Study on the Rule of Concrete Corrosion in Harsh Environment

The surface corrosion of 3 type concrete beams in hostile environment is researched by measuring concrete beams surface corrosion content, and the effect of test condition, concrete strength and corrosion time on concrete beams surface corrosion is analyzed. The result show that corrosion time is positively related to corrosion time; the beginning peeling time is longer with the increasing of concrete compressive strength; the capacity of concrete anti-stripping is increased with the increasing of concrete compressive strength. The formula of predication concrete beams surface stripping is set up by use of test data, which can be present in predicating concrete service life.


Introduction
Early damage of concrete structure under Corrosion environment (salty soil, marine environment, deicer salt) exists almost all over the world [1][2][3][4]. The reason of the concrete strength decrease is a volumetric expansion of sulphate crystal [5][6] .The reason is the steel corrosion which mainly results from free chloride ingression [7][8]. Concrete scaling and damage are accelerated by combination of sulphate crystal and free chloride ingression. Therefore, Concrete surface scaling in chloride salt in solution environment is one important directions of the prediction of concrete service time in corrosive environment and is becoming the hot spot of nowadays researches. In order to extract concrete scaling pattern in corrosive condition more quickly as the concrete scaling pattern in corrosive condition. The influence of test environment、corrosion time and concrete compressive strength on concrete beams surface corrosion, The formula of predication concrete beams surface stripping is set up by use of test data, which can be present in predicating concrete service.

Materials and Mix Proportion
Portland cement with P.Ⅰ52.5 is provided by Huaxin cement company in china. Jian Bi power plant in china presents silica fume Chemical Compositions of cementitious materials is listed by table 1. Lan Zhou in China put forward river sand with 2.5 fineness mode and lime stone aggregate with 19mm maximum. Drinking water. The sample size is 500mm×75mm ×100mm.

Test Procedures
Corrosion solution is Cha Er Han salt lake brine, and is measured by plasma -atomic emission spectroscopy. The wet-dry cycles are determined experimentally as follow: one wet-dry cycle is consist of firstly immersing 50 hours in lab room, then staying 2 hours at room temperature, at last heating 8 hours with manufacture at 60℃ cementitious temperature. Concrete surface peeling is measures at 90d、180d、 270d、330d、360d、480d、540d.
Concrete beams peeling content is computed with equation 1.
△W is concrete beams peeling content at specific corrosion time(g/m 2 ); GMAXis the maximum mass of concrete beams(g); Gt is the mass of concrete beams at t time; SA is concrete beams surface area(m 2 ).   As shown in Figure2(b), concrete beams surface peeling rate is more slowly with increasing of concrete compressive strengths; the earlier concrete surface begins peeling time, the concrete beams surface peeling rate is more sooner.  (2)

Results and discussion
In equation:ML t is concrete beams surface peeling content at t time (g)；hμ t is concrete beams surface peeling depths at t time (mm).

Conclusions
The surface peeling rule of concrete under wet-dry cycle environment was studied and the equation between surface peeling content and corrosion time was established, the major conclusion of this paper as follows: 1)When corrosion time is over the beginning peeling time (BPT), the concrete beam is beginning to peel off; BPT of concrete beams under corrosion environment increased with increasing of concrete compressive strengths.
2) Concrete beams surface peeling rate is more slowly with increasing of concrete compressive strengths; the earlier concrete surface begins peeling time, the concrete beams surface peeling rate is more sooner.
3) The capacity of concrete anti-stripping is increased with the increasing of concrete compressive strength. The formula of predication concrete beams surface stripping is set up by use of test data, which can be present in predicating concrete service life.