At present, early-strength superplasticizer is an environmentally friendly product, but it is a chemical product after all. Workers should avoid direct skin contact when working. Having been engaged in early strength production for many years, the harm should be very small and the toxicity should be very small.
Don't eat it, just wash it with water on your hands. The main raw material of early-strength superplasticizer is naturally biodegradable, and the production process is very environmentally friendly. It may have a pungent odor, but if you don't inhale it for a long time, it shouldn't be a big problem. There is no harm in direct contact and it is not edible. This product can strengthen the strength of concrete and enhance workability. It is a very good product. There is no harm in direct contact. It is weakly alkaline, non-toxic, harmless and inedible.
The water-reducing agent used for concrete is early-strength mother liquor. The five characteristics of early-strength mother liquor are: 1. Green and environmentally friendly: the raw materials used are non-toxic and harmless, and the production process There are no three wastes produced. 2. High concrete hardening and durability: Concrete has high strength at all ages, good volume stability, and outstanding anti-permeability, freeze-thaw resistance, corrosion resistance and carbonization resistance; 3. Wide adaptability: suitable for Portland cement, ordinary silicon Salt cement, slag silicate, fly ash cement, pozzolan cement and various admixtures have wide adaptability. 4. Outstanding comprehensive performance: The product has a high water reduction rate (the water reduction rate can reach more than 35%) and a low slump loss rate, which improves the working performance of concrete and increases the strength and durability of concrete. 5. Good workability of concrete: Fresh concrete has good workability, no segregation, no bleeding, good cohesion, moderate air content, and is suitable for pumping.
As the latest generation of high-performance admixtures, early-strength water-reducing admixtures are increasingly used in engineering applications. From precast concrete components to cast-in-place concrete, from self-compacting concrete, fair-faced concrete to special concrete that requires rapid setting and early strength, from railways, bridges, hydropower and other fields to municipal and civil construction projects, early-strength water-reducing agents are occupying an increasing share. The greater the market share. However, after all, the application time of early-strength water-reducing agent in engineering is still relatively short, and there is relatively little basic research on its application technology. Most users rely on the manufacturer's propaganda, past experience, and even their feelings. It is inevitable that some of them are difficult to apply or even understand. misunderstanding.
Common descriptions of the performance of early-strength water-reducing admixtures are: high water-reducing rate, very good adaptability to cement, good concrete workability, one hour No loss in slump, etc. In fact, the composition of cementitious materials is complex and changeable. From the perspective of adsorption-dispersion mechanism, it is impossible for any admixture to adapt to all situations. The early-strength admixture has good adaptability to cement compared with naphthalene-based water-reducing admixtures.
The workability of concrete can generally be divided into fluidity indicators and stability indicators. Concrete mixed with early-strength water-reducing admixture has better workability, and no obvious segregation or bleeding will occur at higher dosages or higher water consumption. The settlement of concrete in the formwork is also smaller, that is, In terms of stability indicators, the adaptability of early-strength superplasticizers to cement is significantly better than that of naphthalene-based superplasticizers. But in terms of liquidity indicators, this is not necessarily the case.
(1) The adaptability of early-strength superplasticizer is directly related to its dosage
We all know that high-grade concrete with a higher dosage of naphthalene-based water-reducing agent has better fluidity and smaller slump loss; however, medium and low-grade concrete often has poor fluidity and larger slump loss, and appropriately increasing the dosage is The most effective measures to improve adaptability. The same is true for early-strength admixtures. The author used cementitious materials and aggregates commonly used in Beijing to prepare C30 concrete, and used early-strength water-reducing admixtures as admixtures. It was found that the amount of water-reducing admixture (solidification) was between 0.13% and 0.15%. Over time, concrete can obtain better fluidity, but the slump loss is generally larger. No matter what kind of commonly used retarder is mixed and how much dosage is added, when the amount of water-reducing agent reaches 0.16%, most concrete will Good fluidity can be maintained after 1 hour.
(2) Cement with poor adaptability to naphthalene-based water-reducing agents generally has poor adaptability to early-strength water-reducing agents
Generally speaking, cement with high alkali content, high aluminate content or high fineness requires large amounts of water. The higher the dosage of naphthalene-based water-reducing admixture, the greater the slump loss. Similarly, the same rule applies to early-strength water-reducing admixtures. Some cements mixed with naphthalene-based water-reducing agents that have delayed bleeding will also bleed if early-strength water-reducing agents are used, but to a slightly lesser extent. If the cement has abnormal slump loss due to gypsum (the concrete loses fluidity a few minutes after leaving the machine), the use of early-strength water-reducing admixture will not improve it. Only supplementing sulfate ions at the same time can fundamentally solve the problem. , which is consistent with naphthalene-based water reducing agent.
(3) The "adaptability" of a specific early strength product is not as good as that of naphthalene series products
;">Naphthalene series products are products with the same structural properties that are synthesized from the same raw materials under the same process conditions. Early-strength superplasticizers are products with similar molecular structures that are synthesized from different raw materials under different process conditions. The difference in naphthalene series products is mainly reflected in the quality of raw materials and the stability of process conditions, while the difference in early-strength products is based on the difference in chemical molecular structure. Specific to applications, naphthalene series products are suitable for different situations.The adaptability is more reflected in the fluctuation of the optimal dosage within a certain range or the relative size of the slump loss value. For a specific early-strength product, the situation is completely different: if the product can adapt to the concrete material, the concrete will be in good condition and the collapse loss will be small; if it cannot adapt to the concrete material, the result will not be a difference in degree, but may be completely different. If it fails, you must switch to another type of product to solve the problem. In fact, this happens often, especially when northern raw materials are used. The possible reasons are cement minerals, trace elements or grinding aids, etc. That is to say, in terms of "adaptability", the adaptability of a specific early-strength product is not as good as that of naphthalene series products.
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