scholarly journals Effects of Nano-SiO2 and SAP on Hydration Process of Early-Age Cement Paste Using LF-NMR

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Haitao Zhao ◽  
Yi Wan ◽  
Jun Xie ◽  
Kaidi Jiang ◽  
Donghui Huang ◽  
...  
Keyword(s):  
Cement Paste ◽  
Bound Water ◽  
Hydration Process ◽  
Early Age ◽  
Superabsorbent Polymer ◽  
Test Results ◽  
Low Field ◽  
Water To Cement Ratio ◽  
Hydration Model ◽  
Zero Points

The effects of nano-SiO2 and superabsorbent polymer on the hydration process of early-age cement paste are investigated through the physically bound water evolution test by means of the low-field nuclear magnetic resonance technology. The test results show that the hydration process can be characterized by four-stage patterns based on the zero points of the second-order differential hydration curve, i.e., the initial, accelerated, decelerated, and steady periods. The beginning time of each stage is postponed and the hydration duration is prolonged with an increasing water to cement ratio. The beginning time of each stage and the hydration duration are shortened with an increasing content of nano-SiO2. And the beginning time of each stage and the hydration duration are prolonged with an increasing content of superabsorbent polymer. Based on the test data and the Avrami–Erofeev model, a modified hydration model taking the influence of nano-SiO2 and SAP into account is proposed, and the predicted results are consistent with the test results.

scholarly journals Hydration of Early Age Cement Paste with Nano-CaCO3 and SAP by LF-NMR Spectroscopy: Mechanism and Prediction

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Haitao Zhao ◽  
Gaoyang Sun ◽  
Lu Yu ◽  
Kaidi Jiang ◽  
Xiaodong Chen ◽  
...  
Keyword(s):  
Cement Paste ◽  
Initial Period ◽  
Bound Water ◽  
Hydration Process ◽  
Early Age ◽  
Starting Time ◽  
Water To Cement Ratio ◽  
Acceleration Period ◽  
Hydration Model ◽  
Lf Nmr

In this paper, by testing the evolution of the physically bound water using the low-field nuclear magnetic resonance (LF-NMR) technology, the hydration process of cement paste with nano-CaCO3 (NC) and superabsorbent polymer (SAP) at early age is investigated. Results indicate that the hydration process can be divided into four periods according to the zero points of the second-order differential hydration curve: initial period, acceleration period, deceleration period, and steady period. Firstly, with the increase in the water to cement ratio, the starting time of the hydration period is delayed, and the duration becomes longer. Secondly, the addition of NC leads to the speedy arrival of each period and shortens the duration of each period in the hydration process, and the optimal NC content is 1.5%. Thirdly, with the increase in SAP content, the starting time of the hydration period is delayed and the duration becomes longer. Finally, based on the experimental results and the existing hydration model, the modified hydration model considering the content of NC and SAP is proposed.

scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

scholarly journals Difference in Strength Development between Cement-Treated Sand and Mortar with Various Cement Types and Curing Temperatures

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4999
Author(s):  
Lanh Si Ho ◽  
Kenichiro Nakarai ◽  
Kenta Eguchi ◽  
Yuko Ogawa
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Bound Water ◽  
Curing Temperature ◽  
Strength Development ◽  
Early Age ◽  
Cement Type ◽  
A Value ◽  
Water To Cement Ratio ◽  
Novel Method

To improve the strength of cement-treated sand effectively, the use of various cement types was investigated at different curing temperatures and compared with the results obtained from similar mortars at higher cement contents. The compressive strengths of cement-treated sand specimens that contained high early-strength Portland cement (HPC) cured at elevated and normal temperatures were found to be higher than those of specimens that contained ordinary Portland cement (OPC) and moderate heat Portland cement at both early and later ages. At 3 days, the compressive strength of the HPC-treated sand specimen, normalized with respect to that of the OPC under normal conditions, is nearly twice the corresponding value for the HPC mortar specimens with water-to-cement ratio of 50%. At 28 days, the normalized value for HPC-treated sand is approximately 1.5 times higher than that of mortar, with a value of 50%. This indicates that the use of HPC contributed more to the strength development of the cement-treated sand than to that of the mortar, and the effects of HPC at an early age were higher than those at a later age. These trends were explained by the larger quantity of chemically bound water observed in the specimens that contained HPC, as a result of their greater alite contents and porosities, in cement-treated sand. The findings of this study can be used to ensure the desired strength development of cement-treated soils by considering both the curing temperature and cement type. Furthermore, they suggested a novel method for producing a high internal temperature for promoting the strength development of cement-treated soils.

Effect of Carboxylmethyl Cellulose Sulfate (CMC-S) on the Hydration Process of Cement Paste

2013 ◽  
Vol 838-841 ◽  
pp. 123-126
Author(s):  
Feng Yuan Huang ◽  
Xiao Jie Wu ◽  
Wei Feng Ying ◽  
Yong Peng Yu ◽  
Hong Xun Chi
Keyword(s):  
Cement Paste ◽  
Differential Scanning Calorimeter ◽  
Setting Time ◽  
Reducing Agent ◽  
Hydration Heat ◽  
Hydration Process ◽  
Early Age ◽  
Cellulose Sulfate

The application of Carboxylmethyl Cellulose Sulfate (CMC-S) in cement paste was studied. The effect of CMC-S on the setting time of cement paste was investigated. Hydration heat of specimens with different cured age was measured via the Hydration Heat Tester (HHT), and hydration process was recorded via Differential Scanning Calorimeter (DSC). The results indicated that CMC-S was a kind of set-retarding and water-reducing agent; its retarding properties appeared at early age, but after three days, the hydration process of cement paste was even improved.

scholarly journals Analysis of Early Performance of Cement Paste by Low Field NMR

2019 ◽  
Vol 9 (5) ◽  
pp. 896 ◽  
Author(s):  
Dan Jin ◽  
Zejun Lang ◽  
Wu Yao
Keyword(s):  
Cement Paste ◽  
Hydration Process ◽  
Hardened Cement ◽  
Early Hydration ◽  
Setting Times ◽  
Low Field ◽  
Early Performance ◽  
The Times ◽  
Function Relationship ◽  
Space Ratio

The change of the evaporable water content in the early hydration process of cement paste with different water-to-cement ratios was monitored by low field nuclear magnetic resonance (LF-NMR) relaxometry. The hydration degree and gel/space ratio were accordingly calculated and analyzed. The test results show that the first derivative curves of the transverse magnetization are in good agreement with the known five stages of cement hydration process at an early age. The initial and final setting times of the cement paste are closely related to the times the gel/space ratio reaches a fixed value. The early compressive strength of the hardened cement paste exhibits a power function relationship with the gel/space ratio.

Numerical Simulation of Autogenous Shrinkage in High-Performance Cement Paste Based on a Multi-Component Hydration Model

2008 ◽  
Vol 385-387 ◽  
pp. 629-632
Author(s):  
Seung Min Lim ◽  
Han Seung Lee ◽  
Xiao Yong Wang
Keyword(s):  
Numerical Simulation ◽  
Cement Paste ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Curing Temperature ◽  
Hydration Process ◽  
Material System ◽  
Water Mixture ◽  
Hydration Model

Autogenous shrinkage is the term for the bulk deformation of a closed, isothermal, cement-based material system not subjected to external forces. It is associated with the internal volume reduction of cement/water mixture in the course of the hydration process. However, addition of blended components to cement, especially such as fly ash or silica fume, for the high-performance concrete will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, numerical simulation is suggested to predict autogenous shrinkage of high performance cement paste. The simulation is originated from a multicomponent hydration model. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

Effect of Particle Size on Expansive Behaviour of MgO-Based Expansive Agent in Cement Paste

2011 ◽  
Vol 194-196 ◽  
pp. 1143-1146 ◽  
Author(s):  
Zhi Bin Zhang ◽  
Ling Ling Xu ◽  
Ming Shu Tang
Keyword(s):  
Particle Size ◽  
Cement Paste ◽  
Linear Expansion ◽  
Hydration Process ◽  
Early Age ◽  
Hydration Degree ◽  
Expansive Agent ◽  
Effect Of Particle Size ◽  
Higher Temperature

In order to investigate the effect of particle size on expansive behavior of MgO-based expansive agent (MEA), linear expansion of paste containing MEA and hydration process of MEA in paste were measured. The results indicated the expansion of paste increased with the drop of particle size at early age, however, MEA with lager particle size expanded faster at late age. Finally, the expansion of paste increased with the rise of particle size. MEA with larger particle size was detrimental to the soundness of cementitious matarials. These two rules were more obvious to MEA burned at higher temperature. In addition, the hydration degree of MEA increased with the drop of particle size.

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