Experimental Study On The Mechanical Properties Of Sea Sand Concrete Beams Under Marine Environment

The contribution of the ocean to the global economic development is undoubtedly huge.Many coastal areas and island areas are developing rapidly based on their geographical advantages.The use of sea sand nearby for mining and the use of FRP materials to replace steel in engineering construction can not only alleviate or solve the problem of local river sand resources shortage,but also fundamentally solve the problem of steel corrosion.In addition,buildings built in coastal areas and island areas,whether or not in direct contact with seawater,cannot avoid the erosion caused by the Marine environment.Therefore,the study on the mechanical properties of the basic components made of sea sand concrete or under the Marine environment can effectively predict their service life,repair and strengthen them in time to prevent more losses,its significance is self-evident.To study the basic properties of the sea sand concrete under Marine environment and its effect on the mechanical properties of structural members,with the replacement rate of sea sand,the design strength grade of concrete,the concrete mixing water,the service environment and service time,the ratio of longitudinal reinforcement,shear span ratio in change parameters,26 sets(each set of three,a total of 78)standard cube concrete specimen(hereinafter referred to as concrete test block),14 reinforced concrete beams and 18 glass fiber reinforced plastic(GFRP)reinforced concrete beams for static loading test were designed.Before the test,the slump of concrete mixture was obtained.During the test,not only the failure process,failure pattern,stress and strain curve,physical properties and mechanical properties of the concrete test block,but also the crack development situation,failure process,failure pattern,load deflection curve and characteristic point parameters of the beam specimen were obtained.And after the test,the influence of various changing parameters on the mechanical properties of the concrete test block and the concrete beam specimens were analyzed.The results show that the slump of sea sand concrete and seawater mixing concrete with water-cement ratio of 0.43 meets the requirements of plastic concrete without water reducer.After the service of Marine tidal environment,the surface color of sea sand concrete has changed significantly and be affected by Marine organisms.Mixing and curing water,replacement rate of sea sand,service time of Marine environment and Marine service environment have significant effects on the compressive strength of sea sand concrete.For sea sand concrete beams,the peak load first increases and then decreases with the increase of the Marine environment service time,and reaches the maximum value at 180 d.After service in Marine environment,the stiffness of sea sand concrete beams will decrease obviously.The peak loads of reinforced sea sand concrete beams and GFRP reinforced sea sand concrete beams have different regularities in different service environments,the former is the salt spray environment > tidal environment > inland environment,while the latter is the salt spray environment > inland environment > tidal environment.In addition,the crack width of GFRP reinforced sea sand concrete beams under the Marine environment is much larger than that of reinforced sea sand concrete beams,and the cracking load,peak load and specimen energy consumption of the former are also lower than that of the latter.However,the peak deflection and initial stiffness generally do not show regular differences caused by different reinforcements.Finally,based on the test results and the existing standard formula,the calculation formula of the bearing capacity of the sea sand concrete beam in Marine environment is obtained,which can provide reference for its engineering application.