The Effect of Phase Change Materials on the Physical, Thermal and Mechanical Properties of Cement

Round 1

Reviewer 1 Report

The authors have conducted a detailed study on the effect of phase change materials on cement. Though the objective and content of the paper is good, some improvements need to be done.

Major Comments:

1. No literature details are mentioned to support the methodologies explained under Compressive Strength Testing and Water Porosity Test
2. Explanation given for Figure. 10 is inadequate and needs more reasons.

Minor Comments:

1. Our research focuses of on Phase Change Materials (PCMs) as a type of Smart Materials.
2. While requiring less mass/volume of material
3. … should be changed to etc.
4. The sentences Cement material used in this research study has a classification: “CEM II”. & Mixture preparation was realized by mixing cement with different percentages of PCM powder should be annexed with the preceding paragraph
5. Table 1 should be kept next to Figure 1
6. Solidification spelling error in Table 1
7. -1 should be superscripted in W (mK)^-1
8. The below lines can be clubbed to a single paragraph, which will increase the readability of the paper – Ratio of water to (cement PCM) was taken equal to 0.5 for the three configurations. Total mass of samples is 4 kg. Thermal conductivity is measured after 7 days of drying. The measuring device is Fox600 as shown in Figure 2. The optimal Delta of temperature between the plates (lower and upper) suggested by the manufacturer is 20 C. Temperature of the lower plate is equal to T_low = 35 °C and T_up = 15 °C for the upper plate.
9. 2 if written using Mathtype or any other equation software will look good.
10. 3 – Styrofoam spelling error
11. Model number of Perkin Elmer calorimeter should be given
12. Axes Titles of Figure. 12 is not that visible

Reviewer 2 Report

47: What are the most important insights of the paper? They are not mentioned in the abstract. Why should I read it?

54: Grammar: were assessed, just as an example.

69: The energy density for pure materials over the melting point does not depend on a temperature gradient. Theoretically, the whole latent heat of fusion has to be added or subtracted to/from the material without! a change in temperature.

73: Many buildings are exposed to temperatures below 0°C from a global perspective.

93: The description of the wax is incomplete. What is the value for thermal conductivity, the manufacturer or the datasheet has to be added to the references.

105: Figure 1: No source provided in the references.

117: A reference to technical information of the Fox600 should be added to the references.

120: Variables and indices are not listed in the nomenclature.

121: Indices subscript

128: Sentence not complete…thermal conductivity of solid-liquid WHAT?

141: This equation leads to a unit of W/K for the thermal conductivity. That is wrong...

149: Nitrogen as the liquid? Nitrogen in the liquid phase can be used for cooling the sample when high cooling rates are necessary. Did you mean nitrogen atmosphere?

153: Why do you heat the sample up to 80°C if the melting range of the PCM is between 23°C and 27°C?

159: Reference which material testing machine was used.

166: Which forces, how was the stress determined? A sketch would help to understand this mechanical test better. And a description is missing.

168: Numeration of figures is mixed up.

228: Results are too close? Did you mean that the do not spread much?

242: … the thermal conductivity is relatively stable in the 0-5% PCM range… How can you conclude that? You measured PCM fraction of 0/10/20 and 30%.

249: Did you calculate the potential measurement errors? Show error bars in graph…

274: The unit of the temperature? The whole analysis of the DSC measurement is missing. Did you calculate the latent heat of fusion in J/g? What is the specific heat capacity below and above the melting range?

333: Discussion of the strength test is missing. The strength of the 30% PCM sample is half of the pure cement. That would mean that the double amount of cement is necessary to reach the strength of pure cement?

366: PCM in buildings reduce need for air conditioning in summer – how can you conclude that? Therefore, a transient thermophysical analysis of such a buildings is needed. You decreased the heat conductivity with the PCM, but insulation of buildings would has a much higher impact. The latent heat of fusion can be used, but recuperation in the night is necessary. No economic assessment was carried out, at least prices for the raw PCM and the cement would be interesting.