Sulphate attack-induced damage and micro-mechanical properties of concrete characterized by nano-indentation coupled with X-ray computed tomography

The objective of this study is to develop the durability of mortar mixtures against combined chloride and sulfate deterioration by replacing a certain amount of limestone cement with titanium dioxide (TiO2). Marine environments contain high concentrations of chlorides and sulfates. To improve the concrete durability within such conditions, it is important to control the concentration of both ions. The application of TiO2 in concrete has been increasingly considered in recent years. However, the durability issues of mortar made with TiO2 have not been evaluated. To achieve this purpose, an experimental program was designed to assess five different corrosive solutions of chloride and sulfate to investigate different partial cement replacement by TiO2. The compressive strength, surface electrical resistance, mass change, dynamic modulus of elasticity, Rapid chloride migration test (RCMT), Rapid chloride permeability test (RCPT), and half‐cell energy were tested in the binary and ternary solutions. Results indicated that using these nanoparticles as a partial replacement of cement developed the pore structure of the mortar, leading to the improved durability of the mortar and less deterioration in control specimens. Also, the chloride penetration increased by adding sulfate content at early age immersion. With little to no TiO2 in the mortar specimens, chloride ions mitigated the corrosive influences of a sulfate attack.

Section: Introductionmentioning

confidence: 99%

Evaluating the effects titanium dioxide on resistance of cement mortar against combined chloride and sulfate attack

Joshaghani

2018

“…Concrete structures are often affected by various erosion factors in environment, resulting in rapid deterioration. Sulfate corrosion is a common form of chemical erosion . Since the nineteenth century, researchers have concerned about the problem of sulfate corrosion on concrete .…”

Section: Introductionmentioning

confidence: 99%

“…Sulfate corrosion is a common form of chemical erosion. 6 Since the nineteenth century, researchers have concerned about the problem of sulfate corrosion on concrete. 7,8 A case of concrete damage caused by sulfate corrosion was first reported by the American Highway Commission in 1965.…”

Section: Introductionmentioning

confidence: 99%

Effect of creep on the stress–strain relation of fly‐ash slag concrete in marine environments

Gong

Cao

Wang

2019

Lots of concrete structures are located in marine environment, the durability damage of these structures is often the result of the interaction of load, environment, and other factors. In this paper, tests for the stress–strain relation of concrete under the coupled effects of sustained loading, sulfate attack and dry‐wet cycle were conducted. Then, based on the damage stress–strain relation model of concrete under sulfate attack, a calculation method for the stress–strain relation of concrete under the action of sulfate attack and dry‐wet cycle was proposed. Meanwhile, by taking into account the effect of creep on the stress–strain relation of concrete, a time‐dependent stress–strain relation model of concrete was presented. Numerical simulations by the time‐dependent stress–strain relation model demonstrate that the calculated results agree well with the experimental data. Furthermore, the rationality and applicability of the time‐dependent stress–strain relation model were also discussed.

“…In recent years, many researches show that the damage mechanism of cement‐based materials exposed to sulfate was sulfate attack . There are two types of mechanism that need to be involved for the action to be described as sulfate attack .…”

Section: Introductionmentioning

confidence: 99%

Study on the deterioration process of cement‐based materials under sulfate attack and drying–wetting cycles

Chen

Huang

Qian

2017

Self Cite

In this paper, the deterioration process of mortars degraded by sulfate under the restricted and unconstrained condition was investigated, respectively. Sodium sulfate (5 wt%) and dry–wet circulation method was adopted to accelerate the deterioration process. The deformation, damage rate, and porosity were measured by linear variable differential transducers (LVDTs), ultrasonic velocity measuring technology, and X‐ray computed tomography (XCT), respectively. Mass loss and loss rates of flexural strength and compressive strength were also measured to evaluate the deterioration results. Scanning electron microscope (SEM), energy‐dispersive Spectrometer (EDS), and X‐ray diffraction (XRD) were used to analyze the degradation mechanisms. The experimental results indicate that the greater the water–cement (w/c) ratio of mortars, the more serious the deterioration. XCT images and analysis results of porosities show that, among the mortars after being degraded by sulfate solution for 360 drying–wetting cycles, the M30‐SR sample under restricted condition is deteriorated most seriously. SEM/EDS and XRD analysis results indicate that the microstructure of hydration products changed obviously. Sodium sulfate and gypsum are observed after being degraded by sodium sulfate.