Foam concrete is a kind of concrete with lightweight and has ideal strength. Because of the hollow structure in foam concrete, it has the function of absorbing heat and isolating sound.
The density of foamed concrete is 300-1200 kg/m3, and the thermal conductivity is between 0.08-0.3W/ (m ·K).
Foam concrete is widely used in CLC blocks, lightweight partition panels, roof insulation, floor cushion construction, floor heating backfilling, and other occasions.
At the same time, foam concrete is also a good sound absorption material, which can be used in highway sound insulation boards, sound absorption boards, and other fields.
Generally speaking, foam concrete is a kind of building material with multi-function, environmental protection, and economy, which has a wide application prospect.
If the compatibility of polycarboxylate superplasticizer and cement is not good, the concrete mixture is prone to some problems, such as segregation, bleeding, greater slump loss, shorter setting time and so on, so that the concrete mixture can not be transported and poured normally. Reduce the strength and durability of concrete.
There are many factors affecting the compatibility of cement and superplasticizer, and the cement storage temperature is a key factor that can not be ignored. If the cement storage temperature is too high during concrete mixing, it will directly affect the physical and mechanical properties of cement.
Effect of cement temperature on the performance of concrete mixture:
When the cement temperature is above 60 ℃, a small amount of water is secreted from the concrete mixture. When the cement temperature is 100 ℃, the aggregate is separated from the paste, and the cohesion of the concrete mixture becomes worse. The reason for this negative effect is that the cement temperature is high, which makes the concrete mixture temperature rise rapidly in a short time. It is easier to stimulate the water-reducing function of polycarboxylic acid high-performance superplasticizer, release more free water wrapped in the mixture particles in the case of high temperature, and make a small amount of water bleeding in the concrete outlet.
Effect of cement temperature on setting time of concrete:
With the decrease of cement temperature, the setting time of concrete is prolonged, and the initial setting time is more obvious than the final setting time. In other words, the higher the cement temperature, the shorter the setting time of concrete. The reasons for the shortening of setting time caused by high temperature cement are as follows: (1) it will increase the temperature of the mixture in a short time and promote the hydration of cement particles; (2) the superplasticizer releases more free water to react with cement particles, thus forming a stable cementitious system in a shorter time.
With the passage of time, the heat contained in cement temperature is easily transferred to the surrounding particles or environment, the temperature of concrete system gradually approaches to the ambient temperature, and the temperature gap of concrete mixed with cement at different temperatures is gradually narrow. as a result, the difference of the final setting time of concrete is relatively reduced.
Effect of cement temperature on slump and air content loss of concrete:
At the same time, the higher the cement temperature is, the greater the slump loss rate is. The difference of slump loss rate under different temperature conditions increases at first and then decreases. Under the condition of the same slump loss rate, the lower the cement temperature is, the longer it takes to reach the slump loss rate, that is to say, the more beneficial to reflect the slump-retaining performance of the superplasticizer. When the cement temperature is high, in order to reduce the slump loss of concrete, it is necessary to put forward higher requirements for the slump retention of superplasticizer.
Summary,
1. For the concrete with the same mix ratio, with the increase of cement temperature, the adaptability of admixture and cement becomes worse. The higher the temperature is, the more water is consumed, and the fluidity of concrete mixture decreases, resulting in the decrease of concrete and workability. It even leads to the separation or bleeding of aggregate and paste.
2. The higher the cement temperature, the worse the adaptability of cement and superplasticizer, the greater the loss rate of slump and air content, and the shorter the setting time of concrete.
3. The effect of the change of cement temperature on the compressive strength of concrete is obvious. with the increase of cement temperature, the compressive strength of low heat cement concrete increases in the early stage (before 7 days), but the compressive strength of 28 days decreases with the increase of temperature.
4. It is suggested that the cement temperature for concrete mixing should not exceed 60 ℃. When it exceeds 60 ℃, the concrete production system should precool the raw materials of the mixing system as far as possible to avoid excessive temperature rise of the whole mixture system due to high cement temperature. and should strengthen the maintenance of the concrete after entering the warehouse to avoid the temperature cracks caused by the early hydration temperature rising too fast.
Concrete Additives Supplier
TRUNNANO is a reliable concrete additives manufacturer with over 12-year experience in nano-building energy conservation and nanotechnology development.
If you are looking for high-quality concrete additives, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)
We accept payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.
At first, concrete additives were used only to save cement. With the development of construction technology, admixture has become the main measure to improve the performance of concrete.
What are advantages of concrete additives?
It can reduce the water consumption of concrete. Or the fluidity of concrete can be increased without increasing water consumption.
The setting time of concrete can be adjusted.
Reduce bleeding and segregation. Improve workability and water elutriation resistance.
The slump loss can be reduced. Increase the pumpability of pumping concrete.
It can reduce contraction. The addition of expansive agent can also compensate for shrinkage.
Delay the initial hydration heat of concrete. Reduce the temperature rise rate of mass concrete and reduce the occurrence of cracks.
Improve the early strength of concrete. Prevent freezing at negative temperature.
Improve strength, increase frost resistance, impermeability, wear resistance, corrosion resistance.
Control alkali-aggregate reaction. Prevent the corrosion of steel bar and reduce the diffusion of chloride ion.
Made into concrete with other special properties.
Reduce the viscosity coefficient of concrete.
Where are concrete admixtures used?
1. It is suitable for mass concrete, high-strength and high-performance concrete, roller compacted concrete, concrete constructed in hot weather, concrete poured in a large area, concrete produced by cold joints, concrete that needs to be parked or transported for a long time, self-leveling vibration-free concrete, slip form construction or horizontal construction and other concrete that needs to delay setting time.
2. It is suitable for different grades of concrete under the daily minimum temperature of 5 degrees Celsius, as well as various continuous pouring projects of high flow concrete, commercial concrete, pumping concrete, prestress and reinforced concrete.
3. It is not suitable to be used alone for concrete with early strength requirements and steam curing concrete.
Concrete Additives Supplier
TRUNNANO is a reliable concrete additives manufacturer with over 12-year experience in nano-building energy conservation and nanotechnology development.
If you are looking for high-quality concrete additives, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)
We accept payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.
Modern concrete is represented by ready-mixed concrete produced in industrialization, and pumping construction is the mainstream. Mechanical properties are no longer the only technical index of modern concrete, and the control of mixing and rheological properties is particularly important to ensure the construction. At the same time, the requirements to ensure the durability of concrete structures are increasing day by day. In the process of production and use, we should pursue the principle of sustainable development.
Technical characteristics of modern concrete
More complex components
The wide application of mineral admixtures mainly derived from industrial solid wastes diversifies the composition of cementitious materials, which is one of the main characteristics of modern concrete. Conventional mineral admixtures such as ground slag powder and fly ash have become important components of modern concrete, and functional mineral admixtures such as silica fume, ultra-fine stone powder, calcined kaolin and zeolite powder have also been applied in modern concrete. as mineral admixtures, various metallurgical and industrial tailings have been gradually applied to modern concrete. Chemical admixture represented by high-performance superplasticizer is another main feature of modern concrete. the emergence of high-performance superplasticizer greatly reduces the water-binder ratio of concrete, and the strength of concrete has been greatly improved. Ultra-high-strength concrete above C100 has achieved high-rise pumping construction. Some special materials are also gradually applied to modern concrete, such as expansive agent, fiber material, air entraining agent, consistency adjustment material, density adjustment material, durability reinforcement material and so on. In terms of concrete aggregate, high-quality natural aggregate resources are increasingly scarce, machine-made sand and low-grade aggregate have begun to enter the field of ready-mixed concrete, and the water absorption and mud content of aggregate are increasing. With the complexity and diversification of modern concrete components, the initial fluidity of concrete is greatly reduced and it is more difficult to maintain the fluidity of concrete.
Higher construction requirements
The complex structure and harsh construction environment of modern engineering require higher and higher fluidity of concrete. The construction of super high-rise, super-large volume and complex structure requires excellent pumping performance of concrete, and can realize self-compacting construction, so as to reduce labor intensity and ensure the compactness of concrete; long-distance transportation or long-time pouring requires a long time to keep concrete fluidity; nuclear power and hydropower projects require concrete fluidity to be stable and has little fluctuation over time. The super early strength project requires not only high early strength of concrete, but also long construction time; in harsh environment, especially in the high temperature environment above 40 ℃, the hydration rate of cement is intensified, but concrete is still required to be pumped for construction after 3 hours. Therefore, high fluidity and fluidity, good and workability, and can achieve self-compaction is the fundamental to meet the requirements of modern concrete construction.
The problem of shrinkage cracking is more prominent.
The large amount of modern concrete cementitious materials, finer and finer cement, more and more complex components and lower water-binder ratio make the problem of shrinkage cracking more prominent. The simple pursuit of high profit to meet the strength makes the effect of cement through grinding aids become finer and finer, the specific surface area is as high as 420m2/kg, the hydration rate is accelerated, the hydration heat release rate increases, and the internal water consumption rate of concrete is too fast, and the development of high strength reduces the water-binder ratio to 0.18 and free water. The extensive use of ultra-fine mineral admixtures increases the shrinkage of concrete, increases the sensitivity of cracking, and makes concrete more prone to shrinkage cracks, thus reducing the frost resistance, carbonation resistance, corrosion resistance and so on. In addition, with the continuous expansion of the scope of human activities and the progress of construction technology, concrete projects in harsh environments such as dryness, cold and heavy corrosion are increasing day by day, and modern concrete is facing a harsher service environment than traditional concrete. the risk of cracking increases, and the problem of durability is more prominent.
Why is polycarboxylate superplasticizer more suitable for modern concrete?
The traditional lignin sulfonates, naphthalenesulfonic acid condensates and aliphatic superplasticizers have limited dispersion ability and low water reducing rate because of their inherent molecular structure. even if the content is increased, it is difficult to meet the requirements of high fluidity and fluidity of modern concrete under the condition of complex components and low water-binder ratio. Polycarboxylate admixture has flexible molecular structure and strong designability. Through targeted molecular construction, high performance and functionalization can be achieved to meet the different performance requirements of modern concrete, so as to improve the engineering quality.
Concrete Additives Supplier
TRUNNANO is a reliable foaming agents supplier with over 12-year experience in nano-building energy conservation and nanotechnology development.
If you are looking for high-quality polycarboxylate superplasticizer, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)
We accept payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.
Prestressed or precast concrete
Adding polycarboxylate superplasticizer can make the compressive strength of precast concrete reach 40MPa grade at 8h to 18h; the precast concrete mixed with polycarboxylate superplasticizer can get higher early strength under the condition of lower curing temperature and shorter curing time, thus reducing the energy consumption of curing; in addition, it can save cement, reduce vibration energy consumption, reduce noise and improve the turnover rate of the mold.
Shrinkage compensating concrete
When preparing shrinkage compensating concrete, adding a certain amount of polycarboxylate superplasticizer can reduce the water-cement ratio, increase the early shrinkage of concrete and reduce the later shrinkage of concrete, thus saving expansive agent or expansive cement.
Ordinary aggregate concrete
For ordinary aggregate concrete, the addition of polycarboxylate superplasticizer can reduce the pumping pressure and pipe pressure by about 30%; for lightweight aggregate concrete, the addition of polycarboxylate superplasticizer can reduce the pumping pressure and pipe pressure by more than 10%; in addition, the addition of polycarboxylate superplasticizer can reduce the increase of pumping resistance with the increase of pumping speed.
Steel-fiber reinforced concrete
For steel fiber reinforced concrete, the addition of polycarboxylate superplasticizer can reduce the workability loss caused by the addition of steel fiber; of course, compared with the concrete without steel fiber, the amount of polycarboxylate superplasticizer mixed with steel fiber reinforced concrete should be appropriately increased.
Super high strength concrete
Polycarboxylate superplasticizer has good water-reducing dispersion and strengthening effect, so it can be used to prepare ultra-high strength concrete. The study found that the concrete mixed with polycarboxylate superplasticizer (20%), which accounts for 1% to 3% of the weight of the cementitious material, can make the 100-day-old strength as high as 150MPa.
High-alumina cement concrete
In order to ensure the performance of high-alumina cement concrete, the general water-cement ratio is not higher than 0.40 and the cement content is not lower than 400kg/m3, otherwise the strength of concrete, especially in the later stage, will decrease. The reason is that metastable calcium aluminate hydrate is transformed into steady tricalcium aluminate hydrate. If polycarboxylate superplasticizer is added to high alumina cement concrete, the fluidized concrete with good workability can be obtained under the condition of low water-cement ratio, and the later strength of concrete is not affected. That is to say, the 2d compressive strength of high alumina cement superplastic concrete mixed with polycarboxylate superplasticizer is lower than that of standard concrete, while the compressive strength of 180d age is basically the same as that of base concrete, because polycarboxylate superplasticizer has no obvious effect on the hydration rate of high alumina cement.
High-performance concrete with high content of active admixtures such as fly ash, slag, and silica fume
When preparing high-strength concrete with a large amount of fly ash instead of ordinary cement, adding polycarboxylate superplasticizer can improve workability, reduce mixing water consumption by about 20%, and further improve strength. The addition of polycarboxylate superplasticizer into concrete can increase the amount of cement-based substitute materials such as fly ash or slag and reduce the amount of cement without affecting the strength of concrete. therefore, it has outstanding environmental and economic benefits. Similarly, when silica fume is added to cement slurry or concrete, the amount of water needed to achieve the same workability increases with the increase of silica fume content. For this reason, under the condition of a certain amount of silica fume, polycarboxylate superplasticizer can be added to reduce the water consumption of mixing, and polycarboxylate superplasticizer can also be added to increase the amount of silica fume under the condition of a certain amount of water consumption.
Concrete Additives Supplier
TRUNNANO is a reliable foaming agents supplier with over 12-year experience in nano-building energy conservation and nanotechnology development.
If you are looking for high-quality polycarboxylate superplasticizer, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)
We accept payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.
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