阅读说明：本技术 基于碱激发矿渣和硅酸盐水泥的功能梯度混凝土 (Functionally graded concrete based on alkali-activated slag and portland cement ) 是由 周万良 邓欢 詹炳根 于 2021-08-16 设计创作，主要内容包括：本发明公开了基于碱激发矿渣和硅酸盐水泥的功能梯度混凝土,是在碱激发矿渣混凝土的表面覆盖有一层硅酸盐水泥砂浆层或硅酸盐水泥混凝土层,或者是在硅酸盐水泥混凝土的表面覆盖有一层碱激发矿渣砂浆层或碱激发矿渣混凝土层,以提高碱激发矿渣混凝土的抗碳化性能或者硅酸盐水泥混凝土的抗氯离子渗透性能。本发明的功能梯度混凝土具有良好的综合性能,如优良的抗碳化性能、抗氯离子渗透性能等,特别适合氯离子侵蚀严重或既有氯离子侵蚀又有碳化作用的地方使用。(The invention discloses a functionally graded concrete based on alkali-activated slag and portland cement, wherein a portland cement mortar layer or a portland cement concrete layer covers the surface of the alkali-activated slag concrete, or an alkali-activated slag mortar layer or an alkali-activated slag concrete layer covers the surface of the portland cement concrete, so as to improve the carbonization resistance of the alkali-activated slag concrete or the chloride ion permeation resistance of the portland cement concrete. The functionally graded concrete has good comprehensive properties such as excellent carbonization resistance and chloride ion permeability resistance, and is particularly suitable for places with serious chloride ion corrosion or both chloride ion corrosion and carbonization.)

1. Functional gradient concrete based on alkali-activated slag and portland cement is characterized in that: the functionally graded concrete is PC-AAS concrete, and a silicate cement mortar layer or a silicate cement concrete layer covers the surface of the alkali-activated slag concrete to improve the carbonization resistance of the alkali-activated slag concrete;

or the functionally graded concrete is AAS-PC concrete, and the surface of the portland cement concrete is covered with an alkali-activated slag mortar layer or an alkali-activated slag concrete layer so as to improve the chloride ion permeation resistance of the portland cement concrete.

2. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1, characterized in that:

for the PC-AAS concrete, 0 layer, 1 layer or a plurality of other mortar layers or concrete layers are further arranged on the surface of the portland cement mortar layer or the portland cement concrete layer by layer according to performance requirements.

And for the AAS-PC concrete, 0 layer, 1 layer or a plurality of other mortar layers or concrete layers are further arranged on the surface of the alkali-activated slag mortar layer or the alkali-activated slag concrete layer by layer according to performance requirements.

3. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1, characterized in that: the thickness of the portland cement mortar layer or the portland cement concrete layer on the surface of the PC-AAS concrete is more than 10 mm; the thickness of the alkali-activated slag mortar layer or the alkali-activated slag concrete layer on the surface of the AAS-PC concrete is more than 10 mm.

4. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1 or 2, characterized in that: the surface of each mortar or concrete layer is perpendicular to the direction of penetration of the surrounding erosion medium.

5. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1 or 2, characterized in that: the alkali-activated slag concrete, the alkali-activated slag mortar layer or the alkali-activated slag in the alkali-activated slag concrete layer is NaOH-activated slag, KOH-activated slag, water glass-activated slag, Na₂CO₃And Portland cement activated slag, Na₂CO₃And Ca (OH)₂Slag is excited.

6. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1 or 2, characterized in that: the slag in the alkali-activated slag concrete, the alkali-activated slag mortar layer or the alkali-activated slag concrete layer is granulated blast furnace slag of S75, S95 or S105.

7. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1 or 2, characterized in that: the alkali-activated slag concrete, the alkali-activated slag mortar layer or the alkali-activated slag concrete layer may further contain fly ash, volcanic ash and/or silica fume as a modifying admixture.

8. Functionally graded concrete based on alkali-activated slag and portland cement according to claim 1 or 2, characterized in that: the portland cement concrete, the portland cement mortar layer or the portland cement concrete layer may further contain fly ash, volcanic ash and/or silica fume as a modifying admixture.

Technical Field

The invention belongs to the field of novel concrete materials, and particularly relates to functionally graded concrete based on alkali-activated slag and portland cement.

Background

Portland cement (abbreviated as PC) has good carbonization resistance, but the properties such as chloride ion permeation resistance and sulfate resistance are far inferior to alkali-activated slag (AAS). Compared with portland cement, the AAS cementing material is a relatively environment-friendly material, the precursor slag is inactivated by an excitant such as strong base KOH or NaOH to generate hydration reaction to generate hydration products, so that the AAS cementing material has strength, and does not discharge waste gas and dust in production and use links by using industrial waste residue-slag and the like. In addition, AAS also has some excellent performances which silicate series cement does not have, such as good sulfate resistance, chloride ion penetration resistance, soft water erosion resistance and the like. However, AAS also has some performance defects, such as certain pollution to the environment during alkali production, especially poor carbonization resistance, which severely restricts the popularization and application of AAS in practical engineering.

If a silicate cement mortar layer or a concrete layer is covered on the surface of the AAS concrete to form the gradient concrete, the inner AAS concrete with poor carbonization resistance (but good chlorine ion penetration resistance) is protected by the silicate cement mortar layer or the concrete layer with good carbonization resistance (but poor chlorine ion penetration resistance) on the surface layer, so that the gradient concrete with good carbonization resistance and chlorine ion penetration resistance can be obtained. Or covering an AAS mortar layer or a concrete layer on the surface of the portland cement concrete to form another kind of gradient concrete, and protecting the internal portland cement concrete with poor chloride ion permeability resistance (but good carbonization resistance) by utilizing the AAS mortar layer or the concrete layer with good chloride ion permeability resistance (but poor carbonization resistance) on the surface layer, so that the gradient concrete with good carbonization resistance and chloride ion permeability resistance can be obtained.

Based on the thought, the invention provides functionally graded concrete (FGC for short) based on alkali-activated slag and portland cement, and researches the anti-carbonization performance and the anti-chloride ion permeability of the functionally graded concrete. At present, although some gradient concrete research reports exist at home and abroad, the research of preparing the gradient concrete by using alkali-activated slag and portland cement has no relevant report.

Disclosure of Invention

In order to overcome the performance defects of the alkali-activated slag and the portland cement and exert the performance advantages of the alkali-activated slag and the portland cement, the invention aims to provide the functionally graded concrete based on the alkali-activated slag and the portland cement so as to improve the comprehensive performance of the functionally graded concrete, such as good durability of chloride ion permeation resistance, carbonization resistance and the like.

The invention adopts the following technical scheme for realizing the purpose:

the functionally graded concrete based on alkali-activated slag and portland cement mainly comprises two types of structures:

the first kind of functionally graded concrete is PC-AAS concrete (namely Portland cement-alkali activated slab concrete), and a silicate cement mortar layer or a silicate cement concrete layer is covered on the surface of the alkali-activated slag concrete to improve the carbonization resistance of the alkali-activated slag concrete. As shown in FIG. 1, the PC-AAS concrete is obtained by setting the part I in FIG. 1 as AAS concrete and the part II in FIG. 1 as PC mortar layer or PC concrete layer. As is well known, AAS has poor carbonization resistance, which seriously restricts the popularization and application of AAS in practical engineering, but has excellent chloride ion permeation resistance and corrosion resistance, while portland cement has good carbonization resistance but poor chloride ion permeation resistance. For PC-AAS concrete, because the silicate cement mortar layer or the concrete layer on the surface has good carbonization resistance, the time for the inner AAS concrete to start carbonization is greatly prolonged, and meanwhile, the inner AAS concrete has excellent chlorine ion penetration resistance. Therefore, the PC-AAS concrete has good chlorine ion penetration resistance and good carbonization resistance, and provides technical support for popularization and application of AAS in practical engineering.

The second kind of functionally graded concrete is AAS-PC concrete, and the silicate cement concrete is covered with one alkali-activated slag mortar layer or alkali-activated slag concrete layer to raise the chlorine ion permeation resistance of the silicate cement concrete. As shown in FIG. 1, the AAS-PC concrete was obtained by setting the part I to portland cement concrete and the part II to AAS mortar layer or AAS concrete layer. The silicate cement concrete is a building material with the largest application amount and the widest application range in civil engineering, but the chlorine ion permeability resistance and the corrosion resistance of the silicate cement are poor, so that the method for laying the AAS mortar layer or the concrete layer on the surface of the silicate cement concrete is an ideal method for improving the chlorine ion permeability resistance of the silicate cement concrete. The AAS mortar layer or the concrete layer on the surface has excellent chlorine ion penetration resistance, and can effectively prevent or even cut off chlorine ions from penetrating into the internal portland cement concrete, so that the AAS-PC concrete has good chlorine ion penetration resistance, and the internal portland cement concrete has good carbonization resistance, so that the AAS-PC concrete also has good comprehensive performances of carbonization resistance, chlorine ion penetration resistance and the like.

Through research on the carbonization resistance and the chloride ion permeability resistance of the FGC, the following results are found: the silicate cement mortar layer or the concrete layer is covered on the surface of the AAS concrete, so that the time for the AAS concrete to start to carbonize can be greatly prolonged; the AAS mortar layer or the concrete layer is covered on the surface of the portland cement concrete, so that the penetration of chloride ions into the interior can be effectively prevented or even cut off, and the time for the chloride ions to penetrate into the surface of the portland cement concrete is greatly prolonged. Therefore, the AAS functionally graded concrete with the surface covered with the portland cement mortar layer or the concrete layer is suitable for being used in environments with requirements on carbonization resistance and chloride ion resistance (such as a splash zone and a water level lifting zone in the sea), and the portland cement concrete with the surface covered with the AAS mortar layer or the concrete layer is suitable for being used in environments with requirements on chloride ion penetration resistance (such as underwater engineering in the sea and underground engineering in a salinized area). Because the mortar layer or the concrete layer on the surface of the FGC only plays a role of protection and belongs to functional materials, the mechanical property of the concrete with the main structure is not degraded. Particularly, the portland cement concrete with the surface covered with an AAS mortar layer or concrete layer has the characteristics of cost reduction (the cost of the portland cement concrete is lower than that of the AAS concrete) and wide application engineering range when compared with pure AAS concrete, and has excellent chlorine ion permeation resistance, and is a novel structural material with great development prospect.

The mortar layer or concrete layer on the surface of the FGC of the invention is not limited to only one layer: for the PC-AAS concrete, 0 layer, 1 layer or a plurality of other mortar layers or concrete layers can be arranged on the surface of the portland cement mortar layer or the portland cement concrete layer by layer according to performance requirements. For the AAS-PC concrete, 0 layer, 1 layer or a plurality of other mortar layers or concrete layers can be further arranged on the surface of the alkali-activated slag mortar layer or the alkali-activated slag concrete layer by layer according to performance requirements. For example, as shown in fig. 2, the part I is AAS concrete, the part II is portland cement mortar layer or portland cement concrete layer, and the part III is portland cement mortar layer or concrete layer doped with an air entraining agent, so that the carbonization resistance and frost resistance of the part I AAS concrete can be improved, and FGC having good chlorine ion penetration resistance, carbonization resistance and frost resistance can be prepared. For example, when only one AAS mortar layer or concrete layer is covered on the surface of portland cement concrete, such FGC is not suitable for use in environments with carbonization resistance requirements due to poor carbonization resistance of the AAS mortar layer or concrete layer on the surface and significantly reduced chlorine ion permeation resistance after carbonization. As shown in fig. 2, the portland cement concrete is set as part I, AAS mortar layer or concrete layer is set as part II, and portland cement mortar layer or concrete layer is set as part III, so that the chloride ion permeation resistance and carbonization resistance of the portland cement concrete of part I can be improved, and FGC having both good chloride ion permeation resistance and carbonization resistance can be prepared and can be applied to an environment having both chloride ion resistance and carbonization resistance.

The number of the mortar layers or the concrete layers on the surface of the FGC, the type and the proportion of each layer can be analyzed and determined by tests according to the performance requirements, construction conditions and levels of the FGC. However, each of the FGCs disclosed herein is formulated based on two cementitious materials, portland cement and AAS. The FGC of the present invention has good combination properties, such as good carbonization resistance and chloride ion permeation resistance, etc.

The thickness, strength and layer number of the mortar layer or the concrete layer on the surface of the FGC are determined by specific analysis and test according to the environment requirement of the concrete. The larger the thickness of the surface mortar layer or concrete layer is, of course, the better the protection effect on the internal concrete, but the cost of FGC is increased. Higher surface mortar or concrete layer strength is also better for internal concrete protection, but also increases FGC costs. The more the surface mortar layer or the concrete layer is, the more the FGC construction complexity is increased and the engineering cost is increased.

In order to meet the performance requirements, the thickness of the silicate cement mortar layer or the silicate cement concrete layer on the surface of the PC-AAS concrete is more than 10mm, and the thickness of the alkali-activated slag mortar layer or the alkali-activated slag concrete layer on the surface of the AAS-PC concrete is more than 10 mm.

Preferably, the thickness of the portland cement mortar layer or the portland cement concrete layer on the surface of the PC-AAS concrete is generally 20-30 mm. Too thin a mortar bed is easily coated with CO₂Penetration, no protective effect; a mortar layer that is too thick is uneconomical and adds too much to the cost of FGC. The minimum thickness of the surface portland cement mortar layer or concrete layer should be chosen while ensuring that the FGC is not carbonized during the service life.

Preferably, the thickness of the alkali-activated slag mortar layer or alkali-activated slag concrete layer on the surface of the AAS-PC concrete is generally 10 to 20mm, and the AAS mortar layer or concrete layer having such a thickness is hardly penetrated by chloride ions and almost completely prevents the chloride ions from reaching the internal portland cement concrete. The AAS mortar layer on the surface is too thin to be penetrated by the chloride ions for a long time, and too thick is not necessary to increase the cost at the same time.

Preferably, the alkali-activated slag concrete, the alkali-activated slag mortar layer, or the alkali-activated slag concrete layer is alkali-activated slag such as NaOH-activated slag, KOH-activated slag, water-glass-activated slag, Na₂CO₃And Portland cement activated slag, Na₂CO₃And Ca (OH)₂Slag excitation, etc. When the slag is stimulated by NaOH, the doping amount of the NaOH is 4%, and the mortar or concrete with the doping amount has the advantages of higher strength, good chloride ion permeation resistance, lower NaOH consumption, cost saving and the like. When KOH excites slag, the KOH mixing amount is preferably 3-4%, and the mortar or concrete with the mixing amount has high strength and good chlorine ion penetration resistance, and the KOH dosage is low.

Preferably, the alkali-activated slag in the alkali-activated slag concrete, the alkali-activated slag mortar layer, or the alkali-activated slag concrete layer is S75, S95, or S105 granulated blast furnace slag.

Preferably, the portland cement in the portland cement concrete, the portland cement mortar layer or the portland cement concrete layer is six kinds of general purpose cement and other portland series cement, and the strength grade is more than or equal to 32.5 grade.

Preferably, the alkali-activated slag concrete, the alkali-activated slag mortar layer or the alkali-activated slag concrete layer may further contain fly ash, volcanic ash and/or silica fume as a modifying admixture.

Preferably, the portland cement concrete, the portland cement mortar layer or the portland cement concrete layer may further contain fly ash, volcanic ash and/or silica fume as a modifying admixture.

The construction method of FGC in the laboratory comprises the following steps: pouring a layer of mortar in a test mould, compacting the mortar after the mortar is slightly leveled, then directly pouring concrete on the surface of the mortar (the concrete pouring is finished before the mortar is initially set), and then compacting and curing the concrete after the concrete is leveled.

The construction of the FGC on the engineering site is the same as the construction method of other FGC on the site. As the construction technology of FGC has been improved, FGC is adopted in many important projects, and the projects adopting FGC are increased, so that the FGC has no technical obstacle in construction.

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

1. the FGC based on AAS and portland cement of the invention has good comprehensive properties, such as excellent carbonization resistance, chloride ion penetration resistance, sulfate erosion resistance and the like. The FGC of the present invention is particularly suitable for use in locations where chloride attack is severe or where both chloride attack and carbonation are present. Compared with the concrete without a mortar protective layer and a concrete protective layer on the surface, the FGC has strong corrosion resistance, good durability and long service life.

2. Compared with concrete without a protective layer on the surface, the FGC of the invention has the following advantages:

(1) energy conservation and environmental protection: the blast furnace slag is granulated by using industrial waste slag in large quantity regardless of PC-AAS concrete or AAS-PC concrete; meanwhile, the AAS belongs to clinker-free cement, wherein the alkali activator is produced at normal temperature without high-temperature calcination, so that compared with Portland cement, the AAS has the advantages of energy conservation, no emission of waste gas and dust and the like.

(2) Has some excellent performances, such as good carbonization resistance, sulfate corrosion resistance and chloride ion penetration resistance.

(3) Because FGC has strong corrosion resistance, the FGC has good durability and long service life.

(4) After FGC is adopted, the performance defect of poor carbonization resistance, which restricts the popularization and application of the AAS cementing material in practical engineering, is overcome, and a foundation is laid for the large-scale application of the AAS material in engineering.

(5) The AAS mortar layer or concrete layer is added on the surface of the portland cement concrete, so that the anti-chlorine ion erosion performance of the portland cement concrete can be greatly improved, and the method is an important method for improving the anti-chlorine ion permeability of the portland cement concrete.

3. Compared with the concrete coated with the anticorrosive paint on the surface, the FGC of the invention has the following advantages: the anticorrosive paint is generally a high molecular material, is easy to age, has no FGC surface mortar layer or concrete layer with long service life, and is very inconvenient to be coated again once the anticorrosive paint in water loses efficacy. And the service life of the mortar layer or the concrete layer on the surface of the FGC is almost the same as that of the internal concrete (namely, the concrete in the main body structure), so that the problems of failure, replacement, maintenance and the like do not exist in the whole using process.

Drawings

FIG. 1 is a schematic structural view of functionally graded concrete with a mortar layer or a concrete layer on the surface according to the present invention;

FIG. 2 is a schematic structural view of functionally graded concrete with two mortar or concrete layers on the surface.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof will be described in detail with reference to the following examples. The following disclosure is merely exemplary and illustrative of the inventive concept, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

EXAMPLE 1 carbonation resistance of PC-NAS concrete of varying Portland Cement mortar layer thickness

The mass ratio of Portland cement: sand: silicate cement mortar with water of 1:3:0.6 was laid on the surface of NAS (NaOH-activated slag, abbreviated as NAS, which is one of AAS) concrete, and a carbonation test was performed after curing in water for 28 days. When the thickness of the mortar layer is 20mm, the mortar layer is heated at 20 + -2 deg.C and 70 + -5% of humidity and CO₂The carbonization depth of the carbonized concrete in the carbonization box with the concentration of (20 +/-3)% after 28 days is only about 16mm, and is almost the same as that of pure silicate cement concrete with the equivalent strength. And the carbonization depth of the NAS concrete without the silicate cement mortar layer on the surface reaches 21mm after 7 days of carbonization, so that the 20 mm-thick silicate cement mortar layer on the surface of the NAS can effectively improve the carbonization resistance of the FGC. However, after 35 days of carbonation, the FGC carbonation depth had reached 33mm, indicating that the carbonation depth had penetrated the surface portland cement mortar layer to the inside NAS concrete, indicating that the surface 20mm thick portland cement mortar layer has a limited ability to protect the inside NAS concrete from carbonation. And (3) paving a 30mm thick Portland cement mortar layer with the same proportion on the surface of the NAS concrete, carbonizing under the same carbonization condition, wherein the carbonization depth is only 26mm when the NAS concrete is carbonized for 56 days, the carbonization depth does not penetrate through the Portland cement mortar layer on the surface, and the carbonization depth is equivalent to that of pure Portland cement concrete. In contrast, the carbonization depth of pure NAS concrete reaches 66mm when the pure NAS concrete is carbonized for 42 days, and the carbonization depth of the pure NAS concrete reaches 53mm when the FGC with the surface portland cement mortar layer thickness of 20mm is carbonized for 56 days, which is far larger than that of the FGC with the surface portland cement mortar layer thickness of 30 mm. The result shows that the larger thickness of the surface portland cement mortar layer is beneficial to improving the anti-carbonization performance of FGC concrete, the FGC anti-carbonization performance when the thickness of the surface portland cement mortar layer is 30mm is much better than that when the thickness of the surface mortar layer is 20mm, but the thickening of the surface mortar layer increases the FGC cost, so the comprehensive consideration is needed to determine the surface mortar layerLayer thickness.

Example 2 carbonation resistance of NAS-PC concrete of different NAS mortar layer thicknesses

The NAS mortar (slag: NaOH: sand: water: 1:0.04:3:0.6) is laid on the surface of the portland cement concrete. When the thickness of the mortar layer is 20mm, the mortar layer is carbonized under the same carbonization conditions as example 1, the carbonization depth of 7 days of carbonization reaches 20mm, the mortar layer penetrates through the surface, the carbonization depth is equivalent to that of pure NAS concrete, but the carbonization depth of 14 days of carbonization is only 22mm, the carbonization depth is increased by only 2mm compared with that of 7 days of carbonization, the carbonization speed is obviously reduced, and the carbonization speed is always obviously lower than that of the surface NAS mortar layer, which shows that the NAS mortar layer on the FGC surface has poor carbonization resistance and high carbonization speed, and the silicate cement concrete in the FGC surface has good carbonization resistance. The thickness of the NAS mortar layer on the FGC surface is increased to 30mm, the carbonization depth of 14 days of carbonization reaches 30mm, the NAS mortar layer on the surface is penetrated, and the carbonization depth of 14 days of carbonization of pure silicate cement mortar or concrete is only 11 mm. The results also show that the NAS mortar layer on the surface of the FGC has poor carbonization resistance, the internal portland cement concrete has good carbonization resistance, and the effect of covering the NAS mortar layer on the surface of the FGC on improving the carbonization resistance is small.

Example 3 chloride ion resistance of PC-NAS concrete of different Portland Cement mortar layer thicknesses

The mass ratio of Portland cement: sand: silicate cement mortar with water being 1:3:0.6 is laid on the surface of NAS concrete, after 28 days of underwater curing, paraffin is used for tightly sealing four side surfaces of a concrete sample (the surface with the mortar and the surface opposite to the surface are not sealed, so that chloride ions are allowed to permeate into the concrete in a single direction) to carry out a chloride ion permeation resistance test. The concrete is soaked in 10% NaCl solution for a certain time, taken out and sawed, and the chloride ion penetration depth is measured by a 0.1mol/L silver nitrate solution color development method. When the PC-NAS concrete with the surface silicate cement mortar layer thickness of 20mm is soaked for 28 days, the penetration depth of chloride ions reaches 20.1mm, the chloride ions penetrate through the surface silicate cement mortar layer, the penetration depth of the chloride ions is equivalent to that of pure silicate cement concrete, and at the moment, the penetration depth of the chloride ions of the pure NAS concrete is only 4.8 mm. After 35 days of soaking, the chloride ions slowly permeate into the NAS concrete, and the permeation speed is greatly reduced. The thickness of the surface portland cement mortar layer is increased to 30mm, and the penetration depth of chloride ions after soaking for 49 days reaches 28.6mm, which is equivalent to the penetration depth of chloride ions of pure portland cement concrete. The penetration depth of chloride ions of the pure NAS concrete is 5.6mm, which is obviously smaller than that of PC-NAS concrete and pure silicate cement concrete. The result shows that the chlorine ion penetration resistance of the NAS mortar or concrete is far better than that of pure silicate cement mortar or concrete, and the effect of laying a silicate cement mortar layer on the surface of the NAS concrete is not great for improving the chlorine ion penetration resistance.

Example 4 chloride ion resistance of NAS-PC concrete of different NAS mortar layer thicknesses

The NAS mortar (slag: NaOH: sand: water: 1:0.04:3:0.6)) was laid on the surface of portland cement concrete. When the thickness of the mortar layer was 20mm, the chloride ion permeation test was carried out in the same manner as in example 3. The penetration depth of the chloride ions is only 5.0mm when the concrete is soaked in the NaCl solution for 35 days, the penetration depth of the chloride ions is almost stopped increasing along with the prolonging of the soaking time, and the penetration depth is 5.3mm when the concrete is soaked for 49 days, which is equivalent to the penetration depth of the chloride ions of pure NAS concrete. The penetration depth of the portland cement concrete reaches 23.7mm after being soaked for 35 days, and the portland cement concrete is far larger than NAS mortar or NAS concrete, which shows that the penetration resistance of the portland cement concrete is far smaller than that of the NAS mortar or NAS concrete. The thickness of the NAS mortar layer on the surface of the portland cement concrete is increased to 30mm, the chloride ion permeation test result is almost consistent with the FGC with the surface NAS mortar layer thickness of 20mm, chloride ions cannot penetrate through the NAS mortar layer with thick surface, and the NAS mortar or the NAS concrete has excellent chloride ion permeation resistance. Therefore, the surface of the portland cement concrete is covered with a NAS mortar layer, the chlorine ion permeation resistance can be greatly improved, and the chlorine ion permeation channel can be almost cut off when the thickness of the NAS mortar layer on the surface is 10-20 mm.

The present invention is not limited to the above exemplary embodiments, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.