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Use of step anchors BBV‐multibond in the subsoil of Düsseldorf Currently a new stormwater retention tank is constructed nearby the river Rhine in Düsseldorf with dimensions of 36 m × 20 m. The average depth of the required excavation pit is about 13 m. In the area of the working panel, the general subsoil profil consists of fluvial sand and gravel underlain by marine fine sands. The groundwater flows through the porous sandy and gravelly aquifer. The fluctuation rate of the groundwater directly corresponds with the water level of the close by river Rhine and is up to 8 m. A waterproof diaphragm wall with a thickness of 80 cm is necessary for a dry excavation and construction of the tank‐building. The patent multibond anchor system from the company BBV‐Systems GmbH is used to ensure the stability of the diaphragm wall. In comparison of the basic design, which includes up to four layers of conventional grouted anchors, only one layer of multibond anchors, placed above the in‐situ groundwater level, is needed to achieve similar stabilisation effects. Extensive performance tests were successfully carried out and documented during the execution process for the purpose of proving and verifying the load‐bearing capacity of the multibond anchors compared to conventional grouted anchors within the subsoil in Düsseldorf. [ABSTRACT FROM AUTHOR]

At present, sustainability is of major importance in the cement industry, and the use of additions such as silica fume as clinker replacement contributes towards that goal. Special foundations, and particularly micropiles, are one of the most suitable areas for the use of sustainable cements. The aim of this research is to analyse the effects in the very long-term (for 600 days) produced by sulphate attack in the microstructure of grouts for micropiles in which OPC (ordinary Portland cement) has been replaced by 5% and 10% silica fume. This line of study is building on a previous work, where these effects were studied in slag and fly ash grouts. Grouts made using a commercial sulphate-resisting Portland cement were also studied. The non-destructive impedance spectroscopy technique, mercury intrusion porosimetry, and Wenner resistivity testing were used. Mass variation and the compressive strength have also been analysed. Apparently, impedance spectroscopy is the most suitable technique for studying sulphate attack development. According to the results obtained, grouts for micropiles with a content of silica fume up to 10% and exposed to an aggressive sulphate medium, have a similar or even better behaviour in the very long-term, compared to grouts prepared using sulphate-resisting Portland cement. [ABSTRACT FROM AUTHOR]

Nowadays, one of the most popular ways to get a more sustainable cement industry is using additions as cement replacement. However, there are many civil engineering applications in which the use of sustainable cements is not extended yet, such as special foundations, and particularly micropiles, even though the standards do not restrict the cement type to use. These elements are frequently exposed to the sulphates present in soils. The purpose of this research is to study the effects in the very long-term (until 600 days) of sulphate attack in the microstructure of micropiles grouts, prepared with ordinary Portland cement, fly ash and slag commercial cements, continuing a previous work, in which these effects were studied in the short-term. The microstructure changes have been analysed with the non-destructive impedance spectroscopy technique, mercury intrusion porosimetry and the “Wenner” resistivity test. The mass variation and the compressive strength have also been studied. The impedance spectroscopy has been the most sensitive technique for following the sulphate attack process. Considering the results obtained, micropiles grouts with slag and fly ash, exposed to an aggressive medium with high content of sulphates, have shown good behaviour in the very long-term (600 days) compared to grouts made with OPC. [ABSTRACT FROM AUTHOR]

Nowadays, the use of micropiles has undergone a great development. In general, they are made with cement grout, reinforced with steel tubing. In Spain, these grouts are prepared using OPC, although the standards do not forbid the use of other cements, like sustainable ones. Micropiles are in contact with soils and groundwater, in which the presence of sulphates is common. Their deleterious effects firstly affect to the microstructure. Then, the aim of this research is to study the effects of sulphate attack in the microstructure of micropiles grouts, prepared with OPC, fly ash and slag commercial cements, compared to their behaviour when they are exposed to an optimum hardening condition. The microstructure evolution has been studied with the non-destructive impedance spectroscopy technique, which has never been used for detecting the effects of sulphate attack when slag and fly ash cements are used. Its results have been contrasted with mercury intrusion porosimetry and "Wenner" resistivity ones. The 28-day compressive strength of grouts has been also determined. The results of microstructure characterization techniques are in agreement, although impedance spectroscopy is the most sensitive for following the changes in the porous network of grouts. The results showed that micropiles made using fly ash and slag cements could have a good performance in contact with aggressive sodium sulphate media, even better than OPC ones. [ABSTRACT FROM AUTHOR]

This paper presents a study on the possibility of using fly ash cement as grouts for micropiles. This type of special geotechnical work is commonly used for many applications. Generally, micropiles grouts are prepared using Portland cement, although the standards do not restrict the cement type to use, as long as they achieve a strength requirement. In this research, fly ash cement grouts made with w:c ratios 0.40, 0.45, 0.50 and 0.55 were studied from 2 up to 90 days of age. Their microstructure was characterized using the non-destructive impedance spectroscopy technique, electrical resistivity, and mercury intrusion porosimetry. Their durability properties have been studied by determining the water penetration under pressure, and the chloride diffusion coefficient. The compressive strength was also measured and determined, and a maximum water:cement ratio, different for each cement type was obtained. All the results were compared to those obtained for Portland cement grouts. The results obtained confirm that the performance of micropiles made using fly ash cement grouts is adequate, and as it is well know the cements with mineral admixtures provide environmental benefits, so the use of cement including fly ash will contribute to the sustainability, with similar properties to those given by OPC. [ABSTRACT FROM AUTHOR]

At present, sustainability is of major importance in the cement industry, and the use of additions such as silica fume as clinker replacement contributes towards that goal. Special foundations, and particularly micropiles, are one of the most suitable areas for the use of sustainable cements. The aim of this research is to analyse the effects in the very long-term (for 600 days) produced by sulphate attack in the microstructure of grouts for micropiles in which OPC (ordinary Portland cement) has been replaced by 5% and 10% silica fume. This line of study is building on a previous work, where these effects were studied in slag and fly ash grouts. Grouts made using a commercial sulphate-resisting Portland cement were also studied. The non-destructive impedance spectroscopy technique, mercury intrusion porosimetry, and Wenner resistivity testing were used. Mass variation and the compressive strength have also been analysed. Apparently, impedance spectroscopy is the most suitable technique for studying sulphate attack development. According to the results obtained, grouts for micropiles with a content of silica fume up to 10% and exposed to an aggressive sulphate medium, have a similar or even better behaviour in the very long-term, compared to grouts prepared using sulphate-resisting Portland cement.

Nowadays, one of the most popular ways to get a more sustainable cement industry is using additions as cement replacement. However, there are many civil engineering applications in which the use of sustainable cements is not extended yet, such as special foundations, and particularly micropiles, even though the standards do not restrict the cement type to use. These elements are frequently exposed to the sulphates present in soils. The purpose of this research is to study the effects in the very long-term (until 600 days) of sulphate attack in the microstructure of micropiles grouts, prepared with ordinary Portland cement, fly ash and slag commercial cements, continuing a previous work, in which these effects were studied in the short-term. The microstructure changes have been analysed with the non-destructive impedance spectroscopy technique, mercury intrusion porosimetry and the “Wenner” resistivity test. The mass variation and the compressive strength have also been studied. The impedance spectroscopy has been the most sensitive technique for following the sulphate attack process. Considering the results obtained, micropiles grouts with slag and fly ash, exposed to an aggressive medium with high content of sulphates, have shown good behaviour in the very long-term (600 days) compared to grouts made with OPC.

Nowadays, the use of micropiles has undergone a great development. In general, they are made with cement grout, reinforced with steel tubing. In Spain, these grouts are prepared using OPC, although the standards do not forbid the use of other cements, like sustainable ones. Micropiles are in contact with soils and groundwater, in which the presence of sulphates is common. Their deleterious effects firstly affect to the microstructure. Then, the aim of this research is to study the effects of sulphate attack in the microstructure of micropiles grouts, prepared with OPC, fly ash and slag commercial cements, compared to their behaviour when they are exposed to an optimum hardening condition. The microstructure evolution has been studied with the non-destructive impedance spectroscopy technique, which has never been used for detecting the effects of sulphate attack when slag and fly ash cements are used. Its results have been contrasted with mercury intrusion porosimetry and “Wenner” resistivity ones. The 28-day compressive strength of grouts has been also determined. The results of microstructure characterization techniques are in agreement, although impedance spectroscopy is the most sensitive for following the changes in the porous network of grouts. The results showed that micropiles made using fly ash and slag cements could have a good performance in contact with aggressive sodium sulphate media, even better than OPC ones.

• Fundamentals in modeling of buried TES in groundwater environment. • Development of 3-D models for buried hot-water tanks and pits with groundwater flow. • Cross-validation of TES model against FEFLOW. • Understanding the groundwater impact on large-scale TES planning and construction. • Protective measures restricting impact on groundwater and improving TES efficiency. In view of the urgent need for energy efficiency measures, renewables-based district heating (R-DH) can prove an efficient approach to meet the heating demand in cities whereby locally-available renewable resources are exploited. Yet, the renewables experience intermittency, which might lead to seasonal mismatch between heat supply and demand. Therefore, large-scale seasonal thermal energy storage (STES) systems are often envisioned as key elements in R-DH. Given their large volumes, these systems are often installed underground whereby groundwater tables are expected to lead to twofold impacts due to the TES-groundwater interaction. This work reports the development of models for the planning and optimization of STES and, then, conducts a calibration study to attain credibility in the models. Next, it examines the planning of STES under such unfavorable hydrogeological conditions whereby a groundwater flow is anticipated. The results indicate that Darcy flow plays a significant role in increasing the thermal losses that result in increasing groundwater temperature. Therefore, it becomes crucial to provide protective measures to maintain acceptable groundwater quality prescribed by national standards. Hence, the work investigates the role of cut-off wall distance and TES insulation quality to mitigate the TES thermal losses, increase the TES efficiency and reduce the groundwater temperature. [ABSTRACT FROM AUTHOR]

Nowadays, the use of micropiles has undergone a great development. In general, they are made with cement grout, reinforced with steel tubing. In Spain, these grouts are prepared using OPC, although the standards do not forbid the use of other cements, like sustainable ones. Micropiles are in contact with soils and groundwater, in which the presence of sulphates is common. Their deleterious effects firstly affect to the microstructure. Then, the aim of this research is to study the effects of sulphate attack in the microstructure of micropiles grouts, prepared with OPC, fly ash and slag commercial cements, compared to their behaviour when they are exposed to an optimum hardening condition. The microstructure evolution has been studied with the non-destructive impedance spectroscopy technique, which has never been used for detecting the effects of sulphate attack when slag and fly ash cements are used. Its results have been contrasted with mercury intrusion porosimetry and "Wenner" resistivity ones. The 28-day compressive strength of grouts has been also determined. The results of microstructure characterization techniques are in agreement, although impedance spectroscopy is the most sensitive for following the changes in the porous network of grouts. The results showed that micropiles made using fly ash and slag cements could have a good performance in contact with aggressive sodium sulphate media, even better than OPC ones.