Influence of Variotropy on the Change in Concrete Strength under the Impact of Wet–Dry Cycles

Abstract

One of the most dangerous types of cyclic effects, especially inherent in several regions in the world, is the alternating impact of wetting and drying on concrete and reinforced concrete structures. In the current scientific literature and practice, there is not enough fundamental and applied information about the resistance to wetting and drying of variotropic concretes obtained by centrifugal compaction methods. The purpose of the study was to investigate the effect of various technological, compositional, and other factors on the final resistance of variotropic concrete to alternating cycles of moistening and drying. For this, special methods for testing concrete samples were used in the work. It has been established that after strength gain as a result of hydration, there is a tendency for strength loss due to concrete wear. An acidic medium has the most negative effect on the strength characteristics of concretes made using various technologies, compared with neutral and alkaline media. The loss of strength of concrete when moistened in an acidic medium was greater than in alkaline and especially neutral media. The vibrocentrifuged concrete turned out to be the most resistant to the impact of an aggressive environment and the cycles of moistening and drying, compared to the centrifuged and vibrated concrete. The drop in strength was up to 7% less compared to centrifuged concrete and up to 17% less than vibrated concrete.

Prediction of the Compressive Strength of Vibrocentrifuged Concrete Using Machine Learning Methods

“…After molding, the samples were kept for 24 h, and then were taken from the molds and kept for 28 days in appropriate conditions. Then, they were subjected to various types of aggressive influences, such as freeze-thaw cycles; chloride attack, sulfate attack, and wet-dry cycles [5,[8][9][10]42]. The compressive strength of vibrocentrifuged concrete was 58.2 MPa.…”

“…The review made it possible to select the most suitable methods for accurately predicting the strength of concrete with a non-uniform cross-section of elements in terms of thickness. In this regard, there is a scientific deficit, which comprises providing methods for predicting the characteristics of concrete characterized by different cross-sectional properties (the so-called variatropy) [5,[8][9][10]42,43]. Hence, the uniqueness of this work can be discerned in three dimensions: theoretical, applied, and recommendatory.…”

Prediction of the Properties of Vibro-Centrifuged Variatropic Concrete in Aggressive Environments Using Machine Learning Methods

“…After molding, the samples were kept in the molds for 24 h, then removed from the molds and hardened under natural conditions until they reached 28 days of age. The manufactured ring-section elements were sawed on a stone-cutting machine into samples of standard sizes and shapes and were exposed to cycles of freezing and thawing, wetting and drying, and chloride and sulfate attacks [44][45][46][47].…”

“…As a result of laboratory tests to determine the compressive strength of vibro-centrifuged variatropic concrete, a dataset was generated that describes the impact of aggressive environmental factors on the final characteristics [44][45][46][47].…”

The Wetting Behavior of Water Droplets on Silane and Silane/GO-Modified Ettringite Surfaces: Insights into Molecular Dynamics Simulations

“…Throughout its lifespan, the durability of concrete structures has always been a focus of researchers to determine the safe operation and service life of buildings [2,3]. However, in coastal environments, concrete is often subjected to problems such as wave erosion (the damage from waves) [4], carbonation (the damage from reactions to CO 2 ) [5], freeze-thaw cycles (the damage from water freezing and thawing) [4,6], wet-dry cycles (the damage from water loss) [7], and harmful ion erosion (the damage from ion intrusion) [8], which can cause concrete damage and cracking. In cases where important infrastructure concrete structures are damaged and need to be temporarily preserved to achieve rapid rescue [9], special cements, such as sulfoaluminate cement, high-alumina cement, and magnesium phosphate cement, usually play a crucial role [10,11].…”