Evaporation, settlement, temperature evolution, and development of plastic shrinkage cracks in mortars with shrinkage-reducing admixtures

Using natural (Jute) fiber in concrete as a reinforcing material can not only augment the concrete strength but also restrict the use of synthetic fiber which is environmentally detrimental. To achieve this goal, this study evaluated compressive strength, tensile strength and plastic shrinkage of concrete incorporating ‘Natural (Jute)’ fiber of different length (15 mm and 25 mm) with various mix proportions of 0.10%, 0.2%, 0.3% and 0.4% respectively by volume of concrete. Concrete is vulnerable to grow shrinkage cracks because of high evaporation rate in dry and windy conditions. Incorporating of fibers could abate development of this crack. The large length (25 mm) and higher content ( 0.3%) of reinforcing materials (jute fiber) result to the lowering of mechanical properties of JFRC compare to plain concrete. But in the incorporation of short (15 mm) and low fiber content ( 0.3%), enhances the mechanical properties of the same JFRC. Inclusion of 0.3% (15 mm length) fiber gave maximum enhancement of both concrete compressive and tensile strength by 12.4% and 58% respectively compared to the non-fiber reinforced concrete. A drastic suppression of crack occurrence and area of crack between non-fiber reinforced concrete and fiber reinforced concretes was attained. Experimental results of incorporating 0.1–0.4% fiber with 15 mm length in concrete revealed that plastic shrinkage cracks were decreased by 75–99% in contrast to non-fiber reinforced concrete. Therefore, it is concluded that the incorporation of jute fiber in making FRC composite would be one of the favorable methods to enhance the performance of concrete.

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A review on the influence of shrinkage reducing admixtures on concrete

Sustainability Agri Food and Environmental Research ◽

10.7770/safer-v10n1-art2532 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Jerison Scariah James ◽

Angel Rose ◽

Elson John ◽

Sachin Paul

Keyword(s):

Surface Tension ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Common Source ◽

Shrinkage Cracking ◽

Plastic Shrinkage ◽

Concrete Mixtures ◽

Shrinkage Reducing Admixture ◽

Shrinkage Reducing Admixtures ◽

Damage In Concrete

Shrinkage cracking is a common source of distress in concrete structures. In addition to being unsightly, these cracks serve to accelerate other forms of damage in concrete, thereby shortening the service life of structures. One solution to reduce the potential for shrinkage cracking is to incorporate a shrinkage reducing admixture (SRA) in concrete mixtures. SRAs belong to a special type of organic chemicals (i.e., surfactants) that when mixed in water, reduce the surface tension of the liquid, and thereby reduce the magnitude of capillary stresses and shrinkage strains that occur when concrete is losing moisture. Various studies show that SRAs have proven to reduce drying, autogenous, and plastic shrinkage, which has been summarized in this literature. Keywords—Shrinkage Reducing Admixtures, Surfactants, Drying shrinkage, Plastic shrinkage, Autogenous shrinkage.

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Combined Influence of Expansive and Shrinkage Reducing Admixtures on the Shrinkage Behavior of Ultra-High Performance Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.488-489.242 ◽

2011 ◽

Vol 488-489 ◽

pp. 242-245 ◽

Cited By ~ 4

Author(s):

Jung Jun Park ◽

Doo Youl Yoo ◽

Sung Wook Kim ◽

Young Soo Yoon

Keyword(s):

High Performance ◽

High Performance Concrete ◽

Shrinkage Strain ◽

Reducing Agents ◽

Reinforcing Bars ◽

Ultra High Performance Concrete ◽

Free Shrinkage ◽

Shrinkage Cracks ◽

Binder Ratio ◽

Shrinkage Reducing Admixtures

Since ultra-high performance cementitious composite (UHPCC) exhibits remarkable compressive strength and ductility, its application for structural member provides significant reduction of the section. The use of low water-to-binder ratio and admixtures with high fineness induce large shrinkage strain, leading to the possibility of large occurrence of shrinkage cracks due to the restraints of the form and reinforcing bars. Therefore, this study admixes a combination of expansive and shrinkage reducing agents as a solution to reduce the shrinkage of UHPCC. The eventual appropriateness is computed to evaluate the free shrinkage and restrained shrinkage behaviors. From the test results, the admixing of a combination of expansive and shrinkage reducing agents is seen to achieve a reduction of the free shrinkage by 30% to 50% at 28 days and a reduction of the strain of the external steel by about 19%.

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Chemical Shrinkage of Pastes Made with Shrinkage Reducing Admixtures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.466.105 ◽

2011 ◽

Vol 466 ◽

pp. 105-113 ◽

Cited By ~ 1

Author(s):

António Bettencourt Ribeiro ◽

Vasco Medina ◽

Augusto Gomes ◽

Arlindo Gonçalves

Keyword(s):

High Performance ◽

High Performance Concrete ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Chemical Shrinkage ◽

Cement Pastes ◽

Degree Of Hydration ◽

Shrinkage Cracks ◽

Large Application ◽

Shrinkage Reducing Admixtures

Shrinkage Reducing Admixtures (SRA) are being used more often in concrete structures in order to better control shrinkage cracks. High-performance concrete, nowadays with large application, has more proneness to crack at very early age due to the lower W/C. In this type of concrete, autogenous shrinkage is usually more important than drying shrinkage. Autogenous shrinkage is due to the volume decrease inherent to binder hydration reactions. The rate of these reactions is influenced not only by the type of binder but also by the presence of chemical admixtures. It is recognized that SRA delay the hydration, being a secondary effect of this type of admixtures. In this work changes on the degree of hydration of cement pastes with SRA and different binders are presented, using the chemical shrinkage test.

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