A construction method for oyster shell lime in historical buildings

Abstract

This invention relates to a construction method for oyster shell lime in historical buildings. The method includes: 1. Performance prediction: using a calculation model to obtain the surface hardness, volume shrinkage rate, and tensile bond strength of oyster shell lime samples after 28 days of curing; 2. Quantitatively determining the modification strategy: calculating the difference between the predicted performance values ​​of the oyster shell lime samples at 28 days and the target values; calculating the difference between the predicted performance values ​​and the target values ​​of each property at 28 days, ΔP=P 28 -P0, △w=w 28 -w0, △R=R 28 -R0; and determine whether modification is necessary in four situations; III. Adjustment of construction methods: First step, implement the determined oyster shell lime modification plan; Second step, calculate the amount of water Q for the base layer based on the construction environment parameters and the predicted volume shrinkage rate of oyster shell lime; Third step, plastering construction of oyster shell lime wall surface.

Description

Technical Field

[0001] This invention belongs to the field of historical building restoration technology, and specifically relates to a construction method for oyster shell lime in historical buildings. Background Technology

[0002] Oyster shell lime, a natural cementing material widely used in traditional architecture in southern Zhejiang, exhibits performance significantly affected by the curing environment. Even with the same mix ratio, oyster shell lime mortar shows marked differences in key performance indicators such as drying shrinkage, surface hardness, and water absorption under varying construction conditions. Currently, oyster shell lime plastering primarily relies on traditional bricklayer experience, lacking scientific performance prediction, material modification, and construction methods, leading to inconsistent quality in repair projects.

[0003] In existing technologies, methods such as the Abrams formula and the Bolomy formula, based on the water-cement ratio, are used to predict the 28-day strength of ordinary cement-based materials. However, these methods are not applicable to oyster shell lime materials, whose main hardening mechanism is carbonization. The hardening process of oyster shell lime is related to multiple factors such as CO2 diffusion and moisture evaporation, and its performance development law is fundamentally different from that of cement-based materials, making it impossible to directly apply existing prediction models.

[0004] Therefore, how to provide a construction method for oyster shell lime in historical buildings is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a construction method for oyster shell lime plastering in historical buildings. By scientifically predicting key performance parameters such as surface hardness, volume shrinkage rate, and tensile bond strength of oyster shell lime at 28 days of age, and by dynamically adjusting the modification strategy of oyster shell lime and the amount of water poured into the base layer in combination with environmental temperature and humidity, the construction quality of the oyster shell lime plastering layer in historical buildings is ensured to meet protection requirements, effectively preventing common problems such as cracking and peeling, thereby improving the appearance and durability of historical building restoration projects.

[0006] To solve the above technical problems, the present invention includes the following technical solutions:

[0007] A method for applying oyster shell lime mortar to historical buildings includes the following steps:

[0008] Step S1, Performance Prediction: The calculation model obtains the surface hardness, volume shrinkage rate, and tensile bond strength of the oyster shell grey sample after 28 days of curing.

[0009] The first step is to estimate the average on-site temperature T and average relative humidity H;

[0010] Step 2: Preparation of oyster shell lime test blocks: Prepare oyster shell lime paste in the laboratory, place the oyster shell lime paste in a mold and vibrate to form oyster shell lime test blocks, place the oyster shell lime test blocks in a constant temperature and humidity chamber with an average temperature of T and an average relative humidity of H for curing, demold after curing for 72 hours, and continue to place them in the curing chamber for curing for 7 days.

[0011] The third step is to test the surface hardness, volume shrinkage rate and tensile bond strength of the oyster shell specimens after 7 days of curing. The surface hardness P7, volume shrinkage rate w7 and tensile bond strength R7 were measured respectively.

[0012] Step 4: Input the general calculation model to predict the performance of the oyster shell lime specimens at 28 days, including: surface hardness P. 28 Volume shrinkage rate w 28 and tensile bond strength R 28 ;

[0013] Step S2: Quantitatively determine the modification strategy: Based on the predicted performance values ​​of the oyster shell lime test blocks at 28 days, calculate the difference between the predicted and target values; calculate the difference between the predicted and target values ​​of each performance at 28 days, ΔP = P 28 - P0, △w=w 28 - w0, △R = R 28 - R0; and there are four cases:

[0014] Case 1: If △w≤0, △P≥0, and △R≥0, no modification is needed;

[0015] Case 2: If Δw≤0, ΔP, or ΔR is less than 0, metakaolin is used for modification alone;

[0016] Case 3: If △w>0, △P≥0, and △R≥0, use glutinous rice paste for modification alone;

[0017] Case 4: If Δw > 0, and either ΔP or ΔR is less than 0, use a combination of metakaolin and glutinous rice paste for modification;

[0018] Step S3, Adjustment of construction methods:

[0019] Step 1: Implement the determined oyster shell ash modification scheme;

[0020] The second step is to calculate the amount of water Q to be poured into the base layer based on the construction environment parameters and the predicted volume shrinkage rate of the oyster shell lime.

[0021] Step 3: Plastering the oyster shell gray wall surface.

[0022] Further, the preparation method of oyster shell lime pulp in step S1 includes: placing oyster shell lime raw material into a mixing tank, cutting dried hemp fibers into 5mm~10mm segments, weighing an appropriate amount of hemp fibers and water into the mixing tank according to the mass ratio of hemp fibers: oyster shell lime = 1:25 and water: oyster shell lime = 0.8:1; starting an electric mixer and stirring for 60 seconds, scraping the pulp on the tank wall and the mixing head back into the mixing tank. The above operation steps constitute one cycle, and the required oyster shell lime pulp is obtained after 5 cycles.

[0023] Furthermore, the general calculation model formula in step S1 is:

[0024] N 28 =N7×k×[1+1.2×10 -3 ·(T−20)]×[1−2.6×10 -5 ×(H−60) 2 ]

[0025] Where: N 28 N7 represents the surface hardness (Shore D), volume shrinkage rate (%), or tensile bond strength of the oyster shell lime specimen after 28 days of curing, in kPa; N7 represents the surface hardness (Shore D), volume shrinkage rate (%), or tensile bond strength of the oyster shell lime specimen after 7 days of curing, in kPa; k is the calculation coefficient for each property, where the calculation coefficient k is 1.954 for surface hardness, 1.324 for volume shrinkage rate, and 1.855 for tensile bond strength; T is the average temperature during the curing process of the oyster shell lime, ranging from 0 to 40℃; H is the average relative humidity during the curing process of the oyster shell lime, ranging from 30% to 95%.

[0026] Furthermore, the modification of metakaolin alone in step S2 includes: metakaolin dosage y m The unit is %, and the calculation formula is:

[0027] y m =min[15,-2.5·min(△P,△R)].

[0028] Furthermore, the separate modification of the glutinous rice paste in step S2 includes: adding glutinous rice flour at a dosage of G. m The unit is %, and the calculation formula is:

[0029] G m =min(6, 1.5·△w).

[0030] Furthermore, the compound modification of metakaolin and glutinous rice flour in step S2 includes: the amounts of metakaolin and glutinous rice flour being y respectively. m G m The units are all percentages, and the calculation formulas are as follows:

[0031] y m =min[12,-0.8·min (0,△P)△P-1.2·min (0,△R)],

[0032] G m =min(4, 1.25·△w).

[0033] Furthermore, the formula for calculating the amount of water Q applied to the base layer in step S3 is as follows:

[0034] Q=Q min +k·w 28 ·T·(100−H),

[0035] In the formula, Q represents the water volume for the oyster shell lime base layer, in L / m². 2 Q min The minimum water requirement for foundation watering is typically 5, measured in L / m². 2 K is the adjustment factor, usually taken as 3.8 × 10⁻⁶. -4 The unit is L / (m) 2 (·℃·%)

[0036] w 28 The predicted volume shrinkage rate of oyster shell lime after 28 days is %; T is the average temperature during the curing process of oyster shell lime, in °C; H is the average relative humidity during the curing process of oyster shell lime, in °C.

[0037] Furthermore, the raw material for oyster shell ash is a fully matured ash material that has been wet-ground to a fine consistency, and its main component is calcium hydroxide.

[0038] Compared with the prior art, the beneficial effects of the present invention include:

[0039] 1. The present invention provides a construction method for oyster shell lime in historical buildings, which achieves scientific and precise control: a general mathematical model applicable to the multiple properties of oyster shell lime is established, and the long-term performance of oyster shell lime is accurately predicted using early data, transforming the traditional process from relying on experience to a quantifiable and predictable scientific process.

[0040] 2. The present invention provides a construction method for oyster shell lime in historical buildings, which ensures stable material performance: Based on the prediction results of key performance parameters of oyster shell lime, a modification strategy is dynamically formulated to ensure that the performance of each batch of oyster shell lime material can meet the requirements of the restoration project for strength, shrinkage and bonding.

[0041] 3. The present invention provides a construction method for oyster shell lime plaster in historical buildings, which improves construction quality: Based on the performance prediction of oyster shell lime and the adjustment of the amount of water poured into the base layer, the carbonization rate of the oyster shell lime slurry is ensured, the adhesion between the oyster shell lime layer and the base layer is guaranteed, and problems such as cracking and hollowing of the plaster layer are effectively prevented, thereby improving the construction quality of oyster shell lime wall in historical buildings. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the construction method of oyster shell lime in a historical building in Example 1. Detailed Implementation

[0043] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for constructing oyster shell lime mortar in historical buildings according to the present invention. The advantages and features of the present invention will become clearer from the following description.

[0044] Example 1

[0045] The following details the construction method of oyster shell lime in historical buildings according to the present invention.

[0046] Please refer to Figure 1 A construction method for oyster shell lime mortar in historical buildings includes the following steps:

[0047] Step S1, Performance Prediction: The calculation model obtains the surface hardness, volume shrinkage rate, and tensile bond strength of the oyster shell grey sample after 28 days of curing.

[0048] The first step is to estimate the average temperature T and average relative humidity H of the oyster plaster on the walls of the historical building during the construction period, i.e., the construction site.

[0049] The second step involves preparing oyster shell ash blocks in the laboratory and curing them for 7 days, specifically including:

[0050] Preparation of oyster shell lime pulp: Place the oyster shell lime raw material into a mixing tank. Cut the dried hemp fiber into 5mm~10mm fiber segments. Weigh an appropriate amount of hemp fiber and water into the mixing tank according to the mass ratio of hemp fiber: oyster shell lime = 1:25 and water: oyster shell lime = 0.8:1. Start the electric mixer and stir for 60 seconds. Scrape the pulp on the tank wall and the mixing head back into the mixing tank. The above operation steps constitute one cycle. After 5 cycles, the required oyster shell lime pulp is obtained.

[0051] Place the oyster shell slurry in a mold, vibrate to compact it, and then place it in a constant temperature and humidity chamber at temperature T and relative humidity H for curing. After curing for 72 hours, demold it and continue to place it in the curing chamber for curing until 7 days old.

[0052] The third step is to test the 7-day performance of the oyster shell ash specimens, namely surface hardness P7, volume shrinkage rate w7 and tensile bond strength R7.

[0053] The fourth step involves using the temperature and humidity of the curing environment and the various performance parameters measured after 7 days of curing with oyster shell lime cement mortar. Following the general calculation model below, by substituting the corresponding calculation coefficient k for each performance parameter, the surface hardness P of the oyster shell lime cement mortar at 28 days can be obtained. 28 Volume shrinkage rate w 28 and tensile bond strength R 28 ;

[0054] Specifically, the general calculation model formula is:

[0055] N 28 =N7×k×[1+1.2×10 -3 ·(T−20)]×[1−2.6×10 -5 ×(H−60) 2 ]

[0056] Where: N28 N7 represents the surface hardness (Shore D), volume shrinkage rate (%), or tensile bond strength of the oyster shell lime specimen after 28 days of curing, in kPa; N7 represents the surface hardness (Shore D), volume shrinkage rate (%), or tensile bond strength of the oyster shell lime specimen after 7 days of curing, in kPa; k is the calculation coefficient for each property, where the calculation coefficient k is 1.954 for surface hardness, 1.324 for volume shrinkage rate, and 1.855 for tensile bond strength; T is the average temperature during the curing process of the oyster shell lime, ranging from 0 to 40℃; H is the average relative humidity during the curing process of the oyster shell lime, ranging from 30% to 95%.

[0057] Step S2: Quantitatively determine the modification strategy: based on the predicted value P 28 w 28 R 28 Compared with the target value, dynamic decision-making on modification strategies and construction methods specifically includes:

[0058] Based on the predicted performance values ​​of oyster shell ash at 28 days of age, the difference between the predicted values ​​and the target values ​​is calculated.

[0059] When oyster shell lime is used for plastering the walls of historical buildings, the target performance parameters P0, w0, and R0 at 28 days are shown in Table 1 (which can be adjusted appropriately according to the grade and design requirements of the historical building):

[0060] Table 1 Target performance parameters of oyster shell ash at 28 days of age

[0061]

[0062] Calculate the difference between the predicted and target values ​​of each performance item over 28 days, ΔP = P 28 - P0, △w = w 28 - w0, △R=R 28 - R0; and determine:

[0063] If △w≤0, △P≥0, and △R≥0, the oyster shell lime does not require modification treatment and can be applied directly.

[0064] If Δw≤0, ΔP, or ΔR is less than 0, metakaolin is used to modify the oyster shell lime, and the metakaolin content is y. m The unit is %, and the calculation formula is:

[0065] y m =min[15,-2.5·min (△P,△R)],

[0066] If Δw>0, ΔP≥0, and ΔR≥0, glutinous rice paste is used to modify oyster shell ash, with a glutinous rice flour content of G. m The unit is %, and the calculation formula is:

[0067] G m =min(6,1.5·△ w ),

[0068] If Δw > 0, and either ΔP or ΔR is less than 0, then oyster shell ash is modified by compounding metakaolin and glutinous rice flour. The amounts of metakaolin and glutinous rice flour are respectively y m G m The units are all percentages, and the calculation formulas are as follows:

[0069] y m =min[12,-0.8·min (0,△P)△P-1.2·min (0,△R)],

[0070] G m =min(4, 1.25·△w),

[0071] Step S3, Adjustment of construction methods:

[0072] Step 1: Implement the determined oyster shell ash modification scheme;

[0073] The second step is to calculate the amount of water Q to be poured into the base layer based on the construction environment parameters and the predicted volume shrinkage rate of the oyster shell lime.

[0074] Step 3: Plastering the oyster shell gray wall surface.

[0075] Specifically: In addition to modifying the properties of oyster shell lime itself, during plastering, it is also necessary to adjust the amount of water poured into the bricks and mortar of the base layer beneath the oyster shell lime plaster layer based on the construction environment parameters and the predicted volume shrinkage rate of the oyster shell lime. This prevents premature loss of moisture from the mortar, ensures the normal carbonization reaction of the oyster shell lime, and guarantees effective adhesion between the oyster shell lime layer and the base layer. The amount of water poured into the base layer, Q, is expressed in L / m², and the calculation formula is as follows:

[0076] Q=Q min +k· w 28 ·T·(100−H),

[0077] In the formula, Q represents the water volume for the oyster shell lime base layer, in L / m². 2 Q min The minimum water requirement for foundation watering is typically 5, measured in L / m². 2 K is the adjustment factor, usually taken as 3.8 × 10⁻⁶. -4 The unit is L / (m) 2 (·℃·%)

[0078] w 28The predicted volume shrinkage rate of oyster shell lime after 28 days is %; T is the average temperature during the curing process of oyster shell lime, in °C; H is the average relative humidity during the curing process of oyster shell lime, in °C.

[0079] Specifically, the surface hardness test was performed using a Type D Shore hardness tester, and the method was in accordance with GB / T 531.1-2008;

[0080] The test methods for tensile bond strength and volume shrinkage rate are in accordance with JGJ / T 70-2009.

[0081] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method of installing oyster lime in a historic building, characterized by, Comprising the following steps: Step S1, performance prediction: the calculation model obtains the surface hardness, volume shrinkage and tensile bond strength of the oyster shell sample at the age of 28 days of curing: First step, estimate the average temperature T and average relative humidity H on site; Second step, prepare oyster shell test block: prepare oyster shell paste in the laboratory, and then vibrate and form the oyster shell test block in the mold. The oyster shell test block is placed in a constant temperature and humidity box with an average temperature of T and an average relative humidity of H for curing. After 72 hours of curing, it is demolded and continues to be cured in the curing box until 7 days; Third step, after the oyster shell test block is cured for 7 days, the surface hardness, volume shrinkage and tensile bond strength are tested, and the surface hardness P7, volume shrinkage w7 and tensile bond strength R7 are measured respectively; Fourth step, bring into general calculation model to predict the performance of oyster shell ash test block at 28d age, including: surface hardness P 28 , volume shrinkage rate w 28 And tensile bonding strength R 28 ; the general calculation model formula is: N 28 = N7 x k x [1 + 1.2 x 10 -3 - (T - 20)] x [1 - 2.6 x 10 -5 - (H - 60) 2 ] In the formula: N 28 Shore D, volume shrinkage rate % or tensile bonding strength of the oyster shell test block in the 28-day curing period, unit: kPa; N7 is the Shore D, volume shrinkage rate % or tensile bonding strength of the oyster shell test block in the 7-day curing period, unit: kPa; k is the calculation coefficient of each performance, wherein the calculation coefficient k takes the value of 1.954 when calculating the surface hardness, the calculation coefficient k takes the value of 1.324 when calculating the volume shrinkage rate, and the calculation coefficient k takes the value of 1.855 when calculating the tensile bonding strength; T is the average temperature during the oyster shell curing process, ranging from 0 to 40℃, and H is the average relative humidity during the oyster shell curing process, ranging from 30 to 95%. Step S2, quantitatively determining the modification strategy: according to the performance prediction value of the oyster shell test block at the age of 28 days, the difference with the target value is calculated; the difference between the performance prediction value and the target value of each performance at the age of 28 days is calculated, respectively, and the difference is calculated. P 28 - P0, △w = w 28 - w0, △R = R 28 - R0; and four cases: Case 1: if △w≤0, △P≥0, △R≥0, no modification is needed; Case 2: if △w≤0, any one of △P and △R is less than 0, use metakaolin for modification alone; Case 3: if △w>0, △P≥0, △R≥0, use glutinous rice paste for modification alone; Case 4: if △w>0, and any one of △P and △R is less than 0, use metakaolin and glutinous rice paste for compound modification; Step S3, construction method adjustment: First step, execute the determined oyster shell modification scheme; Second step, calculate the base layer watering amount Q according to the construction environment parameters and the predicted oyster shell volume shrinkage; Third step, oyster shell wall plastering construction.

2. The construction method according to claim 1, characterized in that, The preparation method of the oyster shell paste in step S1 comprises: placing oyster shell raw materials into a stirring barrel, cutting dried hemp knife into fiber segments of 5mm-10mm, and adding an appropriate amount of hemp knife and water into the stirring barrel according to the mass ratio of hemp knife:oyster shell=1:25 and water:oyster shell=0.8:1; starting the electric stirrer to stir for 60 seconds, scraping the slurry on the barrel wall and stirring head back into the stirring barrel, and repeating the above steps for 5 cycles to obtain the required oyster shell paste.

3. The construction method according to claim 1, characterized in that, The step S2 of modifying the metakaolin alone comprises: metakaolin content y m , unit is %, and the calculation formula is: y m = min [15, -2.5 min (AP, AR)].

4. The construction method according to claim 1, characterized in that, The modification of the glutinous rice slurry in step S2 includes: the mixing amount of the glutinous rice powder is G m , in percentage, and the calculation formula is: G m = min(6, 1.5 · Δw).

5. The construction method according to claim 1, wherein The compounding and modifying of metakaolin and glutinous rice paste in the step S2 includes that the dosages of metakaolin and glutinous rice powder are y m , G m , unit is %, and the calculation formulas are respectively: y m = min [12, -0.8 min (0, ΔΡ) ΔΡ - 1.2 min (0, ΔR)], G m = min(4, 1.25 · Δw).

6. The construction method according to claim 1, wherein The calculation formula of the base layer watering amount Q in step S3 is: Q = Q min + K - w 28 - T - (100 - H), In the formula, Q is the base layer of oyster shell water, unit is L / m 2 ; Q min is the minimum base water, usually take 5, unit is L / m 2 ; K is the adjustment coefficient, usually take 3.8×10 -4 , unit is L / (m 2 ·℃·%) w 28 To predict the volume shrinkage of oyster shell in 28 days, the formula is: V = 0.000 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 7. The construction method according to claim 2, wherein The oyster shell raw material is a completely matured, finely ground ash material, and the main component is calcium hydroxide.

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