Bond between textile-reinforced mortar (TRM) and concrete substrates: experimental investigation

This paper presents an extended experimental study on the bond behaviour between textile-reinforced mortar (TRM) and concrete substrates. The parameters examined include: (a) the bond length (from 50 mm to 450 mm); (b) the number of TRM layers (from one to four); (c) the concrete surface preparation (grinding versus sandblasting); (d) the concrete compressive strength (15 MPa or 30 MPa); (e) the textile coating; and (f) the anchorage through wrapping with TRM jackets. For this purpose, a total of 80 specimens were fabricated and tested under double-lap direct shear. It is mainly concluded that: (a) after a certain bond length (between 200 mm and 300 mm for any number of layers) the bond strength marginally increases; (b) by increasing the number of layers the bond capacity increases in a non-proportional way, whereas the failure mode is altered; (c) concrete sandblasting is equivalent to grinding in terms of bond capacity and failure mode; (d) concrete compressive strength has a marginal effect on the bond capacity; (e) the use of coated textiles alters the failure mode and significantly increases the bond strength; and (f) anchorage of TRM through wrapping with TRM jackets substantially increases the ultimate load capacity

FRP reinforcement in RC structures

fib Bulletin 40 deals mainly with the use of FRP bars as internal reinforcement for concrete structures. The background of the main physical and mechanical properties of FRP reinforcing bars is presented, with special emphasis on durability aspects. For each of the typical ultimate and serviceability limit states, the basic mechanical model is given, followed by different design models according to existing codes or design guidelines

Rural Origin Areas: Impacts and Practices

AbstractThis chapter looks at the implications, impacts and consequences of rural migration on the areas of origin, where oftentimes portions of the family, and of the family assets, remain

Basalt FRPs for strengthening of RC members

ABSTRACT: The use of FRPs to enhance the structural performance of RC members represents today's common practice. This is mainly due to their high strength to weight ratio, corrosion resistance or ease of application. However, given the current circumstances, the construction industry is in need of a more viable alternative to the commonly used glass and carbon fibres. Hence, the paper discusses two experimental programmes investigating the use of relatively new basalt fibres for strengthening of both compression and flexural members. Application of shear strips in strengthening of an RC beam (University of Sheffield) has shown that even a small amount of basalt FRPs can successfully increase the ultimate load capacity as well as provide anchorage and reduce the brittleness of plate end debonding. Testing of FRP confined concrete cylinders (Magnel Laboratory) has proven basalt to be 14% more effective than glass, yielding an average compressive strength increase of 84% when compared to the unconfined cylinders

Basalt FRPs for strengthening of RC members

The use of FRPs to enhance the structural performance of RC members represents today's common practice. This is mainly due to their high strength to weight ratio, corrosion resistance or ease of application. However, given the current circumstances, the construction industry is in need of a more viable alternative to the commonly used glass and carbon fibres. Hence, the paper discusses two experimental programmes investigating the use of relatively new basalt fibres for strengthening of both compression and flexural members. Application of shear strips in strengthening of an RC beam (University of Sheffield) has shown that even a small amount of basalt FRPs can successfully increase the ultimate load capacity as well as provide anchorage and reduce the brittleness of plate end debonding. Testing of FRP confined concrete cylinders (Magnel Laboratory) has proven basalt to be 14% more effective than glass, yielding an average compressive strength increase of 84% when compared to the unconfined cylinders

Bronchoalveolar lavage fluid cellular profile in workers exposed to chrysotile asbestos

The cellular profile of bronchoalveolar lavage fluid (BALF) in asbestos-exposed population remains controversial. We, therefore, aimed to investigate BALF in apparently healthy individuals that were exposed in asbestos-related work for a long period of time. Participants were selected among employees of a car brakes and clutches factory that used chrysotile asbestos. Selection criteria were an employment history of ≥15 years and the absence of severe respiratory disease. The total number and type of BALF cells, the existence of dust cells, iron-laden macrophages and asbestos bodies were assessed. Thirty-nine workers (25 men), with a mean age of 46.2 ± 4.2 years and a mean employment time of 23.5 ± 4 years, participated. Asbestos bodies were observed in 14 out of 39 (36%) specimens, dust cells in 37 and iron-laden macrophages in all. Those with asbestos bodies had at least 3 times higher probability to have lymphocytosis (lymphocytes > 11%: 64% vs 28%, p = 0.027) and had an increased percentage of iron-laden macrophages compared to those without asbestos bodies (median values: 42% vs 13%, p = 0.08). Smokers (36%) had less lymphocytes compared to non and ex-smokers (median values: 6% vs. 13%, p = 0.002), and iron-laden macrophages count had a positive relation (r = 0.31, p = 0.05) to lymphocyte count. Asbestos-exposed asymptomatic individuals with the presence of asbestos bodies in the BALF are more likely to have lymphocytic alveolitis while concurrent dust exposure and smoking habits hold a significant role. © 2011, SAGE Publications. All rights reserved

Comparative analysis of induced sputum and bronchoalveolar lavage fluid (BALF) profile in asbestos exposed workers

Background: Biological monitoring of healthy workers exposed to hazardous dusts lack validated screening tools. Induced sputum (IS) cellular profile was compared with bronchoalveolar lavage fluid (BALF) profile in asbestos exposed workers in order to assess its usefulness in monitoring workers exposed to asbestos for a long period of time. Methods. IS and BALF analysis was performed in 39 workers of a car brakes and clutches factory that uses chrysotile asbestos. Selection criteria were an employment history of > 15 years and the absence of a diagnosis of pneumonoconiosis. The type of cells, the existence of dust cells, of iron laden macrophages and of asbestos bodies were assessed and compared between IS and BALF samples. Results: 35 IS samples (90%) had dust cells, 34 (87%) iron laden macrophages and in 8 samples (21%) asbestos bodies were found. In most samples neutrophils were dominated. Samples with asbestos bodies (ABs) had significantly higher lymphocytes and lower neutrophils count compared with the samples without ABs. Macrophages and neutrophils in IS and BALF exhibited significant inter-relations (Spearman's rho: 0.26-0.29, p < 0.05) while IS lymphocytes count showed an inverse relation with BALF neutrophils (Spearman's rho: -0.36). Neutrophils and dust cells were highly correlated between the samples (Spearman's rho: 0.35, p < 0.05) while IS dust cells and lymphocytes were inversely related (Spearman's rho: -0.36, p < 0.05). More years of employment in the company was related with more neutrophils (Spearman's rho: 0.26) and less lymphocytes (Spearman's rho: -0.33) count. In multivariate analysis the presence of AB in IS samples was strongly related to the presence of asbestos bodies and lymphocytes count in BALF samples. Conclusions: IS and BALF analysis showed a similar cellular profile indicating that IS sampling in exposed workers to asbestos as a less invasive and expensive method may be useful in providing an insight both for inhalation of dusts and inflammatory processes in the lung. © 2011 Alexopoulos et al; licensee BioMed Central Ltd

ROUND ROBIN TEST ON THE BOND BEHAVIOUR OF EXTERNALLY BONDED FRP SYSTEMS TO CONCRETE

The performance of an externally bonded FRP strengthening system is often limited by its ability to effectively transfer stresses between the FRP reinforcement and the concrete substrate. As evidenced in the literature, debonding of the FRP reinforcement can occur at a level of strain well below its ultimate strain limit and generally results in a brittle type of failure. An accurate characterisation of the bond behaviour between an FRP system and concrete is therefore critical for the optimal design and detailing of a strengthening solution. Although various test methods to examine the local bond behaviour of externally bonded FRP systems have been proposed thus far, their implementation can lead to a wide range of results and a standard methodology has yet to be generally accepted. With these issues in mind, a Round Robin Testing (RRT) programme was carried out to assess the performance and reliability of small scale testing on various externally bonded FRP strengthening systems. Seven laboratories and four manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, EN-CORE, with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). This paper describes the proposed testing programme and summarizes the results obtained by the participating laboratories. The influence of various parameters on the bond behaviour of the examined strengthening systems is discussed and recommendations on testing procedures are given

Round robin test on the bond behaviour of externally bonded FRP systems to concrete

The reliable characterisation of the bond behaviour of an FRP system bonded to concrete is critical for the optimal design and detailing of a strengthening solution. Although various test methods to examine the bond behaviour of externally bonded FRP systems have been proposed thus far, their implementation can lead to a wide range of results and a standard methodology has yet to be generally accepted. With these issues in mind, a Round Robin Testing programme was carried out to assess the performance and reliability of small scale testing on six externally bonded FRP strengthening systems. Seven laboratories and four manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, EN-CORE, with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). This paper describes the proposed testing programme and summarizes the results obtained by the participating laboratories

Bond of FRP strengthening systems for concrete structures: a round Robin test

Although various test methods to examine the local bond behaviour of FRP strengthening systems to concrete have been proposed thus far, their implementation can lead to a wide range of results and a standard methodology has yet to be generally accepted. With these issues in mind, a Round Robin Testing (RRT) programme was carried out to assess the performance and reliability of small scale testing on various FRP strengthening systems, including both externally bonded laminates and near surface mounted reinforcement. Ten laboratories and eight manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, EN-CORE, with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). This paper describes the proposed testing programme and summarized some of the results obtained by the participating laboratories