Fractal characterization of thermal cracking patterns and fracture zone in low-alkali cement matrix modified with microsilica

2020 ◽  
Vol 114 ◽  
pp. 103732
Author(s):  
Maciej Szeląg
2014 ◽  
Vol 805 ◽  
pp. 343-349
Author(s):  
Carine F. Machado ◽  
Weber G. Moravia

This work evaluated the influence of additions of the ceramic shell residue (CSR), from the industries of Lost Wax Casting, in the modulus of elasticity and porosity of concrete. The CSR was ground and underwent a physical, chemical, and microstructural characterization. It was also analyzed, the environmental risk of the residue. In the physical characterization of the residue were analyzed, the surface area, and particle size distribution. In chemical characterization, the material powder was subjected to testing of X-ray fluorescence (XRF). Microstructural characterization was performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The residue was utilized like addition by substitution of cement in concrete in the percentages of 10% and 15% by weight of Portland cement. It was evaluated properties of concrete in the fresh and hardened state, such as compressive strength, modulus of elasticity, absorption of water by total immersion and by capillarity. The results showed that the residue can be used in cement matrix and improve some properties of concrete. Thus, the CSR may contribute to improved sustainability and benefit the construction industry.


2014 ◽  
Vol 5 (4) ◽  
pp. 49-60 ◽  
Author(s):  
Juan Carlos Poveda ◽  
Daniel-Ricardo Molina and ◽  
Edgar-Francisco Pantoja-Agreda

Author(s):  
C.W. Devey ◽  
N. Augustin ◽  
A. Brandt ◽  
N. Brenke ◽  
J. Köhler ◽  
...  

2019 ◽  
Vol 10 (1) ◽  
pp. 107
Author(s):  
Letícia Andreolli Dias ◽  
Daiana Cristina Metz Arnold ◽  
Fernanda Boll Birck ◽  
Adriana Teresinha Silva

A construção civil está em busca constante de materiais alternativos que supram as solicitações exigidas nas estruturas das edificações. Nesse contexto, as fibras têxteis residuais podem ser uma alternativa para as matrizes cimentícias como reforço estrutural contra a fissuração localizada, uma vez que o concreto armado é incapaz de absorvê-las. Por sua vez, a indústria de pneus gera grandes quantidades de resíduos têxteis que são destinados aos aterros sanitários, causando graves impactos ao meio ambiente. Nesse sentido, esta pesquisa buscou avaliar a viabilidade da incorporação de resíduo têxtil em forma de fibras, em concretos, visando aumentar a capacidade de deformação e o controle da fissuração. Para tanto, confeccionou-se um traço 1:2,21:3,21 (cimento:areia:brita) e incorporou-se as fibras nos teores de 2,7 e 3,6 Kg/m³ sobre o volume do concreto. Para caracterização das fibras foi verificada a geometria, o comprimento, o fator de forma e o diâmetro médio. No estado fresco do concreto, analisou-se a influência das fibras quanto à trabalhabilidade e a massa específica. Após, no estado endurecido, avaliou-se a densidade de massa, a resistência à compressão, a resistência à tração por compressão diametral e a resistência ao impacto. Além disso, verificou-se a forma de aderência e de ruptura da fibra na matriz cimentícia através do microscópio óptico. Deste modo, os resultados apontam viabilidade da incorporação de fibra têxtil em matrizes cimentícias, visto que estas diminuiram a fissuração localizada e auxiliaram na absorção de impactos no concreto, porém por se tratar de um assunto inovador, deve-se realizar mais estudos para que o compósito possa ser efetivamente utilizado na construção civil.Palavras-chave: Concreto. Resíduo têxtil. Fissuras localizadas.ABSTRACTThe civil construction is constantly seeking for alternative materials that meet the requirements of the buildings structures. In this context, residual textile fibers may be an option for cement matrix as a structural reinforcement against the localized cracking, considering that the reinforced concrete is unable to absorb them. With regard, the tire industry generates substantial amounts of textile waste that is destined for landfill sites, causing massive impacts to the environment. In this sense, this research sought to evaluate the feasibility of the incorporation of textile waste in the fibers form, in concrete, aiming to increase the deformation capacity and the control of cracking. In order to do so, the trace 1: 2,21: 3,21 (cement: sand: gravel) was made and the fibers were incorporated in the contents of 2.7 and 3.6 kg / m³ on the volume of the concrete. For characterization of the fibers, the geometry, length, shape factor and average diameter were verified. In the fresh state of the concrete, it was analyzed the influence of the fibers on the workability and the specific mass. Later, in the hardened state, the mass density, compressive strength, diametral compression tensile strength and impact strength were evaluated. In addition to that, the adhesion and rupture of the fiber in the cementitious matrix ware checked through the optical microscope. Thus, the results indicate the feasibility of the incorporation of textile fiber in cementitious matrixes, since these reduced the localized cracking and helped in the absorption of impacts in the concrete; however, since it is an innovative subject, more studies may be done so that the composite can be used in civil construction.Keywords: Concrete. Textile residue. Localized cracks.


2018 ◽  
Vol 11 (6) ◽  
pp. 1284-1307 ◽  
Author(s):  
V. Y. SATO ◽  
A. P. L. GALINA ◽  
J. E. S. L. TEIXEIRA

Abstract Brazil is one of the world's largest producers and exporters in the field of ornamental stones. On the other hand, the production and processing of ornamental stones result in a large volume of unused material in the form of sludge, usually discarded inappropriately in sedimentation ponds or landfills. Several researches have been carried out aiming the reuse of this material in cementitious matrixes. In the field of rheology, there are still incipient national studies that use the rheological parameters obtained experimentally to determine the behavior of cement matrix based on Portland cement. Thus, the objective of this work is to characterize rheologically the behavior of cementitious pastes with and without addition of ornamental rock processing residue (RBRO) in its natural condition. Cement pastes were prepared with three a/c ratios (0.45, 0.55, 0.65) and four residue addition contents (0%, 5%, 10%, 15%) and submitted to the flow test. In tests for characterization of the residue, the RBRO presented as a material of specific fineness and mass near the cement, having low reactive activity, indicating that the residue can be used as an inert mineral addition in the cementitious matrix. In the rheological characterization tests of the pulps studied, it was observed in the flow tests that the samples behaved as a non-Newtonian, pseudoplastic and thixotropic fluid.


2015 ◽  
Author(s):  
Rui Zhang ◽  
Donald Vasco ◽  
Thomas M. Daley ◽  
William Harbert

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Nafeesa Shaheen ◽  
Rao Arsalan Khushnood ◽  
Siraj Ud din

For preserving concrete structures and hindering ingress of chemicals through cracks and fissures, repair is inevitable. Microbial calcite precipitation is an intrinsic approach for crack rectification and emulating way of sustainability for reducing anthropogenic greenhouse gases (GHGs) along with conserving the natural resources. In this study,Bacillus subtilisstrain is applied for intrinsic repair of concrete’s cracks because of its high pH endurance and capability of sporulation. For prolonged survival of microorganisms, immobilization technique was employed.B. subtiliswas immobilized through limestone powder (LSP) before adding into cement matrix. Self-healing proficiency ofB. subtiliswas deliberated in terms of mechanical strength regain after cracking at 3, 7, 14, and 28 days. To examine the microstructure and characterization of healing precipitate, micrographical (field emission scanning electron microscopy), chemical (energy dispersive X-ray), and thermal (thermogravimetric analysis) analyses were performed after the healing period of 28 days. The results revealed evident signs of calcite precipitation in nano-/microcracks subsequent to microbial activity. Furthermore, immobilized LSP improved the compressive strength of the analyzed formulations.


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