超高強混凝土的硬化過程
發(fā)布時間：2018-08-14 16:10
【摘要】：超高性能混凝土作為一種新型水泥基材料,具有強度高,耐久性優(yōu)異的優(yōu)點。超高性能混凝土的抗壓強度高于150MPa,約是傳統(tǒng)混凝土的3倍以上。超高性能混凝土具有優(yōu)異的韌性和斷裂能,和高性能混凝土相比,超高性能混凝土的韌性提高了300倍以上,和一些金屬相當,使得混凝土結(jié)構(gòu)在超載環(huán)境下或地震中具有更優(yōu)異的結(jié)構(gòu)可靠性。超高性能混凝土具有優(yōu)異的耐久性能,延長了混凝土結(jié)構(gòu)的使用壽命,降低了維修費用。超高性能混凝土幾乎是不滲透性的,幾乎無碳化,氯離子滲透和硫酸鹽滲透也幾乎為零。盡管超高性能混凝土擁有很多顯著的優(yōu)點,但也存在一些缺陷。超高性能混凝土的膠凝材料用量高達800-1000kg/m3,增大了水化熱,產(chǎn)生收縮。制備超高性能混凝土的原材料通常為水泥、硅灰、石英砂、石英粉、鋼纖維和超塑化劑等,生產(chǎn)成本是普通混凝土的數(shù)倍。為了提高超高性能混凝土中輔助性膠凝材料的活性,生產(chǎn)超高性能混凝土時往往采用蒸汽或蒸壓養(yǎng)護,復雜的生產(chǎn)工藝限制了超高性能混凝土在實際工程中的應用。為了降低超高強混凝土的生產(chǎn)成本,簡化其生產(chǎn)工藝,常溫養(yǎng)護超高性能混凝土成為了一個研究熱點。由于原材料和生產(chǎn)工藝的差異,采用常溫養(yǎng)護超高性能混凝土的硬化過程和傳統(tǒng)熱養(yǎng)護超高性能混凝土可能存在較大差異,鑒于此,本文研究了常溫養(yǎng)護超高性能混凝土的硬化過程。由于鋼纖維對超高性能混凝土的硬化過程影響較小,本文將研究不摻鋼纖維的超高強混凝土的硬化過程。當砂膠比為1.0時,使用天然石英砂配制超高強混凝土的抗壓強度達到131.5MPa。當砂膠比為1.1時,使用機制石英砂配制超高強混凝土的抗壓強度達到139.8MPa。盡管使用機制石英砂配制超高強混凝土的流動度和抗壓強度均大于使用天然石英砂配制超高強混凝土的流動度和抗壓強度,但使用天然石英砂也能配制出性能優(yōu)異的超高強混凝土,當砂膠比為1.0時,使用天然石英砂配制超高強混凝土的抗壓強度達到131.5MPa。綜合考慮超高強混凝土的生產(chǎn)成本和性能,本文采用天然石英砂配制超高強混凝土,采用的砂膠比為1.0。通過三角形正交設計,設計了七組超高強混凝土的膠凝組分,并將膠凝組分和性能的關(guān)系表示為等值線圖。研究結(jié)果表明,在適當摻量下,硅灰可以提高超高強混凝土的流動度和抗壓強度,降低超高強混凝土的孔隙率和氫氧化鈣含量。在一定用量下,礦粉減小了超高強混凝土的流動度、抗壓強度、孔隙率和氫氧化鈣含量。硅灰和礦粉對超高強混凝土的流動度和3d抗壓強度有正的協(xié)同效應,但對超高強混凝土的總水化熱、56d抗壓強度、孔隙率和氫氧化鈣含量有負的協(xié)同效應。通過三角形正交設計,設計了七組超高強混凝土的膠凝組分,并將膠凝組分和性能的關(guān)系表示為等值線圖。研究結(jié)果表明,在適當摻量下,硅灰可以提高超高強混凝土的流動度和抗壓強度,降低超高強混凝土的孔隙率和氫氧化鈣含量,減小了水化加速期出現(xiàn)的時間。在一定用量下,粉煤灰增大了超高強混凝土的流動度和早期孔隙率,減小了超高強混凝土的早期抗壓強度和氫氧化鈣含量。硅灰和粉煤灰對超高強混凝土的流動度和抗壓強度有正的協(xié)同效應,但對超高強混凝土的總水化熱、孔隙率和氫氧化鈣含量有負的協(xié)同效應。為了研究水泥-硅灰-礦粉-粉煤灰四組分水泥基超高強混凝土的硬化過程,選取水膠比,硅灰摻量,礦粉摻量和粉煤灰摻量四個因素及四水平,對超高強混凝土的配合比進行正交設計,并研究其硬化過程。隨著水膠比的增大,超高強混凝土的流動度顯著增大,抗壓強度在不同齡期下均有所降低,孔隙率在不同齡期下均有所增大,氫氧化鈣含量在不同齡期下均有所增大。隨著硅灰摻量的增大,超高強混凝土的流動度顯著減小,抗壓強度先增大后降低,孔隙率在不同齡期下均有所減小,氫氧化鈣含量在不同齡期下均有所減小。隨著礦粉摻量的增大,超高強混凝土的流動度沒有明顯的變化,抗壓強度先增大后減小,孔隙率在早期減小,后期反而增大,氫氧化鈣含量在不同齡期下均有所減小。隨著粉煤灰摻量的增大,超高強混凝土的流動度先增大后降低,早期抗壓強度大幅度降低,后期抗壓強度先增大后降低,早期孔隙率增大,后期對孔隙率影響不大,氫氧化鈣含量在不同齡期下均有所減小。納米二氧化硅和納米碳酸鈣均降低了超高強混凝土的流動度。摻入納米二氧化硅后,超高強混凝土的水化放熱速度不斷增大,水化放熱量先增大后降低。摻入納米碳酸鈣后,超高強混凝土的水化放熱速度不斷增大,水化放熱量不斷降低。隨著納米二氧化硅摻量的增大,超高強混凝土的抗壓強度先增大后降低,隨著納米碳酸鈣摻量的增大,超高強混凝土的抗壓強度先增大后降低。隨著納米二氧化硅摻量的增大,超高強混凝土的孔隙率先減小后增大,隨著納米碳酸鈣摻量的增大,超高強混凝土的孔隙率先減小后增大。隨著納米二氧化硅摻量的增大,超高強混凝土的氫氧化鈣含量不斷減小,隨著納米碳酸鈣摻量的增大,超高強混凝土的氫氧化鈣含量不斷增大。
[Abstract]:As a new type of cement-based material, ultra-high performance concrete has the advantages of high strength and excellent durability. The compressive strength of ultra-high performance concrete is higher than 150 MPa, which is about three times higher than that of traditional concrete. Ultra-high performance concrete has excellent durability, prolongs the service life of concrete structures, and reduces maintenance costs. Ultra-high performance concrete is almost impermeable, almost without carbonization, chlorine. Ion permeation and sulfate permeation are almost zero. Although super-high performance concrete has many remarkable advantages, there are also some defects. The amount of cementitious materials used in super-high performance concrete is as high as 800-1000kg/m3, which increases the heat of hydration and produces shrinkage. The raw materials for preparing super-high performance concrete are usually cement, silica fume, quartz sand and quartz. In order to improve the activity of auxiliary cementitious materials in ultra-high performance concrete, steam or autoclave curing is often used in the production of ultra-high performance concrete. The complex production process limits the application of ultra-high performance concrete in practical engineering. Because of the difference of raw materials and production process, the hardening process of UHPC cured at room temperature may be quite different from that of traditional UHPC cured at normal temperature. In view of this, this paper studies the curing process of UHPC cured at room temperature. The hardening process of ultra-high performance concrete cured at room temperature is studied in this paper because steel fiber has little influence on the hardening process of ultra-high performance concrete. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete prepared with natural quartz sand reaches 131.5 MPa. When the ratio of sand to binder is 1.1 The compressive strength of ultra-high strength concrete prepared with machine-made quartz sand is 139.8 MPa. Although the fluidity and compressive strength of ultra-high strength concrete prepared with machine-made quartz sand are greater than those of ultra-high strength concrete prepared with natural quartz sand, the super-high performance concrete can be prepared with natural quartz sand. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete made of natural quartz sand reaches 131.5 MPa. Considering the production cost and performance of ultra-high strength concrete, this paper adopts natural quartz sand to prepare ultra-high strength concrete. The ratio of sand to binder is 1.0. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the flow of ultra-high strength concrete under certain dosage. Mobility, compressive strength, porosity and calcium hydroxide content. Silica fume and mineral powder have positive synergistic effects on the fluidity and 3D compressive strength of ultra-high strength concrete, but have negative synergistic effects on the total hydration heat, 56d compressive strength, porosity and calcium hydroxide content of ultra-high strength concrete. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the time of hydration acceleration. Fly ash increases the fluidity and early porosity of ultra-high strength concrete, and decreases the early compressive strength and calcium hydroxide content of ultra-high strength concrete. In order to study the hardening process of cement-silica fume-mineral Powder-Fly ash four-component cement-based ultra-high strength concrete, four factors and four levels were selected, i.e. water-binder ratio, silica fume content, mineral powder content and fly ash content. With the increase of silica fume content, the fluidity of ultra-high strength concrete decreases significantly, the compressive strength decreases at different ages, the porosity increases at different ages, and the content of calcium hydroxide increases at different ages. With the increase of mineral powder content, the fluidity of ultra-high strength concrete has no obvious change. The compressive strength increases first and then decreases. The porosity decreases at the early stage, but increases at the later stage. The content of calcium hydroxide decreases at different ages. With the increase of fly ash content, the fluidity of ultra-high strength concrete increases first and then decreases, the early compressive strength decreases greatly, the later compressive strength increases first and then decreases, the early porosity increases, the latter has little effect on the porosity, and the content of calcium hydroxide decreases at different ages. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat increases first and then decreases with the addition of nano-silica. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat decreases with the addition of nano-silica. The compressive strength of concrete increases first and then decreases with the increase of nano-calcium carbonate content, and then decreases with the increase of nano-silica content. With the increase of nano-silica content, the content of calcium hydroxide in super-high strength concrete decreases. With the increase of nano-calcium carbonate content, the content of calcium hydroxide in super-high strength concrete increases.
【學位授予單位】：湖南大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU528
本文編號：2183406
[Abstract]:As a new type of cement-based material, ultra-high performance concrete has the advantages of high strength and excellent durability. The compressive strength of ultra-high performance concrete is higher than 150 MPa, which is about three times higher than that of traditional concrete. Ultra-high performance concrete has excellent durability, prolongs the service life of concrete structures, and reduces maintenance costs. Ultra-high performance concrete is almost impermeable, almost without carbonization, chlorine. Ion permeation and sulfate permeation are almost zero. Although super-high performance concrete has many remarkable advantages, there are also some defects. The amount of cementitious materials used in super-high performance concrete is as high as 800-1000kg/m3, which increases the heat of hydration and produces shrinkage. The raw materials for preparing super-high performance concrete are usually cement, silica fume, quartz sand and quartz. In order to improve the activity of auxiliary cementitious materials in ultra-high performance concrete, steam or autoclave curing is often used in the production of ultra-high performance concrete. The complex production process limits the application of ultra-high performance concrete in practical engineering. Because of the difference of raw materials and production process, the hardening process of UHPC cured at room temperature may be quite different from that of traditional UHPC cured at normal temperature. In view of this, this paper studies the curing process of UHPC cured at room temperature. The hardening process of ultra-high performance concrete cured at room temperature is studied in this paper because steel fiber has little influence on the hardening process of ultra-high performance concrete. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete prepared with natural quartz sand reaches 131.5 MPa. When the ratio of sand to binder is 1.1 The compressive strength of ultra-high strength concrete prepared with machine-made quartz sand is 139.8 MPa. Although the fluidity and compressive strength of ultra-high strength concrete prepared with machine-made quartz sand are greater than those of ultra-high strength concrete prepared with natural quartz sand, the super-high performance concrete can be prepared with natural quartz sand. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete made of natural quartz sand reaches 131.5 MPa. Considering the production cost and performance of ultra-high strength concrete, this paper adopts natural quartz sand to prepare ultra-high strength concrete. The ratio of sand to binder is 1.0. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the flow of ultra-high strength concrete under certain dosage. Mobility, compressive strength, porosity and calcium hydroxide content. Silica fume and mineral powder have positive synergistic effects on the fluidity and 3D compressive strength of ultra-high strength concrete, but have negative synergistic effects on the total hydration heat, 56d compressive strength, porosity and calcium hydroxide content of ultra-high strength concrete. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the time of hydration acceleration. Fly ash increases the fluidity and early porosity of ultra-high strength concrete, and decreases the early compressive strength and calcium hydroxide content of ultra-high strength concrete. In order to study the hardening process of cement-silica fume-mineral Powder-Fly ash four-component cement-based ultra-high strength concrete, four factors and four levels were selected, i.e. water-binder ratio, silica fume content, mineral powder content and fly ash content. With the increase of silica fume content, the fluidity of ultra-high strength concrete decreases significantly, the compressive strength decreases at different ages, the porosity increases at different ages, and the content of calcium hydroxide increases at different ages. With the increase of mineral powder content, the fluidity of ultra-high strength concrete has no obvious change. The compressive strength increases first and then decreases. The porosity decreases at the early stage, but increases at the later stage. The content of calcium hydroxide decreases at different ages. With the increase of fly ash content, the fluidity of ultra-high strength concrete increases first and then decreases, the early compressive strength decreases greatly, the later compressive strength increases first and then decreases, the early porosity increases, the latter has little effect on the porosity, and the content of calcium hydroxide decreases at different ages. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat increases first and then decreases with the addition of nano-silica. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat decreases with the addition of nano-silica. The compressive strength of concrete increases first and then decreases with the increase of nano-calcium carbonate content, and then decreases with the increase of nano-silica content. With the increase of nano-silica content, the content of calcium hydroxide in super-high strength concrete decreases. With the increase of nano-calcium carbonate content, the content of calcium hydroxide in super-high strength concrete increases.
【學位授予單位】：湖南大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU528
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，本文編號：2183406
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