The Influence of Fiber Dispersion on the Properties of MgO Concrete and Engineering Applications

Adding expansion agents to compensate for concrete shrinkage is a common crack resistance technique, but excessive expansion can also increase the porosity of concrete and reduce its strength. The addition of fibers can reduce expansion and improve the compactness of concrete. However, too little fiber will not be effective in inhibition, while too much fiber will cause aggregation. In this study, steel fiber and MgO expansive agent were used at the same time, and the effect of fiber on the mechanical properties of MgO concrete was studied. The results showed that the appropriate amount of MgO (8%) could compensate for the shrinkage of concrete and slightly improve the strength of concrete. When the content reached 10%, MgO produced excessive expansion under free conditions, which reduced the strength of the concrete. After using MgO and steel fiber at the same time, steel fiber could restrain the expansion of MgO, improve the compactness of concrete, produce a "super superposition" benefit, and increase the strength of concrete by 20%. In addition, the reinforcing effect of steel fiber on MgO was closely related to its distribution. In the composite system, steel fiber not only played a "bridge role" but also needed steel fiber to effectively restrain the expansion of MgO and produce self-stress. Only when the steel fibers were evenly distributed could reliable bonding be ensured between the fibers and the matrix, and at this time, the fibers could restrain the expansion of MgO. Considering the uniformity of steel fiber distribution and construction cost, adding 8% MgO and 1% steel fiber has the maximum benefit.