Research On Mix Optimization And Durability Of Dry Concrete

With the development of modern concrete technology, in order to meet differentneeds of production, speed up the process of construction, save costs and resources, dryconcrete has been widely used. Dry concrete means the value of slump is less than10mm, the values of WB within the scope of10~30s. Because of its property of lowwater-cement ratio, and high early strength, thus realized efficiency and economic goalsin the way of demoulding immediately. Currently, many areas of civil engineering hasbeen widely applied in dry concrete, such as in the foundation treatment technology, dryand compacted concrete is required in the construction process; in dam engineering androad engineering, ultra-dry concrete is required; production of prefabricated concreteelements, dry concrete is in the extensive use. Performance of dry concrete is differentfrom ordinary concrete. Presently, the research of ordinary concrete improve gradually,but the study of dry concrete is not yet perfectly. In order to further promote thepopularization and application of dry concrete in civil engineering, the systematic studyof their properties has great significance. This project is carried out in a systematic study,mainly from the following aspects:(1) According to the principles of orthogonal design, combined with localconditions in Qingdao, dry concrete is prepared with local materials and optimize themix proportions. Firstly, research the preparation process and quality control, thepreparation process is mainly introduced a new specimen preparation applied inlaboratory and test about the factors affecting mechanical properties. Research showsthat the most proper load is10KPa, Curing in water is good for strength developmentthan curing in standard room under20℃circumstance. Measures of quality control isproposed, in order to make dry concrete for better application and provide a technicalbasis.(2) Consider for different levels of factors to design the mix proportion by orthogonal method, eventually got the compressive strength of dry concrete in50MPa.Experimental results show: sand rate is45%, the dosage of cementitious material is425kg/m3, the ratio of fly ash and mineral powder is2:1, the compressive strength ishigher and more economic.(3) Analyze the data obtained of capillary water absorption by orthogonal andstudied the different influence factors of water absorption, such as sand ratios, theamount of cementitious material, mixing ratio between fly ash and slag and amount ofmineral admixtures on dry concrete. Experimental results show: sand rate is45%, thedosage of cementitious material is425kg/m3, the ratio of fly ash and mineral powder is2:1, the water absorption resistance of dry concrete performs good. Due to low watercontent in dry concrete, hydration of mineral admixture is restricted, and the best dosagestill need further study.(4) Analyze the data obtained of freezing and thawing cycles by orthogonal methodand systematically studied the different influence factors of freezing resistance, such assand ratio, the amount of cementitious material, mixing ratio between fly ash and slagand the amount of mineral admixtures on dry concrete. Experimental results show that:in the sand ratio of45%, the dosage of cementitious material is425kg/m3, the ratio offly ash and mineral powder is2:1, the frost resistance of dry concrete performs good.Which, due to the less moisture content in the dry concrete, ash mineral admixtures areslow to react, its influence on frost resistance is not good.