scholarly journals Investigation of the early-age performance and microstructure of nano-C–S–H blended cement-based materials

2021 ◽  
Vol 10 (1) ◽  
pp. 1374-1382
Author(s):  
Wei He ◽  
Gang Liao
Keyword(s):  
Cement Paste ◽  
Pore Diameter ◽  
Autogenous Shrinkage ◽  
Blended Cement ◽  
Cement Matrix ◽  
Early Age ◽  
Early Hydration ◽  
Characterization Methods ◽  
Gradual Loss ◽  
Cement Based Materials

Abstract Nano calcium silicate hydrate (nano-C–S–H) has become a novel additive for advanced cement-based materials. In this paper, the effect of nano-C–S–H on the early-age performance of cement paste has been studied, and some micro-characterization methods were used to measure the microstructure of nano-C–S–H-modified cement-based material. The results showed that the initial fluidity of cement paste was improved after addition of nano-C–S–H, but the fluidity gradual loss increased with the dosage of nano-C–S–H. The autogenous shrinkage of cement paste can be reduced by up to 42% maximum at an appropriate addition of nano-C–S–H. The mechanical property of cement paste was enhanced noticeably after adding nano-C–S–H, namely, the compressive strengths were improved by 52% and 47.74% at age of 1 day and 7 days, respectively. More hydration products were observed and pore diameter of cement matrix was refined after adding nano-C–S–H, indicating that the early hydration process of cement was accelerated by nano-C–S–H. This was mainly attributed to seed effect of nano-C–S–H. The detailed relationship between microstructure and early-age performance was also discussed.

scholarly journals Effect of Nano-Materials on Autogenous Shrinkage Properties of Cement Based Materials

Symmetry ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1144 ◽  
Author(s):  
Xiaoyan Liu ◽  
Tingchen Fang ◽  
Junqing Zuo
Keyword(s):  
Carbon Nanotubes ◽  
Calcium Carbonate ◽  
Cement Paste ◽  
Reference Group ◽  
Autogenous Shrinkage ◽  
Cement Matrix ◽  
Nano Materials ◽  
Tricalcium Aluminate ◽  
Cement Based Materials ◽  
Water Swelling

This paper presents an experimental investigation on the effect of nano-montmorillonite, carbon nanotubes, and nano calcium carbonate on autogenous shrinkage of cement based materials. Cement paste with different nano-montmorillonite dosage (1.0 wt.%, 2.0 wt.%, 3.0 wt.%), carbon nanotubes dosage (0.1 wt.%, 0.2 wt.%, 0.3 wt.%), and nano calcium carbonate dosage (1.0 wt.%, 2.0 wt.%, 3.0 wt.%) were compared with the reference group to assess the effects of nano-materials on cement paste. Results show that autogenous shrinkage of cement based materials containing nano-materials mainly occurs in the first 72 h. Nano-materials decrease the autogenous shrinkage of the investigated cement based materials at all ages. Compared with that of the reference group at the age of 168 h, the autogenous shrinkage of NM-modified cement based composites containing 3.0 wt.% NM decreased by as much as 57.4%; the autogenous shrinkage of CNTs-modified cement based composites containing 0.3 wt.% CNTs decreased by as much as 19.4%; the autogenous shrinkage of NC-modified cement based composites containing 2.0 wt.% NC decreased by as much as 17.1%. Electrochemical AC (Alternating Current) impedance spectroscopy results show that the resistance of the pore solution electrolyte of specimens containing nano-materials increases with age, and is less than that of specimens without nano-materials, which illustrates that the pore size of nano-modified cement based material is finer and autogenous shrinkage is smaller. Scanning electron microscope results show that the structure of cement matrix is denser with more hydration products by adding nano-materials. Nano-montmorillonite releases water to reduce self-drying effect during the process of hydration for its well water swelling. Carbon nanotubes have the nanometer filling effect and form a continuous network to restrain the early autogenous shrinkage of cement paste. Nano calcium carbonate not only decreases the porosity of the cement paste, but also reacts with tricalcium aluminate to generate the expanded product calcium carboaluminate for compensating autogenous shrinkage of cement paste.

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.

scholarly journals Can the maturity concept be used to separate the autogenous shrinkage and thermal deformation of a cement paste at early age?

2002 ◽  
Vol 32 (9) ◽  
pp. 1443-1450 ◽  
Author(s):  
Philippe Turcry ◽  
Ahmed Loukili ◽  
Laurent Barcelo ◽  
Jean Michel Casabonne
Keyword(s):  
Cement Paste ◽  
Thermal Deformation ◽  
Autogenous Shrinkage ◽  
Early Age

scholarly journals Gamma irradiation resistance of an early age slag-blended cement matrix for nuclear waste encapsulation

2015 ◽  
Vol 30 (9) ◽  
pp. 1563-1571 ◽  
Author(s):  
Neda Mobasher ◽  
Susan A. Bernal ◽  
Hajime Kinoshita ◽  
Clint A. Sharrad ◽  
John L. Provis
Keyword(s):  
Gamma Irradiation ◽  
Nuclear Waste ◽  
Blended Cement ◽  
Cement Matrix ◽  
Early Age ◽  
Image Position ◽  
Irradiation Resistance

Abstract

scholarly journals Autogenous shrinkage of Eco-cement paste and mortar at early age

2002 ◽  
Vol 13 (3) ◽  
pp. 29-37
Author(s):  
Hiroshi HIRAO ◽  
Masao ISHIDA
Keyword(s):  
Cement Paste ◽  
Autogenous Shrinkage ◽  
Early Age

scholarly journals The Relation between Concrete, Mortar and Paste Scale Early Age Properties

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1569
Author(s):  
Martin Klun ◽  
Vlatko Bosiljkov ◽  
Violeta Bokan-Bosiljkov
Keyword(s):  
Setting Time ◽  
Autogenous Shrinkage ◽  
Solidification Process ◽  
Early Age ◽  
S Wave ◽  
Conductivity Method ◽  
Early Hydration ◽  
High Maturity ◽  
Highly Correlated ◽  
The Cost

Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM’s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous shrinkage and extended early age period, proposed within the RRT+ programme of the COST Action TU1404. The electrical conductivity method, used to follow the solidification process of CBM, is capable of determining the initial and final setting time, and the end of the solidification process acceleration stage for the paste and mortar scale. Simultaneous ultrasonic P- and S-wave transmission measurements revealed that the ratio of velocities VP/VS is highly dependent on the presence of aggregates—it is considerably higher for the paste scale compared to the mortar and concrete scale. The deviation from the otherwise roughly constant ratio VP/VS for each scale may indicate cracks in the material. The non-linear correlation between the dynamic and static elastic moduli valid over the three scales was confirmed. Additionally, it was found that the static E-modulus correlates very well with the square of the VS and that the VS is highly correlated to the cube compressive strength—but a separate trendline exists for each CBM scale.

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