【摘要】：混凝土細集料需求量逐年增長,傳統(tǒng)細集料——天然砂由于過度開采,品質(zhì)下降、成本增加,因此人工破碎的機制砂的應(yīng)用日漸廣泛,也成為了當(dāng)前研究的熱點。本文對機制砂的顆粒形狀、表面質(zhì)地進行了量化表征;探究了機制砂的粉料含量和MB值對混凝土的綜合作用;并對機制砂與河砂粒形差異對混凝土性能的影響進行了研究;通過測試機制砂、河砂混凝土的孔結(jié)構(gòu)及界面過渡區(qū)微觀結(jié)構(gòu)、組成,對機制砂混凝土與河砂混凝土性能差異形成的機理進行了探討。研究發(fā)現(xiàn):采用圖像分析與激光顯微系統(tǒng)量化表征了機制砂4.75~2.36mm顆粒的粒形及表面質(zhì)地:機制砂的圓度及長寬比均大于河砂,其顆粒為不規(guī)則棱角形、針片狀含量高;在0.4μm光源下,部分機制砂試樣的顯微表面面粗糙度低于河砂,河砂的顯微表面反而比一些機制砂更為粗糙;利用XRD定性分析機制砂75μm以上顆粒和75μm以下粉料的礦物組成,其組成只是在相對含量上存在一定差異。機制砂的粉料含量和MB值是一組相互關(guān)聯(lián)的質(zhì)量指標(biāo),不同MB值(0.5、1.0、1.4、1.8、2.2)下,混凝土坍落度達到最大值時機制砂的粉料含量都在10%~15%的范圍內(nèi);高粉料含量(20%~10%)、低MB值(≤1.4g/kg),或高MB值(1.4g/kg)、低粉料含量(10%~5%)的機制砂都可以配制出性能指標(biāo)良好的混凝土。在相同的顆粒級配和粉料組成下,機制砂不規(guī)則的顆粒形狀對配制混凝土的工作性及抗氯離子滲透性能影響不大,此條件下顆粒形狀圓滑的河砂反而獲得了更高的抗壓強度,機制砂不規(guī)則的顆粒形狀并不是其配制混凝土強度高的主要原因,但卻改善了混凝土的抗凍性及早期抗收縮能力,對后期抗收縮能力的影響較小。采用MIP及FE-SEM(EDS)測試了原狀機制砂、原狀河砂混凝土孔結(jié)構(gòu)和界面過渡區(qū)微觀形貌及組成。兩者孔隙率相差不大,因此它們的氯離子滲透系數(shù)相近;原狀機制砂混凝土孔隙更大,因此其抗凍及抗收縮能力較差;原狀機制砂混凝土界面過渡區(qū)更為致密,元素分布均勻,無缺陷,因此其強度更高。
[Abstract]:The demand for concrete fine aggregate is increasing year by year. The traditional fine aggregate-natural sand has been widely used in the field of artificial crushing due to its overmining, its quality and its cost. Therefore, it has also become a hot research topic at present. In this paper, the grain shape and surface texture of machine-made sand are quantitatively characterized, the comprehensive effect of the content of powder and MB value of machine-made sand on concrete is explored, and the influence of the difference between machine-made sand and river sand on the concrete performance is studied. Through testing the pore structure and the microstructure of the interface transition zone of the machine-made sand, the formation mechanism of the performance difference between the machine-made sand concrete and the river sand concrete is discussed. It is found that the grain shape and surface texture of machine-made sand 4.75~2.36mm particles are characterized by image analysis and laser microscopy. The roundness and aspect ratio of machine-made sand are larger than that of river sand. Under 0.4 渭 m light source, the surface roughness of some machine-made sand samples is lower than that of river sand, and the micro-surface of river sand is rougher than that of some machine-made sand, and the mineral composition of machine-made sand above 75 渭 m and powder below 75 渭 m is analyzed qualitatively by XRD. Its composition is only different in relative content. The powder content and MB value of machine-made sand are a group of interrelated quality indexes. When the slump of concrete reaches the maximum value, the powder content of the machine-made sand is in the range of 10% or 15% under different MB values (0. 5 ~ 1. 0. 0 ~ 1. 4 ~ 1. 8 ~ 2. 2); High powder content (20%), low MB value (鈮，

本文編號：2254507