Ana Maria Toma

Gheorghe Asachi Technical University of Iași

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Michael Mehring

Chemnitz University of Technology

Tobias Rüffer

Chemnitz University of Technology

Anca Silvestru

Babeș-Bolyai University

Heinrich Lang

Chemnitz University of Technology

Heinrich Lang

Chemnitz University of Technology

Ionuţ-Ovidiu Toma

Gheorghe Asachi Technical University of Iași

Ciprian I. Raţ

Babeș-Bolyai University

Cristian Silvestru

Babeș-Bolyai University

Alexandra Pop

Babeș-Bolyai University

Małgorzata Krasowska

Bialystok University of Technology

Cooperative Institutions

Gheorghe Asachi Technical University of Iași

Chemnitz University of Technology

Babeș-Bolyai University

Division of Chemistry

Max-Planck-Institut für Kohlenforschung

Ruhr West University of Applied Sciences

Heidelberg University

Technical University of Cluj-Napoca

Laboratoire de Chimie

University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca

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The Use of Natural Zeolites in Cement-Based Construction Materials—A State of the Art Review

Coatings (2023)

Sergiu-Mihai Alexa-Stratulat Ioana Olteanu Ana Maria Toma Cristian Pastia Oana-Mihaela Banu

Natural zeolite is a honeycomb-structured aluminosilicate mineral with an open crystalline structure which makes it suitable for a variety of applications. Given the beneficial effects of zeolites on the properties of cementitious materials, the present paper aims to summarize the recent findings reported in the scientific literature on the use of zeolites in cement-based construction materials. This paper limits the analysis to natural zeolites. The influence of natural zeolites on the workability and setting time of cement-based construction materials revealed that increasing the zeolite content led to a reduction in workability compared to the control mixes. At the same time, the initial and final setting times of cement pastes showed a decreasing trend with an increase in the replacement percentage. The slow pozzolanic reaction of clinoptilolite zeolite results in lower flexural strength and compressive strength values of mortars at the age of 28 days. Blending zeolites with other supplementary cementitious materials resulted in improved values of the mechanical properties of mortar and concrete. The findings regarding the impact of zeolite on the durability of concrete suggest that zeolite shows promise as a viable alternative to cement, with positive effects on various aspects of durability. The majority of the durability factors are interconnected. The presence of conflicting findings is particularly significant in this context, highlighting the need for a comprehensive approach to address these challenges in the future.

Cementitious

Clinoptilolite

Pozzolanic reaction

10.3390/coatings14010018

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Citations (8)

Greening of Concrete Industry by Incorporating Gypsum-Based Industrial Wastes as Supplementary Cementitious Materials

Advanced materials research (2013)

Ionuţ-Ovidiu Toma Daniel Covatariu Ana Maria Toma George Țăranu Mihai Budescu

The paper presents some preliminary results on using a new supplementary Cementitious material based on industrial by-products most of them unrecyclable until recently. The opportunity for using such industrial unrecyclable wastes in construction industry has recently been recognized by researchers as having net benefits for the environment. This strategy has the potential to reduce costs, conserve energy and minimize waste. The concept very much fits into the era of sustainable development. In view of this fact, the effect of curing conditions on the self weight and strength characteristics of an eco-mortar is studied and preliminary encouraging results are presented. The eco-cement, in the form of anhydrous calcium sulphate, is set to replace the ordinary Portland cement in the mix proportion. It is made from industrial wastes and can be entirely recycled after its expiration date. The curing conditions consisted in air curing for 28 days or various time intervals for curing in water until the day of testing. The strength properties at the age of 28 days are investigated in terms of bending tensile strength and compressive strength. The obtained results show that the curing conditions play an important role both on the self weight and on the strength characteristics.

Cementitious

10.4028/www.scientific.net/amr.649.246

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Citations (4)

CCDC 1418493: Experimental Crystal Structure Determination

The Cambridge Structural Database (2016)

Ana Maria Toma Ciprian I. Raţ Anca Silvestru Tobias Rüffer Heinrich Lang

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/cc1jm1v1

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Citations (0)

CCDC 1431257: Experimental Crystal Structure Determination

The Cambridge Structural Database (2016)

Ana Maria Toma Adrian Ionuţ Nicoară Anca Silvestru Tobias Rüffer Heinrich Lang

Crystal (programming language)

10.5517/cc1k1blj

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CCDC 1978876: Experimental Crystal Structure Determination

The Cambridge Structural Database (2020)

Răzvan Şuteu Ana Maria Toma Michael Mehring Anca Silvestru

10.5517/ccdc.csd.cc24f5qh

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Evaluation of the Seismic Vulnerability for P+4 Residential Buildings from the Urban Area of Iaşi Using the Finite Element Method

Deleted Journal (2010)

Ana Maria Toma Gabriela M. Atanasiu

The analysis of the seismic vulnerability for a typical dwelling structure, existing in a developed urban area, subjected to repetitive seismic actions, is performed. This type of residential building is met all over Romania, making more than 50% from the total number of buildings constructed in residential areas, built between 1965 and 1985. The structure chosen for analysis is a P+4 building, made of precast concrete panels. This type of building was selected because many districts in Iasi have been built using this type of project or similar ones, within the mentioned period. The deterministic approach for evaluation is based on modelling and numerical simulations using ETABS vs. 9 software. The methodology uses two types of numerical models. In the deterministic approach, for the first model, the building is considered in its initial state and for the second model in its degraded state, after the structure was subjected to more than two or three major earthquakes. The degradations of the elements were introduced taking into account nine scenarios, considering consecutively the structural elements and the walls with openings having different degrees of damage, from 30%, 60% to 90%. The obtained results study are used to classify the building structures based on their seismic risk and the degree of degradation, in order to fully comprehend and investigate the seismic vulnerability of the existing urban infrastructure.

Precast concrete

Vulnerability

Seismic risk

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Experimental Assessment Techniques for the Dynamic Properties of Concrete

Advanced engineering forum (2017)

Mihai Sergiu Stratulat Oana-Mihaela Banu Ana Maria Toma Petru Mihai Ionuţ-Ovidiu Toma

Recent progress in measurement techniques have given rise to increasing interest in non-destructive testing. Incorporating non-conventional, recycled materials in concrete (i.e. rubber crumbs from discarded tires), the heterogeneity is increased. Based on this, it is of importance to determine to what degree the accepted protocols, valid for traditional materials, are applicable to newly developed construction materials with particular interest to rubberized concrete. Several tests, including parameters missing from the standardized measurement techniques, such as the increasing rate of the frequency during the sweep for finding the resonant frequency of the specimen, were conducted on two types of concrete: traditional and rubberized concrete. The assessment of the dynamic properties was done by means of the forced vibration method and the impact method. The obtained results indicate the fact that current procedures should be applied with care when considering aggregate replacement in traditional concrete by other recycled materials.

Properties of concrete

10.4028/www.scientific.net/aef.21.226

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Citations (1)

Bismuth⋯π arene versus bismuth⋯halide coordination in heterocyclic diorganobismuth(iii) compounds with transannular N→Bi interaction

Dalton Transactions (2017)

Ana Maria Toma Alexandra Pop Anca Silvestru Tobias Rüffer Heinrich Lang

The hypervalent diorganobismuth(iii) halides of type [RCH₂N(CH₂C₆H₄)₂]BiX, (R = Ph, Bz, and MeO) show a strong tendency to associate either by Bi⋯X or by Bi⋯π arene secondary interactions.

Bismuth

10.1039/c7dt00188f

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Citations (25)

Deterministic Method for Assessing the Degree of Degradation for Masonry Condominium Structures in Romanian Urban Areas

Deleted Journal (2012)

Ana Maria Toma

The paper presents an assessment methodology for the degree of degradation of masonry load bearing wall condominium structures based on the deterministic approach. According to the generally accepted definition, a deterministic model is a one in which no randomness is involved in the development of future states. As such, a given input will always produce the same output. In risk analysis the events are completely pre-determined by causality and the analyses are performed in order to determine the effects of assumed events on considered structures. The methodology consists in performing nonlinear Finite Element Analysis on two types of masonry condominium structures frequently met in Romanian urban areas. The second step of the methodology involves using the values of the fundamental period of vibration, evaluated by modal analysis at the end of each earthquake scenario, to compute the degradation coefficient. The evaluation procedure of the degradation state chosen in this deterministic approach is based on a degradation coefficient belonging to the cathegory of maximum softening damage indices. The results are presented in terms of periods of vibrations and modal displacements. The degradation coefficient was computed based on the data resulted from the modal analysis and was used to classify the structures according to the reference intervals.

Degradation

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Evaluation of bismuth-based dispersion energy donors – synthesis, structure and theoretical study of 2-biphenylbismuth(iii) derivatives

Physical Chemistry Chemical Physics (2020)

Ana-Maria Fritzsche Sebastian Scholz Małgorzata Krasowska Kalishankar Bhattacharyya Ana Maria Toma

Intramolecular Bi⋯π arene London dispersion interactions in (biphenyl)_3−xBiX_x amount to ca. 20 kJ mol⁻¹ with distances of 3.8–4.0 Å.

Bismuth

10.1039/c9cp06924k

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Citations (8)