Research On Ultra-high Strength Concrete With Resistance Of Drill-grinding, Spalling And Blast

With the rapid development of economy and huge progress of society, fire and blast incidents occur repeatedly in industrial and civil building, ordnance penetrator is more likely threat to military defense facilities. Research and development on defense material is an urgent and practical issue on military defense facilities, industrial and civil facilities. Attack of ordnance penetrator, for example, consists of three steps:penetrating into the interior of the concrete building with such as to faster speed,producing instantaneous high temperature and then explosive spalling, and last detonating when penetrating to the presetted depth. To defense ordnance penetrator,therefore, concrete defense facilities must have good resistance effect for drill-grinding, explosive spalling and blast, etc. And on this basis, drill-grinding resistance, anti-spalling, anti-blast concrete and Anti DSB concrete combining several functions were studied in this paper, respectively. The following research findings and innovations were obtained:(1) Prepared drill-grinding resistance concrete. The concrete displays the best drill-grinding resistance and strength under the conditions of 0.18 of water-binder ratio, with 20 % of high strength admixture and 10 % volume dosages of brown corundum as aggregate via a new drill-grinding experiment method of Test methods for drill-grinding resistance of concrete, which was applicable to lab, corresponding to ordnance penetrator and was put forward. The mechanism was discussed by DTA/TG、XRD、SEM、MIP and microhardness tester. Results show the compact structure of the cement matrix and interface further promote the aggregate of extreme hardness to play the greatest role in drill-grinding resistance concrete.(2) The mathematical model of drill-grinding resistance of concrete was established for the first time in the theory of two-phase composites. The research results show that the drill-grinding resistance of concrete can be represented by microhardness and volume rate of the cement matrix and aggregate. The establishment of the mathematical model provides guidance for material and mix design of drill-grinding resistance of concrete.(3) Prepared anti-spalling concrete. The spalling of ultra-high-strength concrete under rapid heating and rapid cooling was investigated in lab. Results show that the burst time is extended by the addition of steel fiber, the anti-spalling is improved with the addition of PP fiber or PP and steel fibers, the spalling is unaffected by the type ofaggregate and the content of moisture. The mechanism of spalling resistance was examined by DTA/TG、XRD、SEM and MIP. Results show tubular channels formed with via the melting of PP fiber combined with the capillary porosity due to the dehydration and decomposition of hydration products. The combination of these behaviors relieves internal vapor pressure and prevents specimen spalling.(4) Prepared anti-blast concrete. Result shows steel fiber can drastically improve the anti-blast performance of concrete. It is mainly due to cementation action of steel fiber and the binding cement matrix and restraining effect of steel fiber to internal crack propagation.(5) Anti DSB concrete was investigated and developed with drill-grinding resistance, anti-spalling and anti-blast performances. It is shown that, physical properties(drill-grinding resistance, anti-spalling and microhardness) and mechanical properties(strength, toughness, impact resistance and penetration resistance), volume stability and durability(resistance to freeze-thaw cycle, chlorine ion permeability, and water permeability, carbonation and sulfate erosion) of anti DSB concrete have greatly improved. On the basis of the application of penetration formula, evaluating penetration resistance of Anti DSB concrete, the modified ACE formula is put forward with full consideration to aggregate hardness and toughness of concrete with steel fiber.The successful development of Anti DSB concrete provides necessary theoretical basis and technical support for defending high defense industrial and civil facilities,military defense facilities.