Prediction of the long-term durability of lightweight aggregate concrete mixtures under severe marine environment (original) (raw)
Related papers
Materials and Structures
The paper describes a study that examined and compared the potential durability performance of various geographically distinct South African marine concrete mix types. Mix proportions were designed at two water/binder ratios (0.40 and 0.55) for different material combinations of binder and aggregate types. Sampling was done at 28, 91 and 182 days. Durability performance was inferred from durability index (DI) tests that measure the resistance of concrete to ion, gas and fluid penetration. Comparison was made on the basis of regional concrete type, w/b ratio and mix constituents (binder and aggregate type). All the concrete mixes were further compared to plain CEM I control concrete mixes at each w/b ratio. Results indicate that low w/b ratio and blended binder concrete mixes have low penetrability characteristics. Aggregate type was seen not to have an appreciable influence on the transport properties of concrete. Across the range of geographically different mixes, it was found that with a given concrete grade and binder type, marine concrete mixes are practically comparable. This permits the existing Service Life Prediction Model to be more confidently applied for all marine zones in South Africa with possible application in other geographic regions following further research.
Marine Durability of 30-Year Old Concrete Made with Different Cements
Journal of Advanced Concrete Technology, 2003
Marine durability of 30-year-old concrete specimens made with ordinary portland cement (OPC), high early strength portland cement (HES), moderate heat portland cement (MH), slag cement of type B (SCB), and alumina cement (AL) was investigated. Other parameters include sulfate content in cement, mixing water, and different exposure zones. Compressive strength, chloride ingress, corrosion of steel bars in concrete, microstructure, mineralogy of concrete, and steel-matrix and aggregate-matrix interfaces were investigated. Chloride ingress in concrete was sequenced as OPC, HES, MH>SCB>AL. However, for AL mixed with tap water, corrosion on steel bars in concrete was higher. For SCB and AL, the pore volume at the outer region of the specimens is reduced due to the ingress of chloride and other ions from seawater.
2014
The required or intended “service life” of a structure is a major factor in the design for concrete durability, and may even dictate how the overall design of a structure is approached. The longer the expected life of a structure, the greater the durability (and hence quality) of the concrete required. Performance design and testing is a useful method to overcome the shortcomings of traditional prescriptive specifications and possibly lead to improvements. Most significantly, performance testing and design provides an additional degree of robustness for designs for prestige or strategically critical structures. This paper provides an introduction to performance-based design and includes discussion on the approach to effective durability design for extended service lives of structures for long design lives in extreme environments. A case study is presented where a full probabilistic design was undertaken for reinforced concrete sub-structures and superstructures for a large crossing ...
Experimentation of Durable Concretes, Produced by Traditional Aggregates, in Marine Environment.
International Journal of Engineering Sciences & Research Technology, 2014
This paper describes the effect of durable concrete in marine environment, which is produced by traditional aggregates. For this purpose we have produced concrete of class C30/37 with aggregates from mountain quarry and riverbed. Meanwhile, we have not changed other components of concrete. Water – cement report is 0.42-0.44. During experimental faze, are done comparisons of resistance to compression, water and chlorides penetration. Concrete cubes produced, were treated in marine environment for 3, 7 and 28 days in Durres coastal city, Albania. Finally, results are compared to each other and conclusions are made on this basis.
Toward a probabilistic design of reinforced concrete durability: application to a marine environment
Materials and Structures, 2008
This work aims to propose a complete design methodology for concrete durability problems based on a probabilistic method including an original chloride diffusion modelling compatible with the new performance-based approaches. This is illustrated by the study of a concrete immersed in sea water. The physical and chemical processes that lead to the corrosion of the concrete reinforcement bars are presented first. A chloride penetration model based on Fick's second law is proposed. Next, the durability modelling parameters chosen among the durability indicators (Baroghel-Bouny, Concrete design for structures with predefined service life-durability control with respect to reinforcement corrosion and alkali-silica reaction, 2004; Alexander et al., Mater Struct 41:921-936, 2008) are assessed. They depend on the concrete formulation and the chemical composition of the cement. These indicators are characterized by their statistical distributions, which are realistically specified from a wide literature review. The whole probabilistic modelling is included in a Bayesian network so that it can be easily updated to include new experimental data. The evaluation of the time dependant corrosion risk is estimated for two types of cement: CEM I and CEM I with silica fume. The result shows the effect on the Lind-Hasofer reliability index of the type of cement, the concrete quality and the design options. The quality is integrated through the mean value and the standard deviation of the modelling parameters. The method could be used either directly for cover design or for semi-probabilistic design code calibration.
A design consideration for durability of high-performance concrete
Cement and Concrete Composites, 2001
Environmental factors, especially the climate, have signi®cant in¯uence on concrete structure. This paper aims to investigate the harmful eects of maritime climate on the durability of concrete structures built in coastal areas. Singly reinforced beam specimens of traditional design and those of densi®ed mixture design algorithm (DMDA) were employed to study the potential problems of concrete structure. Results indicate that cracks on the concrete structure, if go unnoticed, may cause failures. Thus, it is important to know the methodology of achieving high strength and durable concrete in order to avoid formation of cracks in the structural member. Ó : S 0 9 5 8 -9 4 6 5 ( 0 0 ) 0 0 0 8 9 -5
A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental, material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration, chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the non-normal random variables from the original physical space into the independent standard normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.