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The ACI Universidad Catolica San Pablo (UCSP) Student Chapter in Arequipa, Peru, organized a technical talk with CHEMA, a Peruvian company with over 50 years of experience in the construction industry, specializing in additives, adhesives, and waterproofing solutions that enhance quality and durability. The company shared valuable insights on innovative construction materials and techniques with ACI members and students, strengthening the link between academia and industry.

This paper analyses the status quo of exterior wall waterproofing technology of prefabricated building, introduces the application of waterproofing coil laying, sealant waterproofing, grouting method, exterior wall waterproofing coating, waterproof concrete and the integration technology of heat preservation and drainage, and analyses their advantages and disadvantages. In the future, the research and application of new materials should be strengthened, and the effects of different waterproof technologies should be quantitatively compared through experiments to further improve the waterproof performance of prefabricated building external walls.

Bacterial cellulose was combined with wood cellulose papers in order to obtain biomaterials with increased barrier properties. For this purpose, different parameters were assessed: two producing bacterial strains (Komagataeibacter xylinus and Gluconacetobacter sucrofermentans), two paper supports to hold bacterial cellulose (filter paper and eucalyptus paper), two kinds of combined biomaterials (composite and bilayer) and two drying temperatures (90ºC and room temperature). Papers with increased barrier properties (100º of water contact angle, 1220s of water drop test and air permeability ˂1µm (Pa·s)-1) were obtained by the addition of bacterial cellulose to each paper support. However, due to the lower initial barrier properties of filter paper, higher improvements were produced with this paper. In addition, bacterial cellulose provided smoother surfaces with higher gloss without a detrimental effect on physical properties. Higher resistance to water absorption was obtained with K. xylinus possibly explained by its longer size fibers than G. sucrofermentans, as analysed by SEM. Smoothness and gloss were specially increased in the bilayer biomaterial although resistance to air and water were further improved in the composite. In this biomaterial drying at high temperature had a detrimental effect. SEM analysis of the products obtained showed the intimate contact among fibers of bacterial cellulose and wood paper. Results obtained show the contribution of bacterial cellulose to improve the properties of paper and its potential for the design of new added value paper products from biomass.

An evaluation method for assessing the difference in the relative humidity (RH) control performance of waterproofing material is proposed. For a demonstration of this evaluation method, two waterproofing materials (urethane coating and cementitious waterproofing material) installed with different methods (positive and negative side of concrete structure respectively) are exposed to temperature conditions representing three seasonal conditions: Summer (40 °C), spring/autumn (20 °C) and winter (4 °C). Condensation level changes on the inner side of the waterproofing material installed specimen is measured, and for derive criteria for comparison, three parameters based on the average RH, intercept RH (derived from a linear regression analysis of RH measurement), and maximum relative humidity are derived for each different waterproofing material installed specimen. Based on quality specification for underground concrete structures, the demonstration evaluation establishes provisional standard criteria of below 70% RH, and all three parameters are evaluated to determine whether the tested waterproofing material/method complies to the performance requirement. Additional analysis through linear regression and cumulative probability density graphs are derived to evaluate the RH consistency and range parameters. The evaluation regime demonstrates a quantitative RH analysis method and apparatus, and a newly designed evaluation criteria is used to compare the RH control performance of positive-side installed urethane waterproofing materials and negative-side installed cementitious waterproofing material.

In order to explore the waterproofing mechanism of F-type socket joint in rectangular pipe jacking tunnel, full-scale tests and finite element numerical calculations were conducted to analyze the sealing performance and failure modes of rubber rings with different heights under different water pressures, revealing the distribution law of contact stress and leakage mechanism of rubber rings. The results show that low-height rubber rings experience leakage at a water pressure of 0.2–0.3 MPa, while the waterproofing ability of medium and high height rubber rings is significantly improved, withstanding 0.7 MPa and 1.0 MPa water pressure, respectively. The 28 mm rubber ring still has no leakage at a 1.6 MPa water pressure. At 0.4 MPa water pressure, the height of the rubber ring increases from 22 mm to 24 mm, the proportion of effective contact stress increases from 35.7% to 78.6%. The waterproofing performance of tunnel joints is jointly determined by the rubber ring height and the proportion of effective contact stress. No leakage occurs at the pipe gallery joint when the proportion of effective stress exceeds 70%. This research provides a theoretical basis for the size selection of waterproofing rubber rings for the rectangular pipe jacking tunnel.

In addition to mechanical compliance, achieving the full potential of on-skin electronics needs the introduction of other features. For example, substantial progress has been achieved in creating biodegradable, self-healing, or breathable, on-skin electronics. However, the research of making on-skin electronics with passive-cooling capabilities, which can reduce energy consumption and improve user comfort, is still rare. Herein, we report the development of multifunctional on-skin electronics, which can passively cool human bodies without needing any energy consumption. This property is inherited from multiscale porous polystyrene-blockpoly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 μm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body midinfrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W·m−2. Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human–machine interface are demonstrated. Notably, the enabled on-skin devices are dissolvable in several organic solvents and can be recycled to reduce electronic waste and manufacturing cost. Such on-skin electronics can serve as the basis for future multifunctional smart textiles with passive-cooling functionalities.

With the rapid development of highway transportation, the volume and construction difficulty of tunnel engineering have been increasing year by yea. Many engineering problems are difficult to solve, among which leakage is one of them. Tunnel waterproofing materials are an important component of controlling leakage and ensuring the safety and reliability of tunnel engineering. This paper provides the types, characteristics, and applications of tunnel waterproofing materials in tunnel engineering. The classification of tunnel waterproofing materials is introduced, including grouting materials, geotextile materials, and waterproofing board materials. Then, the characteristics of each type of material are elaborated in detail, including durability, constructability, and environmental friendliness. Finally, combined with actual engineering cases, the application of these tunnel waterproofing materials in tunnel engineering is discussed. This paper aims to provide a reference for the design and construction of tunnel engineering, and to provide a theoretical and practical basis for the research and application of tunnel waterproofing materials.

Dislocation of segments in shield tunnels significantly contributes to joint leakage, making it crucial to identify the critical dislocation amount of segment linings. To explore the waterproofing mechanism of sealing gaskets under water pressure, a structural coupling finite element analysis model was created. This model simulates water intrusion dynamics at segment joints, analyzing contact stress distribution and waterproof performance across various dislocation amounts. The comparison of finite element calculations with experimental data shows a positive correlation, although simulation results are slightly lower than experimental findings. The analysis demonstrates that lower effective contact stress due to dislocation increases leakage risk. In small deformation ranges, opposite segment constraints can enhance gasket contact, reducing leakage risks. However, exceeding critical dislocation leads to leakage. Findings indicate that as dislocation increases, the effective contact stress between the gasket and groove first decreases, then increases. A dislocation of 9 mm and an opening of 8 mm yield the lowest effective contact stress proportion and worst waterproof performance, marking a critical point for sealing water pressure changes. This study provides a scientific basis for determining critical dislocation amounts, optimizing joint sealing performance, and reducing leakage in shield tunnels.

The paper analyses the influence of high temperatures (70 °C for three months) on the durability of the mechanical properties of waterproofing membranes used on ventilated terraces. The test kits consisted of a concrete substrate, waterproofing membrane (reinforced bitumen sheet or EPDM membrane), and the top layer spot-supported by plastic pedestals. The stress transferred by the pedestals to the substrate was determined through calculations. The changes after ageing were evaluated in the areas between the pedestals and in their locations for their ability to maintain the mechanical load-transferring function, including but not limited to resistance to continuous or instant spot loads. The action mechanism of the ageing processes was investigated by analysing the microstructure of the cross-sections of the tested samples using SEM. After three months of exposure to + 70 °C, the resistance to spot loads of a reinforced bitumen sheet was higher than that of a flexible EPDM sheet. Simultaneously, the tensile values are more favourable for the first sheet type. The impact resistance of the reinforced bitumen sheet increased by 36%, whereas that of the EPDM membrane decreased by 25%. The static puncture resistance of the reinforced bitumen sheet before and after ageing remained at the same level; for the EPDM membrane, the value dropped by 20%. In both cases, microscopic images of the cross-sections of the tested items revealed structural changes in the form of microcracks.

Polymer modified bituminous thick coatings are increasingly used in the construction industry to protect underground parts of buildings from groundwater. When assessing their durability, one vital issue related to their functional properties is the influence of water absorption on the waterproofness of the applied solution as a result of the action of groundwater with different pH values. As part of the research, the water absorption of the products in question was assessed using the method of total immersion in water with pH of 4.0, 7.0 and 7.5 as well as comparatively, as a result of one-way exposure to demineralized water under successively increasing pressure up to 0.5 MPa. The moisture susceptibility of the coatings was assessed both concerning the local surface damage and the continuous waterproofing coating. It was established that the coatings show the highest water absorption when the water pH is 4.0, which simulates the groundwater aggressiveness on construction products. It was proven that moisture absorbed by the coatings is retained within this layer and is not transferred to the substrate on which the coatings are laid. It was also found that water in contact with the tested coatings changes its reaction to alkaline, which can result in contamination of groundwater in the area of waterproofing coating. A modification of the method of assessing the water absorption of polymer modified bituminous thick coatings was proposed, taking into account their use in conditions of use.