How to construct concrete in 40-degree heat? This is the correct way to apply ash in the summer!

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When the temperature exceeds 40 degrees, once the concrete is taken out of the mixer, it’s a race against time. In such a short distance from the mixing plant to the construction site, the slump of the concrete can drop by half. As soon as the workers connect the pipes and see that the mixture has dried out, they have to add water; and this addition of water causes the water-cement ratio to get out of control, resulting in a decrease in the concrete’s strength by one grade. It’s not that the workers are lazy; it’s simply that they have no other options. High-temperature construction isn’t meant to test whether the concrete can withstand such conditions, but rather to check whether temperature control measures have been put in place in advance. Today, I’ll explain once and for all the correct way to apply ash at 40 degrees of high temperature. The first step is to avoid pouring concrete when it’s hot. Instead, pour the aggregate first. Aggregate is the largest component by volume in concrete, and it also acts as a heat reservoir that absorbs a lot of heat. When sand and gravel are exposed to the sun, their internal temperature can reach 50 to 60 degrees; until the temperature of the aggregate drops, it’s not possible to create concrete with a low temperature using cool water. The correct approach is to keep watering the aggregate pile before pouring the concrete, using the evaporation of water to remove heat from the aggregate. It’s not sufficient to water it once and then ignore it; the aggregate needs to remain moist in order to cool down. Sand and gravel should be watered separately in order to control their temperatures. The temperature of the aggregate should also be measured before adding it to the mixture – if the temperature is still high and has not dropped, mixing cannot take place. If this step is skipped, all subsequent measures for temperature control will be ineffective. In the second step, the mix ratio must be adjusted accordingly; retarding agents and water reducers should be used together. Part of the water used in mixing should be replaced with ice water. In hot weather, concrete sets at an astonishingly fast rate, and as transportation time increases, the slump loss occurs very rapidly. If the mix ratio isn’t changed, it’s equivalent to making the mixture drier. The inclusion of retarding water reducers can extend the setting time and control the loss of slump over time. When necessary, ice can be used to replace part of the mixing water; it’s not necessary to replace all of the water with ice water. The temperature of the mixture should be kept below 30 degrees. Using ice water for cooling is more effective than sprinkling water on the aggregates, as it introduces cold material directly into the mixture, rather than relying on cooling the material by sprinkling water on it after it has been heated up. In the third step, misting is used on-site to reduce temperature, along with shading; it is necessary to avoid pouring concrete during periods of high temperatures. The misting is meant to lower the ambient temperature, not by watering the ground, but by using atomized water vapor, thereby slowing down the evaporation rate from the concrete surface. The formwork and rebar are also affected by high temperatures; it is necessary to spray water inside the formwork to cool it down before pouring. Sunshades should be used to cover the rebar frames in order to prevent the formwork and rebar from acting as heat sources. The timing of pouring must be carefully planned – the period from 11 a.m. to 3 p.m. is characterized by high temperatures and strong sunlight, so this time should be avoided. It is better to carry out pouring in the cooler early morning or evening hours, or at night. This is not about compensating for working on weekends, but rather about giving priority to proper concrete curing conditions: it is better to have workers work shifts rather than allow the concrete to cure under high temperatures. In the special plan for concrete work prior to the onset of summer, all aspects such as cooling of aggregates, the ratio of ice to water, the amount of retarding agent to be used, and the timing of pouring are determined in advance. There’s no need to wait until summer to take action; as soon as the temperature reaches 35 degrees, it automatically switches to a high-temperature construction mode. When pouring concrete at a temperature of 40 degrees Celsius, relying solely on the diligence of the workers is not enough to prevent problems. If the aggregate is not cooled, the temperature of the concrete as it exits the mixer is not controlled, the mix ratio is not adjusted, and there is no shading or misting at the construction site, then cracks will definitely appear.