Experimental Study on the Permeation and Migration Rules of Pressurized Water in Textile-Reinforced Concrete (TRC)

As a new type of repairing and reinforcing material, textile-reinforced concrete (TRC) is often used to improve mechanical properties and durability of offshore, port, and hydraulic structures in the corrosive environment. In order to investigate how to quantify the permeability performance of TRC under external pressurized water, standard concrete permeability tests, nuclear magnetic resonance (NMR) tests, and scanning electron microscope (SEM) tests were conducted. These tests considered the effects of fiber grid size, Tex content, and water–cement ratio on the impermeability of TRC. Experimental results show that water gathers around the fiber bundles and migrates upwards along the longitudinal fiber under external water pressure and seeps out from the upper surface of the concrete specimen. Furthermore, based on the concentric annular slit flow theory and hydropower similarity principle, this study established a formula for the permeability of TRC and the calculated values are in good agreement with the experimental values.

Predicting Tensile Strength Growth From Self Compacting Concrete Partially Replaced Cement with Wood and Fly Ash

This paper monitors the growth rate of tensile strength under partial replacement of locally sourced materials, the study monitor the behaviour of tensile between seven and twenty eight days of optimum curing age, modeling and simulation were applied in the study, whereby parameters that generate the attained tensile strength from self compacting concrete were monitored considering various factors such as variation of compaction and water cement ratio, the reaction of these parameters were examined in the study through the simulation, the reflection of these parameters influence where observed in all the trend, the study examined the level of significances of tensile on concrete structure, therefore try to evaluate various reflection effect from permeability and other parameters that were not considered in experimental process, these are developed from self compacting concrete partially replace cement with fly ash and wood. Tensile strength is an important property of concrete due its level of vulnerability to tensile cracking base on different kind of applied loading itself. The influence of permeability as a physical property has definitely affect the durability of concrete, these where observed on the its reflection on tensile strength in all the trend, the rate of permeability effect on tensile were monitored to reflect its reaction through microstructural perspective influence from porosity, pore size, connectivity including its rates of bonding, these correlation includes air content and capillarity, there rate of permeability coefficient on its reduction are determined by the decrease in porosity and void ratios from concrete compaction rate, it is reflected on its variation of tensile strength in self compacting concrete, the rate of permeability reducing at constant rates determined the tensile strength through it microstructural setting on the self compacting concrete, these condition were applied on the simulation to generates the predictive values compared with experimental values by an expert [22], while an improvement were made on it study, these include monitoring of concrete permeability and void ratios effect on tensile, the behaviour of porosity under the influence of permeability and variation concrete void were examined from the permeability influence on tensile strength.

Evaluating Fresh and Hardened Properties of High-Strength Concrete Including Closed Steel Fibres

Background: The tensile strength of the plain concrete is weak. Thus, fibres are embedded in concrete to improve its ductility. However, pulling out steel fibres from concrete structures is one of the most encountered issues in the fiber-reinforced concrete, which hinders using their maximum capacities. Objectives: Thus, closed steel fibres (square shape) were incorporated into concrete mixes to evaluate their impacts against the pulling-out effects and assess the feasibility of applying Closed Steel Fibres (CSFs) on the fresh and hardened concrete properties. Hooked end and straight steel fibres were also investigated for comparison. Methods: The utilized steel fibres were incorporated with lengths of 20, 30, and 40 mm, and volume fractions of 0.25%, 0.50%, and 0.75%. Silica Fume (SF) was involved in the fibre-reinforced concrete mixtures at 7% of the cement weight. Results: Paper outcomes stated that the inclusion of steel fibres involved different impacts on the concrete compressive strength depending on the applied fibre geometries and content. Conclusion: CSFs exhibited better performance against the pulling-out effect from the surrounding concrete structure than those of hooked end and straight steel fibres. However, the addition of CSFs has increased the concrete permeability due to their poor space-filling capacity.

Experience-Based Physico-Chemical Models for Long-Term Reinforcement Corrosion

The long-term corrosion progression of steel reinforcement is important for estimating the life of reinforced concrete infrastructure. Reviews of field experience and results from recent controlled long-term experiments show that the development of reinforcement corrosion is much more complex than the classical empirical Tuutti model. A new, comprehensive model is proposed, referencing observations and inferences from many field and laboratory observations and built on the bi-modal model for the corrosion of steel. It includes the critical roles of air-voids in the concrete at the concrete-steel interface and the effect of long-term alkali leaching as accelerated by the presence of chlorides. Both are affected by compaction and concrete permeability. The role of chlorides in the early stages is confined to pitting within air-voids. These are critical for allowing initiation to occur, while their size influences the severity of early corrosion. Empirical data show that for seawater with an average water temperature in the range of 10–20 °C, the corresponding rate of long-term corrosion ra is in the range of 0.012–0.015 mm/y.

Shrinkage Behavior of Conventional and Nonconventional Concrete: A Review

Concrete is indeed one of the most consumed construction materials all over the world. In spite of that, its behavior towards absolute volume change is still faced with uncertainties in terms of chemical and physical reactions at different stages of its life span, starting from the early time of hydration process, which depends on various factors including water/cement ratio, concrete proportioning and surrounding environmental conditions. This interest in understanding and defining the different types of shrinkage and the factors impacting each one is driven by the importance of these volumetric variations in determining the concrete permeability, which ultimately controls its durability. Many studies have shown that the total prevention of concrete from undergoing shrinkage is impractical. However, different practices have been used to control various types of shrinkage in concrete and limit its magnitude. This paper provides a detailed review of the major and latest findings regarding concrete shrinkage types, influencing parameters, and their impacts on concrete properties. Also, it discusses the efficiency of the available chemical and mineral admixtures in controlling the shrinkage of concrete.