Introduction:
The correct proportion of ingredients of concrete is crucial for achieving the desired properties and strength of the final product. Various factors need to be considered when determining the correct proportions, including the bulking of sand, water content, and absorption.

1. Bulking of sand:
When measuring the sand for concrete, it is important to consider the bulking of sand. Bulking refers to the increase in volume of sand due to the presence of moisture. The moisture forms a film around the sand particles, causing them to separate and occupy more space. If the bulking effect is not taken into account, the concrete mix may have a higher proportion of sand, leading to a weaker and less durable concrete.

2. Water content:
Water is a crucial ingredient in concrete as it is needed for the hydration process of cement. The correct water content is essential to achieve the desired workability, strength, and durability of the concrete. Insufficient water can result in a stiff mix, making it difficult to place and compact the concrete properly. On the other hand, excessive water can weaken the concrete and lead to segregation and bleeding.

3. Absorption:
The absorption of aggregates, such as sand and gravel, also affects the water content in the concrete mix. Aggregates have the tendency to absorb a certain amount of water, which can vary depending on their porosity. If the aggregates are not properly saturated before mixing, they can absorb water from the concrete mix, leading to a higher water-cement ratio and weaker concrete.

4. All the above:
Considering all the factors mentioned above is essential for determining the correct proportion of ingredients in concrete. Neglecting any of these factors can result in an improper mix, leading to a variety of issues such as reduced strength, decreased durability, and poor workability.

Conclusion:
The correct proportion of ingredients in concrete is dependent on factors such as the bulking of sand, water content, and absorption of aggregates. By considering these factors and adjusting the proportions accordingly, it is possible to achieve the desired properties and strength in the final concrete product.