CN102964076A - Alkali and chloride-free enhancement type powder concrete setting accelerator - Google Patents

Abstract

Belonging to setting accelerators in the technical field of building materials, the invention particularly relates to an alkali and chloride-free enhancement type powder setting accelerator suitable for sprayed concrete, mortar, neat cement paste and the like. The alkali and chloride-free enhancement type powder setting accelerator is characterized by comprising the following components by weight: 1-3 parts of gypsum, 3-5 parts of aluminum sulfate, and 4-6 parts of a sulphoaluminate cement clinker. Its production method includes: calcining and dehydrating aluminum sulfate, then grinding it, and mixing the grinded aluminum sulfate with calcium sulfate and the sulphoaluminate cement clinker powder. The invention has obvious quick-setting and strength-enhancing effects, and has no damage to later strength. The concrete setting accelerator provided in the invention has the advantages of no toxicity, no corrosion, simple production process, low cost, as well as obvious economic and social benefits.

Description

A non-alkali and chlorine-free enhanced powdery concrete quick-setting agent

technical field

The invention relates to an accelerator in the technical field of building materials, in particular to an alkali-free and chlorine-free enhanced powder accelerator suitable for shotcrete, mortar, cement paste and the like.

Background technique

Concrete admixture is an indispensable building material product in the process of engineering construction, and is called the fifth component of concrete. Accelerator for shotcrete is a very important product in concrete admixture. Shotcrete accelerator can accelerate the setting speed of concrete mixture, improve the early strength, and can effectively prevent tunnels or underground mines, side slopes, and building foundations from collapsing and landslides, and play the role of temporary support or permanent support . Therefore, shotcrete must reach the initial setting and final setting within the required time, and reach the specified strength. In order to meet the above requirements, accelerators must be added to the concrete.

The development of shotcrete accelerators has a long history and has roughly gone through four stages: the first stage is mainly inorganic accelerators with alumina clinker, soda ash or limestone as the main raw materials; the second stage is to add Composite quick-setting agent made of organic materials with specific functions; the third stage is powder non-alkali quick-setting agent. The fourth stage is liquid accelerator.

The first stage: pure inorganic substance accelerator. There are many kinds of this kind of accelerator at home and abroad. The famous ones abroad include Tricosal and Isecret from the former West Germany, P-500 from Japan, Sigunit and SIKA from Sweden and some products from the former Soviet Union. Most manufacturers in our country produce this kind of products, most of which are made of alumina clinker as the main component and a certain proportion of soda ash is added. The main varieties are Hongxing 1, 711, Yaoshan, Yangquan 1, 782, J85 and so on. This quick-setting agent is alkaline and reduces the strength of concrete in the later stage, and the 28-day strength retention rate is only 60-80%.

The second stage: composite quick-setting agent containing polymer material thickener and other ingredients. Japan has developed acrylic acid amine-sodium acrylate copolymer as a sprayed concrete dust inhibitor; former West Germany has reported a spraying accelerator consisting mainly of triethanolamine and partially saponified polyacrylamide-acrylic acid-acrylonitrile terpolymer. Concrete additives; 8604-type additives developed by the Construction Research Institute of the Ministry of Metallurgy, both of which reduce the amount of rebound, but both need to be mixed with 782-type accelerators with a content of 8%, resulting in a large decrease in the strength of concrete in the later stage .

The third stage: powder non-alkali accelerator. The quick-setting agent uses aluminum hydroxide, aluminum sulfate, montmorillonite, kaolin or a combination thereof as main raw materials, and the alkali content of the quick-setting agent is reduced. However, it is often unable to meet the requirements of construction projects for the early strength of concrete, and the dust is relatively large during spraying.

The fourth stage: liquid accelerator. The liquid accelerator is an improvement on the powder accelerator, and the use of the liquid accelerator effectively reduces the rebound of concrete. At present, the liquid accelerators commonly used in engineering include alkaline liquid accelerators based on sodium silicate and sodium aluminate and low-alkali (or alkali-free) liquid accelerators. Among them, the alkaline liquid quick-setting agent has a high alkali content, which is easy to cause harm to the health of construction workers. At the same time, the strong alkaline accelerator makes the cement form a loose aluminate hydrate structure in the early stage of hydration, which increases the possibility of concrete alkali-aggregate reaction, and has a significant weakening effect on the later strength and durability of concrete. In addition, the price of alkali-free liquid accelerators is generally high, and there are problems of stratification and poor stability after long-term storage.

From the current situation of the application of accelerators, with the economic development and technological progress, the scope of use of accelerators is becoming wider and wider, and the amount of accelerators is increasing. According to statistics, in 2007, the output of accelerators in my country was about 354,000 tons, and in 2009, the output reached 1,007,100 tons, of which powder accounted for 74.32% and liquid accounted for 25.68%. The proportion of liquid accelerators is increasing year by year, but due to the price and performance of liquid accelerators, most of the accelerators used in engineering are powder accelerators.

Contents of the invention

The purpose of the present invention is to provide a non-alkali and chlorine-free concrete quick-setting agent for the deficiencies of the prior art, which can not reduce the strength of concrete while promoting cement setting, no matter it is early strength or late strength.

A non-alkali and chlorine-free enhanced powder accelerator is characterized in that it is composed of the following components by weight:

Gypsum 1~3 parts

Aluminum sulfate 3~5 parts

Sulphoaluminate cement clinker 4~6 parts.

Preferred option one consists of the following components by weight ratio:

gypsum 3 parts

Aluminum sulfate 4.5 parts

Sulphoaluminate cement clinker 5 parts.

Preferred option two consists of the following components by weight ratio:

gypsum 2 parts

Aluminum sulfate 4.5 parts

Sulphoaluminate cement clinker 5 parts.

Said aluminum sulfate is industrial aluminum sulfate, the content _{of Al2O3} is greater than 15%, and the weight of products containing crystal water is calculated as pure aluminum sulfate. In the said sulphoaluminate cement clinker, the content of main components CaO is 60-70%, the content of SiO ₂ is 4-8%, the content of Al ₂ O ₃ is 15-18%, and the content of SO ₃ is 7~8%. The said gypsum is anhydrous calcium sulfate, and can also be calcined and dehydrated calcium sulfate hemihydrate or calcium sulfate dihydrate.

The preparation method of the present invention is as follows: the aluminum sulfate is calcined at 300 DEG C until it becomes anhydrous, then ground, the fineness is passed through a 220-mesh standard sieve, and the sieve residue is less than 5%. The fineness of the sulphoaluminate cement clinker is passed through a 250-mesh standard sieve, and the sieve residue is less than 5%. The calcined and ground aluminum sulfate, sulphoaluminate cement clinker and anhydrous gypsum are uniformly mixed.

The non-alkali and chlorine-free enhanced powder quick-setting agent of the present invention can produce very good effect. It can make the initial setting of cement within 3 minutes and the final setting within 10 minutes. While the early strength develops rapidly, the later strength does not decrease.

The non-alkali and chlorine-free enhanced powder quick-setting agent of the present invention is non-toxic, tasteless, non-irritating, does not harm the human body, and has no corrosion effect on the steel bars inside the concrete.

The non-alkali and chlorine-free enhanced powder quick-setting agent of the present invention has simple preparation method, low cost and low requirements on instruments and equipment, and is suitable for mass industrial production.

Detailed ways

Example 1

Aluminum sulfate is calcined at 300°C to anhydrous, then ground, and the fineness is passed through a 220-mesh standard sieve, and the sieve residue is less than 5%. The grinding fineness of sulphoaluminate cement clinker 1 is passed through a 250-mesh standard sieve, and the sieve residue is less than 5%. The composition of sulphoaluminate cement clinker 1 is shown in Table 1. The calcined and ground aluminum sulfate, sulphoaluminate cement clinker and anhydrite are mixed in a weight ratio of 4.5:5:3.

Example 2

Aluminum sulfate is calcined at 290°C until it is anhydrous, and ground, and the fineness is passed through a 220-mesh standard sieve, and the sieve residue is less than 5%. The grinding fineness of the sulphoaluminate cement clinker 2 is passed through a 250-mesh standard sieve, and the sieve residue is less than 5%. The composition of the sulphoaluminate cement clinker 2 is shown in Table 1. The calcined and ground aluminum sulfate, sulphoaluminate cement clinker and anhydrite are mixed in a weight ratio of 4.5:5:2.

Example 3

Aluminum sulfate is calcined at 310°C to anhydrous and ground, and the fineness is passed through a 220-mesh standard sieve, and the sieve residue is less than 5%. The grinding fineness of sulphoaluminate cement clinker 3 is passed through a 250-mesh standard sieve, and the sieve residue is less than 5%. The composition of sulphoaluminate cement clinker 3 is shown in Table 1. The calcined and ground aluminum sulfate, sulphoaluminate cement clinker and anhydrite are mixed according to the weight ratio of 4.5:5:2.5.

The various performance indicators of the accelerator of the present invention are in compliance with the provisions of the national building materials industry standard JC477-2005 "accelerator for shotcrete". According to the standard, the quick-setting agent in the preparation examples 1, 2 and 3 is added in the cement mortar sample with 12.5% and 11.5% and 12% of the weight of cement respectively, and the setting time and strength of the test are compared with the unmixed quick-setting agent simultaneously. The blank cement of the agent was used for comparison. The test results are shown in Table 2.

Table 1 Composition list of sulphoaluminate cement clinker

Table 2 Accelerator test results

Claims (4)

1. An alkali-free and chlorine-free enhanced powder quick-setting agent is characterized in that it is composed of the following components by weight: Gypsum 1~3 parts Aluminum sulfate 3~5 parts Sulphoaluminate cement clinker 4~6 parts. 2. quick-setting agent according to claim 1, is made up of the composition of following weight ratio: gypsum 3 parts Aluminum sulfate 4.5 parts Sulphoaluminate cement clinker 5 parts. 3. quick-setting agent according to claim 1, is made up of the composition of following weight ratio: gypsum 2 parts Aluminum sulfate 4.5 parts Sulphoaluminate cement clinker 5 parts. 4. The quick-setting agent according to claim 1, in the described sulphoaluminate cement clinker, the content of main components CaO is 60-70%, the content of SiO ₂ is 4-8%, Al ₂ O ₃ The content of SO 3 is 15~18%, and the content of SO ₃ is 7~8%.