Discussion on the reasons for concrete shortage

How to properly handle the problem of concrete shortage? Let's look at the professional answers given by industry experts, as follows:

Premixed concrete, as a product, has two characteristics when delivered: firstly, it is weighed and delivered by volume; secondly, it is signed for by ticket and settled by drawings. In the current buyer's market, the problem of settlement shortage has been plaguing premixed concrete production enterprises.

The shortage comes from two aspects:

First, the enterprise supplies the full amount, but for various reasons, it cannot be settled in full;

Second, the enterprise supplies more than the required amount (excess), even if it is settled in full according to the ticket, it is actually a shortage.

1. Technical aspects: The results caused by technical aspects are two-way, it may be a shortage, or it may be an excess.

1.1. Mix design stage

When calculating by weight, the design bulk density of one cubic meter of concrete has a large deviation from the actual value, and the bulk density of the concrete is not measured during the trial mix. Generally, in this case, there is more excess.

1.2. Quality adjustment stage during production

During production, when the raw materials change and the output performance of the concrete cannot meet the design requirements, the production mix ratio of the concrete must be adjusted. For example, increasing the amount of cementitious materials, adjusting the sand ratio, etc. If the amount of fly ash is increased, it will directly lead to excess; also, the bulk density of waste stone (sand) and other stones (sand) is quite different. When these two kinds of stones (sand) are replaced in equal amounts, it may lead to shortage or excess.

2. Management aspects: The results caused by management aspects are also two-way, it may be a shortage, or it may be an excess.

2.1. Measurement aspects

When the host metering system has instantaneous or frequent metering errors exceeding the standard, it will cause the quality and volume of concrete to be inconsistent with the original design.

2.2. Handling of remaining ash

Inaccurate estimation of the amount of usable remaining concrete returned to the mixing plant will result in errors after replenishment.

3. Construction aspects: The results caused by construction aspects are one-way, only shortage.

3.1. Poor management by the construction party. During the construction of walls and vertical structures, the pump is not stopped during the pouring and moving process, and the formwork leaks during the construction process, which directly causes the concrete transported to the construction site not to reach the designated structural parts, resulting in waste; improper handling of unexpected situations such as noise disturbance, equipment failure, and power failure also causes concrete to be scrapped.

3.2. Errors in formwork and structural components. China's construction standards have an allowable dimensional deviation range for formwork support and structural components after pouring. Under the premise of complying with the standards, the difference in the amount of concrete is also astonishing. This usually occurs in plate-type components.

3.3. Discharge outside the designated area. The mixing plant does not supervise the site effectively, and the construction party cannot record the concrete discharged outside the designated area in time.

4. Malicious acts by customers

4.1. Incomplete drawings in the hands of the budgeter of the mixing plant, especially for projects where several mixing plants jointly supply concrete, there are often discrepancies between the axis division and the current supply.

4.2. Modifications during the process without informing the mixing plant. During the construction process, for various reasons, the design may be changed, and the already poured structural parts are demolished and rebuilt.

4.3. Forcing price concessions during payment. Some construction sites forcibly deduct money when paying the final payment, which also constitutes a shortage in the practical sense.