Research On Basic Performance Of Engineering Sand For Strategic Resource

Cement-based materials are the most widely used artificial building materials in the world,and sand is an important component of cement-based materials.With the extensive use of cement-based materials,the available high-quality sand resources are decreasing.In order to rationally develop and utilize resources and improve social and economic benefits,the influence of sand fineness on the performance of cement-based materials was studied to see whether the strategic resources of engineering sand(fine sand and extra fine sand)were suitable for practical projects.Four kinds of sand of different fineness modulus within the scope of the GB provisions,coarse sand(3.5),medium sand(2.8),fine sand(2.0)and extra fine sand(1.4),were selected for the study.And two water-cement ratios(0.35 and 0.50)were adopted.The effects of different sands on the performance of cement mortar were studied by flexural strength test,compressive strength test,elastic modulus test,consistency test,drying shrinkage test,ring test,stress concentration test and microstructure under electron microscope.The main contents and conclusions were as follows:(1)Through the compression test,flexural test and mortar consistency test of cement mortar,it was found that fine sand and extra fine sand basically met the requirement of strength of masonry mortar,and the consistency met the requirements of practical engineering.(2)Under the electron microscope,the interface between cement and sand was the least obvious for medium sand(MS)samples,followed by coarse sand(CS)and fine sand(FS),followed by extra fine Sand(ES).(3)Under the same water-cement ratio,the shrinkage of the cement mortar was in the order of ME(Mortar mixed with extra fine sand group)> MF(Mortar mixed with fine sand group)> MC(Mortar mixed with coarse sand group)> MM(Mortar mixed with medium sand group).The cement mortar shrinkage decreased with the increase of the sand fineness,and then decreased.Compared to strategic resources engineering sand,the cement mortar shrinkage showed a reduction of about20% by using medium sand.(4)Under the same water-cement ratio,the order of cracking was ME,MF,MC,MM.The limiting stress of M1-M group,M1-F group,M1-E group and M1-Fgroup was 5.8 MPa,4.8 MPa,5.2 MPa and 5.1 MPa,respectively,under the condition of water-cement ratio of 0.50.(5)The results of stress concentration test and traditional ring test to evaluate the shrinkage and crack performance of strategic resource sand showed that the stress concentration test could accurately evaluate the shrinkage and crack performance of cement mortar,and had a basically fixed crack location,short cracking time,high sensitivity,short contraction cracking cycle,low test specimen forming difficulty,and simple operation.Many parts of the world,such as the desert,were lack of coarse sand and sand resources and had only fine sand and superfine sand available.The search for fine sand and superfine sand found in the literature was very limited and the literature was relatively simple.In this paper,a systematic and comparative experimental study on coarse sand,medium sand,fine sand and ultra-fine sand was carried out,which could provide practical examples and references to those cement mortar and cement concrete mix designs with only fine sand or superfine sand.