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International Concrete Abstracts Portal

Showing 1-5 of 57 Abstracts search results

Document: 

18-553

Date: 

January 1, 2020

Author(s):

Manuel A. G. Silva and Miguel Estêvão

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

Glass fiber-reinforced polymer rods, both bare and embedded in concrete or lime mortar, were immersed in an alkaline solution at 20°C for up to 6 months and tested to find the influence of the protective covers on the degradation of the rods. Diffusion and porosimetry studies were used to interpret the results. Reduction of the proportion of larger pores in the mortar cylinders altered the transport of contaminant to the reinforcing bars. Accelerated effects due to immersion in solution at 60°C caused marked degradation of the rods. SEM images revealed damage to the matrix and the interface fiber-resin, mostly noticeable on the resin matrix and in the peripheral region of the rods. Severe loss of capacity of energy absorption was found in low-velocity impact tests after exposure to solution at 20°C for more than 5000 hours. Globally, results showed that the embedment delayed the initiation of damage but did not shield the rods against the maximum intensity of degradation by the alkaline contaminant.

DOI:

10.14359/51719071


Document: 

17-433

Date: 

November 1, 2019

Author(s):

Er-yu Zhu and Ze-wen Zhu

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

A total of 16 pullout specimens were tested to investigate the effect of curing conditions on bond behavior of near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strengthening concrete under curing temperatures from 35 to 65°C (95 to 149°F) and curing times from 6 to 12 hours. It was compared to that of specimens in ambient conditions (16°C [60.8°F]). On these bases, a nonlinear local bond-slip model was proposed. Two key parameters—A and B—are employed in the proposed bond-slip model, the specific expressions of which were mainly related to ultimate pullout load and peak shear stress of the specimen. The results show that the bond behavior of CFRP strip represents a negative quadratic curve with curing temperature and positive inverse tangent curves with curing time, respectively. The nonlinear local bond-slip model, considering the curing temperature-time, is deduced and validated.

DOI:

10.14359/51719148


Document: 

18-283

Date: 

September 1, 2019

Author(s):

Aditya Singh Rajput and Umesh Kumar Sharma

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Increasing cases of reinforcement corrosion in reinforced concrete (RC) elements raise serious concerns for achieving desired strength and ductility despite following the relevant seismic guidelines. The present study is an experimental attempt to evaluate the seismic behavior of corroded RC columns and thereby to examine the effectiveness of advanced composite materials in restoring the seismic behavior of such corroded columns. To this end, seven full-scale RC columns were cast and tested. Six column specimens were corroded using a precalibrated, accelerated corrosion regime, while one specimen acted as a control uncorroded column. Columns were corroded at two nominal degrees of corrosion: 10% and 20%. These corroded columns were then tested for evaluating their seismic behavior, while companion columns with the same degree of corrosion were retrofitted. Retrofitting was aimed at restoring the ductility and strength of corroded columns as well as to achieve increased durability against future corrosion. Advanced composite materials such as ultra-high-performance fiber-reinforced concrete (UHPFRC) and glass fiber-reinforced polymer (GFRP) were employed for retrofitting of columns. The results show an alarming reduction in seismic performance of columns due to corrosion of reinforcement. Corroded specimens when retrofitted with only UHPFRC jacket yielded satisfactory recovery of strength and ductility for 10% corrosion but showed insufficient improvement against 20% corrosion. For columns with 20% corrosion, a combination of UHPFRC and two layers of GFRP worked well in improving ductility and strength.

DOI:

10.14359/51716825


Document: 

18-235

Date: 

May 1, 2019

Author(s):

Nabila Zemour, Alireza Asadian, Ehab A. Ahmed, Brahim Benmokrane, and Kamal H. Khayat

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

This study investigated the effect of several parameters on the bond behavior of spliced glass fiber-reinforced polymer (GFRP) reinforcing bars in self-consolidating concrete (SCC) and normal concrete (NC). A total of 21 full-scale reinforced concrete (RC) beams were tested under four-point bending up to failure. Six influential design Code parameters were investigated, specifically concrete type, casting position, casting height, splice length, beam height, and longitudinal reinforcement type. The experimental results and observations reveal that the SCC and NC beams behaved similarly in terms of failure load, crack pattern, failure mode, and load-deflection response. The bond strength of the spliced bars in the SCC beams was slightly lower than that of the NC. The SCC beams exhibited lower reductions in bond strength than the NC beams due to the casting-position effect. In addition, the experimental findings confirm that the top-bar factor of 1.3, recommended in current design codes, can provide adequate safety margins for GFRP-reinforced NC and SCC beams with a splice length of 40db. Furthermore, the threshold depth of 305 mm (12 in.) provided in current design codes and guidelines appears to be reasonably safe.

DOI:

10.14359/51714459


Document: 

17-235

Date: 

July 1, 2018

Author(s):

Harsh Rathod, Rishi Gupta, Chen Yang, Urmil Dave, and Mohit Garg

Publication:

Materials Journal

Volume:

115

Issue:

4

Abstract:

The significant CO2 gas emission associated with manufacturing of conventional portland cement and its environmental hazard has led to the development of alternate cement binders, one of which is geopolymer concrete (GC). The research work focused on characterizing GC properties, such as workability, compressive strength, and average residual strength. A fiber reinforced GC manufactured only using fly ash and K-silicate solution alone had poor workability, rapid hardening, low compressive strength, and residual strength at ambient curing conditions. However, for another mixture, the compressive strength was increased by more than three times (from 5.3 to 21.7 MPa [0.77 to 3.15 ksi]) when cured at 60ºC (140°F) for 24 hours. On the other hand, it has been found that GC has more determination capacity than the normal cement concrete. As a result, the current form of ASTM standard C1399 for normal concrete cannot be used for evaluating average residual strength (ARS) of fiber-reinforced GC.

DOI:

10.14359/51702189


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