CN117819916A - Preparation method of polypropylene fiber reinforced high-performance coral sand concrete - Google Patents

Abstract

The invention discloses a preparation method of polypropylene fiber reinforced high-performance coral sand concrete. The strength grade of the high-performance coral sand concrete reaches more than C120, and the material comprises the following components: cement, fly ash, silica fume, coral sand, ground blast furnace slag powder, quartz powder, seawater and water reducer are cement and mineral admixture, defoamer and high-performance polypropylene fiber. The coral sand is prepared by controlling the prewetting time of coral sand, the proportion of mineral admixture, proper admixture, stirring form and short-term high-temperature sea water concomitance. The polypropylene reinforced high-performance coral sand concrete has high mechanical properties, good impermeability, compactness and durability, and fills up the defects of low strength, large brittleness, poor fluidity, large mechanical index dispersion and the like of common coral concrete. The raw materials are obtained locally, the preparation method is simple and easy to realize, and the method has important economic value and significance for ocean resource development and island national defense facility construction, and meets ocean requirements.

Description

Preparation method of polypropylene fiber reinforced high-performance coral sand concrete

Technical Field

The invention belongs to the technical field of building engineering materials, and particularly relates to a preparation method of polypropylene fiber reinforced high-performance coral sand concrete.

Background

The construction of the offshore island reef engineering is a bridge-head fort which is promoted by ocean resource development initiative, and is also a whistle array land for coastal portals and national defense safety in China. The engineering significance of coral scraps obtained by local materials for island reef engineering construction has been confirmed. With the increase of the service life of engineering and the influence of severe environments (high temperature, high humidity and high salt) and complex load actions (stormy waves, earthquakes), the working performance of the common coral concrete with the defects of high porosity, obvious defects in aggregate, poor fluidity, obvious brittleness, high construction difficulty, high mechanical index discreteness and the like cannot meet the requirements of the current engineering. Therefore, researchers at home and abroad start with methods of aggregate modification enhancement, cementing material formula improvement, water-gel ratio reduction or stirring preparation technology improvement, and the like, and the problems of limited strength improvement range and poor stability still exist. The related scholars also put forward a method for preparing high-strength coral concrete by batch feeding under the low-pressure environment, but the brittleness defect cannot be improved, the construction is complex, the condition is harsh, the time is long or the uncertain influence on the cementing material and the like is caused along with large-volume hydration heat sealing release, and the risk of failure is high.

Therefore, the method of grading optimization and high-performance fiber modification reinforcement is adopted by adopting the coral sand with finer and lower porosity, and the coral sand is subjected to prewetting treatment before use, so that when the coral sand contacts the cementing material and the quartz powder, the coral sand can infiltrate into open pores of the aggregate to dissolve and fill, redundant water is sucked out, and the internal pores and the reinforced interface are improved while the lower pore water-gel ratio is maintained. The method avoids the difficulty in construction and stirring caused by continuous water absorption of coral aggregate (sand) which is not pre-wetted during the later water adding and stirring, or the great difference in stirring uniformity degree caused by inconsistent local water absorption conditions, which is one of the important reasons for poor stability and discrete mechanical indexes. After the mixed high-performance fiber is added, the defects of aggregate pores and cracks can be bridged, and the mixed high-performance fiber and mortar form a multi-element three-dimensional staggered lap joint, so that the reliable 'hooping' effect is realized, the defect of the common coral concrete can be effectively overcome, the strength and toughness mechanical performance indexes of the coral concrete are greatly improved, and the technical standard of the high-performance coral concrete above C120 level is reached.

Disclosure of Invention

The invention aims to provide a preparation method of polypropylene fiber reinforced high-performance coral sand concrete.

The technical scheme of the invention is as follows:

the high-performance coral concrete is C120-grade polypropylene fiber reinforced coral sand concrete, and the weight percentage of each cubic meter of the high-performance coral concrete is as follows: 26-30% of cement, 1-1.5% of fly ash, 8-12% of silica fume, 40-48% of coral sand, 2-3% of ground blast furnace slag powder, 2-2.5% of quartz powder, 9-13% of sea water, 2-2.3% of water reducer, 0.4-1% of defoamer and 2.0-3.0% of mixed high-performance polypropylene fiber by volume.

The preparation method of the polypropylene fiber reinforced high-performance coral sand concrete comprises the following specific steps:

(1) All raw materials are weighed according to the requirements of the components for standby.

(2) And (3) carrying out seawater soaking pre-wetting treatment on the coral sand weighed in the step (1), wherein the soaking time is 50min, and then taking out and airing for 10min, wherein no large water dripping occurs for standby.

(3) And (3) dry-mixing the cement, the fly ash, the ground blast furnace slag powder, the quartz powder and the like weighed in the step (1) for 2-3min.

(4) And (3) adding the coral sand in the step (2) into the cementing material uniformly stirred in the step (3), and continuously stirring for 2min to a uniform state.

(5) Adding the water reducer and the defoaming agent into seawater or artificial seawater, uniformly stirring, then uniformly and slowly pouring into the step (4), and stirring for 6-8min. And (2) scattering the polypropylene fibers weighed in the step (1) into the fresh slurry in 3 batches, wherein each time is separated by 20 seconds, and continuously stirring for 5 minutes after the completion of the feeding to form the fiber mixture.

(6) And (3) preparing the fiber mixture in the step (5) for molding, demolding after 24 hours, placing the molded fiber mixture in 60-80 ℃ seawater for curing for 7 days, and placing the molded fiber mixture in normal-temperature seawater for curing for 28 days to obtain the high-performance coral sand concrete.

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

1. the chloride ion mobility coefficient. The chloride ion erosion speed of the hot water curing test piece is obviously lower than that of the standard curing test piece, and the descending range is between 32% and 45%. Compared with common coral concrete, the high-performance coral sand concrete has the impermeability level raised from P4 to over P8.

2. The seawater-accompanied coral concrete and the high-performance coral sand concrete contain a large amount of chloride ions, have early strength, and the strength of 7 days can reach 40-70% of the strength (C120) of 28 days. Compared with standard curing, the compressive strength of the coral cement-based composite material is obviously improved 7 days before the coral cement-based composite material is cured under the hot water at 70-90 ℃, and is improved by more than 50% compared with the synchronous standard curing group.

3. Compared with common concrete and high-performance concrete, the coral sand concrete has obvious self-shrinkage effect in the early stage of high-temperature curing, but has no obvious shrinkage phenomenon in the high-performance coral sand concrete with micro-expansion characteristic, and shows good volume stability. The shrinkage is mainly caused by that the hydration reaction process is quickened by hot water curing, the moisture in the pores is rapidly reduced, and the self-shrinkage is rapidly increased; the coral is a porous material, and contains calcium carbonate as main component, and has water absorption and water return effects.

4. Compared with the coral concrete porosity (more than 18%), the high-performance coral sand concrete has the porosity of 4.9% -6.8%. Under the high-temperature hot water curing condition, the porosity of the high-performance coral sand concrete is reduced by more than 23% compared with standard curing, and the compressive strength is improved by 4.10% -9.54% compared with standard curing after 28 days of curing, and the requirements of target strength and guaranteeing construction strength can be met earlier under the low-temperature construction or normal-temperature condition although the lifting range is smaller. In addition, the viscosity-reducing polycarboxylic acid water reducer is beneficial to improving the fluidity of slurry and filling pores.

5. The mixed fibers with different lengths are scattered in batches, so that fiber aggregation is effectively avoided, an effective lap joint and a hooping system are formed, the coral sand concrete is changed from brittle fracture to ductile fracture, and the coral sand concrete has the characteristics of high strength and high toughness.

6. The coral sand is basically saturated after absorbing water for 1-2 hours, and a certain adsorption power is still maintained after prewetting for 50 minutes, but stirring difficulty caused by great water absorption is avoided, meanwhile, the construction difficulty is low, the stability is good, a good aggregate pore filling effect can be achieved without vacuum/negative pressure conditions, and the heating maintenance needs a short time and is easy to operate and realize.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples are included to aid one skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.

Examples:

the polypropylene fiber reinforced high-performance coral sand concrete is C120-grade coral concrete, and each cubic meter comprises the following components: 786.3 The cement, the 32.2 kg fly ash, the 316.3 kg silica fume, the 1186.7 kg coral sand, the ground blast furnace slag powder of 64.4 kg, the 56.3 kg quartz powder, the 275.8 kg seawater, the 32 kg liquid water reducer and the 6.85 kg defoamer are added, and the polypropylene fiber with the volume mixing amount of 2.0% -3.0% is added. Wherein: the cement is ordinary Portland cement with the reference number of 52.5; the fly ash is first-grade Fly Ash (FA); the fineness modulus of the coral sand is 1.8-2.25, and the main grain diameter is 0.5 mm-1.5 mm; grinding the fine blast furnace slag powder to obtain S105 excellent products; the grain size of the quartz powder is 1.2 mu m-1.7 mu m; the seawater is prepared by sea salt according to the seawater components of the south sea; the water reducer uses a viscosity-reducing polycarboxylic acid water reducer with a water reducing rate of more than 25 percent; the defoaming agent is polyether modified organic silicon defoaming agent; the polypropylene fibers have a fiber length of 6mm and 12 mm.

The preparation method of the polypropylene fiber reinforced high-performance coral sand concrete comprises the following specific steps:

(1) All raw materials are weighed according to the requirements of the components for standby.

(2) And (3) carrying out seawater soaking pre-wetting treatment on the coral sand weighed in the step (1) for 50min, and taking out and airing until 10min does not greatly drip water for later use.

(3) And (3) dry-mixing the cement, the fly ash, the ground blast furnace slag powder, the quartz powder and the like weighed in the step (1) for 2-3min.

(4) And (3) adding the coral sand in the step (2) into the cementing material uniformly stirred in the step (3), and continuously stirring for 2min to a uniform state.

(5) Adding the water reducer and the defoaming agent into seawater or artificial seawater, uniformly stirring, then uniformly and slowly pouring into the step (4), and stirring for 6-8min. And (2) scattering the polypropylene fibers weighed in the step (1) into the fresh slurry in 3 batches, wherein each time is separated by 20 seconds, and continuously stirring for 5 minutes after the completion of the feeding to form the fiber mixture.

(6) And (3) preparing the fiber mixture in the step (5) for molding, demolding after 24 hours, placing the molded fiber mixture in seawater at 70-90 ℃ for curing for 7 days, and placing the molded fiber mixture in seawater at normal temperature for curing for 28 days to obtain the high-performance coral sand concrete.

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

1. in the aspect of chloride ion migration coefficient, the hot water curing is obviously lower than the standard curing, and the descending range is between 32 and 45 percent. Compared with common coral concrete, the high-performance coral sand concrete has the impermeability level raised from P6 to over P8.

2. The seawater-accompanied coral concrete and the high-performance coral sand concrete contain a large amount of chloride ions, have early strength effect, and the strength of 7 days can reach 40-70% of the strength of 28 days. Compared with standard curing, the compressive strength of the coral cement-based composite material is obviously improved 7 days before the coral cement-based composite material is cured under the condition of hot water at 60-80 ℃, and is improved by more than 50% compared with the synchronous standard curing group.

3. Compared with common high-performance concrete and ultra-high-performance concrete, the high-temperature curing early-stage has obvious self-shrinkage effect, but in the high-performance coral sand concrete with micro-expansion characteristic, the high-performance coral sand concrete has no obvious shrinkage phenomenon and good volume stability. The shrinkage is mainly caused by that the hydration reaction process is quickened by hot water curing, the moisture in the pores is rapidly reduced, and the self-shrinkage is rapidly increased; the coral is a porous material, and contains calcium carbonate as main component, and has water absorption and water return effects.

4. Compared with the coral concrete porosity (more than 18%), the high-performance coral sand concrete has the porosity of 4.9% -6.8%. Under the high-temperature hot water curing condition, the porosity of the high-performance coral sand concrete is reduced by more than 23% compared with standard curing, the compressive strength is improved by 4.10% -9.54% after 28 days of curing, and the requirements of target strength and construction strength can be met earlier under the low-temperature construction or normal-temperature conditions although the improvement range is smaller. In addition, the viscosity-reducing polycarboxylic acid water reducer is beneficial to improving the fluidity of slurry and filling pores.

5. The mixed fibers with different lengths are scattered in batches, so that fiber aggregation is effectively avoided, an effective lap joint and a hooping system are formed, the coral concrete is changed from brittle fracture to ductile fracture, and the coral concrete has the characteristics of high strength and high toughness.

6. The construction difficulty is lower, the stability is better, the better aggregate pore filling effect can be achieved without vacuum/negative pressure conditions, the heating maintenance time is shorter, and the operation is easy to realize.

The standard curing compressive strength of the high-performance coral sand concrete prepared in the embodiment is 122.63MPa, the maximum heat curing strength reaches 134.32 MPa, and the flexural strength is: 8.42 MPa-11.37 MPa, tensile strength: 7.67 MPa-10.97 MPa, tensile strain above 6%, elastic modulus: 42.31MPa to 44.27MPa; porosity: 4.9% -6.8%.

Claims (5)

1. The high-performance coral sand concrete with the strength grade reaching more than C120 is characterized by comprising high-performance polypropylene fibers and high-strength coral sand concrete, wherein the high-performance coral sand concrete comprises the following components in percentage by weight: 26-30% of cement, 1-1.5% of fly ash, 8-12% of silica fume, 40-48% of coral sand, 2-3% of ground blast furnace slag powder, 2-2.5% of quartz powder, 9-13% of sea water, 2-2.3% of water reducer, 0.4-1% of defoamer and 2.0-3.0% of mixed polypropylene fiber by volume;

the polypropylene fiber is a monofilament short bundle fiber, the 6mm accounts for 38-42%, the 12mm accounts for 58-62%, the tensile strength of the fiber is more than 750 MPa, the elastic modulus is more than 8 Gpa, and the density is 0.92-0.95 g/cm ³ 。

2. The high performance coral sand concrete of claim 1, wherein said cement is a high grade cement such as high grade p.ii 52.5 common portland cement (grade 52.5 portland cement, grade 52.5 ordinary portland cement, grade 52.5 pozzolanic portland cement, grade 52.5 composite portland cement), high grade 52.5 specialty portland cement, high grade aluminate cement, etc.

3. The high performance coral sand concrete of claim 1, wherein the coral sand has an optimized particle size range of: 0.075mm to 2.36mm, wherein the main particle size is 0.5mm to 1.5mm, and the fineness modulus is 1.8 to 2.25.

4. The high-performance coral sand concrete according to claim 1, wherein the water reducer is a viscosity-reducing polycarboxylic acid water reducer with a water reduction rate of more than 25%, and the water consumption is reduced while the fluidity of the slurry is effectively increased, so that the cementing material can infiltrate into pores.

5. A method for preparing the high-performance coral sand concrete according to claim 1, which is characterized by comprising the following specific steps:

(1) Weighing all raw materials according to the component requirements for standby;

(2) Carrying out seawater soaking pre-wetting treatment on the coral sand weighed in the step (1) for 50min, taking out, and airing for 10min without greatly dripping water for later use;

(3) Dry-mixing the cement, the fly ash, the ground blast furnace slag powder, the quartz powder and the like weighed in the step (1) for 2-3min;

(4) Putting the coral sand in the step (2) into the cementing material uniformly stirred in the step (3), and continuously stirring for 2min to a uniform state;

(5) Adding the water reducer and the defoaming agent into seawater or artificial seawater, uniformly stirring, then uniformly and slowly pouring into the step (4), and stirring for 6-8min; then the polypropylene fiber weighed in the step (1) is scattered into the newly mixed slurry in 3 batches, each time interval is 20 seconds, and the mixture is continuously stirred for 5 minutes after the completion of the casting, so as to form a fiber mixture;

(6) And (3) preparing the fiber mixture in the step (5) for molding, demolding after 24 hours, placing the molded fiber mixture in 60-80 ℃ seawater for curing for 7 days, and placing the molded fiber mixture in normal-temperature seawater for curing for 28 days to obtain the high-performance coral sand concrete.