A high-temperature resistant and fire-resistant concrete reinforced with waste glass sand and its preparation method

Abstract

This invention discloses a high-temperature fire-resistant concrete reinforced with waste glass sand and its preparation method, belonging to the field of building materials technology. The high-temperature fire-resistant concrete of this invention is composed of the following raw materials by weight: 35-45 parts waste glass sand, 40-50 parts porous steel slag aggregate, 0.04-0.15 parts silanized nano-aerogel, 3.3-6 parts phosphate-based fire retardant, 0.5-1.0 parts basalt fiber, 15-20 parts silicate cement, 5-10 parts metakaolin, 5-8 parts river sand, and 6-8 parts water. This invention optimizes the gradation of graded pre-sintered waste glass sand and porous steel slag aggregate, adds silanized nano-aerogel, phosphate-based fire retardant, and basalt fiber, and combines gradient mixing and curing processes to ensure the concrete maintains good structural stability at high temperatures, significantly improving its high-temperature resistance and fire resistance.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-temperature resistant and fire-resistant concrete reinforced with waste glass sand and its preparation method. Background Technology

[0002] As waste, waste glass is a type of waste that cannot be incinerated, cannot be naturally degraded in landfills, and cannot be decomposed and treated by general physicochemical methods. The annual discharge of waste glass is enormous, the recycling rate is low, and its accumulation pollutes the environment. Industrial solid wastes such as steel slag also face similar problems. Waste glass and steel slag contain components such as silicon dioxide, and have the potential for resource reuse, urgently requiring effective treatment.

[0003] Meanwhile, concrete, as the most widely used building structural material globally, boasts core advantages such as high strength, low cost, and ease of molding, making it suitable for various engineering scenarios including building structures, industrial facilities, and transportation tunnels. However, conventional concrete has significant shortcomings in high-temperature resistance: in high-temperature environments such as building fires, industrial kiln radiation, and high-temperature conditions in underground engineering, cement hydration products are prone to dehydration and decomposition, and the rapid evaporation of internal pore water generates instantaneous pressure, causing concrete to burst and spall. Simultaneously, the mismatch in thermal expansion coefficients between aggregates and cementitious materials leads to the formation of network cracks, resulting in a sharp decrease in strength and a rapid loss of structural load-bearing capacity. With the increasing demands for higher fire resistance standards in buildings, industrial kiln linings, and high-temperature work areas, stringent requirements are placed on the high-temperature stability, residual mechanical properties, and long-term service reliability of concrete. Existing high-temperature resistant concrete often relies on special aggregates such as expanded clay and refractory bricks, which are not only costly and resource-intensive, but also rely solely on the addition of a single fire-resistant component for optimization. This results in limitations such as poor synergy between thermal insulation and mechanical properties, and low utilization of industrial solid waste, making it difficult to balance environmental friendliness and high-temperature service safety.

[0004] Currently, some studies are using waste glass as a raw material in concrete preparation, but the related technologies still have certain limitations. For example, as shown in Chinese patent CN114656221 A, the properties of silica aerogel change from hydrophobic to hydrophilic above 600℃. Although melting glass powder can form a protective film, incomplete protection at high temperatures may still lead to changes in the aerogel structure, affecting the strength stability of concrete. As shown in Chinese patent CN118388184 A, waste glass fine aggregate needs to be treated with polystyrene. While melting polystyrene at high temperatures can repair cracks, it may release a small amount of harmful gases, and the processing technology is relatively complex, increasing production steps and costs. As shown in Chinese patent CN103570302A, a type of concrete mixed with waste glass is disclosed. The mechanical properties of the concrete are tested by varying glass dosages. Using this method, the strength of the specimen with a glass dosage of 20% is the highest, 1.13 times that of ordinary concrete, significantly improving the concrete's durability. However, the strength, high-temperature fire resistance, and the amount of waste glass incorporated in the concrete produced by this method still need improvement.

[0005] Therefore, developing a waste glass sand concrete with both excellent high-temperature resistance and fire resistance as well as environmental advantages, and its preparation process, has become a technical challenge that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems in existing technologies by providing a high-temperature resistant and fire-resistant concrete reinforced with waste glass sand and its preparation method. This invention optimizes the gradation of graded pre-sintered waste glass sand and porous steel slag aggregate, incorporates silanized nano-aerogel, phosphate-based fire retardant, and basalt fiber, and combines this with a mixing and gradient curing process. The silanized nano-aerogel and phosphate-based fire retardant form a dual fire-resistant barrier of "microporous thermal insulation expansion sealing," while the basalt fiber and curing process inhibit cracking, enabling the concrete to maintain good structural stability at high temperatures and significantly improving its high-temperature resistance and fire resistance. The concrete prepared by this invention exhibits excellent high-temperature resistance, strong fire resistance, stable mechanical properties, and enables efficient utilization of industrial solid waste, making it environmentally friendly.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A high-temperature fire-resistant concrete reinforced with waste glass sand is composed of the following raw materials in parts by weight: 15-20 parts silicate cement, 5-10 parts metakaolin, 35-45 parts waste glass sand, 40-50 parts porous steel slag aggregate, 5-8 parts river sand, 0.04-0.15 parts silanized nano-aerogel, 3.3-6 parts phosphate-based fire retardant, 0.5-1.0 parts basalt fiber, and 6-8 parts water; wherein the waste glass sand is passivated by soaking in oxalic acid solution and pre-sintered at 800-900℃ before use.

[0009] Furthermore, the waste glass sand includes coarse sand and fine sand, the coarse sand having a particle size of 1-3 mm and the fine sand having a particle size of 0.1-1 mm, and the mass ratio of the coarse sand to the fine sand being 1.5:1-2.5:1; the gradation satisfies: the coarse sand accounts for 60%-70% and the fine sand accounts for 30%-40%; the waste glass sand undergoes passivation treatment by soaking in an oxalic acid aqueous solution with a mass concentration of 2-4% at 55-65℃ for 1-3 hours and pre-sintering treatment at 800-900℃, forming an amorphous silicate coating layer on the surface; the pre-sintering treatment is: heating to 800-900℃ at 5-10℃ / min and holding for 20-40 minutes, then cooling to room temperature in the furnace.

[0010] Furthermore, the porous steel slag aggregate has a particle size of 5-10 mm and a porosity of ≥30%; the preparation method of the porous steel slag aggregate includes the following steps: steel slag is crushed to 5-10 mm, acidified with an 8-15% phosphoric acid aqueous solution for 10-15 h, washed with water, and calcined at 500-700℃ for 1-3 h, with a porosity of 30%-35% and a pore size of 50-300 μm.

[0011] Furthermore, the fineness modulus of the river sand is 2.3-2.8; the silicate cement is ordinary silicate cement P·O42.5.

[0012] Furthermore, the silanized nanoaerogel has a particle size of 50-100 nm, a specific surface area of ​​≥800 m² / g, and a contact angle of ≥150°.

[0013] Furthermore, the phosphate-based fire retardant is composed of sodium pyrophosphate and ammonium polyphosphate, with the mass ratio of sodium pyrophosphate to ammonium polyphosphate being 1:1.5-1:2.5. It reacts at high temperature to generate a calcium pyrophosphate expansion layer with a coverage of over 90%.

[0014] Furthermore, the basalt fiber has a length of 6-12 mm and is used after being pretreated with a composite of silane coupling agent and alkaline inhibitor; its tensile strength is ≥2000 MPa, and after pretreatment with KH550 silane coupling agent and alkaline inhibitor, the interfacial bonding strength between the fiber and the cementitious material is ≥3.5 MPa, and the strength retention rate is ≥90% after soaking in an alkaline environment with a pH of 12-13 for 28 days.

[0015] The method for preparing the waste glass sand-reinforced high-temperature fire-resistant concrete includes the following steps:

[0016] Step S1: Weigh out the following by weight: silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand, silanized nano aerogel, phosphate-based fire retardant, basalt fiber, and water.

[0017] Step S2: Mix silicate cement, metakaolin, pretreated waste glass sand, porous steel slag aggregate, river sand, and basalt fiber to obtain a mixed dry material. Pour the mixed dry material into a mixer and stir for 1-3 minutes to make the dry material evenly mixed.

[0018] Step S3: Mix the phosphate-based fire retardant with water at 35-45℃ until homogeneous, then add the mixture to the mixer in step S2 and stir for 2-5 minutes.

[0019] Step S4: Stir the mixture evenly, add the silanized nano aerogel to the mixer in step S3, so that the silanized nano aerogel is evenly dispersed and avoids agglomeration. Continue stirring for 1-3 minutes after adding the silanized nano aerogel.

[0020] Step S5: After mixing is complete, pour the mixture into the mold that has been brushed with release agent and compact it.

[0021] Step S6: Curing is carried out in a constant temperature and humidity chamber for 1 day, 7 days and 28 days under the conditions of temperature 20±2℃ and curing humidity ≥90%. After curing, high temperature and fire resistant concrete reinforced with waste glass sand is obtained.

[0022] Furthermore, in step S3, water is added twice. The first addition of 65-75% of the total water weight is used to disperse the phosphate-based fire retardant, and the remaining 25-35% is added before the addition of the silanized nano-aerogel to adjust the workability of the concrete.

[0023] Furthermore, the stirring in step S2 is slow stirring, with a stirring speed of 130-150 r / min; the stirring in steps S3 and S4 is fast stirring, with a stirring speed of 270-300 r / min.

[0024] This invention relates to a waste glass sand-reinforced high-temperature fire-resistant concrete, an environmentally friendly building material. Its core components include ordinary silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand, silanized nano-aerogel, phosphate-based fire retardant, basalt fiber, and water, precisely proportioned. The waste glass sand undergoes oxalic acid passivation and pre-sintering at 800-900℃, forming an amorphous silicate coating on its surface. The porous steel slag aggregate is crushed, acidified, and calcined to achieve a specific porosity. Through the synergistic effect of its components—such as the phosphate-based fire retardant generating an expansion layer at high temperatures and the basalt fiber reinforcing interfacial bonding—a high-temperature fire-resistant structure is formed.

[0025] This invention integrates waste glass sand and steel slag aggregate into a concrete system, innovatively developing a concrete with significant advantages over traditional concrete. The glass powder melts at high temperatures, filling cracks and encapsulating silica aerogel to form a protective film, enhancing high-temperature resistance. The treated waste glass fine aggregate reduces alkali-silica reaction and can repair cracks at high temperatures, improving residual mechanical properties, while simultaneously achieving efficient utilization of solid waste.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) This invention applies industrial solid waste such as waste glass sand and porous steel slag aggregate to concrete, which greatly improves the utilization rate of solid waste, reduces the use of natural aggregate, reduces the impact on the environment, and conforms to the concept of green environmental protection.

[0028] (2) The silanized nano aerogel and phosphate-based fire retardant form a dual fire barrier of "microporous thermal insulation expansion sealing". Combined with the reinforcing effect of basalt fiber, the concrete can still maintain good structural stability and mechanical properties at high temperature. Its high temperature resistance and fire resistance are significantly better than traditional concrete. The fire resistance effect is further optimized through the synergistic effect of multiple components.

[0029] (3) Waste glass sand is passivated with oxalic acid and pre-sintered to form an amorphous silicate coating layer on the surface, which effectively improves its interfacial bonding performance with cementitious materials and reduces the risk of alkali-aggregate reaction. The special preparation process of porous steel slag aggregate gives it both lightweight and high strength characteristics, which improves the overall performance of concrete.

[0030] (4) The curing process combined with a specific mixing process ensures that the components of the concrete are evenly dispersed, the internal structure is dense, the cracks are reduced, and the durability and long-term stability of the concrete are improved.

[0031] The waste glass sand reinforced high-temperature fire-resistant concrete provided by this invention has the advantages of excellent high-temperature fire resistance, stable mechanical properties, high solid waste utilization rate, and environmental friendliness. It has broad application prospects in the fields of building fireproof structures, tunnel lining, and industrial kiln lining. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0033] Example 1

[0034] The raw material ratio of high-temperature fire-resistant concrete reinforced with waste glass sand is as follows: 300g of ordinary silicate cement P·O4 2.5, 100g of metakaolin, 700g of waste glass sand, 800g of porous steel slag aggregate, 100g of river sand, 1.6g of silanized nano aerogel, 80g of phosphate-based fire retardant, 15g of basalt fiber, and 130g of water.

[0035] In this raw material, the waste glass sand undergoes pretreatment: after sorting and washing, it is jaw crushed, and coarse sand (1-3mm) and fine sand (0.1-1mm) are mixed at a mass ratio of 2:1, with the gradation meeting the requirements of 60% coarse sand and 40% fine sand. It is then passivated by soaking in a 3% oxalic acid aqueous solution at 60℃ for 2 hours, followed by a flow rate of 5℃ / min. The temperature is raised to 850℃ at a heating rate, held for 30 minutes, and then cooled to room temperature in the furnace, forming an amorphous silicate coating layer on the surface; the porous steel slag aggregate has a particle size of 5-10mm and a porosity of 30%, and the preparation method of the porous steel slag aggregate includes the following steps: steel slag is crushed to 5-10mm, acidified with a 10% phosphoric acid aqueous solution for 12h, washed with water, and then calcined at 600℃ for 2h; the fineness modulus of the river sand is 2.3; the silanized nano-aerogel has a particle size of 50-100nm and a specific surface area of ​​800m² / g; the phosphate-based fire retardant is composed of sodium pyrophosphate and ammonium polyphosphate in a mass ratio of 1:2, and in a mass ratio of 1:5 with the cementitious material; the basalt fiber has a length of 6-12mm, is soaked in KH550 silane coupling agent and ethanol solution for 30min, dried, then soaked in an alkaline inhibitor lithium hydroxide aqueous solution for 20min, and dried at 60℃ for 2h. Pretreatment, tensile strength 2000MPa, interfacial bond strength 3.5MPa, strength retention rate ≥90% after 28 days in an alkaline environment of pH 12-13.

[0036] Preparation method:

[0037] (1) Weigh each raw material according to the proportion, mix ordinary silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand and basalt fiber, pour into a mixer and stir slowly at 130r / min for 2min to make the dry material evenly mixed;

[0038] (2) Mix the phosphate-based fire retardant with water at 40°C (add 70% of the total water weight for the first time), add it to a mixer and stir rapidly at 270 r / min for 3 min;

[0039] (3) Add the remaining 30% water to adjust the workability. Divide the silanized nano aerogel into two equal parts and add it in two batches. After each addition, stir quickly at 270 r / min for 1 min to ensure uniform dispersion.

[0040] (4) After mixing, pour the mixture into a mold that has been brushed with release agent and compact it;

[0041] (5) The constant temperature and humidity chamber was used for curing. The temperature was 20±2℃ and the humidity was ≥90% for 1 day, 7 days and 28 days. After curing, the high temperature and fire resistant concrete reinforced by waste glass sand was obtained.

[0042] Example 2

[0043] The raw material ratio of high-temperature fire-resistant concrete reinforced with waste glass sand is as follows: 350g ordinary silicate cement, 150g metakaolin, 900g waste glass sand, 1000g porous steel slag aggregate, 100g river sand, 1.75g ​​silanized nano aerogel, 91g phosphate-based fire retardant, 15g basalt fiber, and 140g water.

[0044] In this raw material, the waste glass sand coarse sand (1-3mm) accounts for 65% and fine sand (0.1-1mm) accounts for 35%, and it is passivated with oxalic acid and pre-sintered at 850℃ as in Example 1; the treatment methods of the porous steel slag aggregate, phosphate-based fire retardant and basalt fiber are the same as in Example 1, wherein the porous steel slag aggregate has a particle size of 5-10mm, a porosity of 32% and a pore size of 50-300μm, the mass ratio of phosphate-based fire retardant to cementitious material is 1:5.5, the basalt fiber has a 28-day strength retention rate of 90% in a pH 12-13 environment, and the fineness modulus of the river sand is 2.5; the silanized nano aerogel has a specific surface area of ​​850m² / g and is added at 0.35% of the total amount of cementitious material.

[0045] Preparation method:

[0046] (1) Weigh each raw material according to the proportion, mix ordinary silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand and basalt fiber, pour into a mixer and stir slowly at 140r / min for 2min to make the dry material evenly mixed;

[0047] (2) Mix the phosphate-based fire retardant with water at 40°C (add 70% of the total water weight, i.e., 98g for the first time), then add it to a mixer and stir rapidly at 285r / min for 3min.

[0048] (3) The remaining steps are the same as in Example 1, with a curing humidity of 92%.

[0049] Example 3

[0050] The raw material ratio of high-temperature fire-resistant concrete reinforced with waste glass sand is as follows: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 110g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, and 160g water.

[0051] In this raw material, the waste glass sand coarse sand (1-3mm) accounts for 60% and fine sand (0.1-1mm) accounts for 30%, and it is passivated with oxalic acid and pre-sintered at 850℃ as in Example 1; the treatment methods of the porous steel slag aggregate, phosphate-based fire retardant and basalt fiber are the same as in Example 1, wherein the porous steel slag aggregate has a porosity of 35%, the phosphate-based fire retardant generates a calcium pyrophosphate expansion layer with a coverage of more than 90% at high temperature, the basalt fiber has an interfacial bonding strength of 4MPa and a length deviation of ≤ ±0.5mm; the river sand has a fineness modulus of 2.8; and the silanized nano-aerogel has a contact angle of 155°.

[0052] Preparation method:

[0053] (1) Weigh each raw material according to the proportion, mix ordinary silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand and basalt fiber, pour into a mixer and stir slowly at 150r / min for 2min to make the dry material evenly mixed;

[0054] (2) After mixing the phosphate-based fire retardant with water at 40°C (adding 70% of the total water weight for the first time), add it to a mixer and stir rapidly at 300r / min for 3min;

[0055] (3) The remaining steps are the same as in Example 1, with a curing humidity of 95%.

[0056] Comparative Example 1

[0057] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass powder (particle size 0.15-0.30mm), 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, and 160g water.

[0058] Compared with Example 3, the difference in Comparative Example 1 is that waste glass powder is used instead of waste glass sand, while the remaining components and their mass ratios are the same as in Example 3. The preparation method is the same as in Example 3.

[0059] Compared with Example 3, this comparative example uses ungraded glass powder instead of graded glass sand, resulting in a single concrete particle size distribution, a decrease in bulk density of 8%, and a 28-day compressive strength of 51.3 MPa. At high temperatures, the glass powder melts and becomes too fluid, failing to form a uniform protective film. The residual compressive strength at 900°C is only 12.3% of that in Example 3.

[0060] Comparative Example 2

[0061] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, 160g water.

[0062] Compared with Example 3, the difference in Comparative Example 2 is that the waste glass sand was only crushed and screened, without oxalic acid passivation and pre-sintering treatment, while the remaining components and their mass ratios were the same as in Example 3. The preparation method was the same as in Example 3.

[0063] Compared with Example 3, the glass sand in this comparative example has no silicate coating layer on the surface, and the alkali-active substances are exposed. The alkali-silica reaction expansion value reaches 0.065% after 28 days. It reacts violently with cement hydration products at high temperature, and network cracks appear on the surface at 800°C, with the maximum crack width reaching 0.5 mm.

[0064] Comparative Example 3

[0065] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, 160g water.

[0066] Compared with Example 3, the difference in Comparative Example 3 is that the waste glass sand was softened by heating at 250-500℃, while the remaining components and their mass ratios were the same as in Example 3. The preparation method was the same as in Example 3.

[0067] Compared with Example 3, this comparative example shows that the glass sand was only softened and not sintered, with no silicate coating on the surface and sharp edges remaining; the 28-day flexural strength decreased by 24.7%; stress concentration occurred at the edges at high temperatures, resulting in cracking at 800℃ and complete disintegration at 1000℃, verifying the necessity of pre-sintering at 850℃ for modifying the glass sand interface and improving its high-temperature stability.

[0068] Comparative Example 4

[0069] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g ordinary steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, 160g water.

[0070] Compared with Example 3, Comparative Example 4 differs in that: ordinary steel slag aggregate that has not undergone acid calcination is used instead of porous steel slag aggregate, while the remaining components and their mass ratios are the same as in Example 3. The preparation method is the same as in Example 3.

[0071] Compared with Example 3, the thermal conductivity of the concrete in this comparative example increased to 0.42 W / (m·K) due to insufficient porosity of the steel slag aggregate; heat conduction was accelerated at high temperatures, and the internal temperature at 900℃ was 120℃ higher than that in Example 3, resulting in a 28.6% decrease in the residual compressive strength.

[0072] Comparative Example 5

[0073] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, 160g water.

[0074] Compared with Example 3, Comparative Example 5 differs in that the basalt fiber was not treated with KH550 silane coupling agent and alkaline inhibitor, while the remaining components and their mass ratios were the same as in Example 3. The preparation method was consistent with Example 3.

[0075] Compared with Example 3, the interfacial bonding strength between the fiber and the cementitious material in this comparative example decreased to 2.1 MPa (a reduction of 47.5%), and the 28-day flexural strength decreased to 5.9 MPa. The fiber deteriorated more rapidly in an alkaline environment at high temperatures, and the fiber strength retention rate was only 45% at 1000°C.

[0076] Comparative Example 6

[0077] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g polycarboxylate superplasticizer, 20g basalt fiber, and 160g water.

[0078] Compared with Example 3, Comparative Example 6 differs in that a polycarboxylate superplasticizer is used instead of a phosphate-based fire retardant, while the remaining components and their mass ratios are the same as in Example 3. The preparation method is the same as in Example 3.

[0079] Compared with Example 3, this comparative example lacks phosphate fire retardant, so it cannot generate calcium pyrophosphate expansion layer at high temperature, and the surface carbonization depth reaches 12.3 mm at 1000℃; and the water-reducing agent loses its dispersing effect after high temperature decomposition, resulting in a 15% decrease in the internal density of the concrete.

[0080] Comparative Example 7

[0081] Raw material ratio: 400g ordinary silicate cement, 200g silica fume, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, and 160g water.

[0082] Compared with Example 3, Comparative Example 7 differs in that silica fume is used instead of metakaolin, while the remaining components and their mass ratios are the same as in Example 3. The preparation method is the same as in Example 3.

[0083] Compared with Example 3, the silanized nano-aerogel in this comparative example changed from hydrophobic to hydrophilic after 600℃, and the structural collapse led to a sharp drop in thermal insulation performance; the internal porosity of the concrete reached 14%, and the strength decreased significantly at 1000℃.

[0084] Comparative Example 8

[0085] Raw material ratio: 400g ordinary silicate cement, 600g fly ash, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, and 160g water.

[0086] Compared with Example 3, Comparative Example 8 differs in that fly ash is used instead of metakaolin, while the mass ratio of the remaining components is the same as in Example 3. The preparation method is the same as in Example 3.

[0087] Compared with Example 3, the comparative example showed a 23.7% decrease in 28-day compressive strength due to the lower activity of fly ash and volcanic ash compared to metakaolin. The stability of the cementing system decreased at high temperatures, and the compressive strength at all temperature ranges of 600℃, 800℃, and 1000℃ showed a decreasing trend. Moreover, the decrease gradually increased with the increase of temperature, which verifies the key role of metakaolin in improving the activity and high-temperature stability of the cementing system.

[0088] Comparative Example 9

[0089] Raw material ratio: 600g ordinary silicate cement, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, and 160g water.

[0090] Compared with Example 3, Comparative Example 9 differs in that: metakaolin is omitted, the amount of ordinary silicate cement is increased to 600g, and the mass ratio of the remaining components is the same as in Example 3. The preparation method is the same as in Example 3.

[0091] Compared with Example 3, this comparative example lacks metakaolin, resulting in reduced activity of the cementitious material system and a 28-day compressive strength of 48.5 MPa. The early hydration of the concrete is insufficient, and the number of internal cracks at high temperatures is twice that of Example 3.

[0092] Comparative Example 10

[0093] Raw material ratio: 400g ordinary silicate cement, 200g metakaolin, 1000g waste glass sand, 1200g porous steel slag aggregate, 120g river sand, 3g silanized nano aerogel, 100g phosphate-based fire retardant, 20g basalt fiber, 160g water.

[0094] Compared with Example 3, Comparative Example 10 differs in that: the raw material components and proportions are exactly the same as in Example 3. The preparation method is different from that of Example 3. The process used is: all raw materials are added to the mixer at one time, stirred at 300 r / min for 5 min, and cured at a constant temperature of 20℃.

[0095] Compared with Example 3, this comparative example did not use the method of adding water in stages and gradient stirring, which led to the agglomeration of aerogel and the failure of local heat insulation. Two 5mm diameter burst pits appeared at 1000℃. In addition, constant temperature curing made the internal structure of the concrete loose, and the 28-day compressive strength dropped to 51.5MPa.

[0096] The products prepared in Examples 1 to 3 and Comparative Examples 1 to 10 were subjected to room temperature mechanical property and high temperature performance tests, respectively. Their compressive strength at 1d, 7d, and 28d, flexural strength at 1d, 7d, and 28d, and compressive strength after high temperature treatment at 600℃, 800℃, and 1000℃ were measured.

[0097] The test results are as follows:

[0098] Table 1 Compressive strength test results

[0099]

[0100] Table 2 Flexural Strength Test Results

[0101]

[0102] Table 3 Compressive strength of concrete before and after high temperature (MPa)

[0103]

[0104] In summary, the waste glass sand-reinforced high-temperature fire-resistant concrete prepared by this invention, through optimizing the pretreatment process of waste glass sand, selecting porous steel slag aggregate, employing the synergistic effect of phosphate-based fire retardant and silanized nano-aerogel, and combining it with gradient stirring and curing processes, exhibits excellent performance in terms of room temperature mechanical properties, high-temperature fire resistance, and volume stability, significantly outperforming all comparative schemes.

[0105] Therefore, the present invention adopts the above-mentioned waste glass sand reinforced high temperature fire-resistant concrete and its preparation method. The prepared concrete has the characteristics of excellent high temperature resistance, strong fire resistance, stable mechanical properties, high solid waste utilization rate, and environmental friendliness. It has important application value in the fields of building fireproof structure and industrial kiln lining.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-temperature resistant and fire-resistant concrete reinforced with waste glass sand, characterized in that, It is composed of the following raw materials in parts by weight: 15-20 parts silicate cement, 5-10 parts metakaolin, 35-45 parts waste glass sand, 40-50 parts porous steel slag aggregate, 5-8 parts river sand, 0.04-0.15 parts silanized nano-aerogel, 3.3-6 parts phosphate-based fire retardant, 0.5-1.0 parts basalt fiber, and 6-8 parts water; wherein the waste glass sand is passivated by soaking in oxalic acid solution and pre-sintered at 800-900℃ before use; The waste glass sand includes coarse sand and fine sand, wherein the coarse sand has a particle size of 1-3 mm and the fine sand has a particle size of 0.1-1 mm, and the mass ratio of coarse sand to fine sand is 1.5:1-2.5:1; the gradation satisfies the following: the coarse sand accounts for 60%-70% and the fine sand accounts for 30%-40%; the waste glass sand undergoes passivation treatment by soaking in an oxalic acid aqueous solution with a mass concentration of 2-4% at 55-65℃ for 1-3 hours and pre-sintering treatment at 800-900℃; the pre-sintering treatment is as follows: heating to 800-900℃ at 5-10℃ / min and holding for 20-40 minutes, followed by cooling to room temperature in the furnace; The porous steel slag aggregate has a particle size of 5-10 mm and a porosity of ≥30%. The preparation method of the porous steel slag aggregate includes the following steps: steel slag is crushed to 5-10 mm, acidified with a phosphoric acid aqueous solution with a mass concentration of 8-15% for 10-15 h, washed with water, and calcined at 500-700℃ for 1-3 h, with a porosity of 30%-35% and a pore size of 50-300 μm. The phosphate-based fire retardant is composed of sodium pyrophosphate and ammonium polyphosphate, wherein the mass ratio of sodium pyrophosphate to ammonium polyphosphate is 1:1.5-1:2.

5. The basalt fibers are 6-12 mm in length and are pretreated with a combination of silane coupling agent and alkaline inhibitor before use.

2. The high-temperature resistant and fire-resistant concrete reinforced with waste glass sand according to claim 1, characterized in that: The fineness modulus of the river sand is 2.3-2.8; the silicate cement is ordinary silicate cement. 42.

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3. The high-temperature resistant and fire-resistant concrete reinforced with waste glass sand according to claim 1, characterized in that: The silanized nanoaerogel has a particle size of 50-100 nm, a specific surface area of ​​≥800 m² / g, and a contact angle of ≥150°.

4. A method for preparing high-temperature resistant and fire-resistant concrete reinforced with waste glass sand as described in any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Weigh out the following by weight: silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand, silanized nano aerogel, phosphate-based fire retardant, basalt fiber, and water. Step S2: Mix silicate cement, metakaolin, waste glass sand, porous steel slag aggregate, river sand, and basalt fiber to obtain a mixed dry material. Pour the mixed dry material into a mixer and stir for 1-3 minutes to make the dry material evenly mixed. Step S3: Mix the phosphate-based fire retardant with water at 35-45℃ until homogeneous, then add the mixture to the mixer in step S2 and stir for 2-5 minutes. Step S4: Add the silanized nano-aerogel to the mixer from step S3 and continue stirring for 1-3 minutes; Step S5: After mixing is complete, pour the mixture into the mold that has been brushed with release agent and compact it. Step S6: Curing is carried out in a constant temperature and humidity chamber at a temperature of 20±2℃ and a humidity of ≥90%. After curing, high temperature and fire-resistant concrete reinforced with waste glass sand is obtained. In step S3, water is added twice. The first addition of 65-75% of the total water weight is used to disperse the phosphate-based fire retardant, and the remaining 25-35% is added before the addition of the silanized nano-aerogel.

5. The method for preparing high-temperature resistant and fire-resistant concrete reinforced with waste glass sand according to claim 4, characterized in that: The stirring in step S2 is slow stirring, with a stirring speed of 130-150 r / min; the stirring in steps S3 and S4 is fast stirring, with a stirring speed of 270-300 r / min.

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