CN100515974C - Three expansion source concrete anti-cracking agent (CMA) - Google Patents

Abstract

The invention relates to a concrete (mortar) expansive agent. The three-expansive-source concrete anti-cracking agent (CMA) described in the present invention consists of 22-42 percent of coal gangue (calcination), 42-62 percent of anhydrite, 3-7 percent of active activating agent, 6.5-10.5 percent of calcinated limestone and 1-3 percent of magnesium oxide; all ingredients are mixed and ground to obtain powder with a surface area of 250-350m<SUP>2</SUP>/Kg; then concrete admixture made from about 0.5 percent of polymer cellulose is required to be added. In preparing concrete or mortar, shrinkage-compensating concrete can be obtained following adding 6-8 percent of expansive agent described in the present invention, which has 0.2-0.8MPa self-stressing improvement for concrete and allows to enhance dramatically anti-cracking and permeability-reducing performance of structures.

Description

Three expansion source concrete anti-cracking agent

Affiliated field

Involved in the present invention is a kind of concrete (mortar) anti-fissuring agent.

Background technology

In general, the crack of buildings is inevitably, but its harmful degree can be controlled.Before the present invention, the expert has carried out long term studies for the Crack Control problem that solves buildings both at home and abroad.Buildings produces fissured major cause to be caused owing to concrete shrinkage and temperature deformation.Moreover along with developing rapidly of construction industry, the especially large-scale underground waterproof engineering of underground waterproof engineering is more and more, and towards large volume and complicated development, claimed structure is from waterproof simultaneously.Adopting the rigid waterproofing technology is the main path that has effectively solved concrete cracking, seepage since the nineties both at home and abroad.The least possible indwelling movement joint when adding architecture construction, even require jointless construction, this just requires concrete that the function of microdilatancy, anti-crack and anti-seepage is arranged.

In concrete, add anti-fissuring agent, the shrinkage strain that utilizes the dilatational strain under the constraint condition to come compensating concrete, offset the whole and most tensile stress that concrete structure produces in contraction process, structure is not split, Crack Control in the scope of harmless crack, be a kind ofly to prevent and reduce distress in concrete, improve the method for concrete impermeability.

The efficient bulking agent of calcium aluminate that people such as Jiang Yunan (calendar year 2001) propose, its proportioning is 10～30% high aluminium cement clinker, 40～70% anhydrite, 10～30% calcined kaolin, 5～20% high alumina slag.Though having certain early expansion and bigger mid-term expands, but since carrying out new cement standard in 2004, its early expansion rate has been difficult to compensate for the early-age shrinkage of new standard cement, most importantly this product lacks stable late expansion, is difficult to improve concrete long-term volume stability.

Summary of the invention

The objective of the invention is to develop a kind of three expansion source concrete anti-cracking agent (CMA), volume reduced when it was used, and had higher early expansion, and expand and stable late expansion suitable mid-term.This anti-fissuring agent is by 22～42% coal gangue (calcining), 42～62% anhydrite, and 3～7% active stimulator, 6.5～10.5% calcined limestone, 1～3% magnesium oxide, common grinding to specific surface area is 250～350m ²The high molecular cellulose that/Kg adds about 0.5% is again made.Wherein used coal gangue (calcining) AL ₂O ₃Content must be greater than 28%, SO in the used anhydrite ₃Content must be greater than 50%, and CaO content must be greater than 85% in the used calcined limestone, and MgO content must be greater than 95% in the used magnesium oxide.

Be a specific examples of invention below

Starting material Chemical Composition (%)

Material name	Loss	SiO 2	AL 2O 3	Fe 2O 3	CaO	MgO	SO 3	∑
									Coal gangue (calcining)	2.70	31.2	32.5	3.01	20.3	3.65	6.51	99.87
Anhydrite	1.21	1.65	4.21	0.03	38.65	1.84	51.9	99.49
									Calcined limestone	/	1.48	3.69	/	94.1	0.68	/	99.95
Magnesium oxide	1.23	1.21	0.37	0.08	0.87	95.8	/	99.56

Three expansion source concrete anti-cracking agent (CMA) proportioning is formed

With above-mentioned described coal gangue (calcining), anhydrite, active stimulator, calcined limestone and magnesium oxide, common grinding to specific surface area is 250～350m ²/ Kg, the high molecular cellulose that adds again about 0.5% can be made into three expansion source concrete anti-cracking agent (CMA).

Three expansion source concrete anti-cracking agent (CMA) Chemical Composition (%)

Title	SiO 2	AL 2O 3	Fe 2O 3	CaO	MgO	SO 3	R 2O	LOSS	∑
										CMA	12.64	15.12	1.32	34.3	3.82	31.24	0.30	1.15	99.89

Directly add in the concrete according to a certain percentage during use, can make concrete (mortar) produce the expansion of appropriateness through participating in hydration reaction, the effectively drying shrinkage and the shrinkage of compensation concrete, a large amount of ore deposits of aquation formation simultaneously have the effect of filling the pore seam mutually makes pore attenuate, reduce, increase compactness, significantly improve the anti-crack and anti-seepage performance of concrete, thereby improved the weather resistance of works.

The mechanism of intumescence of three expansion source concrete anti-cracking agent (CMA) is as follows:

(1) CaOMgO+2H ₂O → CHMH crystal

(2)3CA+3CaSO ₄+32H ₂O→C ₃A·3CaSO ₄·32H ₂O+3(AL ₂O ₃·3H ₂O)

(3)C ₄A ₃S+2CaSO ₄·2H ₂O+34H ₂O→C ₃A·3CaSO ₄·32H ₂O+2(AL ₂O ₃·3H ₂O)

(4)AL ₂O ₃·2SiO ₂+3Ca(OH) ₂+3CaSO ₄+29H ₂O→C ₃A·3CaSO ₄·32H ₂O+C-S-H

From above-mentioned hydration reaction equation as can be known, three expansion source concrete anti-cracking agent (CMA) with cement hydration process in the needle bar shape product that generates, as: periclasite, ettringite and CH crystal, can effectively be filled in the hole of concrete, be subjected to the constraint of reinforcing bar and adjacent, and produce the compressive pre-stress of 0.2～0.8MPa, there is different expansion ore deposits to generate mutually in the different length of times of concrete, the expansion growth curve of concrete is coordinated mutually with the concrete strength curve, help the most effective performance of expansion energy, effectively compensate the contraction of concrete structure.

With reference cement 92～94%, three expansion source concrete anti-cracking agent (CMA) 6～8% behind the uniform mixing, is pressed the every performance of JC476-2001 standard detection, and test-results sees Table 4

Claims (1)

1. three expansion source concrete anti-cracking agent, it is characterized in that: the calcining coal gangue by 22～42%, 42～62% anhydrite, 3～7% active stimulator, 6.5～10.5% Wingdale, 1～3% magnesium oxide, 0.1～1% high molecular cellulose is made, wherein, and coal gangue Al ₂O ₃Content is greater than 28%, SO in the anhydrite ₃Content is greater than 50%, and CaO content is greater than 85% in the Wingdale, and MgO content is greater than 95% in the magnesium oxide.