The Research On Preparation Technologies Of Ultra-high-strength Cementitious Composites

The increasing requirements for cementitious composites in modern architecturalengineering accelerate the emergence and development of ultra-high-strengthcementitious composites.The internal structure’s optimization of ultra-high-strengthcementitious composites improves durability and reduces the shrinkage greatly.Thefrost resistance,the anti-permeability and carbonation resistance improvesignificantly,which extend the service life of buildings. Its mixing of variousindustrial waste as mineral admixtures can significantly reduce resource consumption,environmental pollution and save construction costs that complies with the strategy ofsustainable development.Ultra-high-strength cementitious composites have higherstrength, better durability and reliability, which can effectively reduce the structuralweight to satisfy the structural safety, applicability and simultaneously has goodsocial and economic benefits.Therefore, ultra-high-strength cementitious compositesare attached great importance by more and more countries, which has become adirection of concrete ‘s field and its development prospects are immeasurable.This paper adopted orthogonal test in order to explore the effect to the fluidityand mechanical properties of ultra-high-strength mortar by these aspects includingsand-binder ratio, water-binder ratio,the dosage of silica fume and steel fiber as wellas the rang of sand diameter. It determined the impacts of every factor to provideguidance for the preparation of ultra-high-strength mortar.This paper had also furtherresearch on ultra-high-strength concrete and more detailed study on the effects of thewater-binder ratio, the total amount of binder and the dosage of mineral on thecompressive strength and durability of ultra-high-strength concrete and determinedthe impacts of various factors.Then the parameters of mix proportion were given inthe study,which lay a solid foundation for the practical application ofultra-high-strength concrete in engineering.The research showed:1）The water-binder ratio is the most important factor forthe fluidity of ultra-high-strength mortar and the volume percentage of steel fiber influences the flexural strength and the compressive strength of ultra-high-strengthmortar very significantly through the range and variance analysis.2）Considering therequirements of the fluidity and the strength, the parameters of mix proportion ofultra-high-strength mortar were given in the study.The sand-binder ratio is1.1,thewater-binder ratio is0.2,the dosage of silica fume is10%, the volume percentage ofsteel fiber is2%and the rang of sand diameter is from0.3to2.36mm.3）Thewater-binder ratio is the largest one in the long-term(28d,56d) strength ofultra-high-strength mortar and it is a significant factor in every age.With thewater-cement ratio increases, the compressive strength of ultra-high-strength mortardecreases.Water-cement ratio is a particularly significant factor.The water-binder ratiobecomes smaller, the chloride-penetration resistance becomes smaller and thecarbonation resistance becomes better.4）The influence of the dosage of mineral is thelargest one and it’s a particularly significant or significant factor in the early(3d,7d)strength.It became the indistinctive factor in the last part. The dosage of mineralplays a role in promoting the long-term strength ultra-high-strength concret.When thedosage of mineral is form30%to50%,the chloride-penetration resistance and theanti-carbonation both first increase and then decrease.5）The total amount of binder isnot only the indistinctive factor for the strength of ultra-high-strength concret in everyage,but also the influence of the total amount of binder is the smallest one in allfactors.The resistance to chlorideion penetration and the carbonation resistance willbe enhanced when increasing the total amount of binder appropriately, but theresistance to chlorideion penetration will weaken when the total amount of binder istoo large.6） Considering the requirements of the strength and durability,theparameters of mix proportion were given in the study.The water-binder ratio is0.24,the total amount of binder is600kg/m3and the dosage of mineral is40%.