2.2.3. Hydration heat flow
A conduction calorimeter (TAM Air from Thermometric AB, Sweden) operating at 20 °C was used to measure the hydration heat flow of the cements. At first, sodium gluconate was dissolved in water. The mass ratio of water to cement is 0.5. Four grams of cement was weight into the sealed plastic ampule. After the solution was added into the cement, they were mixed for 2 min by hands. Finally, the paste was put into the calorimeter as soon as possible and measured over a Hesperadin of 3 days.
2.2.4. Analysis of the solid phases assemblage
The pastes were made from the cement and aqueous solution containing different dosages of sodium gluconate. The mass ratio of water to cement is 0.5. After the aqueous solution was added into the cement, mass extinction were mixed for 2 min by using mixer with speed of about 1600 r/min. The fresh paste was poured into plastic bottles. The bottles were sealed, and then stored in a curing box with the temperature of 20 °C ± 1 °C and humidity of 95% ± 4%. Prior to the X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC), hydration was stopped after 30 min, 1 h, 2 h, 5 h, 8 h, 1 d, 3 d and 28 d by submerging small pieces for 7 d in alcohol. And then they were dried in a oven. Some pieces were ground and stored in the desiccator for XRD and DSC.