Preparation And Performance Research Of Pervious Concrete Based On Rheological Properties Of Cement Paste And Aggregate Characteristics

Pervious concrete is the key technical element for constructing sponge city.In the perspective of cementitious materials,paste with low viscosity and yield stress will block the bottom voids of pervious concrete,and paste with high viscosity and yield stress paste may cause uneven distribution of paste on the surface of the aggregate in pervious concrete.Both of these situations will lead mechanical properties and water permeability performance of pervious concrete can not meet the expectations,which will directly affect the construction efficiency of sponge city.In the perspective of aggregate,different types of aggregate have different properties,and different size of aggregate has different specific surface area,Both of these situations will affect the bond performance of aggregate and paste.In the perspective of interface,the mechanical properties of aggregate paste interface transition zone affect the mechanical properties of pervious concrete.These three factors affect the structure and performance of pervious concrete.In order to realize the reasonable design of pervious concrete,the matching relationship between cement paste with different rheological properties and aggregates with different types and geometric characteristics was studied in this paper,which provides theoretical basis for the design and preparation of pervious concrete with different aggregates.Firstly,the influence of water binder ratio and water reducing agent content on the rheological properties and compressive strength of the paste was analyzed,and the paste distribution on the aggregate surface was intuitively analyzed.Then the coating thickness of a grain of aggregate sample was analyzed by using the ultra-depth three-dimensional microscope,and the interface structure of aggregate-paste was analyzed by nanoindentation.The interfacial bonding performance between paste and aggregate was characterized by interfacial mechanical properties.The influence of aggregate type and particle size on the paste adhesion rate,coating thickness and interface structure was analyzed respectively.According to the influence of paste and aggregate on binary materials,four groups of paste mix proportion were selected.Finally,according to the technical specification,twelve groups of pervious concrete mix proportion were designed,and mechanical properties,water permeability and void structure were tested.Moreover,through the analysis of the spatial distribution of voids by CT scanning technology,the rationality of the paste selected was explained.Then the influence of paste rheological properties and aggregate characteristics on mechanical properties,water permeability and spatial distribution of voids was obtained.