Marine Concrete Research Articles

Chloride Ion Corrosion Resistance of Innovative Self-Healing SMA Fiber-Reinforced Engineering Cementitious Composites under Dry-Wet Cycles for Ocean Structures

To evaluate the chloride ion corrosion resistance of proposed innovative self-healing concrete based on shape memory alloys (SMA) and engineering cementitious composites (ECC), a total of 2 kinds of 22 specimens were prepared. Chloride ion corrosion tests of self-healing SMA-ECC concrete under dry-wet cycles were carried out. It was found that the chloride ion erosion depths of SMA-ECC were significantly smaller than that of MC, and the growth rate of erosion depth of SMA-ECC was obviously smaller than that of MC after 15 dry-wet (dry and wet) corrosion cycles. The chloride ion content of SMA-ECC vanished at the erosion depth more than 10 mm, which was consistent with the test result of AgNO3 solution color-rendering test. Test results indicate that, compared to marine concrete (MC), SMA-ECC has a better chloride ion corrosion resistance behavior. Moreover, the chloride ion concentration of SMA-ECC at a chloride ion erosion depth of less than 10 mm decreased more significantly than that of MC, indicating that almost all chloride salt solution reacted in the outer layer of SMA-ECC, which is consistent with the conclusions of 4.1 and 4.2. Finally, based on the erosion distribution of chloride ions and Fick’s second law, a calculation model describing the relationship between the apparent chloride ion diffusion coefficient and the boundary condition of the chloride ion content was proposed.

Valorization of uncontaminated dredged marine sediment through sand substitution in marine grade concrete

Marine sediment disposal is an important economic and environmental issue worldwide. In order to minimize these discharges and optimize resources through a circular economy approach, this study discusses the potential use of fine marine sediments without treatments as a sand substitute in the marine concrete class (XS2, C30/37). The Dreux-Gorisse method was applied to find the concrete formulation containing 10, 20, 30, 40 and 50% sediment by weight. The results show that an XS2 concrete C30/37 with a water to binder ratio of 0.55 could be designed with 10% of sediment replacement content without significantly affecting the concrete properties. However, the optimization of concrete mix design shows that marine concrete (XS2, C30/37) could be designed with 30% of sediment replacement content without significantly affecting the potential durability and the estimated lifetime of the concrete structure.

Improvement in the flexural behaviour of road pavement slab concrete containing steel fibre and silica fume

Cracks in concrete surfaces occur because of steel bar corrosion in reinforced concrete marine structures and other infrastructures, such as pavement slabs. Recently, the use of steel fibre-reinforced concrete (SFRC) to reduce and delay cracking and increase flexure strength has attracted considerable interest. Incorporating steel fibre in concrete delays and controls the tensile cracks of composite materials. This paper investigates the effect of using steel fibre (SF) and silica fume with steel fibre on the compressive strength and flexural behaviour of road pavement slabs (RPSs). Three concrete mixtures of concrete are the first mixture (MCC) is the control mixture, the second concrete mixture (MSFRC) contains steel fibres as an additive with a fraction volume of 1%, and the third concrete mixture (MSFRC–SF) contains steel fibres with a fraction volume of 1% and silica fume with a fraction volume of 10% as an additive. In addition, the effects of the types of curing tap water (TW) and seawater (SW) on concrete were investigated. Compressive strength was assessed at 7 and 28 days, and RPS flexural behaviour was measured at 28 days. The microstructure of concrete was examined using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The compressive strength of the mixes (MSFRC–SF) cured with TW and SW increased by 21.20% and 14.40%, respectively, compared with the control mixture (MCC). The ultimate loads for RPS–MSFRC–TW and RPS–MSFRC–SF–TW increased by about 24.29% and 46.95%, respectively, relative to the ultimate load of RPS–MCC–TW. The ultimate loads for RPS–MSFRC–SW, and RPS–MSFRC–SF–SW increased by about 36.32% and 59.90%, respectively, when the samples were tested with RPS-MCC–SW.

Research on The Chloride Diffusion Modified Model for Marine Concretes with Nanoparticles under The Action of Multiple Environmental Factors

Marine concrete structures are subject to the action of multiple environments during their service time. This leads to increased deterioration in the durability of marine concretes under the combined action of bending load and dry–wet cycles, salt freeze–thaw cycles, and salt spray erosion. The main reason for the damage of concrete under the action of the above three environments is Cl- attack. The free Cl- content (Cl-f) and the free Cl- diffusion coefficient (Df) of concrete can explain the diffusion of Cl- in concrete. This paper considers the actual environment of marine concrete structures and develops the Cl- diffusion modified model for nano-marine concretes under the action of dry–wet cycles, salt freeze–thaw cycles, and bending load and salt spray erosion. The nano-SiO2, nano-Fe2O3, and nano-Fe3O4 were firstly incorporated into ordinary marine concrete, then the Cl- content of each group of marine concrete was measured at different depths, and the Cl- diffusion coefficients were calculated; finally, the Cl- diffusion modified model was established under different environmental factors. The test results show that the total and free Cl- diffusion coefficients of nano-marine concretes were lower than those of ordinary marine concrete, and the nano-SiO2, nano-Fe2O3, and nano-Fe3O4 of the optimum dosage were 2%, 1%, and 2%, respectively. The fitting results of Cl- content have a good correlation, and the correlation coefficient (R) is basically above 0.98.

The Preparation of a Novel Hyperbranched Antifouling Material and Application in the Protection of Marine Concrete

Marine fouling on concrete has become one of the severest problems that damage the surface and even cause internal corrosion of marine concrete. Dissimilarly to the previous abuse of toxic antifoulants, developing hydrophobic waterborne antifouling materials could be regarded as one of the most environment-friendly and potential directions to protect marine concrete. However, the insufficient hydrophobicity, antifouling, and mechanical properties limit their application. Herein, we reported a series of hybrid coatings combining hyperbranched polyglycerol (HPG) decorated waterborne fluoro silicone polyurethane (H) and HPG-grafted graphene oxide (G-HPG) that improve the hydrophobicity, antifouling, and mechanical properties. The hybrid materials were modified by the hyperbranched polyglycerol synthesized based on the anionic-ring-opening reaction between glycerol and ethylene glycol or polyethylene glycol. Remarkably, the hydrophobicity (115.19°) and antifouling properties (BSA absorption of 2.33 μg/cm2 and P. tricornutum attachment of 1.289 × 104 CFU/cm2) of the materials could be developed by the modification of HPG with higher generation numbers and backbone molecular weights. Moreover, the mechanical properties negligibly decreased (tensile strength decreased from 11.29 MPa to 10.49 MPa, same pencil hardness and adhesion grade as H of 2H and grade 2). The results revealed that the HPG of higher generation numbers and backbone molecular weights could benefit materials with enhanced antifouling properties and hydrophobicity. The method of hyperbranched modification can be regarded as potentially effective in developing the durability and antifouling properties of marine antifouling materials.

Strength and durability of marine cement-based mortar modified by colloidal nano-silica with epoxy silane for low CO2 emission

The heavy use of marine concrete consumes a large amount of cement increasing CO2 emission. Improving the strength and durability of marine concrete is an effective strategy to reduce CO2 emission. This study aimed to introduce colloidal nano-silica (CNS) and epoxy silane modified colloidal nano-silica (M-CNS) to improve the mechanical performance and durability of High Sulfate Resistance Portland cement. Meanwhile, the CNS and M-CNS were incorporated to marine cement mortar, and the aggregation of CNS, and the hydration mechanism and micro-mechanism of the mortar were investigated. The results indicated that the workability, mechanical properties and durability of marine cement samples were enhanced with M-CNS addition. When adding 1 wt% M-CNS with grafting rate of 15% (M-CNS1), the chloride diffusion coefficient was reduced by 9.49% and the porosity was reduced by 18.84%. In addition, the compressive strength of cement mortar with M-CNS1 increased by 10.42%, 28.71% and 10.49% compared with blank specimens after curing for 3-, 7- and 28-days. The improvements in strength and durability indicate that M-CNS has a promising application for reducing CO2 emissions by marine concrete industry.

Superhydrophobic coatings based on bionic mineralization for improving the durability of marine concrete

Designing a stable superhydrophobic surface has been a current research focus. A functional bionic mineralized layer is introduced into the coating system to enhance the applicability. In the process of bionic mineralization induced by dopamine, silver ions were in situ reduced to nanosilver by dopamine in the interstices of mineralization products, forming a micro-nano composite structure by the mineralized grains and nanosilver microspheres. Then the superhydrophobic (CA = 153°) antibacterial coating was obtained by silane modification. The characterization of the coating shows that it can significantly improve the antibacterial effect, the mineralization layer and the silane molecular network can delay nanosilver loss. Furthermore, the superhydrophobic coating has extreme stability and its wettability hardly changes under abrasion, biological environment and freeze–thaw conditions, obtaining higher superhydrophobic, antibacterial and anti-icing performance. Considering the above properties, this novel superhydrophobic coating is anticipated to be a promising protective material which solves the corrosion, biofouling and freeze–thaw problems confronting marine concrete.

Effects of CEA on the microstructure evolution and chloride ion migration of marine concrete

In this paper, autogenous shrinkage, compressive strength, microstructure evolution and also chloride migration coefficient of marine concrete with CaO-based expansive agent (CEA) were investigated. The results showed that the autogenous shrinkage of marine concrete was effectively compensated by adding CEA, especially in the early stage. However, as the CEA dosage increased to 12%, re-expansion of concrete in the later stage was observed to cause the problem of poor volume stability of marine concrete. The re-expansion of 12% CEA was due to the rehydration of unreacted CEA. While, Ca(OH)2 produced by CEA hydration accelerated the hydraulic reaction and pozzolanic reaction the of slag in the later stage. As a result, more C-S-H gel was generated to fill the pore and micro-cracks and refine the pore structure, which can partially repair the inner damage of marine concrete in the later stage. Although the chloride migration coefficient gradually increased and the compressive strength decreased with the increase of CEA dosage, the self-healing of partial damage for marine concrete made the chloride ion more difficult transport into the marine concrete. Thus, the impact of CEA dosage on chloride migration coefficient of marine concrete was significantly weakened in the later stage. When the dosage of CEA was no more than 6%, the marine concrete behaved a good volume stability and chloride penetration resistance in the later stage.

A Light at the End of the Tunnel: Using an Improvised Laser Measuring System to Verify the Bore Dimensions of an XI-Inch Dahlgren Shell Gun

ABSTRACT In developing a method to remove marine concretion from the bores of USS Monitor’s XI-Inch Dahlgren shell guns at The Mariners’ Museum and Park, a problem arose: how to determine the curve of the powder chamber to avoid damage during cleaning. Multiple period schematics showed conflicting dimensions, requiring direct measurement. An identical, non-archaeological XI-Inch Dahlgren from USS Kearsarge survives in Naval History and Heritage Command (NHHC) collections, creating the opportunity to verify the dimensions of an un-damaged analog of Monitor's guns. Measuring the Kearsarge Dahlgren represented its own set of challenges. A 3-dimensional laser scan would have been ideal, but neither the Museum nor the Navy’s lab possessed a scanner, and it was not financially viable to rent or purchase one. Even if free services could be found, the Kearsarge gun was in a secure military facility, complicating potential access for a third-party company. Instead, it was necessary to measure the gun’s bore with minimal expenditure. An improvised system was developed using a copy stand and a consumer-grade laser-measuring device. This system was transported to NHHC's storage facilities and successfully used to measure the Kearsarge Dahlgren’s bore, confirming the correct drawing and enabling further treatment of Monitor’s artillery.

Molecular insights into the adsorption of chloride ions in calcium silicate hydrate gels: The synergistic effect of calcium to silicon ratio and sulfate ion

Corrosion of steel bars by chloride ions is one of the main reasons for determining the service life of marine concrete. In this work, the effects of calcium to silicon (C/S) ratio and SO42− concentration on Cl− adsorption in calcium silicate hydrate (C–S–H) gels were systematically studied by molecular dynamics simulations. Atomic-scale results show that higher C/S ratio induces more Cl− adsorption. The presence of SO42− not only reduces the Cl− adsorption but also buffers the adsorption caused by increasing C/S ratio. The Cl− adsorption is caused by the attraction of interlayer Ca (Cah) and hydroxyl groups in low C/S gel, while in high C/S ratio C–S–H gel is mainly contributed by Cah. More Cl− adsorption at the C–S–H interface ensures less Cl− accumulation in zones surrounding the reinforcement. The insights into ion adsorption behaviour should provide useful information for prolonging the durability of marine concrete by designing appropriate compositions.

Research progress on durability of marine concrete under the combined action of Cl− erosion, carbonation, and dry–wet cycles

Abstract Marine concrete is a kind of construction material which is seeking its growing application in marine engineering. However, the marine concrete structures are exposed to aggressive environment and harmful ions. Therefore, it is crucial to improve the durability of marine concrete. The concrete structure located in the tidal zone is subjected to the dry–wet cycles caused by tidal action, chloride ion (Cl−) erosion in seawater, and CO2 erosion in air. When these factors work together, they cause great damage to the marine concrete structure. In view of the three environmental factors, namely, Cl− erosion, carbonation, and dry–wet cycles, taking fly ash, fibers, and nanomaterials as examples, this article expounds the research status of durability of marine concrete, introduces the latest research progress, the addition of fibers, fly ash, and nanomaterials can improve the Cl− corrosion resistance and dry–wet cycles resistance of marine concrete, while the addition of fly ash is unfavorable for carbonation resistance. And the future development trend of marine concrete is prospected.

Durability of Marine Concretes with Nanoparticles under Combined Action of Bending Load and Salt Spray Erosion

The coupling effect of bending load and salt spray erosion during the service of a sea-crossing bridge accelerates the deterioration and durability of concrete and dramatically reduces the load-carrying capacity of the bridge. The effects of nanoparticles on the durability of marine concrete exposed to bending loads and salt spray erosion were studied. In this paper, nano-SiO2 and nano-Fe2O3 were mixed into plain concrete. Free chloride ions (Cl−) were titrated at different concrete depths using a four-point loading device and a self-developed salt spray erosion test chamber. Test results showed that chloride ion levels in the tensile and compressive zones for both nanoconcretes were lower than plain concrete at the same timepoint. The optimal mixtures of the two nanoparticles were 2% and 1%, and the improvement of nano-SiO2 was more significant than nano-Fe2O3. Due to the special properties of nanomaterials, they effectively improved the microstructure of concrete and the composition of cement hydration products. This allowed concrete to become more compact, reduced crack generation, increased the difficulty of Cl− migration inside the concrete, and improved the overall durability of marine concrete upon exposure to bending loads and salt spray erosion.

Experimental and simulation study on chloride diffusion in unsaturated concrete under the coupled effect of carbonation and loading

In this paper, the transport of chloride ions in marine concrete was investigated under coupled environment of carbonization and various static sustained loads. Firstly, the influences of concrete strength, exposed ages of concrete, flexural and compressive loads on chloride ion diffusion in concrete were studied by the salt spray erosion and carbonation erosion alternate test. The result showed that the content of chloride ions decreased with the increasing concrete strength, and increased with age. And the chloride ion content increased with the increase of the flexural stress and they first decreased then increased with the increase of the compressive stress level. Carbonization accelerates the chloride ion transmission and increases the chloride ion content to a certain extent under the experimental conditions. Then, the chloride ion transport equation in partially saturated concrete was formulated considering such multiple factors as carbonization, load, saturation, relative humidity and temperature. On the basis of the established chloride transport equation, the chloride diffusion process of the samples was simulated by using COMSOL software at the macro level, and the calculated results display fine consistency with experimental data. Finally, the multi-phase mesoscopic numerical models were proposed by two-dimensional meso-structure of samples with randomly distributed convex polygon aggregates. It is found that aggregate has a significant impact on the transport path and distribution uniformity of chloride ions.

On the implementation of the interpretable data-intelligence model for designing service life of structural concrete in a marine environment

Modeling the durability design of reinforced concrete structures is a particularly crucial challenge for identifying the behavior of marine concrete. In this research, novel interpretable equation-based models based on Fick's second law of diffusion for designing the service life of structural concrete were presented. To do so, a Machine Learning (ML) approach based on linear and non-linear methods including Multivariate Adaptive Regression Splines (MARS), Gene Expression Programming (GEP), and M5p Model Tree (MT) was performed to predict the apparent surface chloride concentration (Cs) in the zones of the marine environment. A comprehensive database is comprising of 642 field exposure experimental and environmental records was utilized to develop ML methods. The proposed ML models were investigated in terms of performance evaluation, error measurements, and visual consideration, MARS model (r=0.890,WI=93.9%andRMSE=0.804%bindercontent, (tidal zone) and r=0.901,WI=93.5%andRMSE=0.818%bindercontent (splash zone) and r=0.875,WI=86.8%andRMSE=0.883%bindercontent (submerged zone)) outperformed the proposed GEP, MT and empirical equations. Furthermore, simulation of Monte-Carlo analysis was extended to verify the proposed ML predictive models. Evaluation of the sensitivity analysis presented that the water to binder ratio, annual mean temperature, and exposure time were the most influential factors in predicting the Cs of reinforced concrete structures. Also, a parametric assessment has been performed for the presentation of the robustness of the proposed ML model. The modeling results presented new insight into the designing of the service life of reinforced concrete with superiority promotion of ML methods.

Improved peridynamics approach for the progressive fracture of marine concrete

Crack initiation and propagation in marine concrete play a significant role in the security and durability of concrete in ocean construction. Peridynamics (PD), which reformulates classical continuum mechanics in terms of spatial integral equations instead of partial differential equations, has been used successfully to match the fracture patterns observed in experiments. However, the classical bond-based peridynamics (BPD) describe brittle fracture instead of quasi-brittle fracture; this includes the failure of quasi-brittle solid marine concrete. Further, the models have significant surface effects, and the effect of the internal length on nonlocal long-range forces is not reflected. The current work proposes an improved BPD approach to overcome the three drawbacks of fracture analyses of marine concrete. A novel kernel function is incorporated, an effective PD surface effect correction method is used, and the BPD bond stiffness at the boundary is modified. Then, the constitutive force function of the BPD is established based on the linear and nonlinear mechanical behaviours of the progressive fracture of ocean concrete materials, and a corresponding failure criterion is given. The validity and accuracy of the proposed method are demonstrated via numerical analyses and experiments. The proposed method can fully capture the nonlinear deformation and progressive fracture of marine concrete.

Under the Mediterranean I: Studies in Maritime Archaeology

Under the Mediterranean I: Studies in Maritime Archaeology

CO2-Optimal Design of Fly Ash Marine Concrete with Global Warming and Stress Types

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Polymer functional coatings modified by ZrP‐based composites: Preparation and applications on marine concrete

AbstractThe development of high‐performance coatings for concrete structures is essential to ensure their durability and service life. However, most of the proposed developed strategies suffer from various limitations, especially regarding the wear and biological‐corrosion resistances of the coatings. This work reports a facile and efficient method to prepare effective composite coatings by nano‐modification, in which the intercalated composites play structural and functional roles in the corrosion, wear, and biological‐corrosion resistances. An in situ assembly synthesis was used to prepare the intercalated composites. The composites exhibited an innovative alternating skateboard structure and a functional composition. The silane‐emulsion modified with the composites was prepared and coated on the mortar surface to systematically study its performance at the concrete interface. The results indicate the good dispersion stability of the innovative α‐ZrP composites in the silane emulsion and their significant enhancement of the silane coatings' ability to improve the durability of marine concrete. The mechanisms of performance improved by the prepared composites through their unique lamellar structure and interlamellar silver‐nanoparticle composition were also examined. The prepared composite coating exhibits a new strategic approach to solve problems associated with concrete applications and provides technical guidance for surface protection of marine concrete structures.

Forecast of surface chloride concentration of concrete utilizing ensemble decision tree boosted

This study proposes the application of Ensemble Decision Tree Boosted (EDT Boosted) model for forecasting the surface chloride concentration of marine concrete A database of 386 experimental results was collected from 17 different sources covering twelve variables was used to build and verify the predictive power of the EDT model. The input factors considered the changes in eleven variables, including the contents of cement, fly ash, blast furnace slag, silica fume, superplasticizer, water, fine aggregate, coarse aggregate, annual mean temperature, chloride concentration in seawater, and exposure time. The results indicate that EDT Boosted is a good predictor of as verified via good performance evaluation criteria, i.e., R2, RMSE, MAE, MAPE values were 0.84, 0.16, 0.17, and 17%, respectively. Partial dependence plot (PDP) was then developed to correlate the eleven input variables with the . PDP implied that the strongest factor affecting Cs was the amount of fine aggregate content, chloride concentration, exposure time, amount of cement, and water, which is useful for material engineers in the design of the grade.

Forecast of surface chloride concentration of concrete utilizing ensemble decision tree boosted

This study proposes the application of Ensemble Decision Tree Boosted (EDT Boosted) model for forecasting the surface chloride concentration of marine concrete A database of 386 experimental results was collected from 17 different sources covering twelve variables was used to build and verify the predictive power of the EDT model. The input factors considered the changes in eleven variables, including the contents of cement, fly ash, blast furnace slag, silica fume, superplasticizer, water, fine aggregate, coarse aggregate, annual mean temperature, chloride concentration in seawater, and exposure time. The results indicate that EDT Boosted is a good predictor of as verified via good performance evaluation criteria, i.e., R2, RMSE, MAE, MAPE values were 0.84, 0.16, 0.17, and 17%, respectively. Partial dependence plot (PDP) was then developed to correlate the eleven input variables with the . PDP implied that the strongest factor affecting Cs was the amount of fine aggregate content, chloride concentration, exposure time, amount of cement, and water, which is useful for material engineers in the design of the grade.