(2) Aggregate gradation is poor. It is mainly manifested in the stone factory that the stone sieve is divided into 5 10mm, 10 25mm and 20 31.5mm and other grade sales, and the concrete enterprise uses alone to cause the gradation difference. In addition, stone factory small corner material stone chips, often as the so-called "mechanism of sand" sales to concrete enterprises, stone chips grading mostly "two particle content is large, insufficient middle particles", to the preparation of concrete to bring difficulties.
(3) Le module de finesse du sable à granulats fins change considérablement. Le module de finesse varie considérablement en raison des différentes sources et matériaux d'agrégats fins. Les entreprises de béton ont souvent plusieurs fournisseurs de granulats fins, qui traversent les matériaux à venir, exacerbant la fluctuation du module de finesse des granulats fins.
(4) Mauvais matériau d'agrégat. L'agrégat contient un grand nombre de particules faibles altérées, ce qui entraîne une faible valeur de concassage, un taux d'absorption d'eau élevé, d'une part, ce qui entraîne une mauvaise performance du mélange du béton, d'autre part, une faible résistance du béton, une mauvaise durabilité .
(5) différence de forme des grains agrégés. Influencé par le matériau de roche mère agrégée et la technologie de production, la teneur en particules d'aiguilles-flocons dans l'agrégat est élevée. Bien que certaines particules ne soient pas conformes aux spécifications d'aiguille -, la forme irrégulière des particules entraîne une détérioration de l'ouvrabilité et des propriétés mécaniques du béton.
Strengthening the detection of sand aggregate is the key to control aggregate quality. To preliminarily determine the quality of fine aggregate, the method of "experience plus test" is adopted, with experience as the supplement and test as the main. The empirical method of fine aggregate detection is "watching, kneading, rubbing, throwing and washing" and other methods: "watching", that is, watching the gradation, estimating the degree of thickness and fineness, holding a handful of sand in the palm of the hand, carefully watching whether the thickness and fineness of the sand is evenly distributed, the more uniform the gradation distribution of particles at all levels, the better; "Grasp", grasp a hand to estimate the water content of the sand, grasp to see the state of the sand group, the tighter the sand group proves the higher the water content, the lower the other way round; "Rub", grab a handful of sand in the palm, rub with two palms, gently clap hands, see the adhesion of the palm of the mud layer, the mud layer and yellow proves that the sand contains high mud, on the contrary, low mud; "Throw", the sand is held into a group and thrown in the palm of the hand. If the sand group is not loose, it can be determined that the sand is fine, containing mud or high water content. "Wash", grab a handful of sand in the water to wash it, see the degree of muddy water to determine the mud content, but also see the material and grain shape of the sand particles after washing. The empirical detection of coarse aggregate mainly depends on the intuitive methods such as "seeing and grinding". "Look", that is, look at the particle size distribution, look at the coarse aggregate grain shape, look at the surface impurities and mud content, look at the content of weathered soft particles; And then combined with "grinding", that is, two or more coarse aggregate particles in the hand grinding, judging the hardness of coarse aggregate.
S'il y a un doute sur la qualité de l'agrégat après un jugement préliminaire, il doit être testé et vérifié immédiatement pour une analyse quantitative.
