Preparation, Performance Test, and Microstructure of Composite Modified Reinforced Concrete

Shi Hu,Ying Xu

doi:10.1155/2020/5732018

Abstract

To investigate whether the compound modification means which mixes modified Polyvinyl chloride (PVC) aggregate and polypropylene fiber in concrete could gain “positive hybrid effect” and cope with more sophisticated engineering circumstances, four groups of test specimens were prepared: concrete doped with unmodified PVC aggregate, concrete doped with modified PVC aggregate, concrete doped with unmodified PVC aggregate and polypropylene fiber, and concrete doped with modified PVC aggregate and polypropylene fiber. The fiber content is 0.9 kg/m3, the modified solution content is 1 mol/L NaOH, and the replacement amount of PVC fine aggregate in replacement sand is 0%, 5%, 10%, 20%, and 30%. Mechanical property and durability tests were carried out to compare and analyze the measured compressive strength, splitting tensile strength, flexural tensile strength, water absorption rate, and impact failure energy. Moreover, scanning electron microscopy and XRD diffraction were used to analyze micromorphology and crystal structure of concrete. The test results demonstrate that as the content of PVC aggregate increases, the compressive strength, splitting tensile strength, and flexural tensile strength of the concrete decrease significantly, while the brittleness is improved. Meanwhile, the water absorption rate increases and the impact resistance shows an approximately linear increase trend. Under the same content of PVC aggregate, the most effective way to improve compressive strength is to use modified PVC aggregate. The rapid decrease of compressive strength caused by PVC aggregate can be effectively delayed by doping polypropylene fiber and modified PVC aggregate. Adding polypropylene fiber or using the modified PVC aggregate can improve the brittleness, tensile strength, flexural tensile strength, and impact resistance, but they have different modification and reinforcement effects. The concrete prepared by doping polypropylene fiber and modified PVC aggregate has better performance in tensile strength, flexural tensile strength, brittleness, and impact resistance, and the water absorption and the compressive strength of the concrete are enhanced compared with the normal group. Therefore, composite modified reinforced concrete doped with modified PVC aggregate-polypropylene fiber has broad application prospects.

Highlights

In the past one century since the invention of Portland cement in 1824, concrete is the most commonly used construction material
It has the disadvantages of heavy dead weight, low tensile and flexural tensile strength, large internal pores, and poor impact resistance. e existing studies of concrete mainly focus on enhancing the comprehensive properties of green and highperformance concrete, such as durability, high strength, and high workability, rather than a single property [1]
By comprehensively analyzing the study results, we found that the strength of plastic modified concrete decreased significantly and the water absorption increased because of the sidewall effect in the interfacial transition zone between cement and plastic aggregate and poor bonding effect [3,4,5,6,7,8,9,10]. erefore, experiments should be carried out to examine whether the modification method of replacing sand in concrete with recycled Polyvinyl chloride (PVC) particles with a particle size of about 1 mm can cause similar changes in strength, brittleness, and impact resistance

Summary

Introduction

In the past one century since the invention of Portland cement in 1824, concrete is the most commonly used construction material. Mohammed et al [11] used PVC fine aggregate crushed twice and added silica fume as concrete reinforcement material, finding that PVC particles and cement paste were well bonded; Yang et al [29] studied the preparation of high-performance concrete by mixing polyvinyl alcohol fiber, imitation steel fiber, and expansion agent, thereby improving the strength, crack resistance and impermeability of concrete. Erefore, this study used the triple modification and reinforcement technique of PVC particles modified with NaOH and polypropylene fibers to improve the impact resistance of concrete, so that the rapid decrease of strength and the increase of water absorption caused by PVC aggregate can be delayed. Various properties and microstructures of composite modified reinforced concrete were studied by carrying out cube compression test, split tensile test, flexural test, water absorption test, steel wheel wear test, drop hammer impact test, and SEM and XRD tests, expecting to provide reference for mechanism study and engineering application of modified PVC aggregate-polypropylene fiber composite modified reinforced concrete

Test Part

Test Instruments and Methods

Results and Discussion