Abstract
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.
Highlights
The hydration of cement takes place as soon as the cement particles meet water
The purpose of this work is to monitor the evolution of evaporable water throughout the early hydration process of cement paste at different water-to-cement ratios by low field nuclear magnetic resonance (LF-NMR) technique
Considering it is linearly proportional to proton number and water content, the first peak amplitude of the transverse relaxation, which is approximately regarded as fitted magnetization M0 of the samples under the CPMG pulse sequence was collected
Summary
A time-consuming transition of the cement paste, the so-called ‘setting process’, from a liquid state to a porous and hardened solid occurs. It can still be conveniently divided into five stages in common based on the results of heat release tests during the early age, where the heat flow is proportional to the rate of reaction. The early hydration reaction process and microstructure of cement-based materials have definite impacts on the later macroscopic mechanical properties and durability. The chemical and physical changes of cement paste affect the setting and hardening of cement-based materials. Investigation of the rule of hydration, hardening process and strength growth of cement paste is helpful for better understanding the early performance of cement-based materials
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