In situ study of chloride ingress in concretes containing natural zeolite, metakaolin and silica fume exposed to various exposure conditions in a harsh marine environment

The Persian Gulf is well known as one of the most aggressive environments in the world because of its high relative humidity, temperature and concentration of chloride ions. Therefore, studying the deterioration processes, such as the chloride ion penetration process, that lead to severe reinforcement corrosion in aggressive environments is necessary. To improve the durability and serviceability of concrete structures in such environments, several investigations have been conducted that address the addition of silica fume and metakaolin, while less attention has been given to the newly introduced pozzolan called natural zeolite. In this paper, the performance of concretes containing natural zeolite, metakaolin and silica fume and that of concretes with different water-to-binder ratios under various exposure conditions in terms of chloride ion diffusivity were investigated. To achieve this objective, concrete specimens with water-to-binder ratios (w/b) of 0.35, 0.40, 0.45 and 0.50 were fabricated. In addition, to examine the performance of three different pozzolans, other specimens with constant water-to-binder ratios of 0.40 containing 10% natural zeolite, 5% metakaolin and 5% silica fume were prepared. All of the specimens were subjected to four exposure conditions (tidal, splash, atmosphere and soil). The results were obtained from a field exposure site and indicate that natural zeolite exhibits good performance in terms of improving the durability of concrete in harsh environments. In addition, it is concluded that splash zones affect concrete structures more harshly than tidal zones.

[1]  Mohammad Shekarchi,et al.  Long-term chloride diffusion in silica fume concrete in harsh marine climates , 2009 .

[2]  Luping Tang,et al.  Recurrent studies of chloride ingress in uncracked marine concrete at various exposure times and elevations , 1998 .

[3]  Ki Yong Ann,et al.  The importance of chloride content at the concrete surface in assessing the time to corrosion of steel in concrete structures , 2009 .

[4]  Mohammad Shekarchi,et al.  Deterioration of Concrete Caused by Complex Attack in Sewage Treatment Plant Environment , 2012 .

[5]  G. Kakali,et al.  The effect of natural zeolites on the early hydration of Portland cement , 2003 .

[6]  N. Feng,et al.  High-Strength and Flowing Concrete with a Zeolitic Mineral Admixture , 1990 .

[7]  J. Bai,et al.  Chloride ingress and strength loss in concrete with different PC-PFA-MK binder compositions exposed to synthetic seawater , 2003 .

[8]  M. Shekarchi,et al.  Comparing a natural pozzolan, zeolite, to metakaolin and silica fume in terms of their effect on the durability characteristics of concrete: A laboratory study , 2013 .

[9]  L. Lam,et al.  A study on the hydration rate of natural zeolite blended cement pastes , 1999 .

[10]  M. A. Yurdusev,et al.  USE OF ZEOLITE, COAL BOTTOM ASH AND FLY ASH AS REPLACEMENT MATERIALS IN CEMENT PRODUCTION , 2004 .

[11]  Mohammad Shekarchi,et al.  Transport properties in metakaolin blended concrete , 2010 .

[12]  N. Feng,et al.  APPLICATIONS OF NATURAL ZEOLITE TO CONSTRUCTION AND BUILDING MATERIALS IN CHINA , 2005 .

[13]  D. O. Northwood,et al.  Chloride ingress in concrete as measured by field exposure tests in the atmospheric, tidal and submerged zones of a tropical marine environment , 1993 .

[14]  Mohammad Shekarchi,et al.  Durability-Based Design in the Persian Gulf , 2007 .

[15]  J. Bai,et al.  Self-compensating autogenous shrinkage in Portland cement—metakaolin—fly ash pastes , 2000 .

[16]  Wichian Chalee,et al.  Effect of W/C ratio on covering depth of fly ash concrete in marine environment , 2007 .

[17]  M. A. Bader,et al.  Performance of concrete in a coastal environment , 2003 .

[18]  C. L. Page,et al.  Diffusion of chloride ions in hardened cement pastes , 1981 .

[19]  Mohammad Shekarchi,et al.  Use of natural zeolite as a supplementary cementitious material , 2010 .

[20]  John Crank,et al.  The Mathematics Of Diffusion , 1956 .

[21]  Odd E. Gjørv,et al.  Diffusion of chloride ions from seawater into concrete , 1979 .

[22]  C. Poon,et al.  Compressive strength, chloride diffusivity and pore structure of high performance metakaolin and silica fume concrete , 2006 .

[23]  I. Janotka,et al.  Sulphate resistance and passivation ability of the mortar made from pozzolan cement with zeolite , 2008 .

[24]  F. Škvára,et al.  The effect of water ratio on microstructre and composition of the hydration products of portland cement pastes , 2002 .

[25]  K. Rajagopal,et al.  Longterm corrosion performance of rebar embedded in blended cement concrete under macro cell corrosion condition , 2008 .

[26]  M. Murat.  Hydration reaction and hardening of calcined clays and related minerals , 1983 .

[27]  E. Ganjian,et al.  The effect of Persian Gulf tidal zone exposure on durability of mixes containing silica fume and blast furnace slag , 2009 .

[28]  Feng Xiao-xin,et al.  Effect of the composite of natural zeolite and fly ash on alkali-silica reaction , 2003 .

[29]  R Uribe-Afif,et al.  Importance of using the natural pozzolans on concrete durability , 2002 .