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.
As the most widely used material on earth, concrete creates a massive carbon footprint that scientists work to eliminate in various ways.
The world's first graphene-reinforced concrete slab pouring work was recently completed using Concrete. Research projects have shown what the fantastic material graphene can do in this regard. Now we're seeing the first real-world deployment of the technology: Engineers are using graphene to enhance "concrete" to create the foundations of a new gym in the UK.
As the world's strongest artificial material, graphene may have many other potential uses, including in construction. Scientists have successfully incorporated it into the concrete manufacturing to make the finished product stronger and more waterproof. At the same time, one research project even demonstrated how to recycle this graphene from old tires.
The newly poured concrete is the work of scientists from the University of Manchester and national engineering and construction companies. To form the material, the team added small amounts of graphene to water and cement, which both acted as mechanical support and provided an additional catalyst surface for the chemical reactions that turned the mixture into a concrete paste. The result is improved bonding on a microscopic scale, and the material is around 30% stronger than standard concrete.
Dr Craig Dawson from the University of Manchester said: "We have produced a graphene-based additive mixture that does not interfere when used. "This means we can add the additive directly at the batching plant where the concrete is produced. , as part of the existing system, so there will be no changes to production or construction crews laying the floors."
Concrete production accounts for approximately 8% of global carbon emissions. Because graphene concrete is much stronger than traditional concrete, a building would require much less concrete to achieve the same structural strength, which could result in a smaller carbon footprint and cost and significant savings in building materials.
Nationwide Engineering analyzed the data and claimed that if the concrete was used in the global supply chain, it could reduce emissions by up to 2% globally. The material costs about 5% more to produce, but because less material is required, the company estimates it can provide customers with 10% to 20% savings.
TRUNNANO is a supplier of additives for concrete, which is concrete and relative products with over 12 years experience in nano-building energy conservation and nanotechnology development. It accepts 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. If you are looking for other additives for concrete, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com).
The rational use of release agents can effectively improve the appearance and durability of concrete.
With the increasing use of mold release agents, some suggestions on the use of mold release agents are put forward in order to give full play to the application effect of mold release agents.
Try to use a clean water dilution release agent; conditional use of softening water is best.
Minerals such as metal ions in groundwater react with some auxiliaries in the release agent to produce insoluble and floating substances, which leads to the deterioration of the effect of the release agent and the difficulty of normal spraying to affect the construction quality.
In winter construction, this point should be paid more attention to. With the decrease in temperature, the auxiliaries in the release agent have the phenomenon of flocculation and agglomeration, which leads to the deterioration of the solubility of the release agent. During the on-site construction, the release agent can be diluted with warm water. Or follow the step of adding water step by step (first 1 part of the release agent 0.3 parts of water is stirred evenly, and then the rest of the water is added) to ensure the normal mixing of the release agent.
In addition, in the case of low temperature, the emulsifying activity of the auxiliaries in the release agent decreases, which makes the insoluble matter more obvious, so when the temperature is low, the probability of insoluble matter in the water release agent becomes higher.
Spraying water-containing release agents is not recommended when the temperature is below 5 ℃. The main reason is that the separation film can not be formed normally after the release agent is applied.
Release agents in the concrete solidification process will affect the hydration process of cement. Too much release agent may affect the normal setting of cement, seriously leading to direct pulverization of cement.
In the process of construction, the dilution ratio of the release agent should be adjusted according to the actual situation, and the parts of the mold which are easy to accumulate liquid should be scrubbed in time.
During the construction in winter, the concrete admixture should be adjusted in time to avoid mold contamination due to the failure of normal solidification of concrete in the corresponding time; in addition, the dilution ratio of the release agent and the type of release agent should also be adjusted accordingly.
For the facade mold, the dilution ratio of the release agent in winter should be lower than that in summer because the adhesion ability and film-forming ability of the release agent become worse when the temperature is low.
For flat molds, a release agent with stronger isolation performance should be used in winter to prevent concrete from touching the formwork directly before it is completely hardened.
For general water-based release agents, concrete should be poured after the release agent is dried into a film, such as after the milky white of the water-based release agent fades completely.
If the release agent is not completely dry, the isolation can not be brought into full play, the complete isolation layer can not be formed, and the isolation film is uneven, which leads to the difficulty of concrete molding or uneven surface color of concrete.
In the process of winter construction, the release agent should be sprayed at the time of the highest temperature or sprayed first and then smeared to ensure the normal film formation of the release agent to play the best demolding effect.
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Aluminate cement (Aluminate Cement, referred to as AC) is commonly used in special engineering fields, and CA50-A600 is a type of aluminate cement.
CA50-A600 aluminate cement is composed of calcium aluminate (CA) and a certain proportion of gypsum and other minerals, with high compressive strength, corrosion resistance, and good heat resistance, so it is widely used in construction, chemical industry, metallurgy, and other industries.
1. Rapid hardening: CA50-A600 aluminate cement has a fast initial and final setting time and can quickly achieve high compressive strength. It suits emergency repair, high-temperature environments, and engineering projects requiring rapid hardening.
2. High-temperature resistance: CA50-A600 aluminate cement can still maintain high compressive strength and heat resistance at high temperatures, so it is suitable for buildings and equipment in high-temperature environments.
3. Chemical corrosion resistance: CA50-A600 aluminate cement has good corrosion resistance to a variety of acids, alkalis, salt, and other chemical meda and can maintain a long service life in a harsh chemical environment.
4. Wear resistance: CA50-A600 aluminate cement has high wear resistance and can meet the needs of high strength and high wear environments.
5. Low dry shrinkage: compared with ordinary Portland cement, CA50-A600 aluminate cement has lower dry shrinkage, which helps reduce the occurrence of cracks.
1. High-temperature and high-pressure equipment: equipment and structures in high-temperature environments, such as thermal power plants, smelters, chemical plants, etc.
2. Chemical corrosion environment: chemical fertilizer plants, petrochemical plants, and other projects containing acid, alkali, salt, and other chemical media.
3. Wear-resistant floors, such as machinery factories, workshops, warehouses, etc., which need to withstand high-strength wear.
4. High-speed railway: CA50-A600 aluminate cement can be used in track beds, prefabricated sleepers, and supporting structures of high-speed railways because of its high strength, wear resistance, and frost resistance.
5. Underground works: CA50-A600 aluminate cement can provide faster construction progress and longer service life in underground projects such as tunnels and subways.
6. Water conservancy and hydropower projects: in reservoir dams, hydropower stations, drainage systems and other water conservancy and hydropower projects, CA50-A600 aluminate cement has high impermeability and corrosion resistance.
7. Ocean engineering: CA50-A600 aluminate cement shows high corrosion resistance and seawater erosion resistance in offshore platforms, ports, breakwaters and other marine engineering.
8. Emergency repair works: in the emergency maintenance projects of infrastructure such as roads and bridges, CA50-A600 aluminate cement can shorten the construction period and reduce the project cost because of its rapid hardening characteristics.
9. Prefabricated components: CA50-A600 aluminate cement can make prefabricated components, such as pipe piles, bridge supports, etc., to improve engineering quality and construction efficiency.
10. Refractories: CA50-A600 aluminate cement can produce refractories, such as refractory bricks, plates, etc., with good fire resistance.
CA50-A600 aluminate cement has a wide application prospect in many special fields because of its unique physical and chemical properties.
However, because of its relatively high price, its application in ordinary civil construction is limited.
When selecting CA50-A600 aluminate cement, a comprehensive evaluation should be made according to specific engineering requirements and environmental conditions.
TRUNNANO is a reliable concrete additives supplier 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)
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The cracks caused by concrete shrinkage affect not only the bearing capacity, waterproof performance, and safety of concrete but also its durability.
The prevention of concrete shrinkage cracks is mainly from the external and internal aspects of concrete.
Starting from the outside of concrete, mainly through reinforcement, setting expansion joints or post-pouring belts and other means to achieve the restraint and prevention of concrete shrinkage cracking.
On the other hand, it is to avoid the potential factors that may lead to concrete shrinkage cracking as far as possible, such as optimizing the mix proportion of concrete, adding fiber, expansion agent, shrinkage reducing agent, shrinkage reducing polyanionic acid superplasticizer or internal curing, etc.
The main results are as follows:
1) adding fiber to concrete can disperse the internal stress distribution of concrete and homogenize the tensile stress to reduce the shrinkage cracks of concrete.
PP fiber is randomly supported inside the concrete, which helps to restrain the concrete and reduce the shrinkage of the concrete.
Adding fiber can reduce the shrinkage of concrete and improve the splitting tensile strength, flexural strength and toughness of concrete.
Steel fiber, glass fiber and polymer fiber are commonly used in concrete.
However, the addition of fiber can not fundamentally eliminate the existence of cracks.
Moreover, steel fiber is easily eroded by chloride; the organic fiber will age and fail under the action of heat, oxygen, and ultraviolet rays; the dispersion of the fiber also dramatically affects its ability to prevent cracking.
In addition, the fiber also has the problems of high cost and poor compatibility with concrete.
2) Adding an expansive agent to concrete can produce expansive stress to compensate for shrinkage and effectively reduce early shrinkage and deformation of concrete.
Chen Meng mixed expansive agents into concrete and tested the molded specimens under standard and natural curing conditions. The test results show that the best age of the expansive agent is (1-3) d, and coagulation will produce more considerable shrinkage deformation after (3-5) d.
In addition, the effect of an expansive agent is closely related to concrete curing conditions. If cured under natural conditions, the shrinkage strain of concrete with an expansive agent after 28 days of age is the same as that of concrete without an expansive agent.
To ensure the full effect of the expansion agent, the specimens mixed with the expansion agent must be maintained under humidity greater than 95%.
Although expansive agents can compensate for concrete shrinkage to some extent, many factors affect the effect of expansive agents.
Generally speaking, the amount of expansive agent is 10% / 12% of cement quality, and the amount is relatively large, so it is more expensive to add expansive agent to compensate for shrinkage.
The effect of an expansive agent is also challenging to control; on the one hand, it is difficult to control the amount of expansion; on the other hand, the effect of an expansive agent has a great relationship with the humidity of the curing environment, and the concrete mixed with an expansive agent must be wet cured.
In the case of a relatively low water binder, the hydration of the expansion agent will also be inhibited, affecting the expansion effect.
3) Shrinkage reducing admixture
To solve the problem of shrinkage cracking of concrete, the most commonly used solution is to use chemical admixture, which is called shrinkage reducing agent (Shrinkage reducing admixture, SRA).
Concrete shrinkage-reducing agents can effectively reduce the self-shrinkage and drying shrinkage of concrete.
The mechanism of SRA can be summarized as follows:
1) reduction of shrinkage stress caused by surface tension and capillary pressure.
2) due to the slow evaporation of water, the internal humidity of concrete can be better maintained:
3) the total porosity decreases, and the pore structure is refined.
4) the polarity of water decreases, so the solubility of ions decreases, hydration is delayed, and shrinkage is reduced.
5) the adsorption of SRA on pores or C-S-H hinders the accumulation of C-S-H, increases the cavitation pressure of water in pores, and releases part of the tensile stress induced by capillaries, thus reducing the drying shrinkage.
However, SRA will prolong the setting time of concrete, affect the strength, and even lead to a decline in durability.
When SRA is mixed with other admixtures, there is also a compatibility problem.
4. High-performance super absorbent resin
Because of its strong water absorption capacity, superabsorbent resin (Superabsorbent polymer, SAP) can be mixed into concrete materials to carry out internal curing of concrete through the water absorption-release effect of SAP and reduce concrete shrinkage.
However, SAP often hurts the mechanical properties of concrete.
It is generally believed that although the addition of SAP can reduce the self-shrinkage of concrete, the existence of SAP will increase the porosity of concrete, resulting in the decrease of compressive strength and elastic modulus of concrete.
Summary
The cracks caused by shrinkage of concrete affect the mechanical properties, waterproofing and durability of concrete to a great extent.
The cracking problem related to shrinkage is the biggest threat to concrete's durability and structural safety.
To limit the shrinkage of concrete and reduce the shrinkage cracks, the researchers put forward some external measures, such as reinforcement, setting expansion joints and post-pouring belts. Still, they can not eliminate the cracks fundamentally.
Effective measures can be taken from the point of view of materials to reduce concrete shrinkage, such as adding expansive agents, fiber, super absorbent resin, shrinkage-reducing agents, reducing polyanionic acid superplasticizer, etc.
However, these methods still have limitations.
However, the author believes that synthesizing reduced PCE with both water-reducing and shrinkage-reducing functions by introducing functional groups into PCE is a technical measure to kill two birds with one stone.
In the future, the preparation, properties and application properties of reduced PCE should be further studied and explored.
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