scholarly journals Rehabilitation of concrete one-way slabs using precast prestressed concrete prisms

2021 ◽  
Author(s):  
Saeed Gerami ◽  
Dagmar Svecova
Keyword(s):  
Prestressed Concrete ◽  
High Strength Concrete ◽  
High Strength ◽  
Near Surface ◽  
Complex Process ◽  
Before And After ◽  
Near Surface Mounted ◽  
Wire Steel ◽  
Precast Prestressed Concrete ◽  
Crack Widths

The rehabilitation of structures is a complex process that involves many considerations. This paper presents results of a feasibility study on the use of precast prestressed concrete prisms (PCPs) as a near-surface mounted reinforcement for rehabilitation of cracked one-way slabs. The PCPs were cast with high-strength concrete and were concentrically prestressed by one 9 mm diameter stress-relieved seven-wire steel strand. Six identical one-way slabs with a length of 3000 mm were tested. They were loaded until cracking, then fully unloaded and rehabilitated with four PCPs before loading them to failure. Deflected profiles and crack widths of the slabs before and after rehabilitation were compared in this research. This rehabilitation method reduced the magnitude of deflection and crack width of the samples. The cracks induced in the first phase of loading before PCP rehabilitation appeared fully closed after the PCP rehabilitation until five times the original cracking loads of the slabs.

The Frost Resistance of High Strength Concrete Containing Super-Fine Mineral Admixture

2012 ◽  
Vol 512-515 ◽  
pp. 2999-3002 ◽  
Author(s):  
Hong Fang Li ◽  
Yi Xia
Keyword(s):  
Weight Loss ◽  
Frost Resistance ◽  
High Strength Concrete ◽  
Elastic Moduli ◽  
High Strength ◽  
Mineral Admixture ◽  
Limestone Powder ◽  
Strength Concrete ◽  
Before And After ◽  
Lithium Slag

The influence of limestone powder, lithium slag and air-entraining agent on frost resistance of concretes was investigated by freezing-thawing cycle tests. The elastic moduli and weight loss rates of concretes before and after tests were checked. The results show the introduction of limestone powder into concrete is disadvantageous to its frost resistance, which gets worse as limestone powder contents increase. Air-entraining agent used in concrete can improve its frost resistance. The frost resistance grades of concrete containing a certain of air-entraining agent (0.2-0.4‰) can reach F1500, while it is below F300 for limestone powder concrete which is absent of air-entraining agent. The addition of lithium slag into concrete is helpful to frost resistance, and optimum mixing amount is 10%.

Adhesive Applications Used During Repair and Strengthening of 30-Year-Old Prestressed Concrete Girders

2003 ◽  
Vol 1827 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Calvin E. Reed ◽  
Robert J. Peterman ◽  
Hayder Rasheed ◽  
David Meggers
Keyword(s):  
Prestressed Concrete ◽  
Concrete Surface ◽  
Shear Cracks ◽  
Near Surface ◽  
Cfrp Sheets ◽  
Concrete Girders ◽  
Near Surface Mounted ◽  
Load Tests ◽  
Prestressed Concrete Bridge ◽  
Prestressed Concrete Girders

The use of polymer adhesives during the strengthening of 30-year-old prestressed concrete bridge girders is described. The single-T–shaped specimens strengthened in this study were saw-cut from prestressed concrete double-T girders that had been removed from a bridge originally designed for H-15 highway loading and opened to traffic in 1969. Over time, the bridge had been severely overloaded, resulting in numerous flexural and shear cracks in the stems of each girder and large concrete spalls at the tension faces. In 1998, several damaged members were replaced. To investigate the feasibility of repairing or strengthening similar members in the future, the damaged members were retrofitted with carbon fiber–reinforced polymer (CFRP) sheets and then load tested under service and ultimate load conditions. Polymer adhesives were used to seal all visible cracks in the stems, to inject epoxy into all sealed cracks, to fill spalled areas in the tension face of the stems, to apply longitudinal and transverse CFRP sheets to the stems of the members, and to install near-surface-mounted reinforcement (NSMR) in one of the specimens. Results from load tests indicate that excellent bond was consistently achieved between the CFRP sheets and the 30-year-old concrete surface and between the NSMR and surrounding concrete. The success of epoxy injection of the flexural cracks, however, varied. Specifically, the injected cracks in one specimen reopened at an applied load well below the theoretical cracking load for the members.

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