The master pointed out whether adding stones to the concrete test block can improve the strength

This is a method often used by test block makers in on-site construction. Theoretically, crushed stone acts as a skeleton in concrete. Everything has a degree, concrete in the mortar and gravel work together, if the stone is too little, too much, the strength has a slight decrease.

According to my test, the sand rate has little effect on the strength of concrete, generally around 1-2MPa. So adding gravel may help somewhat, but not much. Note that the stone must be a stone in concrete, and I once came across a construction site where the strength of the washed stone was greatly reduced.

From my experience, it is not necessary to add too many stones when making the test block, and generally the concrete in the test mold can be resisted by mud clamping.

It cannot be improved, the reason is that the strength of concrete mainly depends on the water-glue ratio, the lower the water-glue ratio, the higher the strength, that is, the less water, the more cementitious material, the higher the strength.

The strength can be checked by the following methods.

First of all, it is necessary to determine whether the cement, sand, superplasticizer and mixing water meet the requirements, and whether the mix ratio design is reasonable;

whether the molding operation is carried out in accordance with the regulations;

Whether the maintenance can meet the specified conditions.

If your concrete is segregated or lacking stones, then adding suitable stones can improve the skeleton structure of the concrete and increase its strength.

But if you add stones to it too hard, the strength will not necessarily be high, and it will even decrease.

Be appropriate.

Adding an appropriate amount of stones can strengthen the strength, and the one above said that it would be found out, and the test block seems to be a stone! The construction site where I am staying will make a stone! Also, what is the definition of concrete? It's normal to have stones!

No, the mixing plant is proportional and you add stones to reduce the strength.

The strength of pure concrete is very low.

Only concrete with stones is strong enough to bear the load.

Within a certain proportion, the strength of concrete is directly proportional to the proportion of stone.

Methods for Rapidly Improving the Strength of Concrete Test Blocks:

According to the analysis of factors affecting the strength of concrete, measures can be taken to improve the strength of concrete from the following aspects:

1. The use of high-grade cement, such as the use of early strength cement, or the addition of early strength agent in concrete, can improve the early strength change of concrete.

2. Reduce the water-cement ratio as much as possible.

In order to reduce the free water in the concrete mixture, dry hard concrete with a small water-cement ratio and low water consumption is used, or a superplasticizer is mixed into the concrete.

3. Adopt moist heat treatment.

1) Steam curing.

The concrete is cured in atmospheric steam at a temperature below 100 °C. Generally, after 16 20d steam curing, the strength of concrete can reach 70 80 of the 28d strength of curing under normal conditions. The optimal temperature for steam curing varies depending on the type of cement.

When using ordinary cement, the most suitable curing temperature is about 80, and when using slag cement and pozzolanic cement, it is about 90.

2) Autoclaved curing.

The concrete elements are cured in a steamer at a temperature of 175 and a pressure of 8 atmospheres. Under the condition of high temperature, the calcium hydroxide precipitated during the hydration of cement can not only combine with active silicon oxide, but also combine with silicon oxide in a crystalline state to generate hydrous silicate crystals, which accelerates the hydration and hardening of cement, and the strength of concrete is also greatly improved. It is more effective for cement mixed with active materials.

4. Mechanical stirring and vibrating are adopted.

Mechanical mixing can make the concrete mixture more uniform than manual mixing, especially when mixing low-fluidity concrete mixture. The longer the mixing time, the stronger the concrete. However, taking into account the energy consumption and construction progress, it is generally required to be controlled between 2 and 3min.

The use of vibrator pounding time, can improve the fluidity of the concrete mixture, so that the concrete mixture can be well filled with the model, eliminate the bubbles in the concrete, greatly reduce the internal void, improve the compactness of the concrete, thereby greatly improving the strength of the concrete.

There is basically no problem with your steps, but there should be straw bags after watering the ground of the shed, or plastic cover to keep the moisture, and the health period is generally about two weeks

When making test blocks, it is also important to put more stones, vibrate, control the water temperature, maintain the straw bag (or film), and maintain well. That's it!

Put the test block in water for water cultivation, and it is best to keep the water temperature above 20 degrees or higher, so that the early strength will be relatively high.

It is recommended that you quietly put some stones in it when you make the test block. Because there is always a place for a non-secret room to do it manually. There are no tools.

Isn't it? When encountering a small degree of concrete slump, it can't be smashed. There is also demoulding, which must take time to take off, otherwise the strength is not enough if there are few edges and corners.

Dry it for a few more days before sending it, and pay attention to watering! I am careful when I press it.

Don't be too slow.

Put more stones in the test block, and after demolding, water more, preferably in hot water.

Pay attention to the replacement of the water in the pool! There is also a short interval to take it out and light it up!

First of all, the test block should be standardized, as far as possible into the mold of the pebble when forming, insert or vibrate compact, strictly speaking of water curing, the water should be saturated calcium hydroxide liquid, 20 plus or minus 2 temperature, maintenance to break the type, such as taking out the simple maintenance is to maintain the temperature, can not be exposed to the sun in the early stage, keep the test block moist. In fact, the most fundamental thing is the strength of the test block itself, if you are a C20 test block, it is unlikely that commercial concrete wants to reach C30.

2. Fly ash.

Improvement of cement concrete performance.

Improve work performance.

The incorporation of fly ash makes that.

cementitious material. Target.

Total. Increase, concrete working performance is greatly improved, more suitable for pavement slipform paving: Vibration of fly ash cement concrete.

Viscosity. Coefficient.

Reduction, which is conducive to vibration and compacting; The static slump is smaller, which is conducive to preventing edge collapse; The total amount of cementitious material increases, so that the paved pavement is smooth and flat; and the improvement of workability decreased.

Pavers. Forward.

Resistance. Lightened the paver's.

Workload. These improvements in performance are due to the fact that fly ash has a larger one.

Specific surface area. and globular. Microbeads. Right.

Rheology. performance. on the unadulterated fly ash.

Cement concrete.

When paving, in order to vibrate and compact, it is necessary to improve the slump of the concrete, which is easy to collapse. If in order to prevent the collapse of the edge belt, it must be lowered.

Concrete stupid book pure slump.

In this way, the vibrator must be increased.

Vibration frequency. At the same time, the resistance of the machine to move forward increases, which increases the workload of the machine. After the addition of fly ash, this contradiction was harmonized.

Improves bending resistance. Strength.

The use of fly ash in slipform amortization cement concrete can improve the flexural strength, especially to make.

Anaphase. The strength is greatly improved.

Changchang Expressway.

It is used in the Yichang section.

Cement. Dosage of grade fly ash, 12 months.

The flexural strength exceededs. The test results are shown in Table 2.

Table 2: Flexural strength of fly ash concrete varies with.

Age. growth.

Grade fly ash content (kg).

Flexural strength (MPa) 7d28d

After 90d360d.

Note: In this test, the slump is 3 5 cm, the gravel particle size is 5 30 mm, and the sand.

Fineness modulus. , sand rate.

525 cement per 1m3 concrete, 360kg, incorporated.

High-efficiency superplasticizer.

And. Air-entraining agent.

From Table 2, it is known that the flexural strength ratio of fly ash concrete after 28d, 90d, and 360d.

Ordinary concrete.

This is an increase of %-16% and 12%-22%, respectively. The greater the content of fly ash, the longer the age, and the greater the strength.

Due to the low intensity in the early stage, it is necessary to strengthen the health regimen and prolong the health period.

The construction experience of the Yichang section of the Nagatsune Expressway is taken.

Double insurance. health measures, that is, under construction.

Temperature. Above 25, both spray.

Conditioner. Health care, and cover the health care with sacks for 10 days, and strictly control traffic within 28 days.

Specimen compressive strength mpa = specimen failure load (n).

Bearing area of the specimen (mm?).）。Calculations should be accurate to:

When the concrete strength class is C60, the strength values measured with non-standard specimens should be multiplied by the size conversion factor. Its value is: for 100mm 100mm 100mm specimen, when the concrete strength brigade forest accompaniment grade C60, it is advisable to use the standard specimen 150mm 150mm 150mm specimen.

The conversion factor of 150mm 150mm 150mm specimen is.

For example, the failure load of three test blocks of 100*100*100mm is 335kn, 352kn and 318kn, and the compressive strength is equal to (335000+352000+318000) 3 (100*100).

Because 100*100*100 is a non-standard specimen, its compressive strength coefficient ).

The failure load of the three test blocks of 150*150mm is 424kn, 401kn and 396kn, and the compressive strength is equal to (424000+401000+396000) 3 (150*150), because 150*150*150 is the standard test piece, so its compressive strength is the number of spring covers).

Fabrication and maintenance of test blocks.

The test block participating in the concrete strength assessment is divided into the standard test block and the homotrophic test block, the standard test block refers to the test block cured in the standard room, and the specification stipulates that the standard test block is in the temperature 20 2 range, the humidity is greater than 95%, and the curing is 28 days; The isotrophic test block refers to the test block made of concrete randomly selected at the pouring site, and the isotrophic test block is a test block randomly selected at the construction site and accumulated to 600 degrees Celsius at the daily average temperature according to the on-site maintenance conditions.

At the same time, the "Specification" also stipulates that the equivalent maintenance period should not be less than 14d. In the case of high-rise building construction, usually we also have to leave the demoulding test block, in winter, the temperature is lower, the strength of concrete develops slowly, which requires the age of demoulding is longer, in summer, the temperature is high, the strength of concrete develops faster, generally under the on-site curing conditions of 7d, the concrete strength can reach more than 90%, and the age of demoulding can be appropriately shortened.