Relaxation study of cement based grouting material using nuclear magnetic resonance

Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage, by adding a water reducing agent, cement paste for hole sealing was produced. The changes of initial distribution, weighted average values and total relaxation signal intensity of transverse relaxation time (T-2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance (NMR). The results show that there are four peaks in T-2 distribution curves of cement paste: the first peak is related to the bound water in flocculation, the second and the third peaks are related to the water in flocculation, water reducing agent makes it extending towards the long relaxation time, increasing its liquidity, and the fourth peak is related to the free water. By using weighted average values of T-2 and total relaxation signal intensity, hydration process of cement pastes could be roughly divided into four stages: the initial period, reaction period, accelerated period and steady period. By analyzing the periods, it makes sure that the grouting process should be completed in the reaction period in the site, and the drainage process should be started in the steady period. The results have great guiding significance to the hole sealing and methane drainage. (C) 2012 Published by Elsevier B.V. on behalf of China University of Mining & Technology.