Research on the green preparation of manufactured sand by tuff produced in Gansu China and its influence on the properties of concrete

Abstract

Tuff in Gansu Province, China, is a parent rock with abundant reserves. Studying the characteristics of this parent rock and developing advanced technology for manufacturing its sand are valuable scientific endeavors. The physical and mechanical properties, chemical composition, pore structure, and lithofacies of the parent rock of tuff in the study region were examined in this study. The crushing and impact characteristics of the tuff were analyzed to propose a set of novel key processes and parameters for the production of manufactured sand from tuff in the Gansu region. Using the technology proposed in this study, tuff-manufactured sand was produced and used to prepare concrete. The effects of the tuff-manufactured sand on the flowability, hydration process, mechanical properties, pore structure, and interface transition zone (ITZ) of the concrete were systematically studied. The research results show that the SiO2 content in tuff is as high as 55.45 %, making it a neutral alkaline stone with a compressive strength of 48.0 MPa. The Bangde ball milling work index and impact work index of tuff was 9.89KW/t and 6.45, respectively. And the tuff is easy to break and more stone powder will be produced during the preparation of manufactured sand. The “two-stage crushing and three-stage screening” preparation process and key parameters for tuff-manufactured sand were proposed for the first time. Compared with traditional granite, the slump of tuff-manufactured sand concrete was reduced by 2.38 %, and the compressive strength was increased by 8.56 %. The stone powder in the tuff-manufactured sand participated in a hydration reaction before 14 h of hydration. Compared with river sand concrete, the total number of pores of tuff-manufactured sand concrete decreased by 49.18 %, ITZ split tensile strength and ITZ vulnerable point microhardness increased by 30.91 %, ITZ thickness decreased by 21.05 %, and the maximum crack width of aggregate and ITZ contact interface decreased by 0.47 μm after standard curing for 28 d.