Interactions of Biobased Rheology Modifying Agents with Superplasticizer in Cement Paste

2022 ◽  
Author(s):  
Alexander Mezhov ◽  
Kun Zhang ◽  
Wolfram Schmidt
Keyword(s):  
Built Environment ◽  
Cement Paste ◽  
Cement Hydration ◽  
Performance Enhancement ◽  
Environmentally Friendly ◽  
Molecular Structures ◽  
Cement Pastes ◽  
Joint Application ◽  
Different Types

Organic admixtures are an indispensable component of modern concrete. Thus, their purposeful application is not only technically and economically viable but in addition an inevitable tool to make concrete more environmentally friendly. In this context, the use of polysaccharides has increasingly gained interest in the built environment as sustainable resource for performance enhancement. However, due to its origin, biopolymers possess a vast variety of molecular structures which can result in incompatibilities with other polymers present in concrete, such as superplasticizers. The present study highlights effects of the joint application of different types of starches and polycarboxylates with respect to their influence on cement hydration and structural build-up of cement pastes.

Test Methods for Rheological Properties of Self-Compacting Concrete Pastes

2011 ◽  
Vol 338 ◽  
pp. 396-400
Author(s):  
Bao Guo Ma ◽  
Hui Xian Wang ◽  
Jian Huang ◽  
Liu Qing Song
Keyword(s):  
Rheological Properties ◽  
Cement Paste ◽  
Test Methods ◽  
General Study ◽  
Self Compacting Concrete ◽  
Cement Pastes ◽  
Different Types ◽  
Over Time

This paper provides a general study on cement paste flow which derived from self- compacting concretes. Rheometer, Marsh cone and mini-slump cone were used to evaluate fluidity of cement pastes containing superplasticizers of different types and dosages and loss of fluidity over time. There is a superplasticizer saturation dosage beyond which no significant fluidity increase can be found. This paper evaluated the effect of these three methods using rheometer as control and the optimum superplasticizer type for the preparation of self-compacting concrete was suggested.

Hydration of Cement in the Presence of SBR Dispersion and Powder

2011 ◽  
Vol 466 ◽  
pp. 57-63 ◽  
Author(s):  
Ru Wang ◽  
Pei Ming Wang
Keyword(s):  
Polymer Film ◽  
Cement Paste ◽  
Cement Hydration ◽  
Thin Polymer Film ◽  
Cement Pastes ◽  
Thin Polymer ◽  
Significant Difference ◽  
The Stability

Hydration of cement in the presence of SBR dispersion and powder respectively was investigated using the methods of ITC, XRD and ESEM. The results show that both the dispersion and powder of SBR facilitate the formation, enhance the stability of AFt and inhibit the formation of C4AH13 in cement paste; the effect of the powder is more evident than the dispersion. Both the dispersion and powder of SBR delay the formation of C-S-H and Ca(OH)2 in cement paste, and the effect of the dispersion is more evident. Up to 3 days, the structure of the SBR dispersion – or powder – modified cement pastes has no significant difference with that of control paste except due to a thin polymer film on the surface. The two polymers delay the early cement hydration, but have no significant effect after 3 days.

Hydration and Microstructure of Nano Modified Cement Paste

2021 ◽  
Vol 321 ◽  
pp. 9-14
Author(s):  
Gintautas Skripkiūnas ◽  
Ekaterina Karpova ◽  
Rostislav Drochytka ◽  
Jakub Hodul
Keyword(s):  
Cement Paste ◽  
Cement Hydration ◽  
Aqueous Suspension ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Microstructure Observation ◽  
Multi Walled Carbon Nanotubes ◽  
Hardened Cement Pastes ◽  
Walled Carbon Nanotubes

Hydration of cement systems modified by nano additives requires the understanding of its mechanisms. The present research is focused on the investigation of hydration processes in cement pastes modified by multi-walled carbon nanotubes (MWCNTs) suspension. The ultrasonication method was used for homogenization of MWCNTs in the volume of an aqueous suspension. The hydration of cement pastes was assessed by the calorimetry test. The prolongation of cement hydration in case of modification by MWCNT suspension was observed. The microstructure observation by scanning electron microscopy (SEM) was performed for identification of MWCNT's dispergation in hardened cement pastes and for the observation of cement hydration products. The compressive and flexural strength were tested to evaluate the effect of MWCNT on mechanical properties of hardened cement paste.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

scholarly journals Highly efficient reusable superhydrophobic sponge prepared by a facile, simple and cost effective biomimetic bonding method for oil absorption

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiaqi Wang ◽  
Yan Chen ◽  
Qinyao Xu ◽  
Miaomiao Cai ◽  
Qian Shi ◽  
...  
Keyword(s):  
Environmentally Friendly ◽  
Absorption Capacity ◽  
Oil Absorption ◽  
Water Contact ◽  
Water Separation ◽  
Highly Efficient ◽  
Study Results ◽  
Different Types ◽  
Modification Method ◽  
Bonding Method

AbstractSuperhydrophobic sponges have considerable potential for oil/water separation. Most of the methods used for superhydrophobic modification of sponges require toxic or harmful solvents, which have the drawbacks of hazardous to environment, expensive, and complex to utilize. Moreover, the hydrophobic layer on the surface of sponge is often easily destroyed. In this paper, a highly efficient superhydrophobic sponge with excellent reusability was developed by using a facile, simple and environmentally friendly dopamine biomimetic bonding method. Different types of sponges, such as melamine, polyethylene or polyurethane sponge wastes, were used as raw materials to prepare superhydrophobic sponges, which possess the advantages of inexpensive and abundant. The effects of different dopamine polymerization time and different hydrophobic agent dosage on the hydrophobicity and oil absorption capacity of melamine sponges were optimized. The study results showed that the water contact angle of the superhydrophobic sponge could reach 153° with excellent organic solvent absorption capacity of 165.9 g/g. Furthermore, the superhydrophobic sponge retained approximately 92.1% of its initial absorption capacity after 35 reutilization cycles. More importantly, the dopamine biomimetic bonding superhydrophobic modification method can be used for different types of sponges. Therefore, a universally applicable, facile, simple and environmentally friendly superhydrophobic modification method for sponges was developed.

scholarly journals Mechanical and Microstructural Characteristics of Calcium Sulfoaluminate Cement Exposed to Early-Age Carbonation Curing

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3515
Author(s):  
Weikang Wang ◽  
Xuanchun Wei ◽  
Xinhua Cai ◽  
Hongyang Deng ◽  
Bokang Li
Keyword(s):  
Cement Paste ◽  
Pore Diameter ◽  
Performance Enhancement ◽  
Diameter Distribution ◽  
Early Age ◽  
Calcium Sulfoaluminate ◽  
Starting Point ◽  
And Performance ◽  
Curing Pressure ◽  
Carbonation Curing

: The early-age carbonation curing technique is an effective way to improve the performance of cement-based materials and reduce their carbon footprint. This work investigates the early mechanical properties and microstructure of calcium sulfoaluminate (CSA) cement specimens under early-age carbonation curing, considering five factors: briquetting pressure, water–binder (w/b) ratio, starting point of carbonation curing, carbonation curing time, and carbonation curing pressure. The carbonization process and performance enhancement mechanism of CSA cement are analyzed by mercury intrusion porosimetry (MIP), thermogravimetry and derivative thermogravimetry (TG-DTG) analysis, X-ray diffraction (XRD), and scanning electron microscope (SEM). The results show that early-age carbonation curing can accelerate the hardening speed of CSA cement paste, reduce the cumulative porosity of the cement paste, refine the pore diameter distribution, and make the pore diameter distribution more uniform, thus greatly improving the early compressive strength of the paste. The most favorable w/b ratio for the carbonization reaction of CSA cement paste is between 0.15 and 0.2; the most suitable carbonation curing starting time point is 4 h after initial hydration; the carbonation curing pressure should be between 3 and 4 bar; and the most appropriate time for carbonation curing is between 6 and 12 h.

Quantitative Characterization of Hydration of Cement Pastes by Rietveld Phase Analysis and Thermoanalysis

2013 ◽  
Vol 539 ◽  
pp. 19-24 ◽  
Author(s):  
Yong Qi Wei ◽  
Wu Yao
Keyword(s):  
Phase Analysis ◽  
Cement Paste ◽  
Rietveld Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Quantitative Characterization ◽  
Cement Pastes ◽  
Hydration Mechanism ◽  
Spot Check

The quantitative characterization of hydration of cement pastes has always been one of focuses of researchers’ attention. Rietveld phase analysis (RPA), a combination of quantitative X-ray diffraction (QXRD) and the Rietveld method, supplies a tool of an enormous potential for that. Although a few of related researches were conducted by RPA, the reported attention was not paid to the neat cement paste with a low w/c ratio. Therefore, this work aimed at the quantitative study on hydration of such a cement paste chiefly by this method, meanwhile, cooperated with the hyphenated technique of thermogravimetry with differential scanning calorimetry (TG-DSC), as a spot check. Results indicated that RPA was a reliable method in quantitatively characterizing hydration of cement pastes, and gave a clear decription of evolution of all main crystal phases in cement pastes; and that the evolution of monosulphate(Afm_12) was also able to be tracked quantitatively. This will help to understand better the hydration mechanism of cement pastes, as well as to investigate quantitatively effects of mineral and chemical admixtures on hydration of composite cementitious systems.

Assessment of Hydration Degree of Cement in the Fly Ash-Cement Pastes Based on the Calcium Hydroxide Content

2014 ◽  
Vol 875-877 ◽  
pp. 177-182 ◽  
Author(s):  
Xiang Li ◽  
Hua Quan Yang ◽  
Ming Xia Li
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Cement Hydration ◽  
Ash Content ◽  
Content Increase ◽  
Hydration Degree ◽  
Equilibrium Calculation ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

scholarly journals The role of graphene/graphene oxide in cement hydration

2021 ◽  
Vol 10 (1) ◽  
pp. 768-778
Author(s):  
Shaoqiang Meng ◽  
Xiaowei Ouyang ◽  
Jiyang Fu ◽  
Yanfei Niu ◽  
Yuwei Ma
Keyword(s):  
Graphene Oxide ◽  
Cement Paste ◽  
Cement Hydration ◽  
Isothermal Calorimetry ◽  
High Mobility ◽  
Nucleation And Growth ◽  
Early Hydration ◽  
Mobility Of Ions ◽  
Cement Surface

Abstract Graphene (G) and graphene oxide (GO) have been shown to significantly improve the mechanical properties of cement-based materials. In this study, the effect of the G/GO on cement hydration was investigated. First, the zeta potential of G/GO in simulated solutions was tested, and the interaction between G/GO’s surface and Ca2+ was explored. Subsequently, scanning electron microscopy was used to observe the morphology of C–S–H nucleation and growth on the cement surface in the cement paste containing G/GO. Furthermore, XRD and TGA analyses were carried out on the hydration products of the sample. At last, isothermal calorimetry was applied to investigate the influence of G/GO on the early hydration of cement. The results showed that the addition of G/GO significantly accelerates C–S–H nucleation and growth on the cement surface. It is indicated that the high mobility ions derived by G/GO in the cement paste dominate the reason for the accelerated hydration of cement. The presence of G, especially GO, facilitates the mobility of ions, especially Ca2+, thus enhances the interaction between the cement surface and the ions. This strong interaction promotes the C–S–H nucleation and growth, and therefore, the hydration of the cement.

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