Papers by Keyword: Durability of Concrete

Abstract: The disposal of waste marble is a severe concern worldwide, as it is non-biodegradable, leading to dumping issues and environmental pollution. An economically feasible solution to this problem is utilizing it in concrete production that will make the environment green, make the construction industry sustainable, fulfil the high demand for concrete, and convert waste into valuable materials. This study investigates experimentally the feasibility of using waste marble as a partial replacement for coarse aggregate in concrete production. The research focused on preparing M30-grade concrete mixes with varying percentages of waste marble aggregate to replace normal coarse aggregate, ranging from 20% to 100%. The study evaluated the fresh properties, compressive strength, and durability of concrete made with waste marble aggregate. The research findings indicate that the optimal outcome was achieved with a 60% replacement of natural coarse aggregate with waste marble coarse aggregate in concrete production. The workability increases as the percentage replacement of coarse aggregate by waste marble aggregate increases, as found by the slump value test. The compressive strength of the mix having 60% replacement of natural aggregate by waste marble aggregate concrete (WMAC-60) is 10.0%, 11.8% and 12.14, higher than conventional concrete tested at 7, 28, and 56 days, respectively. The durability of WMAC-60 is also improved, with 7.14% and 13% lower chloride ion pass than conventional concrete at 28 and 180 days of a rapid chloride penetration test, respectively. A 6.1% and 6.67% higher resistivity was found in WMAC-60 compared to the conventional concrete at 28 and 180 days of electrical resistivity test, respectively. In brief, waste marble aggregate is an eco-friendly and sustainable method that reduces concrete costs without compromising concrete performance.

Abstract: This research paper presents the findings of an experimental study conducted to investigate the influence of varying sizes and percentages of steel and nylon fibers on the mechanical and durability properties of concrete. The objective of this study was to explore the potential enhancements in concrete performance through fiber reinforcement, considering the two distinct fiber types - steel and nylon. A comprehensive testing program was devised, encompassing a wide range of fiber combinations to assess their individual and combined effects on concrete properties. The concrete specimens were prepared by incorporating different sizes (length and diameter) and proportions (percentage by volume) of steel and nylon fibers into the concrete mix. Mechanical properties, including compressive strength, tensile strength, and flexural strength, were evaluated to determine the impact of fiber reinforcement on the concrete's load-bearing capacity and resistance to cracking. Additionally, the durability properties, chloride ion penetration, and abrasion resistance, were assessed to understand the potential improvement in the concrete's long-term performance under adverse environmental conditions. The experimental results revealed significant variations in the mechanical and durability properties of the fiber-reinforced concrete compared to the conventional concrete mix. Steel fibers demonstrated superior performance in enhancing the concrete's load-carrying capacity and ductility, especially at higher percentages. On the other hand, nylon fibers exhibited exceptional resistance to and abrasion, contributing to improved durability. Notably, the steel and nylon fibers exhibited synergistic effects, leading to a balanced enhancement of mechanical and durability properties. In conclusion, this study provides valuable insights into the benefits of incorporating steel and nylon fibers in concrete, offering an effective means of optimizing the material's overall performance for diverse engineering applications. The results from this research can serve as a basis for developing more resilient and sustainable concrete structures, which can withstand harsh environmental conditions and contribute to the advancement of construction practices. Further exploration into the long-term behavior and cost-effectiveness of fiber-reinforced concrete is recommended for a comprehensive understanding of its feasibility in practical engineering applications.

Abstract: The durability of concrete can be assessed based on the quality of the surface layer of concrete, for which there are a few standardized assessment test methods. Usually, the quality of the surface layer of concrete is evaluated based on its air and water permeability. The aim of this experiment was to compare the outputs which provide some methods for determining the permeability of the surface layer of concrete (GWT, ISAT, TPT, the depth of penetration of water under pressure). The measured values using the individual methods of assessing the permeability of the surface layer of concrete very closely correspond.

Abstract: The strength and durability are the main design parameters of high performance concrete. Concrete should be strict attention to the requirements of various raw materials and mix proportion design in the production process. Engineering example shows that high performance concrete has good durability, economy and environmental protection.

Abstract: The deterioration of concrete durability seriously affects utilization and lifespan of concrete constructions. This paper presented a novel method to improve concrete durability by synthesizing Super-absorbent Resins (SAR) in micro-cracks or capillary-pores of concrete, i.e., the synthesized SAR swell after absorbing water, fill micro-cracks or capillary-pores and prevent water penetration into concrete. The main performance of impermeability, freeze resistance and sulfate resistance related to concrete durability were studied. The results show that the impermeability, freeze resistance and sulfate corrosion resistance of cement mortar handled by SAR are obviously better than cement mortar unhandled by SAR.

Abstract: Fair-faced concrete is a neotype constructional material. It is exposed to the natural environment directly as decorative walls in the acting process, so the request of durability of the concrete is much higher. Through comparison testing, data collection and analysis, find out the difference of durability of fair-faced concrete in different proportioning. It has positive significance to the selection of raw material and construction technology.

Abstract: According to investigations of apparent surface chloride contents and chloride penetration profile of concrete structures exposed to chloride environment, the influences of boundary and initial conditions, geometry parameters such as the geometry dimension and section shape, etc. were discussed. Based on the Fick’s second law of diffusion and different boundary and initial conditions, different analytical models to predict the chloride penetration profile in concrete structural members with different boundary and initial conditions were derived. Some calculations examples were made using those analytical models. Computational results show that the boundary and initial conditions have remarkable influences on chloride penetration profile and service life time of concrete structures. Using prevailing error-function solution model based on the semi-infinite assumption of chloride ingress, the prediction of service life time of concrete structures are over evaluated, in particular for the steel reinforcement in corner of the section. Some modify coefficients should be taken into consideration, concerning the influences of boundary and initial conditions.

Abstract: The mechanism of concrete durability under uniaxial compressive load has been studied through chloride penetration experiments in this contribution. It has been found that there is a good corresponding relationship between chloride penetration resistance of concrete and the applied compressive stress level. With increasing of the applied compressive load, chloride penetration depth and content both decreased firstly. After the compressive load up to a critical level, they began to increase quickly. The apparent diffusion coefficient and chloride concentration at the surface also increase with the same rule. It is shown that chloride penetration of concrete is a complex process. So the effect of mechanical load should be considered as an important factor for prediction of service life of reinforced concrete structures in marine environment.

Abstract: Influence of permeated crystalline materials on durability of hydraulic concrete was studied by impermeability test methods after sulfate attack and freeze-thaw cycling. Microstructure of concrete was analyzed and characterized with SEM and MIP. The results showed that impermeability pressure of concrete with permeated crystalline materials was more than that of standard concrete after sulfate attack and freeze-thaw cycling. Permeated crystalline materials improved on performance of concrete for sulfate attack and freeze-thaw, because that microstructure of interfacial transition zone of concrete with permeated crystalline materials was compact and its pore size distribution was more than that of standard concrete. There were more content of less harmful pore with diameter 20nm~100nm and less content of harmful pore with diameter100nm~200nm and more than 200nm in concrete with permeated crystalline materials than in standard concrete.

Abstract: The durability of concrete structure has become an important field of civil engineering at home and abroad, and how to determine the environmental effects of typical durability of concrete structure key parameters become the key. Proposed by different domestic and foreign scholars to study durability parameters of concrete structure of different models, different models are different in the source, type, model parameters and applicable conditions. In this paper, some typical models are reviewed and analyzed from two major aspects of the durability of concrete, the deterioration of concrete and the steel corrosion.