Long-term durability enhancement of ultra-high-performance concrete via metakaolin and kieselguhr incorporation, freeze-thaw, chloride, sulfate, and shrinkage perspectives

Umara Nasir , Nejib Ghazouani , Khaled Mohamed Elhadi

Abstract

This study investigates the long-term durability of ultra-high-performance concrete (UHC altered with metakaolin (MK) and kieselguhr earth (KE). These materials were used as sustainable alternatives to silica fume and fly ash. Four UHC pastes were developed and tested. Durability performance was evaluated through freeze-thaw resistance, chloride ion permeability, sulfate attack, and drying shrinkage under different curing regimes. All UHC pastes showed excellent freeze-thaw resistance. No mass loss and 100% relative dynamic modulus were recorded after 300 cycles. The control paste exhibited a 23% reduction in modulus of rupture after freeze-thaw exposure. In contrast, the MK and MK-KE pastes showed reductions of only 3.68% and 3.6%, respectively. Chloride permeability was significantly reduced with MK and KE incorporation. Complete replacement of fly ash with MK reduced the total charge passed by 52.9% and increased surface resistivity by 423%. The KE paste showed a 35.2% reduction in charge passed. Sulfate resistance was excellent for all pastes. Length expansion remained below 0.01% at six months, far lower than the ASTM C1012 limit of 0.10%. The MK paste showed the lowest expansion of only 0.001%. Drying shrinkage depended strongly on curing conditions. Under air-dry curing, shrinkage ranged from 748 ue to 1002 ue. The MK paste showed the lowest shrinkage, while the KE paste showed the highest. Under moist curing, shrinkage was significantly reduced. The KE paste recorded the lowest value of 215

Key Words

chloride permeability; drying shrinkage; durability; kieselguhr earth; metakaolin; ultra-highperformance concrete

Address

Umara Nasir — Department of Civil Engineering, University of Engineering and Technology, Taxila, 47050, Pakistan
Nejib Ghazouani — Mining Research Center, Northern Border University, 73213 Arar, Saudi Arabia
Khaled Mohamed Elhadi — Civil Engineering Department, College of Engineering, King Khalid University, Saudi Arabia; Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia

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