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International Concrete Abstracts Portal

Showing 1-5 of 103 Abstracts search results

Document: 

19-427

Date: 

November 1, 2020

Publication:

Materials Journal

Volume:

117

Issue:

6


Document: 

19-459

Date: 

November 1, 2020

Publication:

Materials Journal

Volume:

117

Issue:

6


Document: 

18-314

Date: 

September 1, 2019

Author(s):

Harikrishnan Nair and H. Celik Ozyildirim

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Cracks in bridge decks facilitate the penetration of chlorides that induce corrosion of reinforcing steel. Formation of cracks is related to the shrinkage and properties of the concrete and the restraints to movement. Lightweight concrete with a low modulus of elasticity, high creep, and water in the aggregate pores for internal curing has a reduced cracking potential. To control cracking, shrinkage of concrete can be reduced by using a shrinkage-reducing admixture (SRA). A recent study at the Virginia Department of Transportation (VDOT) investigated the performance of both lightweight concretes and concretes with SRA containing normal-weight aggregates in the field and found that these concretes had no cracks or fewer cracks than were typical of decks constructed with normal-weight aggregates over the past 20 years. VDOT developed a new specification that included lightweight concretes or concretes with normal-weight aggregates and SRA and this specification is being used successfully to reduce cracking in bridge decks. This paper summarizes the work conducted to develop the new specification and includes information on field applications.

DOI:

10.14359/51716830


Document: 

18-013

Date: 

January 1, 2019

Author(s):

Chamila Gunasekera, Sujeeva Setunge, and David W. Law

Publication:

Materials Journal

Volume:

116

Issue:

1

Abstract:

Fly ash geopolymer concrete is a sustainable green construction material that has outstanding mechanical performance and is a low-energy material with a low carbon footprint. In this study, a detailed investigation of the long-term creep and drying shrinkage of three different 100% fly ash geopolymer concretes was carried out up to 1 year of age. Two geopolymers, produced from Gladstone and Pt. Augusta fly ashes, achieved approximately 700 microstrain at the end of 1 year—equivalent to the total creep strain displayed by portland cement (PC) concrete. Moreover, both geopolymer concretes displayed a lower creep coefficient than PC concrete. Hence, AS 3600 or the CEB-FIP model could be conservatively used to predict creep coefficient for two geopolymers. However, the Tarong fly ash geopolymer concrete differed significantly from the other geopolymers and achieved approximately 1900 microstrain after 1 year. The drying shrinkage of Gladstone and Pt. Augusta geopolymer concretes at 1 year are 175 and 190 microstrain, respectively, while Tarong geopolymer and PC concrete achieved 615 and 475 microstrain, respectively. All the fly ash geopolymer concrete showed lower drying shrinkage than the maximum permitted value recommended by AS3600. Incorporation of calcium-aluminasilicate-hydrate (C-A-S-H) gel with the sodium-alumina-silicatehydrate (N-A-S-H) geopolymeric gel was seen to positively affect the packing density of the gel phase. The degree of uniformity and compactness of aluminosilicate gel matrix together with the macroporosity in the 50 nm to 1 μm range was identified as determining the long-term creep and drying shrinkage of the 100% low-calcium fly ash geopolymer concrete.

DOI:

10.14359/51706941


Document: 

17-465

Date: 

September 1, 2018

Author(s):

Akthem Al-Manaseer and Rami Zayed

Publication:

Materials Journal

Volume:

115

Issue:

5

Abstract:

An experimental study was conducted on unsealed concrete I-beam specimens to investigate early-age tensile creep. The tests were conducted on concrete specimens that were moist-cured for 24 hours. The specimens were loaded at 30% of their tensile failure load and tensile creep was monitored for 72 hours. Companion shrinkage specimens were used to measure drying shrinkage while the tensile creep test was performed. The investigation shows that the magnitude of early-age shrinkage exceeds the tensile creep values. The results showed that combined creep and shrinkage strains were increasing when the applied load was increased.

DOI:

10.14359/51706843


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