Glass fiber reinforced polymers (GFRP) have become a preferable material for reinforcing or strengthening reinforced concrete structures due to their corrosion resistance, high strength to weight ratio, and relatively low cost compared with carbon fiber reinforced polymers (CFRP). However, the limited fatigue life of GFRP hinders their use in infrastructure applications. For instance, the low fatigue life of GFRP caused design codes to impose stringent stress limits on GFRP that rendered their use non-economic under significant cyclic loads in bridges. In this paper, we demonstrate that the fatigue life of GFRP can be significantly improved by an order of magnitude by incorporating Multi-Wall Carbon Nanotubes (MWCNTs) during GFRP fabrication. GFRP coupons were fabricated and tested under static tension and cyclic tension with mean fatigue stress equal to 40% of the GFRP tensile strength. Microstructural investigations using scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy were used for further investigation of the effect of MWCNTs on the GFRP composite. The experimental results show the 0.5 wt% and the 1.0 wt% MWCNTs were able to improve the fatigue life of GFRP by 1143% and 986%, respectively, compared with neat GFRP.

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Seal integrity of functional oil wells and abandoned wellbores used for CO 2 subsequent storage has become of significant interest with the oil and gas leaks worldwide. This is attributed to the fact that wellbores intersecting geographical formations contain potential leakage pathways. One of the critical leakage pathways is the cement-shale interface. In this paper, we examine the efficiency of a new polymer nanocomposite repair material that can be injected for sealing micro annulus in wellbores. The bond strength and microstructure of the interface of Type G oil well cement (reference), microfine cement, Novolac epoxy incorporating Neat, 0.25%, 0.5%, and 1.0% Aluminum Nanoparticles (ANPs) with shale is investigated. Interfacial bond strength testing shows that injected microfine cement repair has considerably low bond strength, while ANPs-epoxy nanocomposites have a bond strength that is an order of magnitude higher than cement. Microscopic investigations of the interface show that micro annulus interfacial cracks with widths up to 40 m were observed at the cement-shale interface while these cracks were absent at the cement-epoxy-shale interface. Fourier Transform Infrared and Dynamic mechanical analysis measurements showed that ANPs improve interfacial bond by limiting epoxy crosslinking, and therefore allowing epoxy to form robust bonds with cement and shale.

Polymer concrete (PC) is a commonly used material in construction due to its improved durability and good bond strength to steel substrate. PC has been suggested as a repair and seal material to restore the bond between the cement annulus and the steel casing in wells that penetrate formations under consideration for CO 2 sequestration. Nanoparticles including Multi-Walled Carbon Nano Tubes (MWCNTs), Aluminum Nanoparticles (ANPs) and Silica Nano particles (SNPs) were added to an epoxy-based PC to examine how the nanoparticles affect the bond strength of PC to a steel substrate. Slant shear tests were used to determine the bond strength of PC incorporating nanomaterials to steel; resultsreveal that PC incorporating nanomaterials has an improved bond strength to steel substrate compared with neat PC. In particular, ANPs improve the bond strength by 51% over neat PC. Local shear stresses, extracted from Finite Element (FE)analysis of the slant shear test, were foundto be as much as twice the apparent/averageshear/bond strength. These results suggest that the impact of nanomaterials is higher than that shown by the apparent strength. Fourier Transform Infrared (FTIR) measurements of epoxy with and without nanomaterials showed ANPs to influence curing of epoxy, which might explain the improved bond strength of PC incorporating ANPs.

Polymer concrete (PC) are used in bridge deck overlays due to its superior durability specifically freeze-thaw and corrosion resistance. The excellent durability of PC is related to its impermeable microstructure and good bond to concrete or steel substrates. However, there is an increasing need to improve PC resistance to crack propagation (fracture toughness) to enhance its fatigue resistance and extend its service life. Researchers showed that objective becomes possible using dispersed chopped synthetic fibers (6-12 mm long). However, this approach was criticized for its dramatic impact on PC flowability. Here we suggest improving fracture toughness of PC using Multi-Walled Carbon Nanotubes (MWCNTs).PC mixes were produced using epoxy and standard aggregate with varying contents of MWCNTs being: 0 (Neat), 0.5, 1.0, 1.5 and 2.0 wt.% by weight of epoxy. Flowability of PC incorporating MWCNTs was tested. The tensile strength of PC incorporating MWCNTs was evaluated using direct tension test. A closed loop notched beam three-point bending test fracture test was used to evaluate fracture toughness of PC. The crack mouth opening displacement (CMOD) clip gage was used to provide feedback. The inverse analysis approach was used to extract the bilinear stress-crack opening displacement relation and calculate the fracture toughness (GF) of PC with and without MWCNTs. It is shown that MWCNTs significantly improves the fracture toughness and toughness of PC without significantly impacting its flowability. Microstructural analysis using Fourier Transform Infrared Analysis (FTIR) of polymer used to produce PC explains the effect of incorporating MWCNTs.

The structural design of the bolted fiber reinforced polymer elements is typically governed by the capacity of the joint rather than the fiber reinforced polymer member, while the joint capacity is typically governed by the shear strength of the fiber reinforced polymer. Here, the possibility of improving the shear strength of bolted joints is investigated in the unidirectional glass fiber reinforced polymer plates by incorporating the multiwalled carbon nanotubes during glass fiber reinforced polymer fabrication. Glass fiber reinforced polymer double-shear bolted lap joints were fabricated using up to 1.0 wt% multiwalled carbon nanotubes–-epoxy nanocomposites. Finite element modeling using multicontinuum theory and element deletion techniques was performed to explain the joint behavior. The experimental investigations show that incorporating multiwalled carbon nanotubes improved the shear strength, ductility, and energy absorption significantly. Microstructural analysis proves that a chemical reaction between multiwalled carbon nanotubes and epoxy improves the shear strength of the matrix.

Prefabricated concrete bridge deck panels are utilized in Accelerated Bridge Construction (ABC) to simplify bridge deck construction. Concrete with good bond and shear strength as well as excellent flowability is required to fill bridge deck closure joints. This paper discusses the use of polymer concrete (PC) for bridge deck closure joints in ABC. PC produced using poly methyl methacrylate and standard aggregate was tested. Test results of PC are compared to Ultra-High Performance Concrete (UHPC). Development length, lap splice length and shear strength of unreinforced PC were tested. It is shown that PC has a development length of 3.6 to 4.1 times the reinforcing bar diameter that is close to one-half the development length of 6 to 8 times the bar diameter required with UHPC. PC also showed a shorter splice length compared with that reported for UHPC. Finally, unreinforced PC showed shear strength that is twice that of UHPC. It is evident that using PC in bridge deck closure joints in ABC can improve constructability and provide cost-savings and eliminate reinforcing bar congestion.