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.

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.

INVESTIGATING THE EFFECT OF NANO SILICA ON THE MECHANICAL PROPERTIES OF HARDENED CEMENT PASTE

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Sameer Hamoush ◽  
Miguel Picornell ◽  
Taher Abu-Lebdeh
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Silica Content ◽  
Hydration Process ◽  
Hardened Cement ◽  
Nano Silica ◽  
Hardened Cement Paste ◽  
Cement Replacement ◽  
Water Curing ◽  
Curing Method

This study investigated the compressive strength of hardened cement paste and the formation of calcium silicate hydrate (C-S-H) with the addition of nano silica (SiO2). Through this search, the development of the concretes strength was determined to better understand the process of cement hydration. Compressive strength testing was performed using MTS and Forney testing machines to determine stress-strain curves and elastic modulus of materials. The hydration process and formation of C-S-H and calcium hydroxide (CH) was examined using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). This study also incorporates the use of vacuum curing, in comparison to that of the traditional water curing method. Results indicate an increase in compressive strength using 1%, 3% and 5% of nano silica to cement replacement by volume in comparison to the control mix (without nano silica). The optimum cement replacement to yield maximum strength was of the 1% nano silica content. The formation of C-S-H increases significantly during the early testing days which correspond with the drastic increase in compressive strength. The hydration process continues to increase throughout the 56 day trails at a moderate rate. The traditional water curing method proves to be more efficient and beneficial than of the vacuum curing method. However, vacuum cured results showed only about a 5% reduction in strength after 56 day tests in comparison to the water curing method.

Effects of Polycarboxylate Superplasticizers on Hydration and Microstructure of Hardened Cement Paste

2012 ◽  
Vol 487 ◽  
pp. 692-696
Author(s):  
Rui Jun Gao ◽  
Sheng Hua Lv ◽  
Qiang Cao
Keyword(s):  
Calcium Carbonate ◽  
Cement Paste ◽  
Hydration Product ◽  
Ammonium Persulfate ◽  
Radical Copolymerization ◽  
Nucleation And Growth ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Early Hydration

Polycarboxylate (PC) superplasticizer was synthesized by radical copolymerization using ammonium persulfate (APS) as initiator at 90 °C for 5 h. The effect of PC on the hydration process and microstructure of hardened cement at different hydration ages (4 h, 1 d and 7 d) was investigated. Hydration of cement paste results show that the nucleation and growth of hydration product of ettringite (Aft) was inhibited by PC at the early hydration ages, and the generation of the hydration products of calcium hydroxide (CH) and calcium carbonate (CaCO3) was promoted at late hydration ages. SEM result indicates that PC can make the structure of hardened cement more homogeneous and more density.

Analysis of Cement Hydration Monitoring Using Embedded and External Ultrasonic Transducers

2011 ◽  
Vol 306-307 ◽  
pp. 514-518
Author(s):  
Qian Qian Zhong ◽  
Lei Qin ◽  
Shi Feng Huang ◽  
Xin Cheng
Keyword(s):  
Frequency Spectrum ◽  
Cement Paste ◽  
Health Monitoring ◽  
Cement Hydration ◽  
Piezoelectric Transducers ◽  
Ultrasonic Transducers ◽  
Hydration Process ◽  
Ultrasonic Monitoring ◽  
Early Hydration ◽  
Coupling Problem

This study adopted home-made embedded piezoelectric transducers and external commercial ultrasonic transducers respectively to monitor early hydration processes of cement. This paper discussed the development of ultrasonic amplitude and frequency spectrum during the hydration process. It is proved that the method is effective for monitoring the hydration of cement paste. The embedded transducer could resolve the coupling problem of ultrasonic monitoring and it could be used for the whole life health monitoring of concrete.

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