CN107265969B

CN107265969B - Micro-expansive concrete

Info

Publication number: CN107265969B
Application number: CN201710381418.5A
Authority: CN
Inventors: 史顺才; 龚建昌; 朱玉忠; 王瑞刚; 薛鹏
Original assignee: Beijing Urban Construction Yatai Jintong Concrete Co Ltd
Current assignee: Beijing Urban Construction Yatai Jintong Concrete Co Ltd
Priority date: 2017-05-25
Filing date: 2017-05-25
Publication date: 2019-12-10
Anticipated expiration: 2037-05-25
Also published as: CN107265969A

Abstract

The invention relates to a micro-expansion concrete, which has the technical key points that: the raw materials comprise the following components in parts by mass: 270 parts of cement 265-class cement, 173 parts of water 168-class cement, 730 parts of sand 725-class cement, 1010 parts of gravel, 75-85 parts of mineral powder, 75-80 parts of fly ash, 10.00-10.50 parts of polycarboxylic acid water reducing agent and 36-38 parts of UEA-I type expanding agent. It has no structural crack and raised integral stability of concrete structure.

Description

Micro-expansive concrete

Technical Field

The invention relates to the technical field of concrete materials, in particular to micro-expansive concrete.

Background

With the continuous acceleration of the urbanization process in China, the number of urban population has begun to rise sharply, high-rise buildings are more and more favored by people as building forms capable of accommodating a considerable number of residents, in the building industry, ultra-long concrete is used as one of the main materials applied in the construction process of building engineering, and concrete members of the ultra-long concrete are the most important load-bearing components of building structures.

As is well known, in the process of hydration and hardening of common reinforced concrete, concrete is shrunk to enable reinforcing steel bars in a structure to be subjected to compressive stress and concrete to be subjected to tensile stress, and the existing stress state in the structure enables the structure to be easy to crack; during the pouring process of the concrete, a large amount of heat is generated due to hydration reaction, so that the internal temperature of the concrete structure is increased, and the structural concrete can crack due to overlarge internal and external temperature difference of the structure. The micro-expansion concrete is prepared by adding a certain amount of expanding agent into common concrete to enable the concrete to generate proper expansion, and generating a certain chemical prestress (self-stress) under the conditions of reinforcing steel bars and other constraints, thereby compensating shrinkage and relieving cracking.

When the concrete expands, the concrete is stressed in compression, and the reinforcing steel bars are stressed in tension; when the concrete is shrunk by drying or cooled by cooling, the prestress of the concrete and the prestress of the reinforcing steel bar can be released, so that the shrinkage of the concrete is compensated, and cracks are avoided.

With the rapid development of the construction industry in China, the ultra-long concrete structure is widely applied to the construction engineering and plays an important role in the modern engineering construction, the problem that the ultra-long concrete structure is most likely to appear in the construction process in industrial and civil buildings is structural cracks, and because the tensile strength of the concrete is far lower than the compressive strength, the ultra-long concrete member is easy to crack when the concrete is shrunk or shrunk by temperature change.

Disclosure of Invention

The invention aims to provide micro-expansion concrete which does not generate structural cracks and improves the overall stability of a concrete structure.

The above object of the present invention is achieved by the following technical solutions: the micro-expansion concrete comprises the following raw materials in parts by weight: 270 parts of cement 265-class cement, 173 parts of water 168-class cement, 730 parts of sand 725-class cement, 1010 parts of gravel, 75-85 parts of mineral powder, 75-80 parts of fly ash, 10.00-10.50 parts of polycarboxylic acid water reducing agent and 36-38 parts of UEA-I type expanding agent.

By adopting the technical scheme, the concrete self-waterproof system has the essential problems of improving the compactness of the concrete and preventing the contraction and cracking of the concrete, and the concrete is scientifically compatible, the micro-expansion performance of the concrete can just meet the application in the construction of an ultralong concrete structure, the problem that the compensation contraction capacity is insufficient and the seamless construction is difficult to realize due to small expansion rate can not occur, and the problem that the concrete strength is obviously influenced due to overlarge expansion rate can not occur, so that the concrete generates hydration heat and drying shrinkage after solidification in the solidification process, namely the deformation and compression generated by expansion and contraction are minimum, and the problem that the ultralong concrete structure generates cracks is further solved.

More preferably, the raw material also comprises 8-9 parts by weight of a mixture of sodium laureth sulfate and tetrapolyethylene glycol monolauryl ether.

By adopting the technical scheme, the addition of the sodium lauryl polyether sulfate and the tetrapolyethylene glycol monolauryl ether does not affect the limited expansion rate of the concrete, but can obviously reduce the limited dry shrinkage rate of the concrete, further optimize the compatibility of the concrete and reduce the generation of structural cracks. The concrete is cracked due to the shrinkage stress generated by porous and brittle materials under the action of dry shrinkage and cold shrinkage, so that the concrete loses the self-waterproof function.

More preferably, the weight ratio of the sodium laureth sulfate to the tetrapolyethylene glycol monolauryl ether is 1: 1-2.

By adopting the technical scheme, the proportion of the sodium lauryl ether sulfate and the tetraethylene glycol monolaurate mixed in the concrete is optimized, the limited dry shrinkage rate of the concrete is reduced, and the generation of concrete structure cracks for the construction of an ultra-long concrete structure is reduced.

More preferably, the weight ratio of the sodium laureth sulfate to the tetrapolyethylene glycol monolauryl ether is 1: 1.5.

More preferably, the cement is a p.042.5r portland cement.

By adopting the technical scheme, the cement is relatively stable and has low hydration heat.

More preferably, the sand is zone II sand with a fineness modulus of 2.7.

More preferably, the crushed stones are 5-25mm continuous graded crushed stones.

More preferably, the fly ash is F-class II fly ash, and the oversize fineness of a 45-micron square-hole sieve is 19.5%.

By adopting the technical scheme: the fly ash mineral admixture has a plurality of comprehensive effects such as 'activity effect', 'interface effect', 'micro-filling effect' and 'water reducing effect'. The fly ash mineral admixture can improve rheological property, reduce hydration heat and slump loss, can also improve the pore structure and mechanical property of a concrete structure, and preferably improves the later strength and durability, wherein the mineral powder is S95 grade, and the activity in 28 days is 101%.

By adopting the technical scheme, the mineral powder has a plurality of comprehensive effects such as an activity effect, an interface effect, a micro-filling effect and a water reducing effect. Mineral admixtures such as mineral powder and the like can improve rheological property, reduce hydration heat and slump loss, improve the pore structure and mechanical property of a concrete structure and improve later strength and durability.

Compared with the prior art, the invention has the following beneficial effects:

1. It has no structural crack and raised integral stability of concrete structure.

2. The addition of sodium laureth sulfate and tetraethylene glycol monolauryl ether does not affect the limited expansion rate of the concrete, but can obviously reduce the limited dry shrinkage rate of the concrete, further optimize the compatibility of the concrete and reduce the generation of structural cracks. The concrete is cracked due to the shrinkage stress generated by porous and brittle materials under the action of dry shrinkage and cold shrinkage, so that the concrete loses the self-waterproof function.

3. When the weight ratio of the sodium laureth sulfate to the tetrapolyethylene glycol monolaurate is 1:1.5, the proportion of the sodium laureth sulfate and the tetrapolyethylene glycol monolaurate mixed in the concrete can be further optimized, the limited dry shrinkage rate of the concrete is reduced, and the generation of concrete structure cracks for construction of an ultra-long concrete structure is reduced.

Detailed Description

The present invention will be described in further detail with reference to examples. It should be understood that the preparation methods described in the examples are only for illustrating the present invention and are not to be construed as limiting the present invention, and that the simple modifications of the preparation methods of the present invention based on the concept of the present invention are within the scope of the present invention as claimed.

The concrete has micro-expansion performance, the design and the setting of the limited expansion rate are very important, the expansion rate is small, the compensation shrinkage capacity is insufficient, the seamless construction is difficult to realize, the expansion rate is too large, and the concrete strength is obviously influenced. The design of micro-expansion concrete is mainly characterized by that in the concrete mixing ratio a proper quantity of additive and additive is added, so that the concrete can produce hydration heat and drying shrinkage after solidification, i.e. the deformation produced by expansion and contraction is compressed to minimum.

TABLE 1 sources of raw materials

Raw materials	Manufacturer of the product
		cement	Hebeiyan cement plant
Sand	Hubei Laishui sandstone factory
		Crushing stone	Beijing Yulin lime plant
Fly ash	Sanhe auspicious fly ash processing plant
		Mineral powder	Three river City Daidan Kaiyuan building materials Limited liability company
Polycarboxylic acid water reducing agent	Beijing Rayleigh additive factory
		UEA-I type bulking agent	Limited liability company of Tianjin leopard buildingmaterials
Sodium laureth sulfate	Beijing Huameili biochemistry Co., Ltd
		Tetrapolyethylene glycol monolauryl ether	Yikesideke technologies Co Ltd of Tianjin City

First, production examples and comparative examples

TABLE 2 composition of examples one to nine in Kg

TABLE 3 composition of comparative examples one to two in Kg

Components	Comparative example 1	Comparative example No. two
			Cement	266	266
Sand	729	729
			crushing stone	1007	1007
Fly ash	76	76
			Mineral powder	80	80
Polycarboxylic acid water reducing agent	10.10	10.10
			UEA-I type bulking agent	37	37
Sodium laureth sulfate	0	3.6
			Tetrapolyethylene glycol monolauryl ether	5.4	0
Water (W)	170	170

The examples and comparative examples were prepared as follows.

Metering all materials, metering sand, stone, cement, admixture, water and admixture, feeding and stirring, discharging, conveying (continuously stirring) and homogenizing in a stirring and conveying vehicle, and pumping and pouring in a construction site. The key steps are stirring and transporting: 1. during stirring, the stirring time is prolonged to 90 seconds to ensure that all components are fully homogenized, so that the expansion agent in the concrete hydration process is ensured to uniformly expand at all parts; 2. the pouring process needs to be vibrated to be compact, so that the plastic deformation of the concrete is reduced (which is a construction notice and is not discussed herein); 3. the moisture retention and maintenance are enhanced for not less than 14 days to ensure that the swelling agent is fully hydrated to realize the swelling performance, so that the volume shrinkage of the hydrated gel material is offset.

Secondly, detecting each performance of each embodiment and each proportion

The concrete workability is carried out according to GB/T50080-2016 method for testing the performance of common concrete mixtures.

The compression strength test is carried out according to GB/T50081-2002 'test method for mechanical properties of common concrete'.

The test of the expansion limiting rate and the dry shrinkage limiting rate is carried out according to GB50119-2013 technical Specification for concrete admixture application.

TABLE 4 micro-expansion control of concrete of examples one to eight and comparative examples one to two

According to the detection results in the table 4, the concrete doped with the UEA-I type expanding agent has better micro-expansion effect within 7 days, has stable later expansion performance and reduces the expansion in the air. This is because the most likely problem of the super-long structure during the construction process is the structural crack, which is mainly due to the temperature change caused by the hydration heat released by the cement in the large volume concrete during hydration reaction and the combined action of the concrete shrinkage, which can generate large temperature stress and shrinkage stress. After the UEA-I type expanding agent is doped into concrete components, a proper amount of expansion is generated in the concrete, the self-stress generated under the synergistic action of the reinforcing steel bars offsets and compensates the shrinkage stress of the concrete caused by dry shrinkage and cold shrinkage, and simultaneously, the compactness of the concrete is improved due to the generated micro-expansion.

When the UEA-I type expanding agent is singly compounded with the tetraethylene glycol monolaurate, the limited dry shrinkage of the micro-expansive concrete is improved, and when the UEA-I type expanding agent is singly compounded with the tetraethylene glycol monolaurate, the limited dry shrinkage of the micro-expansive concrete is not influenced. After the UEA-I type expanding agent is simultaneously compounded with sodium lauryl polyether sulfate and tetrapolyethylene glycol monolauryl ether, the limited expansion rate of the micro-expansive concrete is not influenced, but the retraction of the micro-expansive concrete in the air can be better controlled, and the limited dry shrinkage rate of the micro-expansive concrete is reduced. Therefore, the sodium laureth sulfate and the tetrapolyethylene glycol monolauryl ether can reduce the synergistic effect of limiting the dry shrinkage of the micro-expansive concrete, and the two have no choice but to be used.

TABLE 5 micro-expansion control of concrete of examples one to eight and comparative examples one to two

According to the detection results in table 5, it is found that the strength of the present invention can be improved by compounding sodium laureth sulfate and tetrapolyethylene glycol monolauryl ether, and the two are not indispensable.

Claims

1. The micro-expansion concrete is characterized by comprising the following raw materials in parts by weight: 270 parts of cement 265-class cement, 173 parts of water 168-class cement, 730 parts of sand 725-class cement, 1010 parts of crushed stone, 75-85 parts of mineral powder, 75-80 parts of fly ash, 10.00-10.50 parts of polycarboxylic acid water reducing agent and 36-38 parts of UEA-I type expanding agent;

The raw material also comprises 8-9 parts by weight of a mixture of sodium laureth sulfate and tetrapolyethylene glycol monolauryl ether.

2. The micro-expansive concrete according to claim 1, wherein the weight ratio of the sodium laureth sulfate to the tetrapolyethylene glycol monolauryl ether is 1: 1-2.

3. The micro-expansive concrete according to claim 2, wherein the weight ratio of the sodium laureth sulfate to the tetrapolyethylene glycol monolauryl ether is 1: 1.5.

4. The micro-expansive concrete according to claim 1, wherein said cement is a p.042.5r portland cement.

5. The micro-expansive concrete according to claim 1, wherein the sand is zone II sand, and the fineness modulus is 2.7.

6. The micro-expansive concrete according to claim 1, wherein said crushed stones are 5-25mm continuous graded crushed stones.

7. The micro-expansion concrete as claimed in claim 1, wherein the fly ash is class F class II fly ash, and the oversize fineness of a 45 μm square mesh sieve is 19.5%.

8. The micro-expansive concrete according to claim 1, wherein the ore fines are grade S95 and have a 28-day activity of 101%.