Bond Strength of GFRP Bars Embedded in Engineered Cementitious Composite using RILEM Beam Testing

Khandaker Muhammed Anwar Hossain

doi:10.1186/s40069-018-0240-0

Abstract

This paper presents a study on the bond characteristics of glass fiber reinforced polymer (GFRP) bars in engineered cementitious composite (ECC). Ninety beam specimens having variable parameters namely bar diameter, GFRP bar types (standard low modulus ‘LM’ and high modulus ‘HM’), two concrete types (ECC and normal concrete ‘NC’) and embedded length (5, 7 and 10 times bar diameter) were tested as per RILEM specifications. Bond stress–slip characteristics and failure modes of specimens as well as influence of variable parameters on bond strength are described. The performance of various Codes and other existing equations in predicting bond strength of both low/high modulus GFRP bars embedded in ECC compared to NC is described based on experimental results. The bond strength decreased with the increase of embedment length—maximum bond strength reduction of 36% was observed. For both ECC and NC, bond strength reduced with the increase of bar size and ECC produced maximum 1.6 times higher bond strength compared to NC. Code based and other existing equations were found conservative in predicting bond strength of GFRP bars embedded in ECC.

Highlights

During the last decades, tremendous progress has been made on the high performance concrete (HPC)
This paper presents the results of a research conducted on the bond characteristics of both low modulus (LM) and high modulus (HM) glass fiber reinforced polymer (GFRP) bars embedded in engineered cementitious composite (ECC) using transversely reinforced beam specimens of two configurations having variable parameters such as: bar diameter, bar types, embedded length and concrete types
This research indicates that the embedment length of GFRP bars should not be longer than the certain threshold as GFRP bars did not reach their failure load and failure was governed by pullout due to delamination or detachment of sand coating

Summary

Introduction

Tremendous progress has been made on the high performance concrete (HPC). Lee et al (2008) suggested an equation for bond strength of sand-coated and helically wrapped GFRP bars embedded in concrete whose compressive strength ranged between 25 and 92 MPa. The GFRP reinforced ECC is a new technology and can improve strength, ductility, durability, resistance to deterioration against aggressive environment, self-healing capability and overall service life of structures compared to their conventional concrete counterparts (Sherir et al 2015, 2017; Hossain et al 2015a, b). This paper presents the results of a research conducted on the bond characteristics of both low modulus (LM) and high modulus (HM) GFRP bars embedded in ECC using transversely reinforced beam specimens of two configurations having variable parameters such as: bar diameter, bar types, embedded length and concrete types (based on strength class). The findings and conclusions of this research will surely benefit engineers, builders and local authorities involved in designing and constructing structures with GFRP bar reinforced ECC

Experimental Investigation

Results and Discussion

Peak load development and bond stressslip response

20 Beam test Pullout test

Code Based Bond Analyses and Comparison

Conclusions