Examining the Distribution of Strength across the Thickness of Reinforced Concrete Elements Subject to Sulphate Corrosion Using the Ultrasonic Method

Abstract

Sulphate corrosion of concrete is a complex chemical and physical process that leads to the destruction of construction elements. Degradation of concrete results from the transportation of sulphate compounds through the pores of exposed elements and their chemical reactions with cementitious material. Sulphate corrosion can develop in all kind of structures exposed to the corrosive environment. The mechanism of the chemical reactions of sulphate ions with concrete compounds is well known and described. Furthermore, the dependence of the compressive strength of standard cubic samples on the duration of their exposure in the sulphate corrosion environment has been described. However, strength tests on standard samples presented in the scientific literature do not provide an answer to the question regarding the measurement methodology and actual distribution of compressive strength in cross-section of reinforced concrete structures exposed to sulphate ions. Since it is difficult to find any description of this type of test in the literature, the authors undertook to conduct them. The ultrasonic method using exponential heads with spot surface of contact with the material was chosen for the measurements of concrete strength in close cross-sections parallel to the corroded surface. The test was performed on samples taken from compartments of a reinforced concrete tank after five years of operation in a corrosive environment. Test measurements showed heterogeneity of strength across the entire thickness of the tested elements. It was determined that the strength of the elements in internal cross-sections of the structure was up to 80% higher than the initial strength. A drop in the mechanical properties of concrete was observed only in the close zone near the exposed surface.

Tests of Concrete Strength across the Thickness of Industrial Floor Using the Ultrasonic Method with Exponential Spot Heads

“…The compressive strength of concrete samples in their various cross-sections was determined with the use of the non-destructive method calibrated with the destructive tests of the samples. This type of examination is being widely used for the range of building materials, such as concrete, wood, steel, ceramics, and for the diagnostics of building structures [20][21][22][23][24][25]. Tests were carried out with the use of the ultrasound method based on longitudinal wave velocities [26].…”

Ultrasonic Pulse Velocity—Compressive Strength Relationship for Portland Cement Mortars Cured at Different Conditions

“…In addition, NDT-UPV has been successfully used investigating the corrosion of mortar and concrete reinforcement [16,17], and in the study of durability of these construction materials [18][19][20][21][22][23][24]. For instance, non-destructive ultrasonic test methods have been used to monitor microcracking in concrete [24,25]. Ouarabi et al used ultrasonic measurements in self-healing systems to study the kinetics of the recovery thanks to the healing agent performance [21].…”

Functional and adhesive properties of cement-based overlays modified with amorphous silica nanospheres

“…[15] Moreover, the problem of the lower subsurface compressive strength of overlays, which is related to the horizontal direction of their concreting, is also noticeable. [16] The studies of Stawiski and Kania [17] show that the value of strength in the top zone of a floor can sometimes significantly differ from the values of strength in the middle and bottom zones. The way of applying the concrete mix is also important.…”