CN102531494B - Low elastic modulus fiber-enhanced recycled concrete preparation method - Google Patents

Abstract

The invention discloses a low elastic modulus fiber-enhanced recycled concrete preparation method. The method is characterized in that crushed waste concrete is used as a portion of coarse aggregate of concrete; and low elastic modulus fiber is doped in the recycled concrete to improve performance of the recycled concrete. The low elastic modulus fiber-enhanced recycled concrete contains, calculated by 100 weight parts per cubic meter concrete, 32.5R ordinary portland cement 20 to 21 parts, fine aggregate 18 to 20 parts, natural coarse aggregate 34 to 36 parts, recycled coarse aggregate 14 to 26 parts, polypropylene three-branch anti-aging reticular fiber 0.03 to 0.05 parts, and water 8 to 10 parts. Based on the tension resistance, the polypropylene three-branch anti-aging reticular fiber can prevent the development of an interface initial defect crack between fresh mortar and fresh coarse aggregate in the concrete, and can remarkably improve the interface crack between fresh mortar and old mortar of the recycled concrete. The preparation method is simple, and the recycled concrete has reliable mechanical property and wide commercial application prospect.

Description

A kind of preparation method of low-elasticity-modulus fiber reinforcement regeneration concrete

Technical field

The present invention relates to a kind of regeneration concrete that adopts the waste and old concrete preparation, belong to the green construction material field of novel environment friendly, particularly the toughness reinforcing regeneration concrete of a kind of employing low-elasticity-modulus polypropylene fibre.

Background technology

The extensive mode of production makes traditional architecture building and use and to the dismounting of building, seldom consider the disadvantageous effect to resource and environment in the life cycle of whole building from the processing of the exploitation of resource, raw material, buildings for a long time.Utilize the regeneration concrete technology of preparing then can effectively economize on resources, protect environment.At present, the regeneration concrete technology of preparing is considered to the effective ways of developing ecology green concrete, is one of important measures that realize the buildings and resources environment sustainable development.And the coarse aggregate that adopts in the regeneration concrete preparation is the discarded concrete process hand breaking of different sources, the aggregate that processes, compare natural aggregate and since the interface of new mortar and regeneration aggregate weak contact and effects limit such as the initial imperfection of aggregate, the unsettled compressive property that disperses the regeneration concrete Development of Preparation Technology.Can effectively improve carrying out of regeneration concrete internal fissure and utilize its good resistance of filamentary material to split characteristic, be the effective way that realizes the regeneration concrete improved performance, having a good application prospect and development prospect aspect the novel preparation method of green concrete material.

Summary of the invention

The objective of the invention is to, provide a kind of low-elasticity-modulus regeneration concrete preparation method, this method is utilized the good toughened ability of low-elasticity-modulus polypropylene fibre, by reasonable proportioning design, anti-aging three fibers of the polypropylene of admixture certain volume rate have been made low-elasticity-modulus regeneration concrete.This method economy, simple and practical, it meets applicable codes and standards to the requirement of aggregate and strength property, for the preparation of green concrete capable of circulation provides a kind of new method.

In order to realize above-mentioned task, the present invention takes following technical solution:

A kind of low bullet bullet modulus fibre strengthens the preparation method of regeneration concrete, it is characterized in that, this method adopts broken waste and old concrete as concrete part of coarse aggregates, the low-elasticity-modulus polypropylene fibre is mixed the performance of improving regeneration concrete in the regeneration concrete, and concrete preparation follows these steps to carry out:

Step 1, according to following proportioning regeneration concrete is prepared, in every cube of concrete, in 100 parts of weight unit, formed by following material: the 32.5R ordinary Portland cement: 20-21 part, fine aggregate (medium coarse sand): 18-20 part, natural coarse aggregate (natural rubble): 34-36 part, regenerated coarse aggregate: 14-26 part, three anti-aging reticulin fibers of polypropylene: 0.03-0.05 part, water: 8-10 part;

Step 2, adopt jaw crusher to carry out Mechanical Crushing waste and old concrete and clean, sieve, on this basis, regenerated coarse aggregate (JGJ52-2006) is carried out size analysis according to " regular concrete sand, stone quality and detection method standard ", satisfy JGJ52-2006 for the requirement of coarse aggregate continuous grading to guarantee grain gradation of coarse aggregates;

Step 3, for the fine aggregate grain composition, according to " regular concrete sand, stone quality and detection method standard " (JGJ52-2006) requirement, the sand grain composition should preferentially be selected II district sand for use, to satisfy in the concrete process for preparation requirement to the fine aggregate grating;

Step 4 is put into dried mixed the stirring of stirrer according to the parts by weight of formula ratio with dry material such as cement, fine aggregate and three anti-aging reticulin fibers of polypropylene, and churning time is no less than 3 minutes.

Step 5 in gross weight, respectively drops into natural coarse aggregate and regenerated coarse aggregate earlier half material to stirrer and in the step 4 and does mixedly, and stirs, and churning time is no less than 3 minutes;

Step 6 is fed into part natural coarse aggregate and the regeneration aggregate of remainder in the stirrer again, and adds 60% of Total Water in the prescription, stirs batch mixing 5-8 minute;

Step 7 adds stirrer with 30% of Total Water in the prescription and stirs, and after batch mixing 3-5 minute, all the other 10% water is stirred last the adding, and even until concrete mixing, serviceability satisfies the concrete requirement of building.

Advantage of the present invention is:

1, select for use three anti-aging reticulin fibers of low-elasticity-modulus polypropylene that the regeneration concrete performance is improved, utilize the resistance to tension of fiber to stop carrying out of new mortar in the concrete and the initial imperfection crack, interface between aggregate, to the effect that improves significantly of the crack, interface between distinctive new, the old mortar of regeneration concrete.

2, the preparation method is simple, can satisfy the requirement of common low-grade concrete intensity, and can strengthen this concrete performance of resisting cracking and anti-tough performance.In addition, because the coarse aggregate that has used the part building castoff to process has better economic and social benefit from cycling and reutilization, saving cost and environmental protection and energy saving aspect.

Description of drawings

Fig. 1 is three anti-aging reticulin fiber section microcosmic Electronic Speculum SEM figure of polypropylene;

Fig. 2 is the recycled concrete coarse aggregate grading curve;

Fig. 3 is the regeneration concrete mechanical property normalization method contrast of replacement rate 30%.

Fig. 4 is the regeneration concrete mechanical property normalization method contrast of replacement rate 50%.

Fig. 5 is three anti-aging reticulin fiber pictures of polypropylene.

The present invention is described in further detail below in conjunction with drawings and Examples.

Embodiment

The low bullet bullet modulus fibre of present embodiment preparation strengthens regeneration concrete, according to following proportioning regeneration concrete is prepared, in every cube of concrete, in 100 parts of weight unit, formed by following material: the 32.5R ordinary Portland cement: 20-21 part, fine aggregate (medium coarse sand): 18-20 part, natural coarse aggregate (natural rubble): 34-36 part, regenerated coarse aggregate: 14-26 part, three anti-aging reticulin fibers of polypropylene: 0.03-0.05 part, water: 8-10 part.

Three anti-aging reticulin fibers of polypropylene (production of Shaanxi Wanda's engineering materials company limited), it is a kind of cancellated fiber, and three anti-aging reticulin fiber form of fractures of polypropylene are triangle, make compare other sections for the polypropylene fibre of circle can be fully with regeneration concrete in coarse aggregate surperficial contact the synergy that improves between fiber and the aggregate (Fig. 1, Fig. 5).The base-material of it and cement concrete has extremely strong bonding force.Add in the concrete base-material, after stirring, because being subjected to the impact of aggregates such as cement, sandstone, automatically open, become monofilament one by one or involve multidirectional distributed fibers mutually, form a kind of unrest to support system at inside concrete, can extremely effectively control early stage plastic shrinkage crackle and the sedimentation crackle of concrete and sand-cement slurry.Improve concrete impervious, anti-fragmentation, shock resistance greatly, increase concrete toughness and wear resistance, thereby the life-span of buildings is prolonged greatly, greatly reduce the engineering maintenance expense.

In following experiment, the applicant has collected the waste and old concrete of different sources from different removal building sites, the active time of the primary structure of these waste and old concretes itself was respectively 15 years and 40 years, in addition, also collected the discarded concrete of finishing each test that deposit in the laboratory, with its classification, fragmentation, cleaning processing respectively.

Coarse aggregate has the Aggregate of recycled concrete of natural rubble and three kinds of different sourcess respectively.Wherein the natural rubble aggregate is expressed as NA; Adopting the aggregate of laboratory fragmentation is RA-I; Adopt the coarse aggregate of the removal discarded concrete in 15 years of service life preparation to be expressed as RA-II, service life 40 years be expressed as RA-III.

Below be the embodiment that the contriver provides:

Embodiment 1:

1, waste and old concrete is carried out Mechanical Crushing, screening, cleaning etc., the grain gradation of coarse aggregates of preparation should satisfy " regular concrete sand, stone quality and detection method standard " and (JGJ52-2006) show 3.2.1-2 (the grain composition scope of rubble or cobble) to the requirement of aggregate in the 3.2.1 bar.As shown in Figure 2, natural coarse aggregate NA, regenerated coarse aggregate RA-I, RA-II, RA-II I all satisfy the requirement of the coarse aggregate continuous grading of JGJ52-2006.

Determined the relevant particle diameter d of particle by grain composition accumulation curve shown in Figure 2 ₁₀, d ₃₀And d ₆₀, and obtain nonuniformity coefficient And coefficient of curvature

D wherein ₁₀For the granular mass accumulative total percentage ratio less than certain grain diameter is the particle diameter of 10% o'clock correspondence; d ₃₀For the granular mass accumulative total percentage ratio less than certain grain diameter is the particle diameter of 30% o'clock correspondence; d ₆₀For the granular mass accumulative total percentage ratio less than certain grain diameter is the particle diameter of 60% o'clock correspondence.

By in the 3.2.1 bar among the JGJ52-2006 table 3.2.1-2 as can be known, for 5～31.5mm with interior coarse aggregate, as calculated, nonuniformity coefficient K _uScope between (0.37,0.69), and coefficient of curvature K _cScope should be between (0.80,1.53).The nonuniformity coefficient of variant aggregate and coefficient of curvature all satisfy the requirement of the grain composition of JGJ52-2006 as shown in Table 1, illustrate that grading of aggregate is good.

Table 1: coarse aggregate nonuniformity coefficient and coefficient of curvature

2. the fine aggregate grating is carried out size test according to the requirement of the fine aggregate grain composition of table 3.1.2-3 in the 3.1.2 bar among the JGJ52-2006 to sand, and the size test result is as shown in table 2, and through contrast, sand belongs to II district sand, for the preparation concrete is preferentially selected sand for use.

Table 2: fine aggregate particles of natural sand grating test

3. for coarse aggregate, except grain composition, other factors of influential aggregate intensity also, as pin, platy shaped particle content, silt content, crush values index and soundness index etc. can be tested at each index.Present embodiment has mainly been measured crush values index under silt content, crush values index and the saturated surface dry condition thereof of aggregate.Its test-results is as shown in table 3.

Table 3: coarse aggregate silt content and crush values index

As shown in Table 3, the aggregate performance of coarse aggregate all satisfies the dried crush values index request of the silt content of JGJ52-2006, crush values index and saturation plane.

4, being the starting material of regeneration concrete preparation with the regeneration aggregate RA-II that collects, is under 30% the situation, according to following proportioning regeneration concrete to be tried to join to the replacement rate.In every cube of concrete:

32.5R ordinary Portland cement: 500kg;

Natural sand: 471kg;

Natural rubble: 864kg;

Regeneration aggregate RA-II:360kg;

Three anti-aging fiber: 0.9kg of polypropylene;

Water: 185kg.

At first ordinary Portland cement, natural sand and three anti-aging fibers of polypropylene of dry material 32.5R are put into stirrer and stir, churning time was not less than 3 minutes; Secondly, natural aggregate (natural rubble) and regeneration aggregate are done mixed the stirring in the 50% input stirrer according to each gross weight, churning time was not less than 3 minutes; Again, the residue 50% of natural coarse aggregate and regeneration aggregate gross weight is dropped into stirrer, add water while stirring, the weight that wherein adds water is about 60% of gross weight in the proportioning, and batch mixing stirs, and the time is no less than 5 minutes; Again, add stirrer according to 30% of the water yield in the prescription and stir, mixing time was not less than 3 minutes; To remain 10% water at last, to add stirrer even until concrete mixing.

5, for the research regeneration concrete adds fiber to the influence of its mechanical property, according to " standard for test methods of mechanical properties of ordinary concrete " (GB/T50081-2002), many groups of contrast test specimens have been prepared respectively.

First group, do not contain the normal concrete test specimen of regeneration aggregate and fiber, be designated as NC;

Second group, do not contain regeneration aggregate but fibrous test specimen NFC;

The 3rd group, contain regeneration aggregate 30% but not fibrous test specimen RAC-I;

The 4th group, regeneration aggregate 30% but also fibrous test specimen RAC-IF had not only been contained.Respectively four kinds of concrete are carried out cubic compressive strength, axial compressive strength, tensile splitting strength and folding strength test, test-results is as shown in table 4.

Table 4: the regeneration concrete mechanical performance index of replacement rate 30%

With normal concrete NC serve as the contrast test specimen, with the every mechanical index normalized of above-mentioned concrete, the result is as shown in Figure 3.

As shown in Figure 3, compare with normal concrete, for studying fiber to concrete influence, at first only consider fiber to the influence of normal concrete mechanical property and the situation of admixture regeneration aggregate not, the cubic compressive strength of general fibre concrete NFC, axial compressive strength and cleavage strength have reduction in various degree, cubic compressive strength wherein, axial compressive strength and normal concrete are suitable substantially, reduce by 1.84% and 2.15% respectively, arrive 98.2% and 97.8% of normal concrete intensity, tensile splitting strength is big slightly with respect to the ultimate compression strength range of decrease, compare with normal concrete, reduced by 7.24%, but folding strength is compared other performance index after adding fiber, folding strength arrives 1.2 times of normal concrete respective strengths, and amplification reaches 16.77%, so, adding under three anti-aging reticulin fiber situations of less volume polypropylene, the toughness reinforcing performance of concrete anti-folding has had significant raising.

Secondly, considered low replacement rate regeneration aggregate to the influence of concrete performance but the situation of any fiber of admixture not, its cubic compressive strength and folding strength all are higher than the corresponding mechanical performance index of NC, wherein cubic compressive strength is higher than NC about 9.61%, folding strength is a little more than normal concrete about 2.66%, and axial compressive strength is about 5.86% a little less than NC, and cleavage strength is lower than normal concrete 12.8%.

At last, taken all factors into consideration the situation of the low replacement rate 30% of low-dosage, three anti-aging reticulin fibers of low-elasticity-modulus polypropylene and regeneration aggregate thereof, having studied the cross section is that leg-of-mutton polypropylene mesh fiber is to the influence of regeneration concrete mechanical property.Test-results as shown in Figure 3, regeneration concrete RAC-1F is except cleavage strength is lower than normal concrete 17.83%, axial compressive strength and normal concrete are suitable substantially, be lower than normal concrete about 1.37%, and cubic compressive strength and folding strength are all apparently higher than normal concrete, wherein cubic compressive strength reaches 1.13 times of normal concrete, and folding strength arrives 1.17 times of normal concretes, and amplification is between 10-15%.

Therefore, in sum, in the regeneration concrete of the low replacement rate of preparation, three the anti-aging reticulin fibers of polypropylene that add low-dosage can not only satisfy the requirement of the ultimate compression strength of low-grade concrete substantially, and the folding strength of reflection toughening effect improves.

Embodiment 2:

1, the grating of preparation, screening and the fine aggregate of regeneration aggregate is required all identical with the 1st and the 2nd among the embodiment 1, namely according to " regular concrete sand, stone quality and detection method standard " (JGJ52-2006) requirement in 3.2.1 bar and the 3.1.2 bar respectively regeneration aggregate and fine aggregate are carried out size test, make the grating of coarse-fine aggregate all satisfy the requirement of standard.

2, being the starting material of regeneration concrete preparation with the regeneration aggregate RA-II that collects, is under 50% the situation, according to following proportioning regeneration concrete to be tried to join to the replacement rate.In every cube of concrete:

32.5R ordinary Portland cement: 500kg;

Natural sand: 471kg;

Natural rubble: 618kg;

Regeneration aggregate RA-II:600kg;

Water: 192kg;

Three anti-aging fiber: 0.9kg of polypropylene.

To concrete mixing, at first ordinary Portland cement, sand and three anti-aging fibers of polypropylene of the dry material 32.5R of formula ratio to be put into stirrer and stir, churning time is no less than 180 seconds; Secondly, natural aggregate and regeneration aggregate are dropped into 50% of each aggregate gross weight earlier according to weight percent do mixed and stir, churning time is no less than 180 seconds; Again, natural coarse aggregate and regeneration aggregate remaining 50% dropped into stirrer, adds water while stirring, the weight that wherein adds water be in the proportioning gross weight 60%, stir, churning time is no less than 300 seconds; Again, 30% of water weight in the proportioning is added stirrer stir, mixing time was not less than 180 seconds; At last, the water adding stirrer of residue 10% is even until concrete mixing.

3, for the research regeneration concrete adds fiber to the influence of its mechanical property, according to " standard for test methods of mechanical properties of ordinary concrete " (GB/T50081-2002), many groups of contrast test specimens have been prepared respectively.

First group, do not contain the normal concrete test specimen of regeneration aggregate and fiber, be designated as NC;

Second group, do not contain regeneration aggregate but fibrous test specimen NFC;

The 3rd group, contain regeneration aggregate 50% but not fibrous test specimen RAC-II;

The 4th group, regeneration aggregate 50% but also fibrous test specimen RAC-IIF had not only been contained.Respectively four kinds of concrete are carried out cubic compressive strength, axial compressive strength, tensile splitting strength and folding strength test, test-results is as shown in table 5.

Table 5: replacement rate 50% regeneration concrete mechanical performance index

Serve as the contrast test specimen with the normal concrete NC that makes, with concrete every mechanical index normalization method of preparation as shown in Figure 4.

In order to study fiber to the influence of regeneration concrete, considered that fiber is to the influence of concrete mechanical index under three kinds of different operating modes.

At first, do not adding under the regeneration aggregate situation, considering that polypropylene fibre is to the influence of normal concrete.NC compares with normal concrete, and cubic compressive strength, axial compressive strength and the tensile splitting strength of general fibre concrete NFC all decrease, and folding strength reaches 1.2 times of NC.Wherein cubic compressive strength and axial compressive strength reduced by 1.84% and 2.15% respectively, and cleavage strength have reduced by 7.24% a little less than normal concrete.

Secondly, compare with RAC-I among the embodiment 1, it is 50% that the replacement rate of regeneration aggregate increases, and considers that the replacement rate is regeneration concrete changes of properties when not adding the anti-aging reticulin fiber of three of polypropylene at 50% o'clock.As shown in Figure 4, when adding 50% regeneration aggregate, its cubic compressive strength and axial compressive strength are a little more than normal concrete, reach concrete 1.01 times and 1.03 times of contrast respectively, folding strength is almost suitable with normal concrete, arrive 99.5% of its intensity, and the tensile splitting strength range of decrease arrives 89.1% of normal concrete.

At last, namely considered to add the situation that 50% regeneration aggregate adds polypropylene fibre again, test-results as shown in Figure 4, ultimate compression strength is compared with normal concrete with cleavage strength and is changed not quite, wherein cubic compressive strength is a little more than 2.39%, axial compressive strength arrives 96% of normal concrete, and cleavage strength only reduces by 6.1%.And folding strength is compared normal concrete, and amplification reaches 10.9%, near 1.12 times of normal concrete folding strength.

In sum, be 50% regeneration concrete for the replacement rate, add three anti-aging reticulin fibers of polypropylene of low-dosage, by test-results as can be seen, change under the little situation in ultimate compression strength, its folding strength has comparatively significantly to be increased, and has improved the anti-tough performance of regeneration concrete.

Claims (1)

1. the preparation method of a low-elasticity-modulus fiber reinforcement regeneration concrete, it is characterized in that, this method adopts broken waste and old concrete as concrete regenerated coarse aggregate, the low-elasticity-modulus polypropylene fibre is mixed the performance of improving regeneration concrete in the regeneration concrete, and concrete preparation follows these steps to carry out:

Step 1, according to following proportioning regeneration concrete is prepared, in every cube of concrete, in 100 parts of weight unit, formed by following material: the 32.5R ordinary Portland cement: 20-21 part, fine aggregate: 18-20 part, natural coarse aggregate: 34-36 part, regenerated coarse aggregate: 14-26 part, three anti-aging reticulin fibers of polypropylene: 0.03-0.05 part, water: 8-10 part;

Step 2, adopt jaw crusher to carry out Mechanical Crushing waste and old concrete and clean, sieve, carry out size analysis according to " regular concrete sand, stone quality and detection method standard " JGJ52-2006, the regenerated coarse aggregate grain composition of preparation satisfies JGJ52-2006 for the requirement of coarse aggregate continuous grading, and the grating of natural coarse aggregate particle also satisfies JGJ52-2006 for the requirement of coarse aggregate continuous grading;

Step 3, for the fine aggregate grain composition, according to " regular concrete sand, stone quality and detection method standard " JGJ52-2006 requirement, the sand grain composition is selected II district sand for use, to satisfy in the concrete process for preparation requirement to the fine aggregate grating;

Step 4 according to the parts by weight of formula ratio, is put into stirrer with 32.5R ordinary Portland cement, fine aggregate and three anti-aging reticulin fibers of polypropylene and is done mixed stirring, and churning time is no less than 3 minutes;

Step 5 in gross weight, respectively drops into natural coarse aggregate and regenerated coarse aggregate earlier half material to stirrer and in the step 4 and does mixedly, and stirs, and churning time is no less than 3 minutes;

Step 6 is fed into part natural coarse aggregate and the regeneration aggregate of remainder in the stirrer again, and adds 60% of Total Water in the prescription, stirs batch mixing 5-8 minute;

Step 7 adds stirrer with 30% of Total Water in the prescription and stirs, and after batch mixing 3-5 minute, all the other 10% water is stirred last the adding, and even until concrete mixing, serviceability satisfies the concrete requirement of building.

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