Effect of fiber type and content on the mechanical properties and shrinkage characteristics of alkali‐activated kaolin

The brittle nature of geopolymer concretes (GPCs) and curing process required in their production are factors that limit their practical applications. It was not detected any study investigating the effect of polypropylene (PP) fiber length and fiber content on sulfate resistance of GPC. The aim of this study is to investigate the effect of PP fibers used in different content and length on sulfate resistance of GPC cured under laboratory conditions. For this purpose, 6 and 12 mm length PP fibers were added to GPC at rate of 0.5, 1.0, and 1.5% by volume of concrete. Samples were cured in laboratory conditions for 28 days, and then exposed to 5% MgSO 4 solutions. After the sulfate effect, the changes in physical and mechanical properties of GPC such as compressive strength, tensile strength, weight, ultrasonic pulse velocity (UPV), apparent porosity, and external appearance were investigated. In addition, microstructural analyzes were carried out with scanning electron microscope (SEM). As a result, it was determined that PP fiber additive at rate of 0.5% by volume significantly increased the sulfate resistance by preventing crack growth thanks to bridging function occur between binder phase and interface regions. Since the increased fiber length made it difficult to distribute the fibers homogeneously, 6 mm long PP fibers were more effective in improving the sulfate resistance.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of fiber characteristics on sulfate resistance of ambient‐cured geopolymer concrete

Kantarcı

2022

“…Furthermore, the addition of fiber can significantly improve the flexural strength of concrete. 22,23 Researchers have also added polypropylene (PP) fiber to concrete to study the creep properties of concrete. 24,25 Haddad and Smadi 25 demonstrated that PP fiber was superior to steel fiber because of the lower fiber content required and lower cost.…”

Section: Introductionmentioning

confidence: 99%

“…They also found that the inhibitory effect of fiber on creep was strengthened by the increase in fiber content. Furthermore, the addition of fiber can significantly improve the flexural strength of concrete 22,23 . Researchers have also added polypropylene (PP) fiber to concrete to study the creep properties of concrete 24,25 .…”

Section: Introductionmentioning

confidence: 99%

Effect of fiber content and stress–strength ratio on the creep of basalt fiber–reinforced alkali‐activated slag concrete

Zhou

Zheng

Zeng

et al. 2021

Alkali‐activated materials are increasingly being used in practical applications as potential alternatives to Portland cement. If alkali‐activated slag (AAS) is to be applied to prestressed engineering and large‐size structures, it is necessary to study the creep performance of AAS. Existing studies have found that the creep of AAS concrete is larger than that of ordinary Portland cement (OPC) concrete, and adding fiber is an effective way to overcome this defect. In this study, we investigated the creep of basalt fiber–reinforced AAS (FRAAS) concrete for fiber contents ranging from 0% to 0.9% (by volume) at a stress–strength ratio of 0–0.6. After analyzing the experimental results, it was found that the basalt FRAAS concrete had no obvious linear creep range. It was observed that with an increase in the fiber content, the inhibition effect of fiber on creep became stronger initially and then weaker. The inhibitory effect of fiber on creep was strengthened by the increase in the stress–strength ratio. The creep coefficient showed no obvious change when the fiber content was in the range of 0%–0.9%. Based on the existing OPC concrete creep models, a method for predicting the creep of basalt FRAAS concrete was proposed.

Residual mechanical properties of concrete containing lightweight expanded clay aggregate (LECA) after exposure to elevated temperatures

Dabbaghi

Dehestani

Yousefpour

2021

The mechanical properties of light-weight concrete (LWC) in fire are known to be better than those of normal-strength concrete (NSC), both at high temperature (hot properties) and after cooling (residual properties). The objective of this paper is to increase the knowledge of LWC's residual properties by testing a number of mixes containing expanded clay as light-weight coarse aggregate.An experimental program was carried out, in which one normal-weight concrete mix and two lightweight aggregate mixes containing different amounts of LECA were used to fabricate 72 concrete cylinders and 36 concrete prisms. All mixes contained silica fume as a supplementary cementitious material. The specimens were tested at the ambient temperature and after exposure to temperatures of 250, 500, and 750 C to obtain their compressive and tensile strength, modulus of elasticity, and stress-strain response. Results indicate that exposure to temperatures up to 250 C has no significant effect on the mechanical properties of concrete containing LECA just as in normal weight concrete.However, with increasing the temperature, increasing the lightweight aggregate content of the mix resulted in better strength retention after exposure to elevated temperatures. The experimental data are also used to develop equations to evaluate the residual mechanical properties of concrete.