Study On Mechanical Properties Of Plastic-steel Fiber Reinforced Lightweight Aggregate Concrete Under The Effect Of Freezing And Thawing Cycle

Compared with ordinary concrete, the lightweight aggregate concrete is light andits durability is excellent. However, lightweight aggregate concrete is easy to producebrittle failure, and the strength is lower than ordinary concrete. It can effectivelyimprove its mechanical properties and control the expansion of cracks in concrete bymixing fibers. The rational using of lightweight aggregate and fiber can not onlyeffectively improve the concrete brittleness, but also can obviously improve theconcrete durability. Combined with these two kinds of materials, a test was carried outto study the mechanical properties of the plastic-steel fiber reinforced lightweightaggregate concrete in the freeze-thaw environment for gaining a good property concrete.The mechanical properties test of plastic-steel fiber reinforced lightweightaggregate concrete（Fiber content:0kg/m3,3kg/m3,6kg/m3,9kg/m3）after freezing andthawing（0times,50times,100times,150times) was carried out to study the influencelaw of fiber content and freeze-thaw times on compressive strength, splitting tensilestrength, flexural strength, flexural toughness and impact resistance. Considering themechanical properties index, the optimal content of plastic-steel fiber can be obtained.Establishing the model of freeze-thaw damage to predict the durability life ofplastic-steel fiber reinforced lightweight aggregate concrete under the freeze-thawenvironment. Observing the microstructure of concrete with scanning electronmicroscope to analyze the influence of freeze-thaw on macroscopic mechanicalproperties of plastic-steel fiber reinforced lightweight aggregate concrete.The results show that considering the tension-compression ratio, bend-press ratioand impact resistance, the optimal content of plastic-steel fiber is6kg/m3. The frostresistance durability life prediction of plastic-steel fiber reinforced lightweightaggregate concrete shows that the design service life of lightweight aggregate concretecan reach over50years when the fiber content is3kg/m3, and can reach over100yearswhen the fiber content is6kg/m3. The microstructure analysis shows that the interface of fiber-paste is the weakest link in the plastic-steel fiber reinforced lightweight aggregateconcrete, and the freeze-thaw function weakens the bond strength of aggregate-pasteand fiber-paste at the interface transition zone, which results in the decrease ofmechanical properties.