For various reasons such as transportation, pumping, pouring, etc., the concrete is first weighed by the tanker driver. The quality inspector calculates the remaining amount based on the weighing list provided by the tanker driver and the tanker's tare list and then on the same grade or lower grade. Use the following processing methods:
Use at the same level. If the delay time is less than 2H, the cement dose should be increased by 10-15kg/m3 and added by 0.1-0.3% compared to the original mixture after treatment. Or directly reduce the strength level and appropriately increase the amount of the adjusted mixture. The delay is 2 to 4 hours. After treatment, the cement dose should be increased by 20 to 40kg/m3, and the mixture should be increased by 0.4% to 0.6%. Or simply reduce the two strength levels and appropriately increase the amount of the adjusted mixture.
The use of degraded grade must be based on the same raw materials used for degraded and original grade concrete and only apply to concrete below C40 and C40. On the basis of the above, reduce the intensity level for processing.
If the delay time exceeds 4 hours, it should be scrapped or used as non-load-bearing low-grade concrete. If the average daily temperature is within the range of 5-20 ℃, the treatment can be increased by 0.5h as shown in (1). If the average daily temperature is less than 5℃, the treatment can be increased by 1 hour according to (1).
When concrete is transported to the construction site, it is found that the slump of concrete cannot meet the construction requirements. If the slump is lower than the design requirements of 30-50mm, 0.5kg pumping agent can be added to each side according to the square number on the transportation list. For example, if the shipment volume is 8m3, 0.5×8=4kg can be added. If you use 10kg plastic bucket pumping agent, full bucket 11kg, about 2/5 can be added to the bucket, and then add water 3-5s with water pipe, the pumping agent in the hopper into the tank, start the tank quickly rotate for 3 minutes, get on the car to observe whether the concrete mixture is appropriate, can be used in accordance with the requirements.
when the concrete is sent to the construction site to wait for a long time before the use of materials or concrete use time is too long to hit the column, concrete in the discharge tank does not flow, should first estimate the amount of concrete in the tank, and then estimate the amount of concrete in the tank. Calculate the amount of pumping agent per 1kg. After the pumping agent is added, water, rapid rotation, observation and other steps shall be carried out in accordance with the requirements of Article (4). When using partial materials and estimating the amount of inaccuracies, it is better to underestimate than to overestimate. Add a little bit less, and if you don't meet the requirements, you can add a little bit more to meet the requirements. If too much pumping dose is added at one time, the concrete mix will slump too much and the concrete will slow down.
in the initial setting period of concrete, due to high temperature, long transportation distance, long pressing time, concrete slump loss is relatively large. After the test can add the same type of pumping agent or water reducing agent. But the total amount added and the total amount previously added should not exceed 20% of the maximum amount of the admixture. It should be added gradually and less at first. After mixing, the mixing car must turn quickly for about 2 minutes, and measure slump to meet the requirements. The concrete transported to the site cannot be unloaded immediately. Before unloading, the transport truck should be quickly turned for 2 minutes to ensure slump and quality. Concrete beyond the initial setting time should be discarded, not reused. Concrete mixing station before pouring stagnation time is longer, concrete strength loss is more serious, should cause enough attention.