Leakage in below-grade concrete structures are repaired using various types of grout-injection materials, but the selection of optimal material types with a consideration of the environmental degradation factors are not conducted. Different degradation factors can act on the waterproofing membranes or grout-injection materials simultaneously. Especially in the early stages of installation, the injected grout materials in the cracks for leakage repair or for reforming damaged waterproofing layers are subject to complex forms of degradation factors. In such cases, physical property changes to the materials can reduce the waterproofing performance of the grout-injection materials. In this study, a technical evaluation regime is proposed for selecting the optimal repair material to be used in underground concrete structure leakage cracks. In this study, six environmental degradation factors (thermal stress, chemical corrosion, erosion due to ground water flow, hydrostatic pressure, substrate movement, and humidity on concrete surface) are identified. Corresponding evaluation methods based on the ISO TS 16774 test method series were used for each factor to assess the performance evaluation of four different types of grout-injection materials (acrylic resin, epoxy resin, polyurethane foam, and synthetic polymerized rubber gel). Based on the test results, a new comprehensive evaluation regime is presented that allows a quantitative performance comparison between each type of grout-injection material.

Dynamic factor evaluation method calculation methods outlined by Eisenmann (DAF_Eisenmann) and the American Railway Engineering Association (DAF_Area) are used to calculate the dynamic factor during design and for trackside measurement, respectively, in nations where the construction of concrete track structures is relatively new. In this situation, dynamic factor calculation methods may be incorrect, and this is demonstrated by comparison of the respective track types’ total spring constant. A finite element analysis of a standard design railway track is conducted, and the design total spring constant (TSC, or K) obtained from the time history function analysis is compared to the TSC of existing tracks through trackside measurement results. The comparison result shows that TSC obtained by finite element analysis result is 22% higher than that of the trackside measurement value, indicating that the TSC is conservative in the current track design. Considering the proportional relationship between TSC and dynamic factor, it is estimated that the dynamic factor currently being applied in track design is also conservative. Based on these findings, an assessment of the applicability of different dynamic factors (DAF_Eisenmann and DAF_Area), theoretical calculation and field measurement (DAF_Field) using the probabilistic analysis of wheel loads from the field measurement data is conducted. A correlative analysis between DAF_Eisenmann and DAF_Area shows that DAF_Eisenmann and DAF_Area were estimated to be higher by 33% and 27% in ballasted track and by 39% and 30% in concrete track than the dynamic factor derived from field measurement, respectively, which indicates that the dynamic factor currently in use can potentially lead to over-estimation in track design and maintenance.

As opposed to asphalt emulsion waterproofing membrane, Synthetic Rubber Polymer Gel (SPRG) waterproofing materials are not heated prior to installation in concrete structures. SPRG materials are typically required to undergo a screw-mixing process to temporarily reduce the high viscosity and facilitate membrane installation on a concrete surface. However, there is no standard regulation on the duration of screw-mixing time during SPRG construction. Reported construction cases indicate that SPRG are left under constant screw mixing and are reused after hours or days of rest without being replaced with fresh products. When installed in this condition, SPRGs are subject to waterproofing performance degradation. In this study, SPRG viscosity properties are measured after five different screw-mixing procedures (no screw mixing, 10, 20, 30 and 60 min) and are set to rest in storage (2 h, 1, 2, 3, and 7 days). Specimens prepared under the respective screw mixing and storage times are evaluated for their changes in waterproofing properties through a series of ISO TS 16774 standard evaluation methods. A correlative comparison of the property evaluation results is presented to provide the changes to SPRG property and waterproofing performance. These results are then used to propose a general guideline for selecting optimal screw-mixing time with respect to maintaining adequate waterproofing performance and the viscosity recovery property of SPRG.

Track impact factor (TIF) is a coefficient for estimating the increase of train dynamic load and is a major factor for the evaluation of dynamic stability of railway tracks. Many kinds of TIF in ballasted and ballast-less slab tracks consider only speed as a variable in different regions of the world. Because of this lack of clarification, nations such as Korea and those in the Middle East, and South East Asia are implementing overly simplified calculation methods for TIF, resulting in inconsistent maintenance of different railway track types. A comparative analysis of theoretically track support stiffness (TSS) and trackside measurement calculated TSS at wheel-rail contact point shows different values (depending on speed) between ballasted and ballast-less slab tracks. Based on this finding, this paper investigates a TIF formulation method that considers both dynamic wheel load and speed as variables, and a separate application of TIF formulation depending on track types is proposed. A clarified distinction of how these parameters (TSS and TIF) interact differently between ballasted and ballast-less slab track structures can be an important factor in case of track designing and maintenance aspects.

Synthetic Polymer Rubber Gels (SPRG) are used in Composite Modified Bituminous Waterproofing (CMBW) systems for waterproofing in concrete structures. A problem with the current design of SPRG is that when the emulsion breaks, the segregated oil layer can percolate through concrete cracks and cause oil leakage. This study proposes a new evaluation method which assesses the practical performance of SPRG products by testing their susceptibility to filler content settlement and oil leakage. Eight SPRG products used in Korea were used to demonstrate this evaluation method. Each product was installed in a concrete substrate specimen with an artificial crack made in the specimen’s bottom substrate. The specimens were observed for 28 days, and mass of leaked oil, total duration of leakage, average rate of sedimentation, and rheological threshold of initial leakage point were examined as part of the evaluation criteria.

As construction in urban centers increases internationally, many concrete infrastructures are being built at 100 m or more underground, and the influence of groundwater on these facilities is also increasing. Accordingly, the importance of waterproofing and leak-proofing technology for securing long-term durability and safety of underground concrete facilities has been greatly emphasized. The most important required performance of such leak repair technology is to withstand structural behavior and groundwater pressure well. Currently, as a leak repair material for underground concrete facilities, a synthetic rubber-based polymer rubber gel with adhesive flexibility is used internationally. However, quantitative data on how deep the material can perform underground are lacking. In general, the water pressure resistance evaluation of leak repair materials only checks whether it withstands the water pressure of 30 m (0.3 MPa) underground. Therefore, in this study, the toughness of the synthetic rubber polymerized gel (SPRG) leak repair material was calculated using three factors: viscosity, cohesive strength (adhesion strength), and elongation, and an analysis method that can be replaced with water pressure resistance was proposed. In addition, in the correlation between toughness and underground water pressure, it was possible to find out the thickness of the leak repair material used by the underground depth. As a result, it was possible to know the required thickness of the leak repair material according to the depth of the structure to be built underground.