Full-coral aggregate cement concrete mix proportion design method

Abstract

The invention discloses a design method for the mix proportion of full-coral aggregate cement concrete. The design method comprises the following steps: step 1, calculating the water-binder ratio of the full-coral aggregate cement concrete; 2, calculating the net water consumption of the whole coral aggregate cement concrete; 3, calculating the use amount of a gel material of the full-coral aggregate cement concrete; step 4, calculating the use amount of the additive of the full-coral aggregate cement concrete; 5, calculating the cement dosage and the mineral admixture dosage of the full-coral aggregate cement concrete; and 6, calculating the unit dosage of the fine coral aggregate in the saturated surface dry state and the unit dosage of the coarse coral aggregate after water absorption in the mixing and forming process. According to the method, a specific design method of the whole coral aggregate and the cement concrete is given, calculation of the water-binder ratio, selection of the sand ratio, selection of the water consumption and determination of the actual water absorption rate of the coarse aggregate are defined, the mix proportion design method is thoroughly improved, and the generalizability is high.

Description

Technical Field

[0001] The invention relates to the technical field of coral aggregate and cement concrete mix ratio design, and in particular to a full coral aggregate cement concrete mix ratio design method. Background Art

[0002] In recent years, with the rise of island construction in the South my country Sea, there have been many studies on all-coral aggregate cement concrete in China. However, they are all performance studies in one or some aspects, which are basically feasibility application studies, and have achieved considerable results, laying a good foundation for application and promotion. However, these are almost all studies on the performance of all-coral cement concrete, and very few involve research on the mix design of all-coral aggregate cement concrete. In the publicly available "Technical Specifications for the Application of Coral Aggregate Concrete" T / CECS 694-2020, there is no water-cement ratio calculation formula, no effective water consumption reference comparison table, and no sand ratio selection comparison table. The recommended important control indicators are too large and have no reference value. Even experienced highway or water transport test and inspection engineers cannot successfully complete the mix design of all-coral aggregate cement concrete of a certain strength grade in the short term, resulting in the application of all-coral cement concrete engineering can only remain in the laboratory and cannot be promoted. Summary of the invention

[0003] The purpose of the present invention is to provide a method for designing the mix proportion of all-coral aggregate cement concrete. The method provides a specific design method for all-coral aggregate cement concrete, clarifies the calculation of water-binder ratio, the selection of sand ratio, the selection of water consumption and the determination of the actual water absorption rate of coarse aggregate, is highly practical and has great significance for promotion and application.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for designing a mix ratio of all-coral aggregate cement concrete, the design method comprising the following steps:

[0006] Step 1: Calculate the water-cement ratio W / B of all coral aggregate cement concrete:

[0007]

[0008] a a 、a b — regression coefficients, = 0.27 and -0.92, respectively;

[0009] f b —28d compressive strength of cementitious material mortar (MPa).

[0010] f cu,o —Preparation strength of all-coral aggregate cement concrete (MPa);

[0011] Step 2: Calculate the net water consumption of all coral aggregate cement concrete m wo (kg / m 3 ):

[0012] m wo =m' wo *(1-β);

[0013] m' wo —Net water consumption of all coral aggregate cement concrete selected to meet the design slump requirements without admixture (kg / m 3 );

[0014] β—Water reduction rate of admixture (%).

[0015] Step 3: Calculate the amount of gel material m for all coral aggregate cement concrete bo (kg / m 3 ):

[0016]

[0017] Step 4: Calculate the amount of admixture m for all coral aggregate cement concrete ao (kg / m 3 ):

[0018] m ao =m bo *β a ;

[0019] β a —The amount of admixture (%).

[0020] Step 5: Calculate the amount of mineral admixture m for all coral aggregate cement concrete fo (kg / m 3 ) and cement content of all coral aggregate cement concrete m co (kg / m 3 ):

[0021] m fo =m bo *β f

[0022] m co =m bo -m fo ;

[0023] β f —Mineral admixture dosage (%).

[0024] Step 6: Calculate the unit dosage of coral fine aggregate in saturated surface dry state m sb (kg / m 3) and coral coarse aggregate mixing and molding process after absorbing water unit dosage m gx (kg / m 3 ):

[0025] m cp =m fo +m co +m gx +m sb +m wo

[0026]

[0027] m cp —Assumed bulk density of all coral aggregate cement concrete (kg / m 3 ), select within the value range;

[0028] β s —Sand ratio of all coral aggregate cement concrete (%).

[0029] Preferably, in step 1, the strength of the all-coral aggregate cement concrete is calculated according to the following formula:

[0030] f cu,o ≥f cu,k +1.645σ

[0031] σ—standard deviation of concrete strength (MPa);

[0032] f cu,k —Standard value of compressive strength of all-coral aggregate cement concrete cube (MPa).

[0033] Preferably, when the design strength grade of concrete is not greater than C20, the standard deviation of concrete strength σ=4.0; when the design strength grade of concrete is between C25 and C45, the standard deviation of concrete strength σ=5.0; when the design strength grade of concrete is between C50 and C55, the standard deviation of concrete strength σ=6.0.

[0034] Preferably, in step six, the sand ratio β of the whole coral aggregate cement concrete is s It is negatively correlated with the water-to-binder ratio W / B.

[0035] Preferably, in step 7, the assumed bulk density of the all-coral aggregate cement concrete is in the range of 2200 to 2400 kg / m 3 .

[0036] Preferably, in step 1, when the cementitious material 28d mortar strength value (f b ) When there is no measured value, calculate according to the following formula:

[0037] fb =Y f Y s f ce

[0038] Y f —Fly ash influence coefficient, selected within the value range;

[0039] Y s —Influence coefficient of granulated blast furnace slag powder, selected within the value range;

[0040] f ce —28d compressive strength of cement mortar (MPa), measured in the test.

[0041] Preferably, when the 28d cement mortar compressive strength (f ce ) When there is no measured value, calculate according to the following formula:

[0042] f ce =Y c f ce,g

[0043] Y c —Redundancy factor of cement strength grade value, selected within the value range;

[0044] f ce,g —Cement strength grade value (MPa).

[0045] In the present invention, the regression coefficient of the Borromy formula, i.e., the water-binder ratio calculation formula of all-coral cement concrete, is determined; a table for selecting unit water consumption of all-coral aggregate cement concrete is created; a table for selecting sand ratio of all-coral aggregate cement concrete is created; a calculation formula for sand ratio of all-coral aggregate cement concrete and a calculation formula for water absorption rate of coral coarse aggregate are created. Any test and inspection personnel can easily complete the mix ratio design of all-coral aggregate cement concrete from C20 to C50 according to this method, laying a solid foundation for realizing engineering application, and having extremely strong promotion and application value. DETAILED DESCRIPTION

[0046] The present invention is further described:

[0047] A method for designing a mix ratio of all-coral aggregate cement concrete, the method comprising the following steps:

[0048] Step 1: Calculate the water-cement ratio W / B of all coral aggregate cement concrete:

[0049]

[0050] a a 、a b —Regression coefficient, a a =0.27, a b=-0.92;

[0051] f b —28d compressive strength of cementitious material mortar (MPa);

[0052] f cu,o —Preparation strength of all-coral aggregate cement concrete (MPa).

[0053] The regression coefficient of coral coarse aggregate in the Borromee formula was obtained by fitting method. The specific coefficient a was determined based on the water-binder ratio of all-coral aggregate cement concrete and the compressive strength of concrete. a =0.27, a b =-0.92.

[0054] Specifically, the strength of all-coral aggregate cement concrete is calculated according to the following formula:

[0055] f cu,o ≥f cu,k +1.645σ

[0056] σ—standard deviation of concrete strength (MPa);

[0057] f cu,k —Standard value of compressive strength of all-coral aggregate cement concrete cube (MPa).

[0058] When the design strength grade of concrete is not greater than C20, the standard deviation of concrete strength σ=4.0; when the design strength grade of concrete is between C25 and C45, the standard deviation of concrete strength σ=5.0; when the design strength grade of concrete is between C50 and C55, the standard deviation of concrete strength σ=6.0, see Table 1 for details.

[0059] Table 1 Standard deviation of concrete strength σ (MPa)

[0060] Concrete strength ≤C20 C25~C45 C50~C45 Standard deviation of concrete strength 4.0 5.0 6.0

[0061] The formula for calculating the strength of all-coral aggregate cement concrete in this example is based on the condition that the concrete strength is less than C60. However, it is extremely difficult to achieve concrete preparation of C60 and above, and its use will be extremely small. Therefore, the preparation of concrete preparation of C60 and above will not be studied for the time being.

[0062] When the 28d mortar strength value (f b ) When there is no measured value, calculate according to the following formula:

[0063] f b =Y f Y s f ce

[0064] Yf —Fly ash influence coefficient, selected within the value range; specific selection can be made according to Table 2;

[0065] Y s —Influence coefficient of granulated blast furnace slag powder, selected within the value range;

[0066] f ce —28d compressive strength of cement mortar (MPa), measured in the test.

[0067] Table 2 Powder ash influence coefficient (Y f ) and the influence coefficient of granulated blast furnace slag powder (Ys)

[0068]

[0069]

[0070] Note: 1. The upper limit value should be taken when using Class I and Class II fly ash;

[0071] 2. When using S75 grade granulated blast furnace slag powder, the lower limit value should be taken; when using S95 grade granulated blast furnace slag powder, the upper limit value should be taken; when using S105 grade granulated blast furnace slag powder, the upper limit value plus 0.05 can be taken;

[0072] 3 When the dosage exceeds the amount in the table, the influence coefficient of fly ash and granulated blast furnace slag powder should be determined through experiments.

[0073] When the 28d cement mortar compressive strength (f ce ) When there is no measured value, calculate according to the following formula:

[0074] f ce =Y c f ce,g

[0075] Y c —Redundancy coefficient of cement strength grade value, selected within the value range; specific selection can be made according to Table 3;

[0076] f ce,g —Cement strength grade value (MPa).

[0077] Table 3 Redundancy coefficient (Yc) of cement strength grade value

[0078] Cement strength grade 42.5 52.5 Redundancy coefficient 1.16 1.10

[0079] Step 2: Calculate the net water consumption of all coral aggregate cement concrete m wo (kg / m 3 ):

[0080] m wo =m' wo *(1-β);

[0081] m' wo —Net water consumption of all coral aggregate cement concrete selected to meet the design slump requirements without admixture (kg / m 3 );

[0082] β—Water reduction rate of admixture (%).

[0083] In a specific example, when the water-binder ratio of all-coral aggregate cement concrete is in the range of 0.25 to 0.60, the net water consumption (kg / m 3 ) Select according to Table 4:

[0084] Table 4 Net water consumption of all coral aggregate cement concrete (kg / m 3 )

[0085]

[0086] According to Table 4, the net water consumption of all-coral aggregate cement concrete decreases with the increase of the maximum nominal particle size of coral coarse aggregate, and increases with the increase of slump. Based on the water consumption of 90mm slump, the net water consumption of all-coral aggregate cement concrete increases by 5-10Kg / m for every 20mm increase in slump. 3 Water consumption calculation: when the slump increases to above 180 mm, the water consumption that increases accordingly with the slump can be reduced.

[0087] Step 3: Calculate the amount of gel material m for all coral aggregate cement concrete bo (kg / m 3 ):

[0088]

[0089] Step 4: Calculate the amount of admixture m for all coral aggregate cement concrete ao (kg / m 3 ):

[0090] m ao =m bo *β a ;

[0091] β a —Amount of admixture (%);

[0092] Step 5: Calculate the amount of mineral admixture m for all coral aggregate cement concrete fo (kg / m 3 ) and cement content of all coral aggregate cement concrete m co (kg / m 3 ):

[0093] m fo =m bo *β f

[0094] m co =m bo -m fo ;

[0095] β f —Mineral admixture dosage (%);

[0096] Step 6: Calculate the unit dosage of coral fine aggregate in saturated surface dry state m sb (kg / m 3 ) and coral coarse aggregate mixing and molding process after absorbing water unit dosage m gx (kg / m 3 ):

[0097] m cp =m fo +m co +m gx +m sb +m wo ;

[0098]

[0099] m cp —Assumed bulk density of all coral aggregate cement concrete (kg / m 3 );

[0100] β s —Sand ratio of all coral aggregate cement concrete (%).

[0101] Sand ratio of all coral aggregate cement concrete β s It is negatively correlated with the water-binder ratio W / B, that is, the larger the water-binder ratio W / B of all-coral aggregate cement concrete is, the higher the sand ratio β of all-coral aggregate cement concrete is. s The smaller it is, see Table 5 for details.

[0102] Table 5 Sand ratio of all coral aggregate cement concrete (%)

[0103]

[0104] According to Table 5, the net sand ratio of all-coral aggregate cement concrete increases with the increase of the maximum nominal particle size of the coral coarse aggregate, and the net sand ratio of all-coral aggregate cement concrete decreases with the increase of the water-binder ratio. When selecting the sand ratio value in Table 5, the sand ratio can be reduced or increased accordingly for fine sand or coarse sand, and the sand ratio does not change due to the change of slump. The assumed bulk density of all-coral aggregate cement concrete ranges from 2200 to 2400 kg / m 3 .

[0105] Examples:

[0106] Maldives Velana International Airport expansion project, road crash pier, coarse and fine aggregates are all coral coarse and fine aggregates, cement is P.042.5 cement, cement mortar 28-day compressive strength is 48.9MPa, granulated blast furnace slag powder dosage is 15%, water reducer is polycarboxylic acid series slow setting high efficiency water reducer, the measured dosage is 1.2% of cement dosage, the water reduction rate is 40%, the design slump is 120-160mm C40 all coral aggregate cement concrete, the assumed bulk density is 2340kg / m 3 According to Table 1, σ=5.0MPa, f cu,k =40MPa, and the formula for calculating the strength of all-coral aggregate cement concrete is:

[0107] f cu,o ≥f cu,k +1.645σ=40+1.645×5=48.225MPa

[0108] f b =48.9MPa, and the obtained f cu,o =48.225MPa is brought into the water-cement ratio calculation formula of all-coral aggregate cement concrete to obtain:

[0109]

[0110] The gradation design of coral coarse aggregate is: 4.75-9.5mm crushed coral aggregate accounts for 25%, 9.5-19mm crushed coral aggregate accounts for 55% and 19-26.5mm crushed coral aggregate accounts for 20%. The fine aggregate is 0-4.75mm crushed coral sand. According to Table 2, the net water consumption m' of all coral aggregate cement concrete is selected wo =245Kg / m 3 , the admixture is polycarboxylate water reducer, and the measured water reduction rate of polycarboxylate water reducer is β = 40%, so the net water consumption of all coral aggregate cement concrete is:

[0111] m wo =m' wo *(1-β)=245×(1-0.4)=147kg / m 3 .

[0112] Step 3: Calculate the amount of gel material m for all coral aggregate cement concrete bo (kg / m 3 ):

[0113]

[0114] Step 4: Calculate the amount of admixture m for all coral aggregate cement concrete ao (kg / m 3 ):

[0115] m ao =m bo *β a =397*1.2%=4.764kg / m 3

[0116] β a —Amount of admixture (%);

[0117] Step 5: Calculate the amount of mineral admixture m for all coral aggregate cement concrete fo (Kg / m 3 ) and cement content of all coral aggregate cement concrete m co (Kg / m 3 ):

[0118] m fo =m bo *β f =397*15%=60(Kg / m 3 )

[0119] m co =m bo -m fo =397-60=337(kg / m 3 )

[0120] β f —Mineral admixture dosage (%);

[0121] Step 6: Calculate the unit dosage of coral fine aggregate in saturated surface dry state m sb (kg / m 3 ) and coral coarse aggregate mixing and molding process after absorbing water unit dosage m gx (kg / m 3 ):

[0122] m gx +m sb =m cp -m fo -m co -m wo =2340-337-60-147=1796(kg / m 3 );

[0123] According to the maximum nominal particle size of coarse aggregate and water-cement ratio, the sand ratio of this mix ratio is selected as 62%:

[0124]

[0125] m sb =(m sb +m gx )*β s =1769×0.62=1114(kg / m 3 );

[0126] m gx =(m sb +m gx )-m sb =1796-1114=628(kg / m 3 );

[0127] m cp —Assumed bulk density of all coral aggregate cement concrete (kg / m 3 ),

[0128] β s —Sand ratio of all coral aggregate cement concrete (%).

[0129] The above examples are only some illustrations of the concept and implementation of the present invention, and are not intended to limit the same. Under the concept of the present invention, technical solutions that have not been substantially changed are still within the scope of protection.

Claims

1. A method for designing mix proportion of all-coral aggregate cement concrete, characterized by: The design method comprises the following steps: Step 1: Calculate the water-cement ratio W / B of all coral aggregate cement concrete: a a 、a b — regression coefficient; f b —28d compressive strength of cementitious material mortar (MPa); f cu,o —Preparation strength of all-coral aggregate cement concrete (MPa). Step 2: Calculate the net water consumption of all coral aggregate cement concrete m wo (kg / m 3 ): m wo =m' wo *(1-b); m' wo —Net water consumption of all-coral aggregate cement concrete estimated to meet the design slump requirements without admixture (kg / m 3 ); β—Water reduction rate of admixture (%). Step 3: Calculate the amount of gel material m for all coral aggregate cement concrete bo (kg / m 3 ): Step 4: Calculate the amount of admixture m for all coral aggregate cement concrete ao (kg / m 3 ): m ao =m bo *b a ; β a —The amount of admixture (%). Step 5: Calculate the amount of mineral admixture m for all coral aggregate cement concrete fo (kg / m 3 ) and cement content of all coral aggregate cement concrete m co (kg / m 3 ): m fo =m bo *b f m co =m bo -m fo ; β f —Mineral admixture dosage (%). Step 6: Calculate the unit dosage of coral fine aggregate in saturated surface dry state m sb (kg / m 3 ) and coral coarse aggregate mixing and molding process after absorbing water unit dosage m gx (kg / m 3 ): m cp =m fo +m co +m gx +m sb +m wo m cp —Assumed bulk density of all coral aggregate cement concrete (kg / m 3 ), select within the value range; β s —The sand ratio (%) of all-coral aggregate cement concrete should be selected within the value range.

2. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 1, characterized in that: In the step 1, the strength of the all-coral aggregate cement concrete is calculated according to the following formula: f cu,o ≥f cu,k +1.645s σ—standard deviation of concrete strength (MPa); f cu,k —Standard value of compressive strength of all-coral aggregate cement concrete cube (MPa).

3. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 2, characterized in that: When the design strength grade of concrete is not greater than C20, the standard deviation of concrete strength σ=4.0; when the design strength grade of concrete is between C25 and C45, the standard deviation of concrete strength σ=5.0; when the design strength grade of concrete is between C50 and C55, the standard deviation of concrete strength σ=6.

0.

4. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 1 or 2, characterized in that: In step 6, the sand ratio β of the whole coral aggregate cement concrete is s It is negatively correlated with the water-to-binder ratio W / B.

5. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 4, characterized in that: In step 6, the assumed bulk density of the all-coral aggregate cement concrete is in the range of 2200-2400 kg / m 3 .

6. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 1, characterized in that: In the step 1, when the cementitious material 28d mortar strength value (f b ) When there is no measured value, calculate according to the following formula: f b =Y f Y s f ce Y f —Fly ash influence coefficient, selected within the value range; Y s —Influence coefficient of granulated blast furnace slag powder, selected within the value range; f ce —28d compressive strength of cement mortar (MPa), measured in the test.

7. The method for designing mix proportion of all-coral aggregate cement concrete according to claim 6, characterized in that: When the 28d cement mortar compressive strength (f ce ) When there is no measured value, calculate according to the following formula: f ce =Y c f ce,g Y c —Redundancy factor of cement strength grade value, selected within the value range; f ce,g —Cement strength grade value (MPa).

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