scholarly journals Influence of cement type, air-entrained admixture and hydration stabilizing admixture on mortars’ setting time

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Juliana Pippi Antoniazzi ◽  
Gihad Mohamad ◽  
Juliana Machado Casali
Keyword(s):  
Setting Time ◽  
Adiabatic Calorimeter ◽  
Cement Type ◽  
Long Period ◽  
Setting Times

ABSTRACT: Ready mix mortar is a ready to use mixture that uses hydration stabilizing (HSA) and air-entrained (AEA) admixtures in its composition, which modify its properties, especially the setting times. HSA extends the setting time of mortars for a long period, while AEA promotes a greater workability to the mixture. The study determined the temperature of the mortars with the evaluation of the setting times obtained by a semi-adiabatic calorimeter. Two types of cement (CPII-F-40 e CPII-Z-32) and varied contents of HSA (0.0%, 0.6% e 0.9%) and AEA (0.0%, 0.2% e 0.4%) were used. The results showed that the use of HSA decreased the amplitude of the temperature peaks and increased the setting times with cement CPII-Z-32 in relation to cement CPII-F-40. The setting time of the mortars was influenced by the type of cement used and by the contents of the admixtures.

scholarly journals Effect of Gold Nanoparticles and Silicon on the Bioactivity and Antibacterial Properties of Hydroxyapatite/Chitosan/Tricalcium Phosphate-Based Biomicroconcretes

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3854
Author(s):  
Joanna Czechowska ◽  
Ewelina Cichoń ◽  
Anna Belcarz ◽  
Anna Ślósarczyk ◽  
Aneta Zima
Keyword(s):  
Gold Nanoparticles ◽  
Antibacterial Activity ◽  
Tricalcium Phosphate ◽  
Setting Time ◽  
Antibacterial Properties ◽  
Bone Substitutes ◽  
Bacterial Strains ◽  
Setting Times ◽  
Biological Studies

Bioactive, chemically bonded bone substitutes with antibacterial properties are highly recommended for medical applications. In this study, biomicroconcretes, composed of silicon modified (Si-αTCP) or non-modified α-tricalcium phosphate (αTCP), as well as hybrid hydroxyapatite/chitosan granules non-modified and modified with gold nanoparticles (AuNPs), were designed. The developed biomicroconcretes were supposed to combine the dual functions of antibacterial activity and bone defect repair. The chemical and phase composition, microstructure, setting times, mechanical strength, and in vitro bioactive potential of the composites were examined. Furthermore, on the basis of the American Association of Textile Chemists and Colorists test (AATCC 100), adapted for chemically bonded materials, the antibacterial activity of the biomicroconcretes against S. epidermidis, E. coli, and S. aureus was evaluated. All biomicroconcretes were surgically handy and revealed good adhesion between the hybrid granules and calcium phosphate-based matrix. Furthermore, they possessed acceptable setting times and mechanical properties. It has been stated that materials containing AuNPs set faster and possess a slightly higher compressive strength (3.4 ± 0.7 MPa). The modification of αTCP with silicon led to a favorable decrease of the final setting time to 10 min. Furthermore, it has been shown that materials modified with AuNPs and silicon possessed an enhanced bioactivity. The antibacterial properties of all of the developed biomicroconcretes against the tested bacterial strains due to the presence of both chitosan and Au were confirmed. The material modified simultaneously with AuNPs and silicon seems to be the most promising candidate for further biological studies.

Behaviour of Calcium Alkali Orthophosphate Cements under Simulated Implantation Conditions

2008 ◽  
Vol 396-398 ◽  
pp. 213-216 ◽  
Author(s):  
Daniela Jörn ◽  
Renate Gildenhaar ◽  
Georg Berger ◽  
Michael Stiller ◽  
Christine Knabe
Keyword(s):  
Compressive Strength ◽  
Simulated Body Fluid ◽  
Clinical Application ◽  
Body Fluid ◽  
Setting Time ◽  
Great Decrease ◽  
Final Setting Time ◽  
Laboratory Conditions ◽  
Setting Times

The setting behaviour, the compressive strength and the porosity of four calcium alkali orthophosphate cements were examined under laboratory conditions (dry) and under conditions similar to those during clinical application (37°C, contact with body fluid). The results showed an increase of the setting times when specimens were covered with simulated body fluid. Especially, the final setting time (FHZ) was significantly higher for three of the four cements. Furthermore, when specimens were stored in SBF for 16h, an extensive decrease of the compressive strength was noted. The porosity was more than twice as high after 16h in SBF and this may be the cause for the great decrease of the compressive strength.

scholarly journals Properties of Degraded Waste PET-Modified Styrene-Acrylic Emulsions for Cement Slurry Materials

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jinxi Dou ◽  
Guijin Zhang ◽  
Sufang Li ◽  
Chengyu Tian ◽  
Cunlu Ji ◽  
...  
Keyword(s):  
Water Consumption ◽  
Water Retention ◽  
Retention Rate ◽  
Setting Time ◽  
Reduction Rate ◽  
Cement Slurry ◽  
Acrylic Emulsion ◽  
Water Reduction ◽  
Setting Times ◽  
Lower Permeability

The properties of a modified cement slurry based on degraded waste PET-modified styrene-acrylic emulsions are studied. The effects of the modified styrene-acrylic emulsion on water consumption, setting time, retarding effect, water retention, impermeability, and mechanical properties of the cement slurry are comprehensively studied. The results show that the modified styrene-acrylic emulsion has the following impacts on the cement slurry: it significantly reduces the water consumption required to reach a standard consistency, slows down the initial and final setting times, and greatly improves the water retention rate and water reduction rate. When the content of modified styrene-acrylic emulsion is 7.5%, the water reduction rate is 36% and the water retention rate is 97%. The solidified cement slurry with a modified styrene-acrylic emulsion content less than 7.5% has lower permeability and higher flexural strength than a common cement slurry. The compressive strength is reduced but can still reach required values. According to SEM observations, the modified styrene-acrylic emulsion can enhance the bonding strength between the cement particles, reduce the porosity of the structure, and improve the performance of cement-based composites.

Effect of Calcined Red Mud Addition on the Hydration of Portland Cement

2012 ◽  
Vol 727-728 ◽  
pp. 1408-1411 ◽  
Author(s):  
Daniel Véras Ribeiro ◽  
João A. Labrincha ◽  
Márcio Raymundo Morelli
Keyword(s):  
Portland Cement ◽  
Red Mud ◽  
Setting Time ◽  
Cementitious Materials ◽  
Adiabatic Calorimeter ◽  
Hydration Process ◽  
Early Hydration ◽  
Bauxite Ore ◽  
Calorimetric Studies ◽  
Reference Mixture

The red mud (RM) is a solid waste derived from the processing of bauxite ore to produce alumina and it is considered a hazardous waste due to its high pH. This paper describes the use of mud untreated and after calcination at distinct temperatures (450, 650, and 1000°C) attempting to improve its reactivity. The Portland cement was replaced up to 30 wt% red mud, and its addition changed the hydration process, evaluated by calorimetric studies of early hydration and setting time. By comparing with the reference mixture (without red mud), the obtained results confirm the potential of the red mud to be used as pozzolanic additive to cementitious materials. Temperature of hydration was monitored by a quasi-adiabatic calorimeter (Langavant). The hydration temperature increases with RM addition, particularly if calcined in the same interval (450-650°C). In this condition, the hydration process is accelerated.

Preparation of Calcium Phosphate Cement Utilizing Dicalcium Phosphate Dihydrate and Calcium Carbonate

2014 ◽  
Vol 608 ◽  
pp. 280-286
Author(s):  
Nudthakarn Kosachan ◽  
Angkhana Jaroenworaluck ◽  
Sirithan Jiemsirilers ◽  
Supatra Jinawath ◽  
Ron Stevens
Keyword(s):  
Calcium Carbonate ◽  
Calcium Phosphate ◽  
Calcium Phosphate Cement ◽  
Raw Materials ◽  
Setting Time ◽  
Dicalcium Phosphate ◽  
Dicalcium Phosphate Dihydrate ◽  
Cement Pastes ◽  
Setting Times ◽  
Phosphate Dihydrate

Calcium phosphate cement has been widely used as a bone substitute because of its chemical similarity to natural bone. In this study, calcium phosphate cement was prepared using dicalcium phosphate dihydrate (CaHPO4.2H2O) and calcium carbonate (CaCO3) as starting raw materials. The cement pastes were mixed and the chemistry adjusted with two different aqueous solutions of sodium hydroxide (NaOH) and disodium hydrogen phosphate (Na2HPO4). Concentrations of the solution were varied in the range 0.5 to 5.0 mol/L with the ratio of solid/liquid = 2 g/ml. The cement paste was then poured into a silicone mold having a diameter of 10 mm and a height 15 mm. Setting times for the cement were measured using a Vicat apparatus. XRD, FT-IR, and SEM techniques were used to characterize properties and microstructure of the cement. From the experimental results, it is clear that different concentrations of Na2HPO4 and NaOH have affected the setting times of the cement. The relationship between concentration of NaOH and Na2HPO4 and setting time, including final properties of the cement, is discussed.

Effect of Anhydrite on the Early Hydration Performance of Rapid Setting and Hardening Belite Sulfoaluminate Cement

2017 ◽  
Vol 898 ◽  
pp. 1990-1995 ◽  
Author(s):  
Ming Zhang Lan ◽  
Bin Feng Xiang ◽  
Jian Feng Wang ◽  
Xu Dong Zhao ◽  
Xiao Ying Wang
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
High Strength ◽  
Cement Clinker ◽  
Hydration Kinetics ◽  
Early Hydration ◽  
Free Lime ◽  
Calcium Sulfoaluminate ◽  
Setting Times ◽  
Rapid Setting

In order to investigate the early hydration behavior of rapid setting and hardening belite sulfoaluminate cements, the methods of X-ray Diffraction, Scanning Electron Microscope, Compressive Strength test and Setting Times test were used to identify and quantify the hydration kinetics and microstructure of this new-found cements in China. The results showed that the main mineral compositions of high belite sulfoaluminate cement clinker included calcium sulfoaluminate (4CaO·3Al2O3·CaSO4), belite (2CaO·SiO2), ferrite phase, free gypsum and free lime. It was found that not only the setting time and compressive strength but also the composition of hydration products were influenced by anhydrite to some extent. Meanwhile, a mass of AFt and AFm generated along with the hydration process at different ages, overlapped, crossed and penetrated through calcium silicate hydrate gel and aluminum oxide to form a relatively dense structure which could contribute to the high strength of cement.

scholarly journals Effect of Copolymer Latexes on Physicomechanical Properties of Mortar Containing High Volume Fly Ash as a Replacement Material of Cement

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
El-Sayed Negim ◽  
Latipa Kozhamzharova ◽  
Yeligbayeva Gulzhakhan ◽  
Jamal Khatib ◽  
Lyazzat Bekbayeva ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
High Volume ◽  
Physicomechanical Properties ◽  
Partial Replacement ◽  
Setting Times ◽  
High Volume Fly Ash ◽  
Scanning Electron

This paper investigates the physicomechanical properties of mortar containing high volume of fly ash (FA) as partial replacement of cement in presence of copolymer latexes. Portland cement (PC) was partially replaced with 0, 10, 20, 30 50, and 60% FA. Copolymer latexes were used based on 2-hydroxyethyl acrylate (2-HEA) and 2-hydroxymethylacrylate (2-HEMA). Testing included workability, setting time, absorption, chemically combined water content, compressive strength, and scanning electron microscopy (SEM). The addition of FA to mortar as replacement of PC affected the physicomechanical properties of mortar. As the content of FA in the concrete increased, the setting times (initial and final) were elongated. The results obtained at 28 days of curing indicate that the maximum properties of mortar occur at around 30% FA. Beyond 30% FA the properties of mortar reduce and at 60% FA the properties of mortar are lower than those of the reference mortar without FA. However, the addition of polymer latexes into mortar containing FA improved most of the physicomechanical properties of mortar at all curing times. Compressive strength, combined water, and workability of mortar containing FA premixed with latexes are higher than those of mortar containing FA without latexes.

Mechanical Strength Improvement of Apatite Cement Using Hydroxyapatite/Collagen Nanocomposite

2016 ◽  
Vol 720 ◽  
pp. 167-172 ◽  
Author(s):  
Arief Cahyanto ◽  
Kanji Tsuru ◽  
Kunio Ishikawa ◽  
Masanori Kikuchi
Keyword(s):  
Fracture Surface ◽  
Mechanical Strength ◽  
Setting Time ◽  
Control Group ◽  
Scanning Electron Micrographs ◽  
Setting Times ◽  
Apatite Cement ◽  
Xrd Patterns ◽  
Mechanical Strengths ◽  
Scanning Electron

The combination of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) which are known as one system of apatite cements already used in the medical and dental application. In spite of several advantages of apatite cements, such as self-setting ability and biocompatibility, their mechanical strengths are still low. The aim of this study is to improve the mechanical strength of the TTCP-DCPA apatite cement using the hydroxyapatite/collagen nanocomposite (HAp/Col). The apatite cement powder was prepared using an equimolar TTCP and DCPA with addition of 10% and 20% of the HAp/Col. That without the HAp/Col was used as a control group. Each group was mixed with 1 mol/L Na1.8H1.2PO4 aqueous solution at powder/liquid ratio of 0.5 and hardened at 37°C and 100 % of relative humidity for 24 hours. A setting time of the cement was evaluated using Vicat needle according to ISO 1566 for dental zinc phosphate cements. Morphology of the cements set were observed by the scanning electron microscopy (SEM), and crystalline phases were identified by the powder X-Ray diffractometry (XRD). The mechanical strength of the cement set was evaluated by the diametral tensile strength (DTS). The setting times of cements were the shortest for the cement with HAp/Col and the longest for the control. XRD patterns of the cement at 24 hours after mixing revealed that all cements changed into apatite from the mixture of TTCP and DCPA. The DTSs of cements were the highest for the cement with 20% HAp/Col and the lowest for the control with significant differences between the cement with 20 % HAp/Col and respective other two cements. The scanning electron micrographs of the surface and fracture surface of the cements suggested that the cement with HAp/Col showed denser structure in comparison to the control and the HAp/Col fibers and/or sheets covered the fracture surface. The HAp/Col would act as reinforcement fibers as well as an adhesive of apatite granules formed by the reaction between TTCP and DCPA. The setting time and mechanical strength of apatite cement was statistically significant improved by adding 20% HAp/Col.

The Preparation and Performance Research of the Desulphurization Gypsum Plaster Material

2013 ◽  
Vol 327 ◽  
pp. 32-35
Author(s):  
Huan Qi Zhao ◽  
Guo Zhong Li
Keyword(s):  
Citric Acid ◽  
Negative Impact ◽  
Setting Time ◽  
Sodium Hexametaphosphate ◽  
Moderate Amount ◽  
Setting Times ◽  
Gypsum Plaster ◽  
And Performance ◽  
Cementing Material ◽  
Performance Research

The cementing material is the desulfurization gypsum. The fly ash is a admixture. A moderate amount of additive is mixed. A gypsum plaster material of micro swelling and good workability, plasticity was produced. The representative two retarders, the sodium hexametaphosphate and the citric acid, were researched. The effects of the retarders on the setting times and the mechanical properties of the desulfurization gypsum were studied. The retarding effect of the citric acid is the most prominent, but its negative impact on the flexural and compressive strength of the plaster gypsum is very large. Considering the setting time and the strength, the sodium hexametaphosphate is the best retarder of the desulfurization gypsum plaster material.

Preparation and Characterization of Silk Fibroin/Calcium Phosphate Composite

2011 ◽  
Vol 332-334 ◽  
pp. 1655-1658
Author(s):  
Biao Wang ◽  
Rui Juan Xie ◽  
Yang Yang Huang
Keyword(s):  
Compressive Strength ◽  
Calcium Phosphate ◽  
Silk Fibroin ◽  
Solid Phase ◽  
Setting Time ◽  
Testing Machine ◽  
X Ray Diffraction ◽  
Acicular Crystal ◽  
Setting Times

In this paper, calcium phosphate cement (CPC) was prepared with tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) system as solid phase and phosphate buffered solution (PBS) as liquid phase, then silk fibroin (SF) was added into CPC to form silk fibroin/calcium phosphate composite. To study the effect of SF on the properties of composite, different mass fraction of SF was added into the composite. The surface morphology was observed by Scanning Electron Microscope. The setting time was investigated by ISO Cement Standard Consistency Instrument. The structure of the composite was studied by X-ray diffraction and infrared spectroscopy. Mechanical properties of samples were tested by Instron Universal Testing Machine. The results showed that the particles of SF could be seen obviously in the surface of all composite, and acicular crystal of hydroxyapatite (HA) was formed in the hardening body of both the composite and the pure CPC. The acicular crystal of HA derived from composite with SF appeared to be thinner. The setting times of the composites were all between 9 to 15min. Compared to pure CPC, the compressive strength and work-of-compressive of composites were all improved. The compressive strength of the composite with 1% SF increased obviously.

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