Research On Performance Of High Fliud Structural Lightweight Aggregate Concrete

This paper deals with high fluid concrete in which high strength ceramsite made from shale was used as coarse aggregate. Effects of cement content, water-cement ratio, sand percentage, mineral admixture, grading and pretreatment of lightweight aggregate on compressive strength and workability of high fluid structural lightweight aggregate concrete have been studied. The rules of water absorption of high strength lightweight aggregate under different pressure and effects on uniformity of high fluid structural lightweight aggregate concrete have been studied too. And the measures resolving separation of mixture of high fluid structural lightweight aggregate concrete are presented. It can be concluded as following:â‘ Water absorptivity of high strength ceramsite is different from that of extra-light ceramsite. In atmospheric pressure, water absorption rate of high strength ceramsite is very small, which 1hour and 75 days water absorption rate is only 2% and 5.7% respectively. But under additional pressure, the rate increases greatly. Under pressure of 30MPa,it reaches 11.1% in 10 minute.â‘¡ Water absorption rate of high strength ceramsite in concrete is lower than in water, and it is influenced by water-cement ratio, the higher w/c ratio, the bigger water absorption rate. And the lower w/c ratio in concrete is, the less obvious changes of water absorption rate by outer pressure and time are. In addition, water absorption rate of high strength lightweight aggregate in concrete under pressure decreases with its initial containing water rate increasing. â‘¢To obtain high fluid structural lightweight aggregate concrete with good uniformity, it is necessary to limit the max grain size of lightweight aggregate to 20mm, cement content to 500kg/m~3 and slump of concrete mixture to 260mm. In addition, vibration has great effects on uniformity of high fluid structural lightweight aggregate concrete. There is obvious separation of lightweight aggregate from mortar in mixture of high fluid structural lightweight aggregate concrete with slump of 220mm when vibrated for 10 minutes. Lightweight aggregate concrete can be densified in itself when the slump is in the range of 180~260mm.â‘£ We have been produced high fluid structural lightweight aggregate concrete which apparent density is 1800kg/m~3 and 28d compressive strength is 50~60MPa byusing high strength lightweight aggregate, controlling cement content, w/c ratio, sand ratio correctly and adding superplasticizer and mineral admixture.The tests of axial compressive strength, flexural strength, elastic modulus and impermeability show that the concrete produced in this paper has excellent mechanical and durable properties.