Influences of MgO and PVA Fiber on the Abrasion and Cracking Resistance, Pore Structure and Fractal Features of Hydraulic Concrete

Abstract

Abrasion resistance and cracking resistance are two important properties determining the normal operation and reliability of hydropower projects that are subjected to erosion and abrasive action. In this study, polyvinyl alcohol (abbreviated as PVA) fiber and magnesium oxide expansive agents (abbreviated as MgO) were used together to solve the problems of cracking and abrasive damage. The effects of PVA fiber and MgO on the mechanical property, abrasion and cracking resistance, pore structures and fractal features of high-strength hydraulic concrete were investigated. The main results are: (1) The incorporation of 4–8% Type I MgO reduced the compressive strength, splitting tensile strength and the abrasion resistance by about 5–12% at 3, 28 and 180 days. Adding 1.2–2.4 kg/m3 PVA fibers raised the splitting tensile strength of concrete by about 8.5–15.7% and slightly enhanced the compressive strength and abrasion resistance of concrete. (2) The incorporation of 4–8% Type I MgO prolongs the initial cracking time of concrete rings under drying by about 6.5–11.4 h, increased the cracking tensile stress by about 6–11% and lowered the cracking temperature by 2.3–4.5 °C during the cooling down stage. Adding 1.2–2.4 kg/m3 PVA fibers was more efficient than adding 4–8% MgO in enhancing the cracking resistance to drying and temperature decline. (3) Although adding 4% MgO and 1.2–2.4 kg/m3 PVA fibers together could not enhance the compressive strength and abrasion resistance, it could clearly prolong the cracking time, noticeably increase the tensile stress and greatly lower the racking temperature; that is, it efficiently improved the cracking resistance to drying and thermal shrinkage compared with the addition of MgO or PVA fiber alone. The utilization of a high dosage of Type I MgO of less than 8% and PVA fiber of no more than 2.4 kg/m3 together is a practical technique to enhance the cracking resistance of hydraulic mass concretes, which are easy to crack. (4) The inclusion of MgO refined the pores, whereas the PVA fiber incorporation marginally coarsened the pores. The compressive strength and the abrasion resistance of hydraulic concretes incorporated with MgO and/or PVA fiber are not correlated with the pore structure parameters and the pore surface fractal dimensions.

Effect of Municipal Solid Waste Slag on the Durability of Cementitious Composites in Terms of Resistance to Freeze–Thaw Cycling

“…According to the work of Wang et al, the addition of polyvinyl alcohol fibers PVA at 1.2–2.4 kg/m 3 combined with expansive MgO can significantly improve the splitting and compressive strength of the cement composite. The addition of MgO, which reacts with water to form magnesium hydroxide, counteracts shrinkage during drying, further enhancing the effect of PVA fibers [ 46 , 47 , 48 ]. Importantly, all samples containing slag and subjected to the frost resistance test achieved higher abrasion resistance.…”

Mechanical Properties and Durability of Geopolymer Recycled Aggregate Concrete: A Review

“…Abrasion resistance is mainly determined by weight loss. Wang et al [ 104 ] found that the addition of PVA fibers could improve the abrasion resistance of the concrete. The same effect was observed for NS, although only a slight effect was observed at 1% and 2% dosing.…”

Evaluating the Influence of Carbon Fiber on the Mechanical Characteristics and Electrical Conductivity of Roller-Compacted Concrete Containing Waste Ceramic Aggregates Exposed to Freeze-Thaw Cycling

“…Te carbon fber (CF) has been used extensively in concrete building projects to enhance its mechanical properties [10,11]. According to [12], steel, asbestos, glass, metallic glass ribbons, polymeric, carbon, natural fbers, and textile reinforcements were employed to reinforce the cement matrix [13,14]. Carbon fbers have specifc advantages over other types of fbers utilized in cement-based composites [12].…”