# Research on the Mechanical Properties and Modification Mechanisms of Orthogonal Optimization Composite Cement-Based Thin Spray On-Liner

## TL;DR

This paper improves thin spray on-liner for coal mines by combining cement with acrylic emulsion, basalt fiber, and rubber powder to enhance strength and flexibility.

## Contribution

A novel composite cement-based thin spray on-liner with optimized mechanical properties and modification mechanisms is developed.

## Key findings

- The optimal composite TSL has a polymer–cement ratio of 1.75, 1% basalt fiber, and 3% rubber powder.
- The composite modification increases elongation to 121%, tensile strength to 2.28 MPa, and adhesive strength to 1.66 MPa.
- Acrylic emulsion, basalt fiber, and rubber powder together improve compactness, crack resistance, and elongation.

## Abstract

Thin spray on-liner (TSL) is a new type of rock support technology, but ordinary cement-based TSL has low tensile strength and poor toughness, which makes it difficult to meet the challenges of large deformation of coal mine roadway perimeter rock surface maintenance. A high-performance composite cement-based TSL was obtained by adding acrylic emulsion, basalt fiber and rubber powder to modify ordinary Portland cement. The orthogonal test and range analysis method were used to systematically study the change law of the physical and mechanical properties of the composite cement-based TSL, determine its reasonable ratio, and further microscopic analysis to find out the modification mechanism. The results show that the reasonable ratio of composite cement-based TSL is as follows: polymer–cement ratio is 1.75, basalt fiber content is 1%, and rubber powder content is 3%; that is, the viscosity is 20,000 mps, and the elongation, tensile strength and adhesive strength in 28 d are 121%, 2.28 Mpa, and 1.66 Mpa, respectively. When the acrylic emulsion-basalt fiber-rubber powder is compositely modified, the acrylic emulsion cures and the cement hydration product to form a three-dimensional space network structure, which increases the compactness, the basalt fiber reduces the porosity of the matrix, inhibits the development of matrix cracks, and the rubber powder improves the elongation of the matrix and jointly improves the mechanical properties of TSL. This study provides a theoretical basis for the preparation of composite cement-based TSL.