Research On Long-term Properties And Durability Of High Strength Structural Lightweight Aggregate Concrete

As an important part of lightweight concrete, compared with ordinary concrete, HSLC is provided with advandages: high strength to density ratio, well durability, well anti-seismic, remarkable economical efficiency and so on, which has a widely prospects in some places such as large-span bridge, tall building and ocean engineering. Up to now, research of HSLC mostly focused on design of mix proportion, early mechanics and some of durability, but relatively less on long-term properties. There is a theoretical and actual significance in production and construction of HSLC to pay attention to the research on long-term deformation properties and durability.In this paper, long-term drying-shrinkage, resistance to diffusion of Cl-of HSLC and effect of main factors on HSLC which made from shale ceramiste with low water absorption and high strength are studied . At the same time, the mechanics, frost resistance and impermeability are tested separately. The research results can be concluded as follows:①Not only the drying-shrinkage of HSLC in later ages is higher than ordinary concrete, but also is remarkable higher than ordinary concrete in early ages. Drying-shrinkage of HSLC reaching to stabilization period need much more time, and drying-shrinkage of HSLC still increased greatly after 180d ages.②There is a disadvantage on drying-shrinkage by produce HSLC with methods of reducing maximum size of aggregate or reducing content of aggregates, though it is good for improving strength of HSLC. In this paper, a concrete of strength grade LC60 with ceramiste range from 5 to 16 mm was produced, which drying-shrinkage value in 180d reached to 780μm/m, it is greatly higher than that of ordinary concrete in the same grade.③It has a complicated influence on shrinkage of HSLC of water to cement ratio (W/C). It is nonlinearity relationship between W/C and drying shrinkage of HSLC, which existing a critical W/C. In this paper, the W/C critical value is 0.45. Drying-shrinkage of HSLC is lower as W/C increasing when it below the critical value; drying-shrinkage of HSLC whose W/C exceeds the value is higher as the W/C increasing. Cement content has an obvious influence on drying-shrinkage of HSLC: drying-shrinkage is sensitive to the cement content when cement content is lower; and the sensitivity decrease obviously when cement content reached to a extent. Also there is a critical value which called worst cement content between cement content and drying-shrinkage of HSLC. In this paper, the worst cement content is between 500kg/m~3 and 550kg/m~3.④Capability of resistance to diffusion of Cl-of HSLC is lower than ordinary concrete in the same level in early ages(28d), but the later increasing extent is obviously higher than that of ordinary concrete. Capability of resistance to diffusion of Cl-of HSLC is higher than ordinary concrete in 60d ages. In author's opinion, it can reflect the real capability of resistance to diffusion of Cl-of HSLC by delay the test ages in the judgement of capability of resistance to diffusion of Cl-of HSLC.⑤In regard to HSLC which maded from shale ceramiste with low water absorption and high strength, pre-wetting of aggregate just has some extent bad influence on resistance to diffusion of Cl-of HSLC in early ages(28d), but no obviously effect in later ages(60d). It has the same capability of resistance to diffusion of Cl- for both HSLC with pre-wetting and with no pre-wetting.⑥The difference of effect of content of mineral admixtures to resistance to diffusion of Cl-of HSLC mostly focus on early ages, and the difference decrease with the increasing of ages.