they provide important economical and ecological benefits (Mehta and Monteiro 2006). There are numerous studies on using natural pozzolan as cement replacement, no detailed research was conducted in the past to investigate the potential use of scoria in production of blended cements in Syria
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