Study On Hydration And Properties Of Cement-based Material With Fine Soil

Construction waste soil is solid waste generated during the construction of modern cities and is a type of construction waste.With the development of urban construction projects,old city reconstruction and rail transit projects,a large amount of waste soil will be generated,which will seriously restrict urban development.Current treatment methods such as backfilled,roadbed,etc.only transfer the waste soil,and the added value of the prepared product is extremely low.Although the sintering method can produce building materials,the production process has high energy consumption,large pollution,and easy generation of toxic gases.In this paper,the non-calcination method is used to grind the soil to a certain particle size and replace the cement to prepare the paste and mortar pieces.The effect of the soil on the mechanical strength and the hydration performance of the mortar are studied.The carbonization test and the dry-wet cycle test are carried out to study the effect of soil on the durability of the mortar.The main research contents and conclusions are as follows.?1?The soil with different ground time was added to the cement to prepare the mortar.The content of the soil was 5%-20%.The fluidity of the mortar was tested during the preparation.The mechanical strength was tested after curing for 3d,7d and 28d.The study found that increasing the amount of soil and prolonging the ground time will reduce the fluidity of the slag,and increasing the amount of soil will reduce the flexural and compressive strength to different degrees.However,when the dosage is below 15%,the prolonged ground time will increase the early flexural and compressive strength.When the amount of soil is 20%or cured for 28d,the grinding time of soil will not increase the strength significantly.?2?The effects of soil on cement hydration performance were studied by using three different ground time,the amount of soil is 10%and 20%.It is found that the hydration heat and heat flow release after the soil mixed in.And the samples with ground soil is higher than the samples with the non-ground soil.The hydration products are mainly AFt and Ca?OH?₂.After mixed with the ground soil,more Ca?OH?₂ is formed due to the promotion of cement hydration reaction.And a large amount of long fiber products are formed in the hydration of the cement with soil.?3?The effects of soil on the durability of the mortar specimens were studied by exposing the mortar specimens mixed with different soil to high concentration?20±3%?CO₂ and sulfate dry and wet circulation.It has been found that the increase in the amount of soil will increase the depth of carbonation to some extent.During the dry-wet cycle,the weight of the mortar rises fastest during the first ten dry-wet cycles,and this process also makes the samples structure denser.After dry-wet cycle for 50 times,the flexural and compressive strength of the specimens mixed with 10%non-ground soil and ground for 1 min were higher than those of the standard curing specimens,and samples with 20%soil have lower flexural strength and higher compressive strength than the standard specimens.Under the microscopic morphology,it is observed that in the case of sulfate attack,the calcium content of the hydration product in some areas will be lost and form the skeleton of the hydration products.