Experimental Study on Mechanical Properties of High-Ductility Concrete against Combined Sulfate Attack and Dry–Wet Cycles

Abstract

Concrete will deteriorate and damage under sulfate attack.In order to study the degradation characteristics of HDC under sulfate attack, the mechanical properties of high-ductility concrete (HDC) were investigated using the uniaxial compressive strength test of HDC specimens soaked in different concentrations of sulfate solution and subjected to different times of dry–wet cycles. The variations in the compressive strength, loss rate of compressive strength, and the max compressive strength under the action of sulfate attack and dry–wet cycles were analyzed. The analytical expressions of damage variables were given. SEM was used to observe the microstructure of the sample, and the microdamage mechanism of the HDC was explored. The deterioration of the HDC was found to be the result of the combined action of sulfate attack and dry–wet cycles and was caused by physical attack and chemical attack. PVA prevented the rapid development of deterioration. On the basis of the change of compressive strength, the damage variable was established to quantitatively describe the degree of damage to HDC. The experimental results showed that with the increase in the number of dry–wet cycles, the compressive strength of HDC generally increased first and then decreased. As the concentration of the sulfate solution increased, the loss rate of the compressive strength of HDC generally increased and the max compressive strength gradually decreased. With the increase inthe number of dry–wet cycles, HDC first showed self-compacting characteristics and then gradually became destroyed. Compared with ordinary concrete (OC), HDC is superior to OC in sulfate resistance and dry–wet cycles. This study provided a test basis for the engineering application of HDC in sulfate attack and dry–wet cycles environment.

Correlation Analyses on Physical and Mechanical Parameters of Concrete in Marine Environments

“…The scholarly literature is rich in studies on the physical and mechanical properties of concrete materials in marine environments, with some studies regarding the damage evolution of concrete [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. According to Dehwah [ 14 ], no apparent damage was observed in concrete samples soaked in a compound solution of sodium sulfate (Na 2 SO 4 ) and sodium chloride (NaCl); by contrast, serious deterioration was found in samples treated with a compound solution of magnesium sulfate (MgSO 4 ) and sodium chloride (NaCl).…”

Study of the Structure and Properties of Electrical Sand Concrete under Prolonged Exposure to Sulfate Environment

“…This type of mineral matrix corrosion is characterized by certain destruction mechanisms, including chemical reactions between active sulfate ions and hydrates of cement stone, primarily tricalcium aluminate [ 26 , 28 ], accompanied by a physical impact caused by an increase in internal pressure due to recrystallization of new formations [ 22 , 27 ]. Some works consider both the general mechanisms of sulfate corrosion [ 29 , 30 ] and specific variants of its development, such as sulfate corrosion at low temperatures [ 31 , 32 ] or processes of delayed formation of ettringite [ 33 , 34 ]. The destructive effect of sulfate corrosion is the cause of numerous costly repairs and a significant number of structural failures [ 28 , 35 ].…”

“…In studies [ 30 , 32 ], the mechanism of sulfate corrosion of a mineral matrix is considered as a heterogeneous process. Previously [ 26 , 27 ], it was considered as a process with a constant diffusion coefficient in time, which does not correspond to reality due to the presence of deceleration processes, which require a detailed study of diffusion processes (diffusion control of the reaction).…”

“…To date, the most significant patterns of control of this process are established, such as temperature and concentration of sulfate ions. Thus, [ 32 , 39 ] the intensification of the process of sulfate corrosion can be achieved by regulating the heat–humidity regime. In studies [ 29 , 32 ], it was found that at an ambient temperature of up to 10 °C, the process of corrosion of set cement in a hydrosulfate environment proceeds more intensively than under normal conditions (air temperature 18–22 °C and relative air humidity 100%).…”

“…At the same time, an important aspect is the retention of the concentration of the aggressive environment during the first 28 days of testing by 1–2 orders of magnitude lower than the actual concentrations of the influencing media due to the high probability of distortion of the chemical mechanism of corrosion [ 28 , 29 ]. In this regard, the concentration range of the sodium sulfate solution is accepted in the range from 3 to 5% [ 30 , 31 , 32 , 33 , 34 ]. To improve the accuracy of the correspondence of physical and chemical processes to real conditions, it is recommended in [ 33 , 36 , 41 ] to use a 1% solution of sodium sulfate.…”