Research on and Model Analysis of Flexural Mechanical Properties of Basic Magnesium Sulfate Cement Concrete Beams

Abstract

This study presents a comprehensive investigation into the mechanical properties of Basic Magnesium Sulfate Cement Concrete (BMSC) in comparison to Ordinary Portland Cement Concrete (OPC) within reinforced concrete components. The main objective is to evaluate BMSC's applicability for practical engineering purposes, with a focus on its with early high strength, improved toughness, and superior crack resistance compared to conventional concrete. Experimental procedures involved fabricating beam specimens using OPC concrete with a C40 strength grade, alongside BMSC beams with varying strength grades (C30, C40, and C50). These specimens underwent bending resistance tests to analyze crack patterns and mechanical characteristics. The findings reveal that BMSC beams demonstrate enhanced bending and tensile properties at equivalent strength grades compared to OPC beams. Particularly, cracking mainly occurred at the mid-span region of BMSC beams, characterized by narrower cracks, indicating superior crack resistance. However, it was noted that the toughness of BMSC beams decreases as the strength grade increases. The maximum mid-span deflection of the BMSC test beam was smaller than that of the OPC test beam, which was 3.8 mm and 2.6 mm, respectively. The maximum crack width of the OPC beam was 4.7 times that of the BMSC beam. To facilitate practical implementation, the study developed calculation models for estimating the crack bending distance and ultimate bending distance in BMSC beams, offering valuable tools for engineering design and optimization. Overall, this research provides significant insights into the mechanical behavior of BMSC, presenting potential advantages for structural engineering applications.

Keywords: Basic Magnesium Sulfate Cement Concrete (BMSC); Ordinary Portland Cement Concrete (OPC); beam; cracking moment; ultimate bending moment.

Figure 1

Details of beam size and section reinforcement. (a) L = 1500, b × h = 120 mm × 200 mm. (b) L = 2300 mm, b × h = 150 mm × 200 mm.

Figure 2

Size distribution curve of magnesium oxide.

Figure 3

Beam making and maintenance. (a) Grinding before attaching strain gauges to beam reinforcement. (b) Attaching strain gauges to beam reinforcement. (c) Pouring the beam.

Figure 3

Beam making and maintenance. (a) Grinding before attaching strain gauges to beam reinforcement. (b) Attaching strain gauges to beam reinforcement. (c) Pouring the beam.

Figure 4

The schematic diagram of the normal section bending loading device. (a) L = 1500 mm. (b) L = 2300 mm.

Figure 4

The schematic diagram of the normal section bending loading device. (a) L = 1500 mm. (b) L = 2300 mm.

Figure 5

Beam failure mode and three-sided crack expansion diagram. (a) PC40; (b) JM40; (c) JM40a; (d) JM50.

Figure 5

Beam failure mode and three-sided crack expansion diagram. (a) PC40; (b) JM40; (c) JM40a; (d) JM50.

Figure 6

Strain of measuring points at different heights of mid-span section of the beam. (a) OPC; (b) BMSC.

Figure 7

Relative bending distance-deflection curves of Portland Cement concrete beams and BMSC concrete beams.

Figure 8

Deflection-length curve of the beam. (a) PC40; (b) JM40.

Figure 9

Load-strain curve of steel bar in flexural reinforced concrete beams under longitudinal tension. (a) OPC; (b) BMSC.

Figure 10

The relationship between the crack width and the number of cracks and the load of reinforced concrete beams.