Acoustic behavior of Portland cement paste with additive of sodium gluconate during hydration

The ultrasonic pitch-catch experiment was conducted to study the hydration behavior of Portland cement paste with additive of sodium gluconate (SG) by using the tailor-made piezoelectric transducer. The X-ray diffraction (XRD) analysis shows that the intensity of the diffraction peak of Ca(OH) 2 decreases with increasing the SG content, especially when the SG content is larger than 0.1wt.%. The compressive strength of the hardening cement paste when SG content is larger than 0.05wt.% decreases remarkably. The ultrasonic waveforms appear at hydration age of 2 h, and amplitudes of waveform of the cement pastes with SG contents of 0.15wt.% and 0.2wt.% are obviously larger than those with SG content of 0.05wt.% in the early hydration stage. The hydration process of cement paste in 300 h can be classified into three stages based on the head wave amplitude variation, that is, the fluctuation variation period, the rapid increasing period and smooth increasing period. The acoustic propagation time changes greatly with hydration before hydration age of 48 h, indicating that the hydration and hardening process of the cement paste is violent in 48 h. The proposed ultrasonic monitoring method opens a new perspective for hydration behavior study of the cement paste with additive of sodium gluconate.