Should the water absorption rate of light aggregate in high strength light aggregate concrete be as

The core problem is the stability of the water absorption rate of light aggregate, if it is stable, it can increase the amount of water to be absorbed by the aggregate when batching, and it can also ensure the performance of light aggregate concrete.

In the past, the low water absorption rate of light aggregates was particularly pursued, because high water absorption aggregates would cause concrete workability to drop sharply, especially when pumping, more water would enter the aggregate under pressure. Therefore, the earliest lightweight aggregate concrete was basically transported by hopper. One of the ways to solve the problem when it comes to pumping is:

Soak the light aggregate in water in advance, and saturate the light aggregate to dry before use, so that the mixing water of the concrete will no longer be absorbed. Method 2: Reduce the water absorption of the light aggregate itself, such as changing the raw materials and processes of the production of light aggregate, so that the light aggregate produces closed bubbles as much as possible, or the light aggregate is hydrophobic, etc.

In recent years, due to the increasing application of high-strength and high-performance concrete, the water-glue ratio of concrete has decreased significantly, and a new problem has arisen, that is, the mixing water is far from enough cement hydration needs, so that the pore humidity of concrete is greatly reduced, resulting in the increase of the self-shrinkage of concrete (the pore water is transformed from the convex liquid level to the concave liquid surface, which will produce a larger shrinkage force on the concrete). A new technology or method to solve this problem is called "internal curing", that is, the use of superabsorbent resin or light aggregate, pre-absorbent saturation, mixed into the concrete, and then the resin or light aggregate contained in the moisture is released from the inside of the concrete, maintaining the internal moisture of the pores, effectively reducing the self-shrinkage of the concrete.

Therefore, it is also meaningful to make good use of the high water absorption rate of light aggregates. The correct way is: soak the light aggregate in water first, and drain it before use, that is, the saturated surface is dry.

1. Classification of light aggregates.

1) Classified according to the particle size of light aggregate.

1) Light and coarse aggregate particle size is not less than 5mm, and the maximum loose bulk density is less than 1000kg;

2) Light and fine aggregate particle size less than 5mm, maximum loose bulk density less than 1200kg.

2) Classified according to the ** of light aggregates.

1) Natural light aggregate Naturally formed porous rock, processed light aggregate. Such as pumice, volcanoes and light sand.

2) Artificial light aggregate is a light aggregate made of local materials as raw materials and processed into light aggregates. Such as shale ceramite, natural gangue, expanded slag beads, cinder and its light sand.

3) Industrial Waste Light Aggregate Light aggregate made of industrial waste as raw material and processed. Such as fly ash ceramsite and finely ground into pellet shale ceramsite.

3) Classified according to the particle size of light aggregates.

1) Spherical type.

2) Ordinary type.

3) Gravel type 2, light aggregate concrete is divided into natural light aggregate concrete according to the type of light aggregate. Such as pumice concrete, porosyl concrete and porous tuff concrete.

Artificial light aggregate concrete. Such as clay ceramsite concrete, shale ceramsite concrete, expanded perlite concrete and concrete made of organic light aggregates. Industrial waste light aggregate concrete.

Such as cinder concrete, fly ash ceramsite concrete and expanded slag bead concrete.

According to the type of fine aggregate, it is divided into: all-light concrete. Light aggregate concrete using light sand as fine aggregate. Sand light concrete. Light aggregate concrete, partially or wholly using ordinary sand as fine aggregate.

The first floor means water content.

The aggregate is still watered!

It's not that it's just as small as it should be, it's not too big. If it is too large to absorb water, it will hinder the hydration process. However, it is no problem to calculate the mix ratio with this factor in mind.

It's better to be smaller. The water absorption is small, and the less water in the aggregate is released after mixing.

The intensity is higher.

Water absorption rateDue to the large external force of waste concrete in the crushing process, a large number of microcracks will appear inside the aggregate, so that the water absorption rate and water absorption rate of the aggregate are much higher than that of natural aggregates. Studies have concluded that aggregates absorb 6-8 times more water than natural aggregates. It is generally believed that the water absorption rate of recycled fine aggregate is more than 10%, while the water absorption rate of recycled coarse aggregate is generally about 5%.

Due to the large porosity of the recycled aggregate, the recycled aggregate can be saturated with water in a short time. The high water absorption of recycled aggregate needs to be considered in the design of recycled concrete mixture.

The high water absorption and low apparent density of coarse aggregate are caused by the waste mortar attached to the surface of the aggregate, so there is a certain correlation between the water absorption rate of coarse aggregate and the apparent density. According to the domestic research results, there is a relationship between the apparent density and water absorption rate of recycled coarse aggregate as shown in the following formula.

where: —Apparent density of recycled coarse aggregate, g cm 3;

w - water absorption rate of coarse aggregate, %.

Check the specifications for mixing concrete yourself.