TY - CONF A1 - Quercia, G. A1 - Spiesz, P. A1 - Hüsken, Götz A1 - Brouwers, J. ED - Jacobsen, S. ED - Justnes, H. ED - Cepuritis, R. ED - Hornbostel, K. ED - Peng, Y. T1 - Effects of amorphous nano-silica additions on mechanical and durability performance of SCC mixtures N2 - In the recent years the application of nanotechnology in building materials has increased exponentially. One of the most referred and used nano-materials is amorphous silica with particles size in the nano-range, even though its application and effect in concrete has not been fully understood yet. It has been reported that nano-silica (nS) addition increases the compressive strength and reduces the overall permeability of hardened concrete due to the pozzolanic properties which are resulting in finer hydrated phases (C-S-H gel) and densified microstructure (nano-filler and anti leaching effects). These effects enhance the durability of concrete structures such as bridges, quays or off-shore oil facilities in marine environments. In this study two different types of nano-silica were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD) but produced in two different processes (fumed powder silica and precipitated silica in colloidal suspension). The influence of nanosilica on SCC was investigated with respect to the properties of concrete in the fresh state (workability) and hardened state (mechanical properties and durability). Additionally, the densification of microstructure of the hardened concrete was verified by SEM and EDS analyses. The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its mechanical properties and durability. Considering the reactivity of the two nano-silica studied, colloidal type shown more reactivity at early age, which influenced all the final SCC properties. T2 - ICDC 2012 - International congress on durability of concrete CY - Trondheim, Norway DA - 2012-06-18 KW - Nano-silica KW - Concrete KW - Self Compacting KW - Durability KW - Chloride and Freeze-thaw PY - 2012 SN - 978-82-8208-031-6 SP - A2-4, 1-15 AN - OPUS4-30540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Brouwers, J. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Khayat, K. H. ED - Feys, D. T1 - Effects of superplasticizer and viscosity-modifying agent on fresh concrete performance of SCC at varied ambient temperatures N2 - Varying ambient temperatures in plants or on construction sites during casting of SCC can cause serious problems affecting the fresh concrete performances, such as rheological properties and setting time, with consequences for the hardened properties in the structure. By sensible choices of the components, the robustness of SCC mixtures against temperature variations can be improved. However, this aspect has not been the focus of intensive research yet. In this study the effects of varied ambient temperatures on the early performance of differently composed SCC mixtures are investigated, with emphasis on changes in rheology, early deformations, heat evolution and setting. Focus is placed on the study of the influence of the polycarboxylate ether molecule type as well as different viscositymodifying agents on the temperature robustness. Effects on the relevance for practical concrete applications are evaluated, which will provide a reliable framework of possible actions on the appropriate use of admixtures for SCC. T2 - SCC 2010 - 6th International RILEM Symposium on self-compacting concrete / 4th North American conference on the design and use of SCC - Desgin, Production and Placement of self-consolidating concrete CY - Montreal, Canada DA - 2010-09-26 KW - Polycarboxylate KW - Modified starch KW - Rheology KW - Self-compacting concrete KW - Temperature KW - Yield stress KW - Viscosity PY - 2010 SN - 978-90-481-9663-0 DO - https://doi.org/10.1007/978-90-481-9664-7_6 N1 - Serientitel: RILEM bookseries – Series title: RILEM bookseries VL - 1 IS - 2 SP - 65 EP - 77 PB - Springer AN - OPUS4-22126 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Quercia, G. A1 - Hüsken, Götz A1 - Brouwers, H.J.H. T1 - Effect of olivine nano-silica additions on the fresh and hardened behaviour of cement pastes and mortars N2 - The high demand for sustainable and durable building materials requires profound knowledge on the material properties. In this respect, the phenomena occurring at nano-level are of crucial importance for the design of new building materials. Therefore, all around the world, increasing amounts of funding are being directed to research projects dealing with material properties on nano-level, which is claimed to have tremendous potential for the future. One of the most referred to and used cementitious nano-material is amorphous silica with a particle size in the nano-range, even though its application and effects on concrete have not been fully understood yet. Olivine (Mg,Fe)2Si04 is the fastest weathering siiicate mineral dissolving easily in acid. Düring dissolution in acid the metallic ions (Mg2+,Fe2+) are replaced by H+, yielding Si(OH)4 monomers and metallic ions in solution. After cleaning treatments an amorphous nano-silica is obtained. The produced olivine nano-silica (OnS) has a specific surface area between 100 and 400 m2/g, the size of the primary particles, which are agglomerated in Clusters, ranges from 10 to 25 nm and the impurity content is below 5 % IV. Literature related with the application of OnS in cement based materials is scarce; only one research work performed by Justnes and Ostnor 121 is available. Thus, the effect of adding OnS in cement based Systems has been not studied. Based on this, the present research aims on elucidating the effects of OnS in the fresh and hardened state of cement pastes and mortars. T2 - 1st International conference on the chemistry of construction materials CY - Berlin, Germany DA - 07.10.2013 KW - Nano-silica KW - Self compacting concrete KW - Durability KW - Chloride KW - Freeze-thaw PY - 2013 SN - 978-3-936028-75-1 SP - 179 EP - 182 AN - OPUS4-30410 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Babski, Veronika A1 - Hüsken, Götz A1 - Pirskawetz, Stephan A1 - Ehlers, Noah A1 - Kühne, Hans-Carsten A1 - Brouwers, H.J.H. ED - Fehling, E. ED - Middendorf, B. ED - Thiemicke, J. T1 - Characterisation of Ultra-High Performance Fibre Reinforced Concrete (UHPFC) under tensile loading by acoustic emission and optical deformation analysis N2 - During the past 20 years, innovative developments in concrete technology have enabled the production of ultra-high performance fibre reinforced concretes (UHPFC) for the protection and preservation of concrete structures. The main characteristics of UHPFC comprise high compressive and flexural strength as well as high ductility compared to normal strength, normal weight concrete (NSC). This paper focuses on the analysis of crack formation and crack propagation in UHPFC under tensile loading under quasistatic conditions by using acoustic emission (AE) and optical deformation analysis (ODA). AE is a non-destructive technique to monitor the development of micro structural damage processes caused by external forces. In this context, AE allows for a continuous monitoring of changes in the microstructure (cracks) over time and the corresponding localisation by appropriate algorithms. The AE measurements were performed along with ODA at the surface of the samples in order to analyse the deformation behaviour of the samples and the crack propagation. For the tests, a UHPFC reference mixture was developed and tested with three different volume percentages of steel fibres (1.0 V.-%, 2.0 V.-%, and 3.0 V.-%). This paper shows that the application of AE is a suitable method to analyse the crack propagation in UHPFC specimens under tensile loading and to localise the crack initiation. Furthermore, insights into the failure mechanism of the fibres are offered by the analysis of the signals of the AE measurements, which allows for a better understanding of UHPFC and its general performance. T2 - 4th International Symposium on Ultra-High Performance Concrete and High Performance Materials (HiPerMat) CY - Kassel, Germany DA - 09.03.2016 KW - UHPFC KW - Tensile loading KW - Acoustic emission KW - Crack formation KW - Optical deformation analysis KW - Crack propagation PY - 2016 SN - 978-3-7376-0094-1 SP - 1 EP - 9 PB - Kassel University Press CY - Kassel AN - OPUS4-36893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Quercia, G. A1 - Spiesz, P. A1 - Hüsken, Götz A1 - Brouwers, H.J.H. T1 - Chloride intrusion and freeze-thaw resistance of self-compacting concrete with two different nano-SiO2 T2 - 18. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 2012-09-12 KW - Nano-SiO2 KW - Concrete KW - Self compacting KW - Durability KW - Chloride and freeze-thaw KW - Nano-silica PY - 2012 SN - 978-3-00-034075-8 VL - 2 IS - 3.07 SP - 2-0123 - 2-0136 AN - OPUS4-26542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hüsken, Götz A1 - Brouwers, H.J.H. T1 - The influence of the fines on the early-age behavior of zero-slump concrete T2 - 18. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 2012-09-12 KW - Zero-slump concrete KW - Green-strength KW - Compaction behavior KW - Intensive compaction test PY - 2012 SN - 978-3-00-034075-8 VL - 2 IS - 3.07 SP - 2-0001 - 2-0008 AN - OPUS4-26541 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Roussel, N. ED - Bessaies-Bey, H. T1 - A simple test method to assess the influence of PCEs on the rheology of flowable cementitious systems N2 - Today’s superplasticizers for self-compacting concrete and high Performance cementitious materials are very versatile. Typically superplasticizers are composed of a polycarboxylic backbone equipped with polyethylene oxide graft chains of variable length and grafting degree. The mode of operation of these admixtures is based on the steric repulsion of the particles upon adsorption. The adsorption is strongly depending upon the charge density of a superplasticizer and the time dependent Adsorption processes control the retention of the flow performance – an important issue particularly for ready-mix and construction site concrete. However, the properties of polycarboxylic superplasticizers typically remain a black box for users. The paper suggests a simple and rapid test method, which can be conducted without sophisticated equipment, to qualitatively distinguish between two types of superplasticizers based on the adsorption mechanism. Interpreting the results in the right way provides a powerful tool to choose the right admixture for individual time dependent flow specifications. T2 - 1st international RILEM conference on rheology and processing of construction materials and 7th RILEM conference on self-compacting concrete CY - Paris, France DA - 02.09.2013 KW - Adsorption KW - Polycarboxylate ether KW - Rheology KW - Slump flow PY - 2013 SN - 978-2-35158-137-7 IS - Chapter 2.1.1 SP - 1 EP - 8 AN - OPUS4-29929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Lindemann, Mathias A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Brouwers, H.J.H. ED - Bernal, S.A. ED - Provis, J.L. T1 - Structural investigations on one-part geopolymers after different drying regimes T2 - 34th Cement and concrete science conference CY - Sheffield, UK DA - 2015-09-14 KW - Geopolymers KW - One-part mix PY - 2015 SP - 37 EP - 40 AN - OPUS4-34554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten T1 - Investigations on one-part geopolymers synthesized from different silica sources N2 - One-part geopolymers, synthesized from three different silica sources and sodium aluminate, were investigated regarding their microstructure and the evolution of their compressive strength on curing at slightly elevated temperatures. The effect of thermal treatment was studied up to 1000 °C and for the investigation of the chemical durability specific samples were treated with sulfuric acid (H2SO4, pH = 1). Depending on the silica feedstock, different degrees of reaction were observed. One of the silicas had a significantly higher reactivity. For two of the silicas, significant amounts of zeolites occurred as reaction products besides geopolymeric gel, whereas the more reactive silica source lead to the formation of a rather fully condensed geopolymeric network. The composites indicated promising behavior on heating in so far as no distinct shrinkage step occurred in the temperature range of dehydration. Up to 400 °C the residual strength of those mixes increased. Above 800 °C the samples underwent new phase formation. After exposure to sulfuric acid (pH 1; 70 d) specimens showed a residual compressive strength of about 77 % of the reference, indicating high acid resistance. T2 - 6th International Conference on Non-Traditional Cement & Concrete CY - Brno, Czech Republic DA - 19.06.2017 KW - Geopolymers KW - Zeolites KW - Thermal properties KW - Acid resistance KW - Chemical durability PY - 2017 SN - 978-80-214-5507-8 SP - 299 EP - 306 AN - OPUS4-40774 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Brouwers, H.J.H. A1 - Jäger, Christian ED - Bílek, V. ED - Kersner, Z. T1 - 27Al-1H and 27Al-29Si Double resonance NMR of one-part geopolymers N2 - The production and processing of ordinary Portland cement are responsible for nearly 5% of the world C02 emissions. Due to the world’s increasing requirement for building materials, this air pollution is growing up in the next decades. Alternative cement such as geopolymers can reduce these emissions effectively, Conventional geopolymer binders, produced ffom fly ash or metakaolin as aluminosilicate source and water-glass or alkali hydroxide Solutions as activator, are often used and studied. It is known that under appropriate conditions the starting materials form a three-dimensional aluminosilicate structure and create a gel-like matrix, In our case, a silica source from wastewater treatment of chlorosilane production and solid sodium aluminate as starting materials are initiated to harden by water. This procedure is known as “just add water” or “one-part” geopolymer formulation. These composites have significant advantages for use on construction site, but their Chemical structure is not extensively analyzed. In this work, a well known one-part geopolymer is investigated by 'H and 27A1 magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Furthermore, it is shown that overlapping NMR lines can resolved with echo experiments and T2 - NTCC2014 - International conference on non-traditional cement and concrete CY - Brno, Czech Republic DA - 16.06.2014 KW - Geopolymers KW - One-part formulation KW - Zeolite Na-A KW - NMR KW - REDOR PY - 2014 SN - 978-80-214-4867-4 SP - 91 EP - 94 PB - Novpress AN - OPUS4-31224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -