Modeling Compressive Strength of Eco-Friendly Volcanic Ash Mortar using Artificial Neural Networking

Forecasting the compressive strength of concrete is a complex task owing to the interactions among concrete ingredients. In addition, an important characteristic of the concrete failure surface is its six-fold symmetry. In this study, an artificial neural network (ANN) and adaptive neuro fuzzy interface system (ANFIS) were employed to model the compressive strength of natural volcanic ash mortar (VAM) by using the six-fold symmetry of concrete failure. The modeling was correlated with four parameters. To train and test the projected models, data for more than 150 samples were collected from the literature. Furthermore, mortar samples with varying proportions of volcanic ash were prepared in the laboratory and tested, and the results were used to validate the models. The performance of the developed models was assessed using numerous statistical measures. The results show that both the ANN and ANFIS models accurately predict the compressive strength of VAM with R-square above 0.9 and lower error statistics. The permutation feature analysis confirmed that the age of specimens affects the strength of VAM the most, followed by the water-to-cement ratio, curing temperature, and percentage of volcanic ash.

Simulation of the Effects of Angle of Attack and Projectile Contour in Damage Development in Reinforced Concrete

The impact of projectiles in reinforced or unreinforced concrete is of prime importance in applied mechanics and engineering. Parameters such as penetration depth, velocity or energy of the projectile, and the geometry and the angle of attack of the projectile are the most critical factors, among several others, that determine whether the concrete body will tolerate damage due to the impact or not. For numerical simulations of damage, the Riedel-Hiermaier-Thoma (RHT) concrete failure is an established approach, which is also used in this research. In this work, numerical simulations have been performed on shooting a rigid large-scale projectile with different tip contours at a concrete target that is reinforced with steel. For each tip contour, the angle of attack varied. The penetration depth of the projectile tip and the damage of the target were reported for the different tip contours as a function of the angle of attack. The results show that the maximal damage occurred at ~45° of the angle of attack, while penetration of the projectile into the target increased with increasing the angle of attack.

Assessing Deteriorated Concrete Structures

In today’s society, concrete structures are deteriorating for a variety of reasons. In order to properly repair these structures, it is important to completely understand the root cause of each type of deterioration. Over the years, engineers have developed methods for identifying the causes of concrete failure. This paper recognizes the different forms of concrete deterioration, identifies the test methods which have been developed to locate these concrete defects (both non-destructive and destructive), reviews different case studies which have been performed on concrete parking structures implementing these test methods and draws conclusions from surveys which were conducted of professionals in the rehabilitation engineering field. Additionally, this research project develops a strategy which is meant to aid with the selection of concrete test methods to be used in diverse concrete deterioration situations.

Assessing Deteriorated Concrete Structures

In today’s society, concrete structures are deteriorating for a variety of reasons. In order to properly repair these structures, it is important to completely understand the root cause of each type of deterioration. Over the years, engineers have developed methods for identifying the causes of concrete failure. This paper recognizes the different forms of concrete deterioration, identifies the test methods which have been developed to locate these concrete defects (both non-destructive and destructive), reviews different case studies which have been performed on concrete parking structures implementing these test methods and draws conclusions from surveys which were conducted of professionals in the rehabilitation engineering field. Additionally, this research project develops a strategy which is meant to aid with the selection of concrete test methods to be used in diverse concrete deterioration situations.

Study on the Strength Performance of Recycled Aggregate Concrete with Different Ages under Direct Shearing

In order to study the mechanical properties of recycled aggregate concrete (RAC) at different ages, 264 standard cubes were designed to test its direct shear strength and cube compressive strength while considering the parameters of age and recycled aggregate replacement ratio. The failure pattern and load–displacement curve of specimens at direct shearing were obtained; the direct shear strength and residual shear strength were extracted from the load–displacement curves. Experimental results indicate that the influence of the replacement ratio for the front and side cracks of RAC is insignificant, with the former being straight and the latter relatively convoluted. At the age of three days, the damaged interface between aggregate and mortar is almost completely responsible for concrete failure; in addition to the damage of coarse aggregates, aggregate failure is also an important factor in concrete failure at other ages. The load–displacement curve of RAC at direct shearing can be divided into elasticity, elastoplasticity, plasticity, and stabilization stages. The brittleness of concrete decreases with its age, which is reflected in the gradual shortening of the elastoplastic stage. At 28 days of age, the peak direct shear force increases with the replacement ratio, while the trend is opposite at ages of 3 days, 7 days, and 14 days, respectively. The residual strength of RAC decreases inversely to the replacement ratio, with the rate of decline growing over time. A two-parameter RAC direct shear strength calculation formula was established based on the analysis of age and replacement rate to peak shear force of RAC. The relationship between cube compressive strength and direct shear strength of recycled concrete at various ages was investigated.

A Theoretical Framework for Service Life Prediction of Reinforced Concrete Structures in Chloride Environment using Load Factors

Service life modeling of reinforced concrete structures in a chloride environment is mainly performed without considering the loading effects. Different loading effects can produce different service life results. This study presents a theoretical framework for the modeling of the service life of reinforced concrete structures in a chloride environment using loading factors, showing that, depending on the loading nature (either compression or tension), different diffusion results could be obtained. This paper also highlights various approaches to service life modeling, such as the deterministic, probabilistic, and semi-probabilistic, which consider different ways to estimate the service life of reinforced concrete structures in chloride environments. The importance of various distributions for the input parameters in the chloride ingress modeling was examined. The proposed framework includes a procedure to estimate the probability of concrete failure in chloride environments.