scholarly journals Alkaline activation of mortars made from solid construction waste [Activación alcalina de morteros fabricados a partir de residuos sólidos de construcción]

2021 ◽  
Vol 5 (2) ◽  
pp. 79-84
Author(s):  
César Arévalo Aranda ◽  
Segundo Acevedo Zavaleta ◽  
Alexander Vega Anticona
Keyword(s):  
Calcium Hydroxide ◽  
Compression Test ◽  
Alkaline Solution ◽  
Room Temperature ◽  
Buenos Aires ◽  
Coarse Sand ◽  
Recycled Concrete ◽  
Mix Design ◽  
Cement Mortars ◽  
Sieving Process

In the present investigation the influence of the percentage by weight of replacement of portland cement (PC) by recycled concrete powder (RCP), alkaline activated, in percentages of 10%, 20%, 30%, 40% and 50%, was evaluated. which were selected from construction rubble left in the Buenos Aires spa, Víctor Larco Herrera district, Trujillo province. After being washed, they went to the grinding and sieving process (400 mesh), using only the through material. Specimens were manufactured according to the ASTM C-109 standard for the compression test in cement mortars, for the alkaline solution NaOH (4M) was used. The mortars obtained were cured in an oven at 70 ° C for 72 hours, and subsequently the curing was completed at room temperature, for a total time of 28 days. The results of the average compression test were 12.15 MPa, in the case of the PC mortar and 14.25 MPa in the best case (PC mortar and RCP-10%), the increase being 17.28%. The mix design using coarse sand and binder was kept constant at (3: 1), while the water / cement ratio (w / c) was 0.6 in all cases. The reason for the increase in compressive strength is due to the reaction between the RCP particles, alkaline solution and the calcium hydroxide produced during the hydration of the cement particles, which generate gels (CASH), which occupy the spaces left by the hydration process of the aforementioned cement particles, as they need calcium hydroxide. For all cases of the compression test, a total of 10 repetitions were carried out.

Enhanced Thermal Stability of Esterified Lignin in Different Solvent Mediums

2018 ◽  
Vol 9 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Sharifah Nurul Ain Syed Hashim ◽  
Sarani Zakaria ◽  
Chin Hua Chia ◽  
Sharifah Nabihah Syed Jaafar
Keyword(s):  
Thermal Stability ◽  
Alkaline Solution ◽  
Room Temperature ◽  
Hydroxyl Groups ◽  
Aqueous Alkaline Solution ◽  
Alkali Lignin ◽  
Weight Percentage ◽  
H Nmr ◽  
Ft Ir ◽  
Thermal Stability Of

In this study, soda alkali lignin from oil palm empty fruit bunch (EFB-AL) and kenaf core (KC-AL) are esterified with maleic anhydride under two different conditions, namely i) pyridine at temperature of 120°C for 3h and ii) aqueous alkaline solution at room temperature for 4h. As a result, the weight percentage gain (WPG) of the esterified EFB-AL (EFB-EL) and esterified KC-AL (KC-EL) in pyridine demonstrated a higher compared to aqueous alkaline solution. The FT-IR results of EFB-EL and KC-EL in both solvents exhibited some changes at the carbonyl and hydroxyl groups. Furthermore, the esterification process induced the carboxylic peak to appear in both alkali lignin samples. The outcome is confirmed by conducting H-NMR analysis, which demonstrated ester and carboxylic acid peaks within the spectral analysis. Finally, the TGA results showed both EFB-EL and KC-EL that are exposed to aqueous alkaline actually possessed better thermal stability and higher activation energy (Ea) compared to the esterified samples in pyridine.

Microscopic Analysis and Study of High-Performance Seawater All-Coral Concrete

2019 ◽  
Vol 815 ◽  
pp. 216-222
Author(s):  
Chao Chen ◽  
Jin Ming Liu ◽  
Yang Yang ◽  
Zhi Guo Guo
Keyword(s):  
Mechanical Properties ◽  
Natural Environment ◽  
High Performance ◽  
Work Performance ◽  
Room Temperature ◽  
Microscopic Analysis ◽  
Internal Curing ◽  
Mix Design ◽  
Binder Ratio ◽  
Water To Binder Ratio

The ocean islands are far from inland and the concrete sandstone aggregates are scarce. In this paper, high-performance seawater all-coral concrete was developed by seawater mixing and room temperature maintenance design, and by optimizing the water-to-binder ratio, regulating internal curing, changing auxiliary cementing materials and blending ratio, incorporating expansion agent, adjusting fiber blending, etc. Combined with the consideration of work performance and mechanical properties, the concrete self-shrinkage is adjusted to further optimize the mix design. The mechanical properties of the optimized high-performance seawater all-coral concrete were studied, and the relevant durability tests were carried out according to the natural environment characteristics of the island. This is of great significance to the construction of island projects, repair and construction, and construction of protective projects [1].

Structural Concrete with Recycled Aggregate: Advances in Mechanical Properties, Durability and Sustainability

2016 ◽  
Vol 847 ◽  
pp. 553-558 ◽  
Author(s):  
Marc Antonio Liotta ◽  
Marco Viviani ◽  
Carlotta Rodriquez
Keyword(s):  
Cement Mortar ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Mix Design ◽  
Elastic Behavior ◽  
Structural Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Ordinary Concrete

A large number of tests has been carried out in the last 15 years all around the world to study the possibility to use recycled concrete aggregates (RCA) to produce structural concrete.Earlier tests indicated that RCA concrete had lower properties in comparison to ordinary concrete, such as lower elastic modulus, a more brittle post-elastic behavior, lower workability, higher shrinkage and creep.Most of these issues have been addressed to the content of cement mortar remaining in adhesion to the aggregate after the recycling processes and that cannot be totally eliminated without high economic and ecological costs. This cement mortar which has undergone the crushing process creates zones of weakness in the RCA, causes higher water absorption, higher concrete porosity and causes the decay of the aforementioned properties.More recent tests prove that Recycled Concrete shows this peculiar problems only with a percentage of substitution of standard aggregates with RCA higher than 30%. Under this percentage recycled aggregate concrete (RAC) can be considered as a standard concrete, on condition that an appropriate mix design is performed.

scholarly journals An Alternative Process for Leaching Chalcopyrite Concentrate in Nitrate-Acid-Seawater Media with Oxidant Recovery

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 518 ◽  
Author(s):  
César I. Castellón ◽  
Pía C. Hernández ◽  
Lilian Velásquez-Yévenes ◽  
María E. Taboada
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Alkaline Solution ◽  
Sodium Nitrite ◽  
Sodium Nitrate ◽  
Room Temperature ◽  
Leaching Test ◽  
Copper Concentrate ◽  
Leaching Process ◽  
Chalcopyrite Concentrate

An alternative copper concentrate leaching process using sodium nitrate and sulfuric acid diluted in seawater followed by gas scrubbing to recover the sodium nitrate has been evaluated. The work involved leaching test carried out under various condition by varying temperature, leaching time, particle size, and concentrations of NaNO3 and H2SO4. The amount of copper extracted from the chalcopyrite concentrate leached with seawater, 0.5 M of H2SO4 and 0.5 M of NaNO3 increased from 78% at room temperature to 91% at 45 °C in 96 h and 46 h of leaching, respectively. Gas scrubbing with the alkaline solution of NaOH was explored to recover part of the sodium nitrate. The dissolved salts were recovered by evaporation as sodium nitrate and sodium nitrite crystals.

scholarly journals In vitro antimicrobial activity of different gutta-percha points and calcium hydroxide pastes

2007 ◽  
Vol 21 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Juliane Maria Guerreiro Tanomaru ◽  
Fernanda Geraldes Pappen ◽  
Mário Tanomaru Filho ◽  
Denise Madalena Palomari Spolidorio ◽  
Izabel Yoko Ito
Keyword(s):  
Antimicrobial Activity ◽  
Calcium Hydroxide ◽  
Staphylococcus Epidermidis ◽  
Room Temperature ◽  
Statistical Evaluation ◽  
Micrococcus Luteus ◽  
Triphenyltetrazolium Chloride ◽  
Gutta Percha ◽  
Zones Of Inhibition

The aim of this study was to evaluate the antimicrobial activity of different trademarks and compositions of gutta-percha points and calcium hydroxide pastes used in endodontic therapy. The evaluated material consisted of gutta-percha points containing calcium hydroxide (RoekoTM), gutta-percha points containing chlorhexidine (RoekoTM), two convencional gutta-percha points (Endo PointsTM and RoekoTM) and two calcium hydroxide pastes (CalenTM and Calen/PMCC TM). Antimicrobial tests included five species of microorganisms: Escherichia coli (ATCC10538), Staphylococcus epidermidis (ATCC12228), Staphylococcus aureus (ATCC6538), Pseudomonas aeruginosa (ATCC27853), and Micrococcus luteus (ATCC9341). The Agar difusion method was employed. The plates were kept at room temperature for 2 h for prediffusion and then incubated at 37°C for 24 h. The triphenyltetrazolium chloride gel was added for optimization and the zones of inhibition were measured. Statistical evaluation was carried out using analysis of variance and Tukey Test. The obtained results showed that all microbial species used in the study were inhibited by the gutta-percha points containing chlorhexidine and by the calcium hydroxide pastes (CalenTM and Calen/PMCC TM), with similar results (p > 0.05). No antimicrobial activity was observed for the other groups. It was concluded that the gutta-percha points containing chlorhexidine presented antimicrobial activity, whereas the gutta-percha points containing calcium hydroxide did not.

Precursors Influence on CaCu3Ti4O12 Synthesis

2012 ◽  
Vol 727-728 ◽  
pp. 1313-1316 ◽  
Author(s):  
Maria Virginia Gelfuso ◽  
Gabriel Moreira Lima ◽  
Daniel Thomazini
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Dielectric Constant ◽  
Calcium Carbonate ◽  
Calcium Hydroxide ◽  
Room Temperature ◽  
Microstructural Analysis ◽  
Copper Nitrate ◽  
N Powder ◽  
Scanning Electron

In this work CCTO have been synthesized in two different chemical precursors: calcium hydroxide and copper sulfate were used to compose CCTO-S powder while calcium carbonate and copper nitrate were used to form CCTO-N powder. Calcinations conditions were dramatically different in terms of shelf time and temperature. The CCTO phase was fully obtained for 3 hours of calcination in CCTO-N against the 24 hours to form the same phase in CCTO-S powder. Ceramic bodies densities values for CCTO-S samples were 95% of theoretical density (5.05 g/cm3) and 98% for CCTO-N. The dielectric constant, at room temperature, was obtained for ceramics processed by two routes. Microstructural analysis was conducted by Scanning Electron Microscopy (SEM) and it was performed to explain the dielectric constant differences between CCTO-S and CCTO-N ceramics.

Study of Carbonizing Processes for Sintered Dolomite

2007 ◽  
Vol 336-338 ◽  
pp. 2552-2555 ◽  
Author(s):  
Jing Hua Xue ◽  
Min Fang Han ◽  
Qing Yun Wang
Keyword(s):  
Calcium Carbonate ◽  
Calcium Hydroxide ◽  
Magnesium Hydroxide ◽  
Room Temperature ◽  
Xrd Analysis ◽  
Magnesium Carbonate ◽  
Crystal Phase ◽  
Carbonization Process

It is the easy and widely used way to make light calcium carbonate and magnesium carbonate from dolomite by carbonizing process. During this process, the dolomite is calcined at different temperature, from 700°C to 950°C to get the mixture including either calcium carbonate and magnesia or calcia and magnesia. Then the mixture is blended with water in different temperature from room temperature to 80°C. As a result, it is supposed to get calcium hydroxide and magnesium hydroxide, but XRD analysis reveals that it is not accord with the theory. Magnesium hydroxide can not be obtained during this reaction. After the carbonization process, the calcium carbonate and a kind of mixture which is composed with different crystal phase of Mg5(CO3)4(OH)2[H2O]4 have been produced, instead of magnesium carbonate. The magnesia is gotten when the mixture is calcined at 450~750°C.

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