Answer:
Step-by-step explanation:
a) To calculate the capillary porosity and total porosity for a concrete made with a water-to-cement (w/c) ratio of 0.52 and a cement paste binder that is 70% hydrated:
Capillary porosity refers to the interconnected network of small capillary voids within the concrete, while total porosity includes both capillary porosity and other types of pores present.
Given that the cement paste binder is 70% hydrated, we can assume that the remaining 30% of the paste consists of pores.
1. Capillary Porosity:
Capillary porosity is typically estimated as a percentage of the total volume of the cement paste binder. Since the cement paste binder makes up the entire volume of the concrete, the capillary porosity in this case is also 70%.
2. Total Porosity:
Total porosity includes both capillary porosity and the remaining non-capillary pores. In this case, the non-capillary porosity is 30% since the cement paste binder is 70% hydrated. Therefore, the total porosity is 70% + 30% = 100%.
b) If the w/c ratio is reduced to 0.42, the amount of water available for hydration decreases, which can affect the porosity of the concrete.
1. Capillary Porosity:
The capillary porosity is still 70% because it depends on the degree of hydration of the cement paste binder and is not affected by the w/c ratio.
2. Total Porosity:
To determine the total porosity, we need to consider the capillary porosity and the non-capillary porosity resulting from the reduced water content. However, without specific information about the relationship between the w/c ratio and non-capillary porosity, we cannot calculate the exact total porosity. We can only say that the total porosity will likely decrease due to the reduced water content.
c) If the cement paste is cured for a longer time and is 85% hydrated:
1. Capillary Porosity:
The capillary porosity remains the same as the degree of hydration does not affect it. It will still be 70%.
2. Total Porosity:
To determine the total porosity, we need to consider both the capillary porosity and the non-capillary porosity resulting from the hydration process. With the cement being 85% hydrated, we can assume that the non-capillary porosity is 15%. Therefore, the total porosity will be 70% + 15% = 85%.
Please note that these calculations provide estimates based on general assumptions and simplifications. The specific properties and behavior of concrete can vary depending on various factors and mix proportions.