Showing papers by "Francisca Puertas published in 2017"
TL;DR: In this article, the kinetic, the mechanical development and the microstructure of an alkali-activated blended Portland cement produced from the mixture of a granulated blast furnace slag and Portland cement in proportion 80% and 20% respectively were studied.
122 citations
TL;DR: Workability and rheology of AAM and fly ash (AAFA) mortars have been studied in this article, showing that AAS and AAFA mortars are more sensitive to changes in the liquid/solid ratio than OPC mortars.
87 citations
TL;DR: In this article, the results of alkali-activating waste glass in pursuit of a new type of alkaline activated materials (AAMs) were discussed. But the main reaction product was a Si-high, Al-low gel.
67 citations
07 Aug 2017
TL;DR: In this article, a trip back in time to the origins of the alkali activation is made to explain the most characteristic and important chemical concepts. But they still cannot say or establish that alkaline cements (alkali activated materials or geopolymers) are based on a clean chemical to the environment, due to production processes of alkaline solutions such as sodium silicates emit large amounts of CO2 into the atmosphere.
Abstract: Portland cement is considered an excellence building material. This is due mainly to its high performance, its good quality/price ratio and the raw materials from which it is made can be found almost everywhere in the world. However, the development of alternative Portland cements obtained through processes involves lower emission of CO2 into the atmosphere is a priority research and great interest worldwide. Alkaline activation constitutes an alternative to Portland cement, preferably amorphous or vitreous aluminosilicates and alkaline activator (such as NaOH, Na2CO3 or sodium silicates hydrates). The aluminosilicates may be natural products such as metakaolin or industrial by-products such as blast furnace slag or aluminosiliceous fly ash. These cements and concretes obtained by alkali activating aluminosilicates are characterised by high mechanical strength, low heat of hydration and high impermeability, as well as resistance to high and low temperatures and sulphate, seawater and acid attacks. Moreover, the preparation of these alkaline cements requires lower energy than in the manufacturing process of Portland cement. However, we still cannot say or establish that alkaline cements (alkali activated materials or geopolymers) are based on a clean chemical to the environment, due to production processes of alkaline solutions such as sodium silicates emit large amounts of CO2 into the atmosphere. This article aims to make a trip back in time to the origins of the alkali activation to explain the most characteristic and important chemical concepts.
49 citations
TL;DR: In this paper, the authors used NaOH and a mixture of NaOH+Na2SiO3 as activators of a high content of natural volcanic pozzolan (NP) and the synergic effect of the addition of granulated blast furnace slag up to 30% were performed.
36 citations
University of Aveiro1, Spanish National Research Council2, University of Hasselt3, Technion – Israel Institute of Technology4, Katholieke Universiteit Leuven5, University of Belgrade6, Saints Cyril and Methodius University of Skopje7, Politehnica University of Bucharest8, Scientific and Technological Research Council of Turkey9, Riga Technical University10, University of Pannonia11, University of Minho12, University of Sheffield13
TL;DR: In this article, the authors give new and more complete insights on the recycling of several industrial wastes, on four groups of construction materials: (1) construction materials based on Portland cements (both as cement itself and as concrete), (2) construction material based on alkali-activated binders, (3) ceramics and glass-ceramics, and (4) gypsum for each byproduct a separate section will describe the technical (and chemical) aspects of the use as part of a construction material and the resulting radiological properties of the designed product
Abstract: The cementitious materials and ceramic industries are frequently looked as targets for the recycling and valorization of several wastes, residues, and by-products, generated from a wide variety of industries In general, only technical (and chemical) aspects are covered on each attempt for recycling a waste in a particular product, while radiological features are rarely considered This chapter aims to give new and more complete insights on the recycling of several industrial wastes, on four groups of construction materials: (1) construction materials based on Portland cements (both as cement itself and as concrete), (2) construction materials based on alkali-activated binders, (3) ceramics and glass-ceramics, and (4) gypsum For each by-product a separate section will describe (1) the technical (and chemical) aspects of the use as part of a construction material and (2) the resulting radiological properties of the designed product, when they are available Some ceramic industries also use radiologically active components, namely zircon and zirconia (in glazes, refractories, etc) The radiological consequences of their production, further use/manipulation by other industrial sectors (eg, ceramic glazes and frits production), and on the final costumers are also briefly reported
23 citations
University of Pannonia1, University of Hasselt2, University of Aveiro3, Spanish National Research Council4, Frederick University5, Josip Juraj Strossmayer University of Osijek6, National Technical University of Athens7, University of Novi Sad8, Kaunas University of Technology9, University of Tartu10, Technion – Israel Institute of Technology11
TL;DR: In this article, the authors present an overview on the parameters to be considered during the selection of NORM by-products as feedstock for the construction industry, specifically for the production of cement, concrete, and ceramics.
Abstract: Naturally occurring radionuclides are present in the Earth crust; however, their distribution is not homogeneous. When primary or secondary raw materials containing relatively low concentrations of naturally occurring radionuclides are introduced in an industrial process then the radionuclides can become more concentrated in the produced (by-)products. For example, during the production of purified metals, throughout the purification process, also other elements, such as naturally occurring radionuclides, become concentrated in the by-products. In order to assure radiation protection of the population, it is important to map the potential exposure for workers and the general public. There is an extensive literature available regarding the presence of naturally occurring radionuclides in various by-products; however, it can be hard to review and even to interpret for the regulators and members of the industry in order to assure the safe use of by-products for example in construction. To solve this problem data mining and text processing have been applied to the ever-increasing numbers of publications (More than 39,000 filtered publications have been processed up to the Jan. 6, 2017), and the NORM4Building database has been compiled based on the analysis of the collected data. Based on this database using text analysis methods the most NORM prone raw materials and industries have been identified. This chapter gives a concise overview on the parameters to be considered during the selection of NORM by-products as feedstock for the construction industry, specifically for the production of cement, concrete, and ceramics. In the frame of this chapter the technical and radiological properties of the most representative industrial processes (such as coal mining and combustion; iron and steel production; the alumina, the zirconia, and the phosphate industry; etc.) and their by-products are discussed, especially considering the needs of the construction industry and the new European Basic Safety Standards.
15 citations
TL;DR: A methodology including software tools for analysing NORM building materials and residues by low-level gamma-ray spectrometry with focus on the natural radionuclides and Monte Carlo simulations for efficiency and true coincidence summing corrections has been developed.
11 citations
TL;DR: In this article, the isotherms for PCE and BNS superplasticiser adsorption on four sands with different fineness and compositions commonly used to prepare mortars and concretes were analyzed.
Abstract: The choice of a superplasticiser (SP) for concrete is of great complexity, as it is well known that properties of the end product are related to admixture and its compatibility with concrete components. Very few studies have been conducted on the compatibility between SPs and the sand of mortars and concretes, however. Practical experience has shown that sand fineness and mineralogical composition affect water demand and admixture consumption. Clay-containing sand has been found also to adsorb SPs, reducing the amount available in solution for adsorption by the cement. This study analysed the isotherms for PCE and BNS superplasticiser adsorption on four sands with different fineness and compositions commonly used to prepare mortars and concretes. BNS-based SP did not adsorb on sands, while PCE-based admixtures exhibited variable adsorption depending on different factors. The adsorption curves obtained revealed that the higher the sand fineness, the finer the particle size distribution and the higher the clay material, the greater was PCE admixture adsorption/ consumption.
7 citations