Straw mortar composite building block pretreatment method

Abstract

According to the pretreatment method for the straw mortar composite building block, the thermal performance of the straw mortar composite building block is improved by optimizing pretreatment conditions and changing the type of the building block. The method comprises the following specific steps: crushing rice or wheat straws into small sections with the length of 3-5cm by using a mechanical crusher; soaking with a 1-5% sodium hydroxide solution for 5-25 minutes; washing the straws with clear water for multiple times until the pH value is close to neutral, and then drying the straws in a drying oven at 60 DEG C until the weight is constant; mixing the pretreated straws into the cement mortar according to the proportion of 10-18%, and fully and uniformly stirring; pouring the mixed mortar into an I-type, II-type or III-type triple test mold, and curing for 28 days after molding, so as to obtain the modified straw mortar composite building block. Experimental results show that the pretreated straw mortar composite building block is remarkably superior to the prior art in the aspects of heat conductivity coefficient, thermal diffusion coefficient, thermal resistance and the like.

Description

Technical Field

[0001] The invention relates to the technical field of soil heavy metal early warning, and in particular to a straw mortar composite building block pretreatment method. Background Art

[0002] With the development of social economy and the enhancement of environmental awareness, the search for green building materials that can replace traditional building materials has become a research hotspot. China produces more than 700 million tons of crop straw every year (Xie Guanghui et al., 2010). These biomass resources are suitable for use as building materials due to their light weight, porosity, and good thermal insulation. However, the bonding force between untreated straw and cement mortar is weak, mainly because the wax layer and sugar substances on the surface of the straw hinder the bonding between the two and reduce the performance of the composite material.

[0003] However, existing research on the optimization of pretreatment conditions is not systematic and comprehensive enough. The pretreatment effects under different conditions vary greatly, and further research is needed to determine the optimal parameters. In addition, existing research is mostly limited to laboratory scale and lacks verification of large-scale production and practical application.

[0004] In summary, developing an efficient and stable straw pretreatment method to improve the comprehensive performance of straw mortar composite blocks has important scientific significance and application value. Summary of the invention

[0005] The present invention proposes a method for preparing high-quality straw mortar composite building blocks by optimizing pretreatment conditions. The specific technical scheme is as follows: A straw mortar composite building block pretreatment method, characterized in that it comprises the following steps: The rice or wheat straw is crushed into small pieces with a length of 3 to 5 cm using a mechanical crusher; Soak the crushed straw in 1-5% sodium hydroxide solution for 5-25 minutes; The straw was rinsed with clean water several times until the pH value was close to neutral, and then dried in an oven at 60°C to constant weight to obtain powdered straw; Add the pre-treated straw into cement mortar at a ratio of 10-18% and mix thoroughly; Pour the mixed mortar into the triple test mold, first fill it to half the height of the mold, tamp it evenly, then fill the mold to the top, and continue tamping until the mortar surface is flat; The molded specimens were left to stand for 2 days before being demolded, numbered, and placed in a standard curing box for 28 days to obtain modified straw mortar composite blocks.

[0006] Furthermore, the concentration of the sodium hydroxide solution is preferably 5%.

[0007] Furthermore, the straw is preferably soaked in the sodium hydroxide solution for 24 minutes.

[0008] Furthermore, the ratio of the straw added to the cement mortar is preferably 18%.

[0009] Furthermore, the water-cement ratio of the cement mortar is 0.85, the water consumption is 409 kg / m³, and the mixing time is 101 seconds.

[0010] Furthermore, the curing conditions of the composite building blocks are 80% relative humidity and 20°C temperature.

[0011] Furthermore, the structures of the composite building blocks include type I, type II and type III.

[0012] Compared with the prior art, the present invention has the following advantages and features: Improving the thermal performance of straw mortar by changing the block type: The present invention designs three different types of blocks (type I, type II, and type III), and the structural design of each type of block is optimized to improve the thermal performance of straw mortar composite blocks. The experimental results show that different types of blocks show significant differences in thermal conductivity, thermal diffusivity, and thermal resistance. In particular, type III blocks have the lowest thermal conductivity (0.257 W / (m·K)), the smallest thermal diffusivity (0.263 mm² / s), and the highest thermal resistance (33.835 K / W), showing excellent thermal insulation performance. This shows that the thermal performance of straw mortar composite blocks can be significantly improved through reasonable block structure design.

[0013] Improving the thermal performance of straw mortar by pretreatment: The present invention effectively removes the wax layer and some sugar substances on the surface of the straw through pretreatment with sodium hydroxide (NaOH) solution, increases the specific surface area and porosity of the straw, makes the surface of the straw rougher, and thus significantly enhances the bonding force between the straw and the cement mortar. The interfacial compatibility between the pretreated straw and the cement mortar is significantly improved, making the overall structure of the composite block more stable and strong. In addition, sodium hydroxide treatment can also improve the water absorption and water retention of the straw, which helps to improve the strength and stability of the composite material. The experimental results show that the pretreated straw mortar composite block is superior to the untreated sample in terms of thermal conductivity, thermal diffusion coefficient and thermal resistance, indicating that the pretreatment method has a significant effect on improving the thermal performance of the straw mortar composite block. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of type I building blocks in the present invention; Figure 2 It is a structural schematic diagram of type II building blocks in the present invention; Figure 3It is a schematic diagram of the structure of the type III building block in the present invention.

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. The other drawings obtained are all within the protection scope required by the present invention. DETAILED DESCRIPTION

[0016] The following combination Figure 1-3 , the contents of the present invention are described in detail through specific embodiments. Example

[0017] 1. Raw material preparation Rice straw: Select fresh and dry rice straw and use a straw crusher to crush it into small pieces with a length of 3 to 5 cm.

[0018] Cement mortar: Ordinary Portland cement and fine sand are selected and mixed at a water-cement ratio of 0.85. The water consumption is 409 kg / m³ and the mixing time is 101 seconds.

[0019] 2. Preprocessing Preparation of sodium hydroxide solution: Prepare 5% NaOH solution.

[0020] Soaking treatment: The crushed rice straw was soaked in the NaOH solution of the above concentration for 24 minutes.

[0021] Cleaning and drying: After soaking, rinse the straw with clean water several times until the pH value is close to neutral, and then dry it in an oven at 60°C to constant weight to obtain powdered straw.

[0022] 3. Preparation of composite building blocks Mixed mortar: Add the pre-treated straw into cement mortar at a ratio of 18% and mix thoroughly.

[0023] Molding: Pour the mixed mortar into the triple test molds of Type I, Type II and Type III respectively, first fill it to half the height of the mold, tamp it evenly, then fill the mold again, and continue tamping until the surface of the mortar is flat.

[0024] Curing: The molded Type I, Type II, and Type III specimens were left to stand for 2 days before demolding and placed in a standard curing box for 28 days at a relative humidity of 80% and a temperature of 20°C.

[0025] 4. Performance Testing Thermal conductivity and thermal diffusivity test: The thermal conductivity and thermal diffusivity of the composite blocks were measured using a HS-DR-5 transient plane heat source method thermal conductivity instrument.

[0026] Thermal resistance calculation: According to the formula R=λAL, R is the thermal resistance of the material (unit: K / W), L is the thickness of the material (unit: m), A is the cross-sectional area perpendicular to the heat flow direction (unit: m²), and λ is the thermal conductivity of the material (unit: W / (m·K)). Where L=0.09m, A=0.01035m 2 5. Results and Analysis It can be seen from the table that the type I, type II and type III straw mortar composite blocks prepared by the method of the present invention are superior to the prior art in terms of thermal conductivity, thermal diffusion coefficient and thermal resistance. In particular, the type III block has the lowest thermal conductivity (0.257 W / (m·K)) and the highest thermal resistance (33.835 K / W), showing excellent thermal insulation performance.

Claims

1. A straw mortar composite block pretreatment method, characterized in that: The following steps are involved: The rice or wheat straw is crushed into small pieces with a length of 3 to 5 cm using a mechanical crusher; Soak the crushed straw in 1-5% sodium hydroxide solution for 5-25 minutes; The straw was rinsed with clean water several times until the pH value was close to neutral, and then dried in an oven at 60°C to constant weight to obtain powdered straw; Add the pre-treated straw into cement mortar at a ratio of 10-18% and mix thoroughly; Pour the mixed mortar into the triple test mold, first fill it to half the height of the mold, tamp it evenly, then fill the mold to the top, and continue tamping until the mortar surface is flat; The molded specimens were left to stand for 2 days before being demolded, numbered, and placed in a standard curing box for 28 days to obtain modified straw mortar composite blocks.

2. The pretreatment method according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is preferably 5%.

3. The pretreatment method according to claim 1, characterized in that: The straw is preferably soaked in the sodium hydroxide solution for 24 minutes.

4. The pretreatment method according to claim 1, characterized in that: The ratio of straw added to cement mortar is preferably 18%.

5. The pretreatment method according to claim 1, characterized in that: The water-cement ratio of the cement mortar is 0.85, the water consumption is 409 kg / m³, and the mixing time is 101 seconds.

6. The pretreatment method according to claim 1, characterized in that: The curing conditions of the composite building blocks are 80% relative humidity and 20°C temperature.

7. The pretreatment method according to claim 1, characterized in that: The structures of the composite building blocks include type I, type II and type III.

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