The Feasibility Study On Application Of Slag Mixed Sand In Masonry Mortar

With the trend of Chinese economy growing steadily and economic development entering a new normal state,the construction industry is still an important pillar of the vigorous development of the national economy and enriching the industry.The increasing demands for concrete,mortar and other building materials have brought serious challenges to the supply of sand and stone,especially the production of natural river sand being difficult to meet the needs of building materials market.With the continuous exploitation of the river sand,river sand resources are increasingly exhausted,while the quality of river sand is also worse than before,which results in the supplies and demands contradiction for building sand increasingly prominent.Therefore,the study of new sand source and qualified fine aggregate has become a new trend in the development of building materials.At the same time,the increasing amount of municipal solid waste is poor,which will cause serious harm to the surrounding ecological environment.Waste incineration is an important way for garbage utilization,but the remaining 10%to 20%of the slag still needs to be effectively treated.So the special pretreated waste incineration slag and natural river sand is mixed into slag mixed sand as fine aggregate used in masonry mortar,which not only can solve the problem of garbage and its slag treatment after incineration,turning waste into treasure,reducing environmental pressure,but can also alleviate the shortage status of natural river sand resources,and be described as two birds with one fell swoop.In this paper,two kinds of incineration slag(Longhai,Xiamen),three different mixing ratios(5:5,6:4,7:3)of the slag mixed sand were prepared to make masonry mortar with seven strength grades from M5 to M30 with the workability and strength as examination index.Moreover,this paper studies the feasibility of preparing masonry mortar by using slag mixed sand from technical,economic and environmental aspects.The main results and conclusions are as follows:(1)Due to the differences in the incineration process,the differences in the physical and chemical properties of the waste slag from different sources lead to the different properties of the prepared slag mixed sand,which have certain effects on the results of the preparation of masonry mortar.So that the two kinds of slag mixed sand masonry mortar's workability,mechanical properties,volume stability,etc.are different.Although the two kinds of mixed sand grain gradation are in the ? area,but both the apparent density,bulk density and fineness modulus,Longhai slag mixed sand is smaller than Xiamen mixed sand.In addition,light material,mud content,SO3,Cl-and other harmful ingredients,Longhai slag mixed sand has higher detection results.(2)The grade ranges of masonry mortar by using different sources and proportions of mixed sand to prepare are different.The slag mixed sand from Longhai could be prepared M5,M7.5,M10,M15 four strength grades masonry mortar with the workability and mechanical properties qualified when the ratio is 5:5;the ratio of 6:4 can only be prepared M5,M7.5 masonry mortar.And the slag mixed sand in Xiamen could be prepared a total of seven strength grades masonry mortar from M5 to M3 0 with the qualified workability and strength when the ratio is 5:5.The ratio of 6:4 can be prepared to a total of five-strength grades masonry mortar from M5 to M20.The ratio of 7:3 can only be prepared to the M5,M7.5 masonry mortar.The results show that the mixing proportion of slag mixed sand and the source of slag have a great impact on the performance of masonry mortar.In comparison,Xiamen mixed sand is suitable for the preparation of all grades of masonry mortar from M5 to M30,Longhai mixed sand could be prepared to make masonry mortar below M20 grade.(3)Compared with the river sand,the performance of the two kinds of slag mixed sand is not as good as the former,like the fineness modulus,the apparent density,the bulk density being lower and the porosity being higher than that of the river sand.Therefore,the kinds of masonry mortar are different in performance.Compared with the mortar prepared by river sand,the apparent density of the mortar prepared by the mixed sand is smaller and the water absorption is higher,but the workability and volumetric stability are generally better than the river sand mortar.In addition,the higher the slag substitution rate,the better the water retention rate and the cohesion of the mixed sand mortar,but the intensity will have negative influence.(4)The chemical composition and mineral composition of the two kinds of slag were analyzed by electron probe and X-ray diffractometer.By using image processing techniques,the grain-forming characteristics of slag mixed sand were analyzed from two perspectives:angularity and morphology.The internal pore structure of masonry mortar was analyzed used the method of water absorption and internal image analysis.From the physical and chemical level,the mechanism of the slag mixed sand in masonry mortar is studied and analyzed.(5)From the aspect of technique,the two kinds of slag mixed sand are successfully prepared certain strength grade masonry mortar,can replace the natural river sand for masonry mortar.From the mortar raw material preparation cost analysis,the application of slag in masonry mortar can fully reflect the low price of mixed sand.From the perspective of environmental protection,slag mixed sand instead of natural river sand as fine aggregate not only won't harm the environment,but also be conducive to the use of waste resources,environmental protection and saving resources.Therefore,it is considered that slag mixed sand is feasible as the alternative material of river sand to make masonry mortar.