International Concrete Abstracts Portal

The durability of reinforced concrete is often compromised by chloride penetration, leading to corrosion of reinforcing steel and reduced structural strength. To improve the sustainability and longevity of concrete structures, it is crucial to model and predict chloride permeability (CP) accurately, thereby minimizing the time and resources required for extensive experimental testing. This paper presents a proof-of-concept study applying Artificial Neural Networks (ANN) to predict CP in concrete structures. The model was trained on a small but carefully controlled experimental dataset of 10 concrete mixtures, considering four key parameters: water-to-cementing materials ratio, silica fume content, cementing materials content, and air content. Despite the limited dataset size, which constrains generalizability and statistical robustness, the ANN captured nonlinear relationships among the input parameters and CP. The comparison between experimental and simulated CP values showed reasonable agreement, with errors ranging between –242 and 420 Coulombs. These results establish the trustworthiness and reliability of the proposed model, providing a valuable tool for predicting CP and informing the design of durable and sustainable concrete structures.

Titanium alloy bars (TiABs) have recently been accepted as a structural material for near-surface-mounted retrofit (NSMR) of reinforced concrete structural elements. This paper shows that TiABs in NSMR applications can be used simultaneously as anodes in impressed current cathodic protection (ICCP) to prevent corrosion of the existing reinforcement. Following a successful proofof-concept study performed for small-scale prisms, dual-purpose TiABs were used as longitudinal and shear reinforcements to retrofit large-size structural beams. Prior to structural tests, the specimens were investigated to characterize the TiAB functionality within the ICCP system. During ICCP, cathodic potentials were in the expected linear region of the cathodic polarization curve of the steel reinforcing bars, and the 100 mV potential shift (decay) criterion following shutoff was satisfied upon the interruption of the protection current. The applied current and potential to achieve the required cathodic potentials were stable and were satisfactorily maintained while achieving the structural retrofit requirements.

Despite all the recent advances in the development of threedimensional (3-D) concrete printing (3DCP), this technology still has many unresolved problems. In most of the completed projects with the application of 3DCP, the focus was mainly on mastering the printing of vertical walls, while horizontal structural elements were produced with conventional methods—that is, using formwork, which reduces the level of technology automation, or using prefabricated elements, which makes the construction dependent on their availability and supply. In this contribution, the authors propose new methods of manufacturing slabs and beams directly on site by extruding concrete onto a textile reinforcement mesh laid on a flat surface. Specimens obtained from a slab produced following this method were used for mechanical testing and investigation of the concrete-reinforcement interface zone. Finally, as proof of the feasibility of the proposed approach, a demonstrator representing a full-scale door lintel was manufactured.

An experimental investigation was carried out on concrete into the effectiveness of integral permeability-reducing admixtures as possible alternatives to the traditional external waterproofers. The efficiency of hydrophobic water repellents and crystalline pore blockers were evaluated in concretes incorporating fixed water-cementitious materials ratio (w/cm) and different cementitious material types covering OPC, fly ash, and granulated blast-furnace slag. Three different test methods were employed to evaluate the water penetration resistance of concrete. To isolate the benefits that are achieved by varying the mixture design parameters, statistical factorial analysis of variances was carried out to discover the significance of each variable. Results indicated that the effect of w/cm and cementitious material is more pronounced compared to the addition of permeability-reducing admixtures. It was also demonstrated that the admixtures can be effective in reducing water penetration; however, their effect is varied in different mixtures. Caution must be exercised when using such admixtures in different concrete mixtures.

Loading protocols and acceptance criteria are available in the literature for load tests on buildings. For bridges, proof load tests are interesting when crucial information about the structure is missing, or when the uncertainties about the structural response are large. The acceptance criteria can then be applied to evaluate if further loading is acceptable, or could lead to permanent damage to the structure. To develop loading protocols and acceptance criteria for proof loading of reinforced concrete bridges, beam experiments were analyzed. In these experiments, different loading speeds, constant load level times, numbers of loading cycles, and required number of load levels were evaluated. The result of these experiments is the development of a standard loading protocol for the proof loading of reinforced concrete bridges. Based on these limited test results, recommendations for acceptance criteria are also proposed.