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.
Foam concrete, also known as lightweight cellular concrete (LCC), low-density cellular concrete (LDCC), and other terms, is defined as a cement-based slurry with a plastic mortar containing at least 20% foam per volume. Since coarse aggregate is not used in most cases to produce foam concrete, the correct term should be mortar rather than concrete; It can also be called "foam cement". The density of foam concrete usually varies from 400kg/m3 to 1600kg/m3. Density is usually controlled by replacing all or part of the fine aggregate with foam.
Foam Concrete History
The 1930s blacksmith bridge was filled with foam concrete.
The history of foam concrete dates back to the early 1920s when autoclaved aerated concrete was produced primarily for insulation. Detailed studies on the composition, physical properties, and production of foam concrete were first carried out in the 1950s and 1960s. Following this study, new admixtures were developed in the late 1970s and early 1980s, which led to the commercial use of foam concrete in construction projects. Originally, it was used for void filling and ground stabilization in the Netherlands. Further research carried out in the Netherlands has contributed to the wider use of foam concrete as a building material. Recently, continuous foam generators are being used to make foam concrete. Foam is produced by mixing the foaming agent with compressed air to make "aircrete" or "foam create". This material is fireproof, insect-proof, and waterproof. It provides significant heat and sound insulation and can be cut, carved, drilled, and molded using woodworking tools. This building material can be used to make foundations, subfloors, building blocks, walls, domes, and even arches reinforced with fabric.
Foam Concrete Manufacturing
Foam concrete usually consists of cement slurry or fly ash, sand, and water, but some suppliers recommend using pure cement and water as well as foaming agents to make a very lightweight mixture. The slurry is further mixed with synthetic inflatable foam in a concrete mixing plant. The foam is created using a foaming agent, which is mixed with water and air from a generator. The foaming agent must be able to produce highly stable bubbles that are resistant to the physical and chemical processes of mixing, placement, and hardening.
The foam concrete mixture can be poured or pumped into molds or poured directly into structural elements. Due to the thixotropic behavior of foam bubbles, foam enables the slurry to flow freely, making it easy to pour into selected forms or molds. Viscous materials can take up to 24 hours to cure (or as little as 2 hours if the steam curing temperature reaches 70°C to speed up the process. Depends on variables, including ambient temperature and humidity. Once cured, the resulting product can be released from its mold. A new application in the manufacture of foam concrete is to cut large concrete blocks into blocks of different sizes by cutting machines using special steel wires. The cutting action takes place before the concrete has completely cured.
Concrete Foaming Agent Supplier
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Chemical admixtures are in high demand in concrete technology to improve their properties such as durability, fluidity, setting and mechanical properties. Among these chemical admixtures,superplasticizers are mainly used to improve fluidity at relatively low water-cement ratios (W/C). First-generation superplasticizers (SP) such as sulfonated naphthalene formaldehyde condensate (SNF) and sulfamic acid formaldehyde condensate (ASF) can disperse cement particles through an electrostatic repulsion mechanism. A new generation of SP is based on polycarboxylate ether comb copolymers with carboxyl groups and poly(ethylene oxide) (PEO) side chains. PCE copolymers can generate electrostatic repulsion and steric hindrance, therefore, they provide better performance than the older generation. The molecular weight and side chain length of PCE can be easily tailored to make it superior to other kinds of SP.
Free radical polymerization (FRP) is widely used to prepare PCE copolymers, but has less control over molecular weight and molecular weight distribution (even with chain transfer agents to control the polydispersity index D = Mw/Mn values are usually higher than 1.5 molar mass) , producing polymer chains with broad molar mass distributions and potential variations in chemical composition Monomers with different reactivity. Over the past two decades, the controlled radical polymerization technique has been developed as a general method that provides free radical synthesis of polymers with predetermined molecular weights and narrow molar mass dispersion. Reversible addition-fragmentation chain transfer (RAFT) polymerization is a controlled/living radical polymerization technique that is compatible with a wide variety of monomers. Only very few studies have used RAFT polymerization to prepare PCE superplasticizers, focusing on block copolymers ignoring their potential applications in PCE random copolymers.
To gain an accurate understanding of the effects of side chain length and charge properties on PCE adsorption behavior, we employed RAFT polymerization in this work to obtain well-defined copolymers with different side chains and functions, enabling a more systematic assessment of the structural parameters of PCE. Performance. This is the first study to report the use of well-defined copolymers (D < 1.3) to compare the effects of side chain length and charge type of PCE on the dispersibility of cement pastes. In this study, two copolymers containing COO - or SO 3 - as charge types (PCE and PSE, respectively) were synthesized to investigate the effect of specific functional negatively charged groups on the adsorption and rheological properties of cement pastes. influences. On the other hand, in the case of PCE copolymers, three different PEO side chain lengths were employed to study their effect on cement fluidity. Adsorption studies, zeta potential measurements, mobility and rheological properties are also explored in this work.
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Foamed cement, as a new building insulation material, has the advantages of good heat preservation, heat insulation and sound insulation, and a high fire rating. It is generally a light and porous structural material made of a chemical foaming agent to produce bubbles in the cement slurry. It is widely used in wall insulation, roof insulation, foundation backfill, and so on, with broad prospects.
However, foamed cement preparation, slurry easy segregation, bleeding, products easy cracking, poor toughness, and other problems are very common. Our years of research in the laboratory have found that these problems can be effectively solved by adding modified polypropylene fibers.
Polypropylene fiber is more commonly used, but the surface of ordinary polypropylene fiber is smooth, the molecular chain does not contain polar groups, and when mixed with foamed cement, there are problems such as poor dispersion performance and poor binding performance with the basic interface, which seriously weaken its effect, so it is very important for surface modification.
Surface chemical grafting modification of polypropylene fiber is the use of peroxide as initiator, the first introduction of active center in the polypropylene fiber, and then with functional monomers, such as acrylic acid, maleic anhydride, graft copolymerization, the introduction of polar branch chain in the fiber, to improve the hydrophilicity, adhesion and so on.
After acrylic chemical graft modification, polypropylene fiber and cement matrix to be enhanced chemical bonding force, improve the interface bonding between the two, inhibits foam cement native new cracks and constraints in the extension of crack and extension, thus can reduce the plastic shrinkage cracking of foamed cement and refine the plastic shrinkage crack.
Suppliers of Concrete Additives
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 CLC foaming agents, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)
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Concrete is an indispensable raw material in the construction of construction projects. In the process of preparing concrete, in order to improve the performance of concrete, it is necessary to add water reducing agent after adding water, stone, sand and cement. Then sufficient mixing can greatly improve the fluidity and strength of concrete. The more common superplasticizers in daily work are mainly polycarboxylate superplasticizers. This water reducing agent is widely used due to its advantages of high water reduction rate, high slump retention performance, and good economy.
1 Analysis of the mechanism of action of polycarboxylate superplasticizers
Polycarboxylate superplasticizer is mainly composed of carboxylic acid grafted polymer, light brown, is a transparent liquid. Its main mechanism of action includes two kinds of maintaining dispersion mechanism and dispersion mechanism. Polycarboxylate superplasticizers are currently widely used in the field of construction engineering because polycarboxylate superplasticizers have very stable chemical properties compared to ordinary superplasticizers; they are transparent liquids and are easy to transport. In this way, a lot of transportation costs are saved, and the waste of resources is also reduced.
At present, the most used polycarboxylate water reducer is mainly acrylic acid as the main chain, but it is the hydroxyl and carboxyl molecules that play a role. These two molecules can combine with water molecules in concrete, thereby promoting The flocculation structure is destroyed, so that the microstructure of the concrete changes, which makes the concrete set and harden faster. The relevant chemical molecules in the polycarboxylate water reducer will be combined with the cement particles, which will speed up the fluidity of the concrete, and then obtain the desired ideal state, which can further highlight the characteristics of the concrete. However, in the process of actually using polycarboxylate water reducer, this water reducer has higher requirements on the outside temperature range during the use of concrete. Whether the construction temperature is too high or too low, it will affect the characteristics of the polycarboxylate water reducer, so that the ideal effect cannot be achieved.
2 Water reduction rates of different dosages
In this paper, ten kinds of water reducing agents (PCE-1~PCE-10) are selected for analysis, and the specific water reducing rate is shown in Figure 1.
When the content of polycarboxylate superplasticizer is 0.15%, the water reduction rates of PCE-1, PCE-2, PCE-4, PCE-6 and PCE-7 are all higher than 20%, showing a higher Water reducing rate; once the content of polycarboxylate water reducing agent is higher, that is, when it reaches 0.2%, these water reducing rates will be higher (25%-30%); When the dosage is not higher than 0.3% and not lower than 0.25%, the water reduction rates of PCE-2, PCE-4, PCE-6, PCE-7 and PCE8 all reach (30%) ~35%).
3 Analysis of the influence of concrete raw materials on polycarboxylate water reducer
3.1 Influence of cement on polycarboxylate superplasticizer
There are essential differences between ordinary lignosulfonate-based superplasticizers, naphthalene-based superplasticizers and polycarboxylic acid-based superplasticizers. Polycarboxylate superplasticizers have the advantages of being environmentally friendly, harmless, strong in slump retention and high in water reduction rate, so they are widely used. However, this water reducing agent also has certain defects, that is, the problem of poor adaptability, but this is also a common defect of ordinary water reducing agents. For example, when a certain cement is applied, there may be characteristics such as poor fluidity of the cement slurry and poor water reduction effect, and the main reason for this phenomenon is due to the molecular structure of the substance itself. composition and surface properties.
3.2 Influence of fine aggregate on polycarboxylate superplasticizer
Machine-made sand and natural sand are the more commonly used fine aggregates in concrete, and are one of the raw materials for concrete preparation. Natural sand is divided into three types: river sand, mountain sand and sea sand. However, it should be noted that in the process of preparing concrete, do not use a large amount of polycarboxylate water-reducing agent. Once excessive, it will inevitably react with fine aggregates, which will not only affect the slump of concrete, but also affect the concrete. strength is adversely affected. In addition, another important factor that affects the adaptability of concrete and polycarboxylate superplasticizers is the content of stone powder in the sand. If sand with high stone powder content is used in the process of preparing concrete, it is very likely to have a series of effects on the fluidity of concrete. In addition, other characteristics of fine aggregates will also affect the adaptability of concrete and polycarboxylate superplasticizers, such as the thickness of sand. Generally speaking, if the fineness of the sand is less than the standard value, it will cause rapid loss of fluidity of the concrete. At the same time, the sand ratio and the residual sulfate and chloride ions in the sea sand will reduce the water of the polycarboxylate system. The adaptability of the agent has a certain degree of influence. In addition to the above factors, the content of mud in the sand will also affect the adaptability and performance of the polycarboxylate superplasticizer. The main reason is that the soil has a strong adsorption force, and this strong adsorption force will affect the water reducing rate of the water reducing agent. The mud content of different substances will also be different. Generally speaking, the content of soil in the sandstone will have a greater effect on the polycarboxylate superplasticizer. When the mud content in the sandstone exceeds 3%, the performance of the water reducer will be significantly reduced. , even adding an appropriate amount of mixing will not promote the fluidity of concrete.
3.3 Influence of coarse aggregate on polycarboxylate superplasticizer
Another important factor affecting polycarboxylate superplasticizer is coarse aggregate. This performance is mainly reflected in the gradation of the stone and the content of needle flakes. Even for stones with the same gradation, if the acicular content of the stones increases, the flow rate of the concrete will inevitably slow down, and the decrease in expansion may lead to bleeding or segregation. In addition, the water absorption of coarse aggregates with different thicknesses will also be different. Generally speaking, the water absorption of fine aggregate is higher than that of coarse aggregate. Even changing the air content or dosage of the water reducing agent cannot achieve the expected purpose. Only by adjusting the mix ratio of concrete can it be changed. Therefore, in the actual construction process, it is necessary to continuously adjust the stone gradation and the mud content of the sand according to the actual situation of the raw materials, and seek the best solution.
4 Conclusion
In summary, admixtures play a vital role in the preparation of high-performance concrete, and are therefore indispensable raw materials in the preparation of concrete. At present, polycarboxylate superplasticizers are widely used due to their many advantages. In order to better promote the further development of this superplasticizer, the mechanism and influence of concrete raw materials on polycarboxylate superplasticizers must be investigated. Carry out in-depth research, and at the same time focus on mastering its laws, so that high-performance polycarboxylate water reducers can be prepared in the later stage.
TRUNNANO is a concrete additives supplier with over 12 years experience in nano-building energy conservation and nanotechnology development. 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.
If you are looking for high quality polycarboxylate superplasticizer, please feel free to contact us and send an inquiry.
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