What is the methylene blue value of stone powder in artificial sand?

It is used to determine whether the particle size in the fine aggregate is less than the particle content, mainly the soil, or the stone powder with the same chemical composition as the parent rock being processed.

Methylene blue. The purpose of the values is to determine the presence of expansive clay minerals in the fine aggregate and to determine their content in order to assess the cleanliness of the aggregate. Fine aggregates that are less than or less than can also be used for quality inspection of mineral fines.

When the pass rate in the fine aggregate is less than 3%, this test can be omitted, that is, it is regarded as qualified.

Methylene blue is an antidote and is a dark green, copper-shiny columnar crystal or crystalline powder. Odorless. When high concentrations directly make hemoglobin.

Oxidation to methemoglobin. At low concentrations, under the action of reduced CoQ I dehydrogenase, it is reduced to methylene blue, which can reduce the reduced iron protein to hemoglobin.

i.e. the MB value. Determine whether the sand is dominated by stone powder or mud powder. If the MB value is less than that, it is mainly stone powder, and if it is greater than that, it is mainly mud powder.

I have the impression that methylene blue is used to measure the content of stone powder. There is a difference between mud and stone powder.

The mud content represented by machine-made sand methylene blue is qualified. Methylene blue value of this family: used to determine whether the particle size in the fine aggregate is mainly soil or stone powder with the same chemical composition as the processed parent rock.

Methylene blue MB value: Methylene blue MB value test is a test method specially used to detect whether a substance less than 75 m is pure stone powder or soil. Because the appearance characteristics of machine-made sand are different from natural sand, the appearance of natural sand is yellow, and the mud content can be judged from the appearance.

Most of the machine-made sand is gray-white or black, with sharp grains and a lot of stone powder. The stone powder content of the machine-made sand is set at 3%, 5% and 7% respectively according to the concrete strength grade, which is 2% wider than that of natural sand.

Methylene blue detects the mud content of sand and gravel:

Effect of MB value of machine-made sand on mechanical properties of pavement concrete:

When the strength of concrete is low, especially in machine-made sand concrete, the tendency of segregation and water leakage is more obvious, and the free water in the concrete is easy to accumulate on the surface of the coarse aggregate, which weakens the interface transition zone of concrete and reduces the mechanical properties of concrete.

When the machine-made sand contains a certain amount of mud powder (i.e., the MB value increases), the water retention of the freshly mixed concrete is improved, the enrichment of free water on the surface of the coarse aggregate is improved, the performance of the interface transition zone of the hardened concrete is improved, and the mechanical properties of the pavement concrete are improved to a certain extent.

But on the other hand, the increase of the mud powder content in the machine-made sand hinders the normal reaction of cement hydration, reduces the strength of the cement stone, and with the increase of the mud powder content, a large amount of free water inside the concrete is adsorbed by the mud powder, and a large number of microcracks are formed inside after hardening, which reduces the mechanical properties of the machine-made sand concrete.

When the MB value is small (i.e., when the mud powder content is low), the enhancement effect of the MB value is more obvious, and the mechanical properties of the concrete show an enhancement trend. However, when the MB value is large, the deterioration of mud powder is more significant, resulting in a downward trend in the mechanical properties of concrete.

The two effects jointly affect the mechanical properties of concrete, but the effects of the effects show different states with the change of MB value. Eggplant.

The change trend of the MB value of manufactured sand on the mechanical properties of C50 strength grade concrete is basically the same as that of C30 strength grade concrete. However, it can be seen from the changes in compressive and flexural strength of C50 machine-made sand concrete that the change of MB value has a weak effect on the compressive strength of C50 concrete, that is, the fluctuation amplitude is small, but the impact on the flexural strength of concrete is very significant, and the flexural strength of C50 concrete is reduced by up to 15%, and the reduction of flexural strength of C50 concrete is significantly higher than that of C30 concrete. For C50 concrete with high strength grade, due to the high amount of cementitious material and low water glue ratio of high-strength grade concrete, the water retention effect of MB value improvement concrete is no longer obvious in new concrete, and the effect of hindering cement hydration caused by the increase of MB value is significantly amplified, that is, the deterioration effect of high-strength grade concrete is more significant with the increase of MB value.