Influencia de las nanopartículas de CuO y los residuos de boro en las propiedades de morteros de cemento

In this study, compressive and flexural strength, thermal properties, and pore structure of mortars modified with two types of boron waste and different amounts of CuO nanoparticles were investigated. The binders were prepared with 3% of borogypsum or borax waste and nano-CuO at concentration up to 4%. The setting time, compressive and flexural strength at 3, 7, and 28 days, DTA/TG, XRD, BET, and water absorption tests were carried out, and optimal nano-CuO percentages were determined. It was observed that nano-CuO addition in the range 2%–2.5% can improve mechanical properties, reduce the amount of unreacted portlandite, increase water absorption resistance, and decrease the setting time for borogypsum-containing mortars. The optimum nano-CuO replacement ratio changes between 0.5%–1% for borax waste-containing mortars. The results showed that nano-CuO was able to promote hydration reactions, act as a nanofiller, and provide a kernel for nucleation reactions.En este estudio, se investigaron las resistencias a compresión y flexión, las propiedades térmicas y las estructuras porosas de morteros modificados con dos tipos de residuos de boro y distintas cantidades de nanopartículas de CuO. Los morteros se prepararon con un 3 % de boro-yeso o residuos de boro y nano-CuO, en concentraciones de hasta el 4 %. Se realizaron ensayos de tiempo de fraguado, resistencias mecánicas a 3, 7 y 28 días, ATD/TG, DRX, area BET y absorción de agua y se determinaron los porcentajes óptimos de nano-CuO. Se observó que la adición de nano-CuO en el rango del 2 – 2,5 % mejora las propiedades mecánicas, reduce la cantidad de portlandita sin reaccionar, aumenta la resistencia de absorción del agua y disminuye el tiempo de fraguado en morteros que contienen residuos de boro. Los resultados muestran que el nano-CuO favorece las reacciones de hidratación, actua como nanofiller y proporciona un punto para las reacciones de nucleación

GRAPHENE OXIDE AS ADDITIVE FOR INCREASING THE STRENGTH AND DURABILITY PERFORMANCE OF EXISTING CONCRETE STRUCTURES

Graphene and graphene-based nanosheets (GNS) have valid mechanical, thermal and electrical properties, enabling interesting applications for improving structural strength and durability. If combined with the Ordinary Portland Concrete (OPC), they can enhance its mechanical behaviour, an analogous improvement in terms of strength can also be seen in Ultra-High-Performance Concrete (UHPC). These features appear very useful in case of the restoration of existing concrete structures, thanks to the durability properties due to the GNS. Providing a wide state of the art about the use of GNS in concrete structures, this paper shows the strength improvements achievable in term of strength and durability. The benefits are finally discussed in relation to the restoration of existent concrete buildings

Study on Portland Cement Pastes Containing Sanitary Ware Ceramic Wastes at Elevated Temperatures

Resistance of Portland cement pastes incorporated 20 wt. % sanitary ware ceramic nano-powder wastes to firing temperatures from 100 up to 600 ℃ was investigated. Results revealed that all physical and mechanical properties were improved and gradually enhanced with firing temperatures, but only up to 400 ℃, and then adversely affected with any further increase of firing temperatures than 400 ℃, i.e. water absorption and total porosity decreased, whereas bulk density was enhanced. Water absorption and total porosity were decreased by 10 and 4 %, respectively, while bulk density was increased by 2.25 %. Furthermore, flexural and compressive strengths were also improved and increased by 1.69 and 1.2 %, respectively. Fourier transform infrared spectra (FT-IR) showed the disappearance of free lime and ettringite on firing. Scanning electron microscopy (SEM) showed that the crystal phase growth of the formed hydration products as a result of both normal hydration and pozzolanic reactions at ambient temperature were developed and modified due to the temperature exposure. The hardened cement pastes can withstand and resist only up to 400 ℃

Carbonation resistance enhancement of cement mortars with recycled plastics using ethylene-vinyl acetate and nanosilica

Carbonation resistance enhancement of cement mortars with recycled plastics using ethylene-vinyl acetate and nanosilica Plastic has surpassed most of the man-made materials, and it has been accumulated as “waste” in the environment for several decades. Replacement of natural aggregates in concrete with recycled waste plastic (RWP) attracted great attentions in recent years due to the high potentials of recycling waste plastic. This employment of RWPs in concrete, however, was accompanied by reduction in mechanical properties and durability performances (e.g., carbonation) due to the poor interactions between RWP and cement matrix. The aim of this study is to lessen the mechanical defects of cement mortars with RWPs and enhance the carbonation resistance by employing Ethylene-vinyl acetate (EVA) and nanosilica (nS) in the mortar mixtures. 2 to 4 % of EVA and nS were substituted for cement in mortars with 10 and 15 % RWPs. Strength and carbonation resistance of the mortars were measured. Microstructure was investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Results showed that as much as 5.5 % improvement in strength and 50% reduction in carbonation depth were recorded for mortars with the EVA-nS addition. EVA created polymer films around the RWPs to improve cohesion with the cement matrix, while nS filled the pores and enhanced the material compactness. Our findings would pave a path to fabricate stronger and more durable cement mortar with RWP

De-aluminated metakaolin-cement composite modified with commercial titania as a new green building material for gamma-ray shielding applications

Sustainable disposal of dealuminated metakaolin (DAK) is a crucial environmental issue for the alum production industry. In previous studies, DAK was utilized as eco-friendly cementitious materials, but only 10 wt% was used instead of cement as DAK's high percentage has a detri-mental effect on the mechanical properties, so the environmental problem of DAK has not yet been solved. In this study, commercial titanium oxide (TiO2) was incorporated in a cement matrix containing DAK that reached 50 wt% to benefit from TiO2's properties in enhancing the me-chanical performance of binding materials and producing cementitious blends used as blocking materials against harmful gamma radiation. Five pastes were prepared to reach the main target; ordinary Portland cement (OPC), OPC-10%DAK (D10), OPC-30%DAK (D30), OPC-50%DAK (D50) and OPC-45%DAK-5%TiO2 (D45-T5). By means of a mini-slump test, all fresh blends have very close flowability using the appreciated additions of polycarboxylate superplasticizer. The hardened composites were cured in tap water for up to 28-days. Compressive strength results at 28 days for OPC, D10, D30 and D50 were 80, 94.6, 60.8 and 57.6 MPa, respectively. An obvious turning point in strength value from 57.6 to 88 MPa after replacement of DAK by 5 wt% TiO2 (D45-T5). A gamma-ray shielding test was performed using two radioactive isotopes (Co-60 and Cs-137). The inclusion of 5% TiO2 has a great impact on the development of shielding power of D45-T5 compared with OPC; the linear attenuation coefficient (mu) values were enhanced from 0.127 +/- 0.003 cm(-1) to 0.199 +/- 0.007 cm(-1) at 661.6 Kev and from 0.118 +/- 0.003 cm(-1) to 0.144 +/- 0.005 cm(-1) at 1332.5 Kev. The unique properties of specimens containing the anatase phase may be attributed to the fact that the TiO2 may act as a nano-filler and active seeds for the formation of further hydration products such as CSHs, CAHs and CASHs as detected by X-ray diffraction (XRD), thermal analyses techniques (TGA/DSC) and scanning electron microscope (SEM/EDX). TiO2 caused rearrangement of the textural structure of D45-T5 composite to meso pores, as proved by N-2-adsorption/desorption technique. Moreover, the TiO2's tetragonal struc-ture makes it has dosimetric characteristics of high adsorbent for gamma rays

Multifunctional Hybrid Materials Based on Polymers: Design and Performance

Multifunctional hybrid materials based on polymers have already displayed excellent commitment in addressing and presenting solutions to existing demands in priority areas such as the environment, human health, and energy. These hybrid materials can lead to unique superior multifunction materials with a broad range of envisaged applications. However, their design, performance, and practical applications are still challenging. Thus, it is highly advantageous to provide a breakthrough in state-of-the-art manufacturing and scale-up technology to design and synthesize advanced multifunctional hybrid materials based on polymers with improved performance.The main objective of this interdisciplinary book is to bring together, at an international level, high-quality elegant collection of reviews and original research articles dealing with polymeric hybrid materials within different areas such as the following:- Biomaterials chemistry, physics, engineering, and processing;- Polymer chemistry, physics and engineering;- Organic chemistry;- Composites science;- Colloidal chemistry and physics;- Porous nanomaterials science;- Energy storage; and- Automotive and aerospace manufacturing

Cement degradation in CO2 storage sites: a review on potential applications of nanomaterials

© 2018 The Author(s) Carbon capture and sequestration (CCS) has been employed to reduce global warming, which is one of the critical environmental issues gained the attention of scientific and industrial communities worldwide. Once implemented successfully, CCS can store at least 5 billion tons of CO2per year as an effective and technologically safe method. However, there have been a few issues raised in recent years, indicating the potential leakages paths created during and after injection. One of the major issues might be the chemical interaction of supercritical CO2with the cement, which may lead to the partial or total loss of the cement sheath. There have been many approaches presented to improve the physical and mechanical properties of the cement against CO2attack such as changing the water-to-cement ratio, employing pozzolanic materials, and considering non-Portland cements. However, a limited success has been reported to the application of these approaches once implemented in a real-field condition. To date, only a few studies reported the application of nanoparticles as sophisticated additives which can reinforce oil well cements. This paper provides a review on the possible application of nanomaterials in the cement industry where physical and mechanical characteristics of the cement can be modified to have a better resistance against corrosive environments such as CO2storage sites. The results obtained indicated that adding 0.5 wt% of Carbon NanoTubes (CNTs) and NanoGlass Flakes (NGFs) can reinforce the thermal stability and coating characteristics of the cement which are required to increase the chance of survival in a CO2sequestrated site. Nanosilica can also be a good choice and added to the cement by as much as 3.0 wt% to improve pozzolanic reactivity and thermal stability as per the reports of recent studies

Geopolymers in construction - Recent developments

Geopolymers are inorganic materials that result from the alkali activation of aluminosilicates. The aluminosilicates source materials can either occur naturally (e.g. kaolin, metakaolin, rice husk ash, volcanic rock powders) or are produced by industrial processes (e.g. fly-ash, blast furnace slag). While the potential application of geopolymers as construction materials (e.g. concrete manufacturing and soil stabilization) has been studied in the past, their widespread use has been limited. This is mainly because the technology is still relatively new and research in this field is still emerging. However, the use of geopolymers in lieu of conventional binders (e.g. cement and lime) has substantial environmental advantages particularly in terms of the energy expended for their production and greenhouse gas emissions. The current trend to enhance sustainability practices in the construction industry has recently driven research in this area. This paper aims to offer a comprehensive overview of past studies on geopolymers synthesised from various precursors, the factors affecting geopolymerisation process, their microstructural characteristics as well as mechanical, chemical, thermal and environmental properties of geopolymers. Further, recent developments associated with the use of geopolymers as construction materials in civil engineering applications have also been discussed. Research findings show that geopolymers can achieve comparable or superior performance to conventional binders and/or concrete in terms of shear strength and durability but with a reduced environmental footprint

Toxicological profile of calcium carbonate nanoparticles for industrial applications.

Calcium carbonate nanoparticles (CaCO3NPs) derived from CO2 are promising materials for different industrial applications. It is imperative to understand their toxicological profile in biological systems as the human and environmental exposures to CaCO3NPs increases with growing production. Here, we analyse the cytotoxicity of CaCO3NPs synthesized from a CaO slurry on two cell lines, and in vivo on zebrafish (Danio Rerio). Our results demonstrate the CaCO3NPs in vitro safety as they do not cause cell death or genotoxicity. Moreover, zebrafish treated with CaCO3NPs develop without any abnormalities, confirming the safety and biocompatibility of this nanomaterial