Concrete slump cone test

Slump cone test Standards: EN 12350-2, BS 1881:102, ASTM C143

Concrete slump cone: This entry was reviewed by the “Encyclopedia of Science Popularization” scientific encyclopedia entry preparation and application work item.
Concrete slump mainly refers to the plasticizing performance and pumpability of concrete. The factors that affect the concrete slump mainly include gradation change, water content, weighing deviation of the scale, and the amount of admixture, which are easily overlooked. Cement temperature, etc. Slump refers to the workability of concrete, specifically to ensure the normal progress of construction, including the water retention, fluidity and cohesion of concrete.
Workability refers to whether the concrete is easy to operate and uniformly dense. It is a very comprehensive performance that includes fluidity, cohesion and water retention. The impact and ease of use mainly include water consumption, water-cement ratio, sand ratio, including cement varieties, aggregate conditions, time and temperature, and additives.
The slump cone of concrete should be determined according to the conditions such as the structural cross-section of the building, the steel bar content, the transportation distance, the pouring method, the transportation method, the vibrating capacity and the climate. When selecting the mix ratio, it should be considered comprehensively, and the smaller Slump.

Test Methods

The slump cone test method: use a trumpet-shaped slump barrel with an upper mouth of 100mm, a lower mouth of 200mm, and a height of 300mm. Fill the concrete in three fillings. After each filling, use a ram to distribute the uniformity from outside to inside After hitting 25 times, smash it and smooth it. Then pull up the bucket, and the concrete will collapse due to its own weight. Use the height of the bucket (300mm) minus the height of the highest point of the concrete after the collapse, called the slump. If the difference is 100 mm, the slump is 100.

Slump classification

Level Name Slump (mm)
T1 low plastic concrete 10 ~ 40
T2 plastic concrete 50 ~ 90
T3 fluid concrete 100 ~ 150
T4 large flow concrete ≥160

Slump expansion method

This method is suitable for the determination of the consistency of concrete mixtures with a maximum aggregate size of not more than 40 mm and a slump of not less than 10 mm.
There is no measurement method that can fully reflect the workability of concrete mixtures. In the construction site and the laboratory, slump test is usually done to determine the fluidity of the mixture, supplemented by intuitive experience to assess cohesion and water retention.
The method of slump test is: put the concrete mixture into the standard cone slump cylinder according to the prescribed method, after it is filled and scraped flat, lift the cylinder vertically upward and move it to the side. The concrete mixture will collapse due to its own weight. Then measure the size of the downward slump. The size (mm) is the slump. As the index of fluidity, the greater the slump, the better the fluidity.
When the slump is greater than 220 mm, the slump cannot accurately reflect the fluidity of the concrete. The average diameter of the concrete after expansion is the slump expansion, which is used as the fluidity index.
While performing the slump test, the cohesiveness and water retention of the concrete mixture should be observed in order to comprehensively assess the workability of the concrete mixture.
The evaluation method of cohesion is: tap lightly on the side of the collapsed concrete cone with a ram, if the cone gradually sinks, it means that the cohesion is good; if the cone collapses, part of it will crack or segregate It means that the cohesiveness is not good.
The water retention is evaluated by the degree of precipitation of the thin cement slurry in the concrete mixture. After the slump cylinder is lifted, if more thin cement slurry is precipitated from the bottom, and the concrete mixture of the cone part is also exposed due to the loss of slurry, it indicates that the water retention performance of the concrete mixture is not good. If there is no dilute cement slurry or only a small amount of dilute cement slurry is precipitated from the bottom after the slump cylinder is lifted, it means that the concrete mixture has good water retention.

Problem solved

Slump requirements for commodity pumped concrete
There is no standard requirement for the slump of concrete. The concrete slump of the corresponding part will be explained in the construction drawings. The mixing station is mixed according to the designed slump requirements. Generally, fly ash and additives are added to increase The fluidity of concrete. The slump is high, as long as the water ash is better than the control, there will be no segregation. Generally, the slump of concrete above plus or minus zero is about 150mm. If it is an underwater cast-in-place pile, the slump will be larger, generally about 180mm-200mm.
What to do if the slump detection does not meet the requirements
Concrete slump is a standard used to judge the quality of concrete construction and workability in actual construction. If the slump is large, it will easily cause the segregation of the mixture. If it is too small, it will bring difficulty to the construction and can be changed without change. In the case of water-cement ratio, change the amount of aggregate, or add cement slurry to change.
In high-temperature construction, the slump of concrete should not be less than 70mm, the slump of concrete in general on-site construction is 100 ± 20mm, and the slump of construction can be increased to 160mm in high temperature and harsh environments.

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