Ultrafine Cement Hydration Characteristics And High Early Strength Concrete, Preparation Of Technical Studies,

The production of Gravelless Rail Board has the problems of expensive cement and lower durability,the mineral components and hydration products of PⅡ42.5, P.O.42.5 and superfine cement and the effect of mineral admixtures on the hydration of cement were studied.This paper provided the preparation technical method of high early-age strength concretes with PⅡ42.5 and mineral admixtures as replacement for superfine cement.Adopting three kinds of cement,that is PⅡ42.5,P.O.42.5 and superfine cement, this paper studied the compressive strength of harden pastes with different W/B and different mineral admixtures.The non-evaporable water was studied by the method of weight loss in burning,the content of Ca(OH)₂ was compared by the means of XRD, and SEM,the microstructure was observed by SEM.This paper studied also the relationship between the 16h compressive strength of concrete and the height peak and the arriving time of temperature in concrete by measuring the temperature curve of inner concrete,the durability of high early strength concrete was studied.The main conclusions of this paper are as following:1.The mineral components of PⅡ42.5,P.O.42.5 and superfine cement are the same, but superfine cement has highest content of C₃S.2.Three kinds of cement have the same hydration process and hydration production, the difference is the quantity of hydration.The content of non-evaporable water in harden pastes containing superfine cement if highest,the second is PⅡ42.5,the lowest is P.O.42.5.3.In view of microstructures,the hardened paste of three different cements are same.The content of Ca(OH)₂ is highest in harden pastes containing superfine cement. When the mineral admixtures is added into pastes,the content of Ca(OH)₂ decreases obviously.Among three kinds of mineral admixtures,the decrease degree of Ca(OH)₂ content is the highest in hardened paste containing silica fume,the second is that containing ground granulated blast slag,the lowest is that containing special mineral admixtures.4.The relationship between the 16h compressive strength of concrete and the height peak and the arriving time of temperature in concrete is obvious.The highest early strength can be achieved by means of increasing the peak of temperature and shortening the arriving time.The content of ground granulated blast slag increases,the 16h strength decreases.When silica fume is added into concrete,the peak of temperature in concrete increases,so the early strength of concrete increases.5.The high early strength concrete can be prepared with PⅡ42.5 and mineral admixtures as replacement for superfine cement.The 16h strength of concrete under natural curing can achieve 48MPa.In order to improve the durability of concrete,the mineral admixtures must be added into concrete.6.The application of PⅡ42.5 and special mineral admixtures as replacement for superfine cement to producing the double-block sleepers can reduce the costs and improve the durability of concrete.