Frost Resistance Of High Performance Concrete

Author : Ahmed Jasem Al-Basha
Publisher :
ISBN 13 :
Total Pages : 156 pages
Book Rating : 4.:/5 (12 download)

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Download or read book Frost Resistance of Concrete Cladded with Locally Produced Ultra-high Performance Concrete Cured at Elevated Temperatures written by Ahmed Jasem Al-Basha and published by . This book was released on 2017 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra-high performance concrete (UHPC) is concrete that exhibits compressive strength in excess of 150 MPa. In addition to its high compressive strength, UHPC displays other characteristics such as low porosity, high density, and excellent durability and resistance to chemical and physical attack. These properties have made UHPC a progressively more popular material in a variety of structural applications and an increasingly common topic of research. The present work built upon previous research and investigated the use of different materials in UHPC mixture proportions and elevated temperature curing regimens (greater than 95°C). The purpose of this work was to maintain economical mixture proportions for locally produced UHPC while achieving greater mechanical performance and durability properties. The mixture proportions and curing regimens developed were then used to produce high quality, modular UHPC elements to be used as cladding for normal strength concrete (NSC) to improve frost resistance. Five elevated temperature curing regimens were developed and several material substitutions were investigated to determine optimal curing temperature and mixture proportions to improve compressive and flexural strengths. A curing regimen consisting of two days wet curing at 95°C followed by four days dry curing at 200°C was adopted as the main regimen and a finer stucco sand was used to replace the coarser sand that was initially used. The new curing regiment and UHPC mixture achieved compressive and flexural strengths 36.6% and 29.7% greater, respectively, than UHPC produced with the original mixture and curing regimen. Freezing and thawing testing (ASTM C 666 procedure A) was performed on UHPC and NSC prisms as well as NSC prismatic cores coated with mortar and NSC prismatic cores cladded with modular UHPC elements. Measurements of mass and transverse frequency were performed in accordance with ASTM C 215. Results showed that initial dynamic elastic modulus and durability factor (DF) for the new UHPC were only 7.1% and 0.3% lower than comparable values from the original UHPC mixture. Additionally, the NSC cores with mortar and cladding showed improvements in average number of freeze-thaw cycles sustained and DF. The coated cores had an 80.2% increase in number of freezer-thaw cycles sustained and 264.7% improvement in DF compared to plain NSC prisms, while cladded cores lasted 127.5% longer and had DF values that improved by 176.5% compared to plain NSC prisms. The DF of cladded NSC cores was lower than that of the coated cores due to loss of cladding as specimens deteriorated.