基于流變特性的混凝土組成設(shè)計方法
發(fā)布時間：2019-03-07 19:03
【摘要】：新拌混凝土的工作性能關(guān)系著混凝土的澆筑、施工、密實等過程,對混凝土的力學性能和耐久性能有重要的影響。傳統(tǒng)混凝土工作性的評價方法主要通過坍落度、稠度、擴展度、擴展時間等單一參數(shù)進行表征,偏重于經(jīng)驗性和主觀性,且缺乏科學精度;另外,在滿足經(jīng)濟性和混凝土質(zhì)量時原材料組成的優(yōu)化設(shè)計也缺乏相應(yīng)的理論指導(dǎo)。本文在不同富余漿體厚度、骨料堆積狀態(tài)和三元膠凝組成時采用屈服應(yīng)力、塑性粘度等流變參數(shù)評價了混凝土的工作性能,根據(jù)混凝土組成與流變參數(shù)之間的關(guān)系對各配比參數(shù)進行了優(yōu)化,并提出了基于流變特性的混凝土組成設(shè)計方法。保持水灰比和砂率不變,建立了富余漿體厚度與坍落度、流變參數(shù)之間的關(guān)系。結(jié)果發(fā)現(xiàn),改變富余漿體厚度主要是通過影響屈服應(yīng)力來影響混凝土的工作性能。流變參數(shù)與富余漿體厚度之間存在著良好的y=axb函數(shù)關(guān)系。隨著富余漿體厚度的增加,新拌混凝土的屈服應(yīng)力和塑性粘度明顯降低,坍落度明顯升高;當富余漿體厚度相對較高時,屈服應(yīng)力和塑性粘度趨于穩(wěn)定。在固定水灰比和骨料參數(shù)下,通過建立不同富余漿體厚度時工作性能與流變參數(shù)間的關(guān)系,能夠確定混凝土中適宜的膠凝材料用量。保持水灰比和水泥用量不變,測試了不同砂率時混凝土的流變參數(shù),結(jié)果發(fā)現(xiàn)隨著砂率的升高,屈服應(yīng)力和塑性粘度先逐漸降低后升高,坍落度逐漸增大而后基本保持不變。根據(jù)砂率與流變參數(shù)的關(guān)系,能夠確定出最佳砂率。將粗骨料分為5-10 mm、10-15 mm和15-20 mm三個粒徑段,根據(jù)單純型重心設(shè)計法設(shè)計不同粗骨料組成的混凝土。綜合考慮混合粗骨料的堆積密度、比表面積和新拌混凝土的坍落度、屈服應(yīng)力、塑性粘度,能夠確定粗骨料的最佳比例組成。在固定水膠比、膠凝材料總量和砂率時,取水泥質(zhì)量分數(shù)為0.4~1.0、粉煤灰和礦粉質(zhì)量分數(shù)均為0~0.6,根據(jù)單純型重心設(shè)計法建立了三元膠凝組成與混凝土流變參數(shù)、力學強度的函數(shù)關(guān)系,并對三元膠凝材料體系進行了優(yōu)化。基于本研究所用原材料,在滿足力學強度條件下,當新拌混凝土具有適宜的流動性能和流變性能時,粉煤灰最佳摻量為15~20%,礦粉最佳摻量為15~25%。根據(jù)上述研究成果,提出了基于流變特性的混凝土組成設(shè)計方法,能夠合理的控制混凝土中的砂石比例,綜合考慮多種性能因素確定適宜的膠凝材料用量和膠凝體系組成。不僅能夠控制新拌混凝土的流動性、穩(wěn)定性、勻質(zhì)性等性能,還能夠降低膠凝材料總量和水泥用量,能夠有效地提高混凝土的質(zhì)量。
[Abstract]:The working performance of fresh concrete is related to the pouring, construction and compacting process of concrete, and has an important influence on the mechanical properties and durability of concrete. The traditional evaluation methods of concrete workability are mainly characterized by single parameters such as slump, consistency, expansion time and so on, which emphasize on experience and subjectivity, and lack of scientific precision. In addition, the optimization design of raw material composition is also lack of corresponding theoretical guidance when the economy and quality of concrete are satisfied. In this paper, the rheological parameters such as yield stress, plastic viscosity and so on are used to evaluate the performance of concrete in different thickness of residual slurry, aggregate accumulation state and three-dimensional cementitious composition. According to the relationship between concrete composition and rheological parameters, the composition parameters of concrete are optimized, and the design method of concrete composition based on rheological properties is put forward. The relationship between the thickness of residual slurry, slump and rheological parameters is established by keeping the ratio of water to cement and sand ratio unchanged. It is found that the effect of yield stress on the performance of concrete is mainly due to the change of residual slurry thickness. There is a good y=axb function relationship between rheological parameters and residual slurry thickness. With the increase of residual paste thickness, the yield stress and plastic viscosity of fresh concrete decrease obviously, and the slump increases obviously, and when the thickness of surplus paste is relatively high, the yield stress and plastic viscosity tend to be stable. Under the condition of fixed water-cement ratio and aggregate parameters, the relationship between working performance and rheological parameters of different residual slurry thickness can be established, and the appropriate amount of cementitious material in concrete can be determined. The rheological parameters of concrete with different sand rates were tested with the same ratio of water to cement and cement content. The results showed that with the increase of sand ratio, the yield stress and plastic viscosity decreased at first and then increased, and the slump increased gradually and then remained unchanged. According to the relationship between sand rate and rheological parameters, the optimum sand rate can be determined. The coarse aggregate is divided into three segments: 5-10 mm,10-15 mm and 15-20 mm. The concrete with different coarse aggregate composition is designed according to the simple design method of gravity center. Considering the bulk density, specific surface area and slump of fresh concrete, yield stress and plastic viscosity, the optimum proportion of coarse aggregate can be determined by considering the bulk density of mixed coarse aggregate, specific surface area, slump of fresh concrete, yield stress and plastic viscosity. When the ratio of water to cement is fixed, the total amount of cementitious material and sand ratio are fixed, the mass fraction of cement is 0.4 脳 1.0, the mass fraction of fly ash and mineral powder is 0. 6%. According to the simple gravity center design method, the three-dimensional cementitious composition and the rheological parameters of concrete are established. The function relation of mechanical strength and the optimization of ternary cementitious material system were carried out. Based on the raw materials used in the study, under the condition of satisfying mechanical strength, when fresh concrete has suitable flow and rheological properties, the optimum content of fly ash and mineral powder is 15? 20% and 15? 25% respectively. Based on the above research results, the design method of concrete composition based on rheological properties is put forward, which can reasonably control the proportion of sand and stone in concrete, and determine the appropriate amount of cementitious material and the composition of cementitious system comprehensively considering various performance factors. It can not only control the fluidity, stability, homogeneity and other properties of fresh concrete, but also reduce the total amount of cementitious material and cement content, and can effectively improve the quality of concrete.
【學位授予單位】：中國建筑材料科學研究總院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528
本文編號：2436368
[Abstract]:The working performance of fresh concrete is related to the pouring, construction and compacting process of concrete, and has an important influence on the mechanical properties and durability of concrete. The traditional evaluation methods of concrete workability are mainly characterized by single parameters such as slump, consistency, expansion time and so on, which emphasize on experience and subjectivity, and lack of scientific precision. In addition, the optimization design of raw material composition is also lack of corresponding theoretical guidance when the economy and quality of concrete are satisfied. In this paper, the rheological parameters such as yield stress, plastic viscosity and so on are used to evaluate the performance of concrete in different thickness of residual slurry, aggregate accumulation state and three-dimensional cementitious composition. According to the relationship between concrete composition and rheological parameters, the composition parameters of concrete are optimized, and the design method of concrete composition based on rheological properties is put forward. The relationship between the thickness of residual slurry, slump and rheological parameters is established by keeping the ratio of water to cement and sand ratio unchanged. It is found that the effect of yield stress on the performance of concrete is mainly due to the change of residual slurry thickness. There is a good y=axb function relationship between rheological parameters and residual slurry thickness. With the increase of residual paste thickness, the yield stress and plastic viscosity of fresh concrete decrease obviously, and the slump increases obviously, and when the thickness of surplus paste is relatively high, the yield stress and plastic viscosity tend to be stable. Under the condition of fixed water-cement ratio and aggregate parameters, the relationship between working performance and rheological parameters of different residual slurry thickness can be established, and the appropriate amount of cementitious material in concrete can be determined. The rheological parameters of concrete with different sand rates were tested with the same ratio of water to cement and cement content. The results showed that with the increase of sand ratio, the yield stress and plastic viscosity decreased at first and then increased, and the slump increased gradually and then remained unchanged. According to the relationship between sand rate and rheological parameters, the optimum sand rate can be determined. The coarse aggregate is divided into three segments: 5-10 mm,10-15 mm and 15-20 mm. The concrete with different coarse aggregate composition is designed according to the simple design method of gravity center. Considering the bulk density, specific surface area and slump of fresh concrete, yield stress and plastic viscosity, the optimum proportion of coarse aggregate can be determined by considering the bulk density of mixed coarse aggregate, specific surface area, slump of fresh concrete, yield stress and plastic viscosity. When the ratio of water to cement is fixed, the total amount of cementitious material and sand ratio are fixed, the mass fraction of cement is 0.4 脳 1.0, the mass fraction of fly ash and mineral powder is 0. 6%. According to the simple gravity center design method, the three-dimensional cementitious composition and the rheological parameters of concrete are established. The function relation of mechanical strength and the optimization of ternary cementitious material system were carried out. Based on the raw materials used in the study, under the condition of satisfying mechanical strength, when fresh concrete has suitable flow and rheological properties, the optimum content of fly ash and mineral powder is 15? 20% and 15? 25% respectively. Based on the above research results, the design method of concrete composition based on rheological properties is put forward, which can reasonably control the proportion of sand and stone in concrete, and determine the appropriate amount of cementitious material and the composition of cementitious system comprehensively considering various performance factors. It can not only control the fluidity, stability, homogeneity and other properties of fresh concrete, but also reduce the total amount of cementitious material and cement content, and can effectively improve the quality of concrete.
【學位授予單位】：中國建筑材料科學研究總院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528
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