Applying low hydration heat cement, whether for the use in sealing and reinforcing mortars or in the concrete placing and conventional mortars, can reduce some of the problems associated with increasing the temperature of concrete, but it should be borne in mind that the use of special types of cements, does not mean to ignore the necessary precautions. Although at normal temperatures, low-hydration heat cement is hydrated longer than the conventional cement, its hydration rate increases by the temperature increase. Regardless of the type of cement, the workability loss occurs faster when is heated, than when it is cold. The concrete temperature may be lower at all stages if low-temperature cement is used, but under evaporative conditions, water evaporation is accelerated in mixing, transportation, injection, expansion, and curing. Taking the following measures to minimize this evaporation is necessary for preventing problems such as plastic cracking:
Using accurately the sealing products such as NSG-Z90, NSG-B70, NSG-N50, PP fibers, and PLC mesh, selecting good quality cement, using soil-free two times cleaned sand, using silica instead of stone powder or using the good quality stone powder, mixing accurately the mortar, etc.
Concrete, cement and Sealing Materials Storage
In order to achieve the best possible quality and quantity of different types of mortar including the facade and floor cementing mortars, mass concrete, sealing mortars, pointing paste, stone, and ceramic tile installation mortars, etc., it is better to leave every working day required material in a cool, shady place the day before. All concrete additives as well as NSG concrete sealing, repair, and reinforcement products such as NSG-Z90, NSG-B70, NSG-N50, NSG-SQ2000, NSG-MA700, NSG-PADAB, etc. must be stored under the storage conditions before use.
When the air temperature is between 15°C and 22°C and both the water and the stone grains are cold, the share of the heat transfers to the fresh concrete by the cement is small, but some more unwanted heat is transferred to the fresh concrete by the hot cement in really hot conditions. Therefore, hot cement should be avoided as much as possible, especially in mortars that are used for cement laying, sleekingو or sealing and dehumidifying the structures.
Mixable Water in Concrete Materials, and Sealing with NSG-Z90, NSG-B70, NSG-N50:
According to experience, the required water for producing concrete and the sealing mortars must be of the neutral pH type (neither acidic nor alkaline) and, as far as possible, have a maximum temperature of 20°C. Sometimes it is recommended to cool the water, which is theoretically desirable, but practically, in high amounts of concrete placing, the required amount of ice is rarely available in a short time and at a reasonable rate. Note that curing and water spraying of the cementation and sealing mortars that are under direct sunlight such as the tanks, pools, and outdoor areas should be started as soon as the primary setting is over.
In cases where the water is supplied through water storage tanks, the tanks should be covered with veneers or aerated covers or protected from the sunlight by placing them in the shade and painting with reflective paints.
If the water is obtained from the water supply pipe or long hoses connected to the city main pipes, their heat absorption should be minimized by placing a cover or mounding soil on them and, if possible, by burying the pipe.
Measuring, Mixing, and Transporting
There should be no unnecessary delay between producing and placing the concrete, even in optimal conditions.
Mixing NSG-Z90, NSG-B70, and NSG-N50
Whether it is for sealing, strengthening, dehumidifying, or for raising the flexural and tensile coefficients of the concrete and hardening mortars for stone and ceramic installation, mixing is better to be done before consumption on the same day. The mixed wet mortar should not be left for a long time in dry hot weather. Since the high temperature accelerates the reduction of concrete workability so the best and only way is to place concrete immediately after mixing.
It is also not recommended to add water to the hardened mortar (that is hydrated up to 60%) and to mix it again. (Only a small amount of water can be added to mortars when they have just started to dry and there is still no sign of hardening. Mixing some NSG-N50 or NSG-B70 to the mortar or concrete that has been made for sealing and strengthening with NSG products, can compensate the lost properties of the mortar, and increase the resistance, and hardness of the mortar.)
Concrete Placing and Finishing the Concrete Surfaces
Concrete vibration should be done very carefully such that air does not remain in the concrete. The trapped air in the concrete mass and mortar will cause it to become honeycombing.
It is desirable that the concrete is placed in such a way that it is vibrated quickly in the last stage of placement in the mold. NSG-N50, NSG-B70, and NSG-Z90 have unique properties because they consist of nano-copolymers. The conditions should always be such that the water in the deep parts of concrete and mortar is transferred to the concrete surface at a sufficient speed and uniform. Otherwise, the concrete surface shrinks and cracks form.
These cracks cause many significant problems in the waterproof concrete and mortars that are used for the construction of pool, roof, roof garden, façade, toilet, as well as flooring halls and parking lots, and all other places in which sealing and dehumidification is important. Although these cracks are not of structural importance in reinforced concrete and non-waterproof materials in which sealing and moisture are not important, sometimes these cracks penetrate deeply and may cause corrosion and eventual the hidden weakness of the structure in the vicinity of reinforcing bars.
Therefore, it is strongly recommended to use NSG-N50 and NSG-B70 before making concrete and mortar. In addition, immediate measures should be taken to positively reduce evaporation after vibrating the concrete.
The suggested procedures are:
Building temporary windbreaks in the direction of the wind, fine water spraying at the earliest possible time (to increase the amount of moisture of the air that is in contact with concrete) and direct spraying as soon as the primary setting (approximately 6 to 8 hours after concrete placing), and applying covers such as wet cotton gunnies on the concrete or mortar surfaces.