Study On The Early Hydration Performance Of Cement-Glass Powder Composite Cementitious Materials

With the development of the society,the researchers gradually realize that the rapid rise in industrial technology brings convenience to human life.At the same time,it also brings a large number of harmful industrial derivatives,such as fly ash,waste glass,slag,radioactive substances and so on.Random piling and landfill of these will lead to environmental pollution,reducing available land and endangering human health.If appropriate measures are taken,these waste resources can also be turned into treasure,so as to realize the recycling of resources and implement the concept of sustainable development.Concrete,as a traditional building material,is widely used in China.Concrete is indispensable for house,road and Bridge constructions.Cement mortar,as a cementing material,plays a crucial role in concrete performance.Many scholars try to replace partial cement by using cheap materials or recyclable materials,so as to protect the environment,save costs and reuse resources on the premise of ensuring the corresponding performance of concrete.The tests chose the conventional P.O 42.5 Portland cement as a base material(the specific surface area is 357m~2/g).Three kinds of waste glass powder were selected,in which the fineness of A(the specific surface area is 240m~2/g),the fineness of B(the specific surface area is 380m~2/g)and the fineness of C(the specific surface area is705m~2/g).Cement and glass powder composite was used for the performance analysis.The experiment chose four ages of 3 d,7 d,14 d and 28 d to study the early performance of cement and glass powder composite cement materials.According to the mixing ratio,8 sets of test blocks were prepared.Each set has 3 samples,divided into 4 ages,leading to a total of 96 samples.We conducted comparative analysis,and obtained a series of results of standard consistency water consumption,initial and final setting time,strength,chemically bound water,hydration heat,nitrogen adsorption,SEM electron microscopy,and XRD analysis.The test results show that:(1)After the addition of glass powder B close to the fineness of cement,the water consumption of the standard consistency of each group of composite cementing materials was compared,and it was found that with the increase of the glass powder content,the water consumption also decreased,indicating that the glass powder only played a physical filling role in the early stage;(2)After replacing part of cement with glass powder of equal quality,the initial and final setting time of composite cementitious materials is related to the content of glass powder.The higher the content is,the longer the initial and final setting time is.The fineness of glass powder has no obvious influence on the initial and final setting time;(3)When glass powder is added,the compressive strength and flexural strength of cement-glass powder composite cementitious material obtained have obvious changes with the content,fineness and water-glue ratio of glass powder.The glass powder group was added into the comparison,When glass powder No.B is added,the content is 10%and the water-glue ratio is 0.4,the mechanical properties were the bettert;(4)Glass powder was added to slow down the early hydration rate of the cementitious material.The content of chemical binding water in the early stage was less,and the heat of hydration in the early stage was also reduced;(5)The pore size distribution of cement-glass powder composite cementitious material has little influence on the content,fineness and water-cement ratio of glass powder.The maximum pore size is about 12nm.For comparison,glass powder groups were added,and The lowest cumulative porosity was found in group B glass powder with 10%admixture and 0.4 water-gel ratio;(6)Through SEM electron microscope scanning,hydration products of glass powder and cement will fill the pores,making the structure dense.In early 3d images,many unhydrated cement particles and glass powder particles can be found;At the age of 28d,it can be seen that most of the pores are filled by hydration products;(7)In the XRD of the composite cementing materials with different proportions in each group,it can be seen that the most hydration products are calcium hydroxide,and the"secondary hydration reaction"occurs between glass powder and calcium hydroxide to generate c-h-s gel to fill the pores.