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See detailGravel wash mud, a quarry waste material as supplementary cementitious material (SCM)
Thapa, Vishojit Bahadur UL; Waldmann, Danièle UL; Simon, Claude

in Cement and Concrete Research (2019), 124(105833),

The suitability of gravel wash mud (GWM), a sludge waste from gravel quarrying, is examined for its use as a partial Ordinary Portland cement (OPC) clinker substitute. The gravel wash mud was dried ... [more ▼]

The suitability of gravel wash mud (GWM), a sludge waste from gravel quarrying, is examined for its use as a partial Ordinary Portland cement (OPC) clinker substitute. The gravel wash mud was dried, milled into a fine powder and calcined at 750°C, 850°C and 950°C. In this study, various characterisation methods including particle size distribution (PSD), X-ray fluorescence (XRF), X-ray diffraction (XRD) and the simultaneous thermal analysis (STA) were applied on the calcined GWM powders to determine the optimal calcination temperature. Over 200 specimens were prepared based on different cement paste and mortar mixes to investigate the potential of calcined GWM powders as SCMs. The pozzolanic activity of the GWM powders was verified by applying strength-based evaluation methods, simultaneous thermal analysis and SEM on hardened samples. Very promising strength-enhancing capacities were observed for samples containing GWM powders calcined at 850°C with a OPC replacement level of 20 wt.%. [less ▲]

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See detailAssessment of the suitability of gravel wash mud as raw material for the synthesis of an alkali-activated binder
Thapa, Vishojit Bahadur UL; Waldmann, Danièle UL; Wagner, Jean-Frank et al

in Applied Clay Science (TOP10 Journal in Mineralogy) (2018), 161(C), 110-118

Gravel wash mud (GWM), a waste product from gravel mining was dried and processed into a fine powder to be activated by different concentrations of sodium hydroxide (NaOH) solutions for the synthesis of ... [more ▼]

Gravel wash mud (GWM), a waste product from gravel mining was dried and processed into a fine powder to be activated by different concentrations of sodium hydroxide (NaOH) solutions for the synthesis of an alkali-activated binder. The GWM powders were thermally treated at five different calcination temperatures 550, 650, 750, 850 and 950°C. The characterisation of the raw material comprises the particle size distribution (PSD) by laser granulometry, the chemical and mineralogical composition by X-ray fluorescence and X-ray diffraction analysis respectively, and simultaneous thermal analysis. The performance of the alkali-activated binders was examined using compression strength tests and the microstructure was observed using scanning electron microscopy (SEM). The GWM was classified as an aluminosilicate raw material with kaolinite and illite as main clay minerals. Furthermore, a mean particle size around 6.50μm was determined for the uncalcined and calcined GWM powders. The SEM images of the developed binders showed the formation of a compact microstructure, however, relatively low strengths were achieved. This preliminary study highlights an example of an aluminosilicate prime material, which shows very promising chemical and mineralogical characteristics, but its suitability for alkaline activation without further additives was not confirmed as far as performance-based criteria are considered. [less ▲]

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See detailA short review on alkali-activated binders and geopolymer binders
Waldmann, Danièle UL; Thapa, Vishojit Bahadur UL

in Pahn, Matthias; Thiele, Catherina; Glock, Christian (Eds.) Vielfalt im Massivbau - Festschrift zum 65. Geburtstag von Prof. Dr. Ing. Jürgen Schnell (2018)

In the recent years, the trend for reusing waste products or industrial by-products to reduce the amount of Ordinary Portland Cement (OPC) in concrete constructions has become an important task for ... [more ▼]

In the recent years, the trend for reusing waste products or industrial by-products to reduce the amount of Ordinary Portland Cement (OPC) in concrete constructions has become an important task for industries and research institutions. OPC is the second most used material in the world after water and statistics confirm that the life cycle of OPC contributes to the generation of up to 5% of the annual CO2 emissions worldwide. Mostly responsible for this negative environmental performance of OPC are the high CO2 emissions related to the cement production processes, namely the deacidification of limestone and the burning of the clinker raw materials at high temperatures above 1400°C. The current demand for cementitious binder is higher than ever whereas the incentive of building sustainable and robust constructions is gaining increasingly in importance. There is a need for development of new more durable and environmental friendly binders as an alternative to OPC binders. Therefore, the research on cement alternatives has risen over the last decades and a lot of research work has been carried out to fulfil the requirements of the market. In this work, the concepts of alkali activated materials and geopolymers are presented, and their properties are compared and discussed. A short historical review is given. Furthermore, the reaction mechanisms and hydration products of these binders are characterized and explained by referring to literature. Finally, novel binders based on waste materials are presented before closing with a short outlook on remaining questions and future challenges. [less ▲]

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See detailInfluence of the sheet profile design on the composite action of slabs made of lightweight woodchip concrete
Waldmann, Danièle UL; May, Andreas; Thapa, Vishojit Bahadur UL

in ELSEVIER Construction & Building Materials (2017), 148C(September 2017), 887-899

The trend for using renewable materials in construction to create sustainable and robust buildings is currently gaining in popularity. Therefore, in this work, the applicability of dense lightweight ... [more ▼]

The trend for using renewable materials in construction to create sustainable and robust buildings is currently gaining in popularity. Therefore, in this work, the applicability of dense lightweight woodchip concrete in constructive engineering is investigated. Here, the material is used as a top concrete layer on composite floors with profiled sheets and is analysed with regard to its load-bearing behaviour and composite action. One specific concrete mixture which fulfils the requirement for minimum strength of LC 20/22 is used for the test series. The scale of the study comprises 22 plate elements in total. The varied parameters are the shear spans, profiled sheet types and sheet thicknesses. Each examined sheet has an undercut profile with additional embossment. On the basis of experimental results, the influences of the varied parameters and profile forms on the load-bearing and composite behaviour are discussed. This study provides important key findings which show that dense lightweight woodchip concrete can transfer sufficient longitudinal shear forces to the composite joint. [less ▲]

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See detailMechanical characterisation of alkali activated clay - based geopolymer binder made out of gravel wash mud
Thapa, Vishojit Bahadur UL; Waldmann, Danièle UL; Wagner, Jean-Frank et al

Poster (2017, April 03)

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits and classifies all forms of inorganic polymeric material ... [more ▼]

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits and classifies all forms of inorganic polymeric material synthesised by chemical reaction of aluminosilicates and an alkaline activating solution. The production of geopolymer binder comprises in two main procedures: calcination and geopolymerisation. The synthesised geopolymer shows interesting characteristics like good mechanical properties, high strength and good durability. [less ▲]

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See detailMechanical characterisation of alkali activated clay - based geopolymer binder made out of gravel wash mud
Thapa, Vishojit Bahadur UL; Waldmann, Danièle UL; Wagner, Jean-Frank et al

in Iacobescu, Remus Ion; Malfliet, Annelies (Eds.) Proceedings of the 5th International Slag Valorisation Symposium (2017, April)

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits1 and classifies all forms of inorganic polymeric material ... [more ▼]

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits1 and classifies all forms of inorganic polymeric material synthesised by chemical reaction of aluminosilicates and an alkaline activating solution. The production of geopolymer binder comprises in two main procedures: calcination and geopolymerisation. The synthesised geopolymer shows interesting characteristics like good mechanical properties, high strength and good durability. [less ▲]

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See detailMasonry blocks from lightweight concrete on the basis of Miscanthus as aggregates
Waldmann, Danièle UL; Thapa, Vishojit Bahadur UL; Dahm, Franz et al

in Barth, S; Murphy-Bokern, D; Kalinina, O (Eds.) et al Perennial Biomass Crops for a Resource Constrained World (2016)

Detailed reference viewed: 161 (41 UL)
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See detailMasonry blocks from lightweight concrete on the basis of miscnathus as aggregates
Waldmann, Danièle UL; Thapa, Vishojit Bahadur UL; Dahm, Franz et al

in Barth, Susanne; Murphy-Bokern, Donal; Kalinina, Olena (Eds.) et al Perennial Biomass Crops for a Resource-Constrained World (2016)

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See detailUse of recycled concrete in construction in Luxembourg
Waldmann, Danièle UL; Thapa, Vishojit Bahadur UL

in Cahier Scientifique - Revue Technique Luxembourgeoise (2015)

Construction and demolition waste constitutes a major portion of total waste production in the world, and most of it is used in landfills. The re-use of concrete rubble collected from demolished ... [more ▼]

Construction and demolition waste constitutes a major portion of total waste production in the world, and most of it is used in landfills. The re-use of concrete rubble collected from demolished structures is an important issue. After crushing and screening, there is the possibility of appropriately treating and reusing such waste as aggregate in new concrete, especially in lower level applications. Different aspects of the topic beginning with a brief review of the European initiatives and definition in terms of C&D waste generated and recycled aggregates produced from C&D waste are given. Along with a brief overview of C&D waste, a summary of the situation in Luxembourg in use of recycled aggregate is discussed. This writing concludes by identifying some of the major barriers in more use of recycled aggregate concrete, including lack of awareness, lack of knowledge, barriers of specifications/codes for reusing these aggregates in new concrete. [less ▲]

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