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.

Alkali-activated materials (AAMs) are regarded as an alternative cementitious material for Portland cement with regards to sustainable development in construction. The purpose of this work is to investigate the properties of activated blast-furnace slag (BFS)–steel slag (SS) with sodium carbonate (NC), taking into account BFS fineness and Na₂O equivalent. The hydration was investigated by rheological behavior and pH development. The hydrates were characterized by TG-DTG and XRD, and the microstructure was analyzed by SEM and MIP. Results showed that the rheology of activated BFS-SS pastes was well-fitted with the H-B model and affected by BFS fineness and NC mixture ratio. It was found that BFS fineness and NC ratio played a crucial role in the initial alkalinity of SS-BFS-based pastes. As such, lower BFS fineness and higher NC ratio can dramatically accelerate the formation of reaction products to endow higher mechanical strength of BFS-SS pastes. However, the effect of NC ratio on the microstructure development of BFS-SS based AAMs was more obvious than BFS fineness.

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.

Yield stress parameter derivation was conducted by stress-strain curve analysis on four types of grout injection leakage repair materials (GILRM); acrylic, epoxy, urethane and SPRG grouts. Comparative stress-strain curve analysis results showed that while the yield stress point was clearly distinguishable, the strain ratio of SPRG reached up to 664% (13 mm) before material cohesive failure. A secondary experimental result comprised of three different common component ratios of SPRG was conducted to derive and propose an averaged yield stress curve graph, and the results of the yield stress point (180% strain ratio) were set as the basis for repeated stress-strain curve analysis of SPRGs of up to 15 mm displacement conditions. Results showed that SPRG yield stress point remained constant despite repeated cohesive failure, and the modulus of toughness was calculated to be on average 53.1, 180.7, and 271.4 N/mm², respectively, for the SPRG types. The experimental results of this study demonstrated that it is possible to determine the property limits of conventional GILRM (acrylic, epoxy and urethane grout injection materials) based on yield stress. The study concludes with a proposal on potential application of GILRM toughness by finite element analysis method whereby strain of the material can be derived by hydrostatic pressure. Comparative analysis showed that the toughness of SPRG materials tested in this study are all able to withstand hydrostatic pressure range common to underground structures (0.2 N/mm²). It is expected that the evaluation method and model proposed in this study will be beneficial in assessing other GILRM materials based on their toughness values.

This study sought to investigate the adhesion strength reduction of reclaimed butyl rubber self-adhesive waterproofing sheets after exposure to a chemical erosion environment. Ranges from 0 to 45% mixture ratio (with changing intervals of 5% ratio) of reclaimed butyl rubber replaced the new rubber content of commercial butyl rubber self-adhesive waterproofing sheets for testing, based on the optimal results for the reclaimed butyl rubber content in order to ensure performance that meets the standard criteria. The research results confirmed that performance degradation was relatively greater when exposed to an acidic environment that was responsible for chemical deterioration. It was also confirmed that, given the deterioration environment described above, the reclaimed butyl rubber content should be limited to 44% so as to ensure an adhesion performance similar to that of the untreated test sample (reclaimed butyl rubber content of 67%). Based on the above results, it was suggested that the optimal mixing range of reclaimed butyl rubber should be up to 44% of the total rubber content, considering performance degradation after field application in the production of self-adhesive waterproofing sheets.

Waterproofing in pavements can determine the waterproofing performance of the entire bridge structure. In this study, two types of pavement layers, asphalt concrete (APC) and latex-modified concrete (LMC), are investigated as options to improve the waterproofing performance of bridge structures with either APC or LMC-type pavement by installing a double-sided adhesive waterproofing sheet. The material performance of the proposed waterproofing sheet was evaluated for deterioration factors such as temperature change, chemical erosion, cracking behavior, and water pressure as stipulated in the Korean industrial standards (hereinafter referred to as KS) for bridge waterproofing materials. The waterproof sheet was directly installed on to specimens with the respective two pavement types to evaluate the field application performance. As a result of the evaluation, the physical waterproofing performance of the proposed waterproofing sheet satisfies all standard quality conditions, and as a result of direct application to APC and LMC pavement, the waterproof performance is at least 8% to 130% higher than the standard quality standard in APC pavement, and LMC pavement shows high performance, up to about 320%. Therefore, it is expected that the newly proposed waterproofing sheet as a bridge deck surface waterproofing material can be considered as a feasible option to improve the waterproofing performance for both APC and LMC pavement.