Preparation and Properties of Masonry Mortar from Spontaneous Combustion Coal Gangue

To solve the problem of gangue stockpiling, this paper intends to study the feasibility of preparing masonry mortar based on spontaneous combustion gangue. After crushing the spontaneous combustion gangue, the gangue below 4.75 mm was selected, and substituted manufactured sand to prepare masonry mortar in equal quantity. The single factor test method was used to select the replacement rate of spontaneous combustion gangue, water-binder ratio (W/B) and water reducer dosage as variables to explore their effects on the basic properties of fresh mortar mixtures, such as fluidity, apparent density and water retention of fresh mortar, and the mechanical properties of hardened mortar. The anti-frost resistance of gangue mortar was evaluated by a freezing-thawing cycle test. SPSS.20 software was used for variance analysis, and the results showed that the replacement rate of spontaneous combustion gangue, W/B and water reducer dosage on mechanical properties of mortar differences are significant (P < 0.001). With the increase of the replacement rate of spontaneous combustion gangue, the mortar strength decreases, and with the rise of W/B, the mortar strength raises first and then reduces, while with the increase of the water reducer dosage, the mortar strength increases first and then decreases. Spontaneous combustion gangue mortar shows better anti-frost resistance under the freezing-thawing cycle. After 50 freezing-thawing cycles, the maximum mass and strength loss rate of mortar specimens are 2.4 % and 12.67 %, respectively. When the replacement rate of spontaneous combustion coal gangue is 100 %, the mechanical properties and anti-frost resistance of mortar both meet the requirements of the standard and realize the maximum utilization of gangue waste resources. This paper aims to provide theoretical support for the application of spontaneous combustion gangue in masonry mortar.