Mechanical Properties of Concrete with Recycled Plastic Waste

Plastics are a vast group of synthetic or semi-synthetic materials that are often made of polymers. Because of their plasticity, plastics can be molded, extruded, and pressed into solid objects of different sizes. Its extensive use is due to its flexibility, as well as a number of other properties such as light weight, durability, and low manufacturing costs. The high use of plastics has resulted in an increase in solid waste, with domestic waste accounting for a significant portion of it. Since this waste is not biodegradable and takes up a lot of space, it is considered a serious environmental problem. To overcome these adverse effects, recycling plastic waste and using it in concrete can be an effective way to protect the environment. In this study, an attempt was made to experimentally evaluate the mechanical properties of concrete with recycled PET plastic wastes. The effect of this type of plastic waste was investigated by adding it in three different lengths: 22 mm, 45 mm, and a combination of both lengths 22 + 45 mm. For each length of fiber, it was added in three percentages to concrete 0.1, 0.3 and 0.5 % of cement weight. Several experiments were carried out on concrete mixtures such as slump test, compressive test, splitting tensile test, flexural test, and ultrasound pulse velocity test. The findings showed that PET waste in the form of fibers could be incorporated into concrete and achieve adequate compressive strength. When the ultrasound test results were compared to the results of previous tests, it was discovered that normal concrete containing plastic waste in the form of fibers performed exceptionally well.

Performance of Self-Healing Cementitious Composites Using Aligned Tubular Healing Fiber

From the perspective of improving the self-healing method in construction, a tubular healing fiber was adopted as a container to improve the encapsulation capacity, which was available using a micro-capsule as a container. Knowing the direction of the stresses to which structure members are subjected, this research investigated the influence of aligning tubular healing fibers parallel to intended stress into a cementitious composite to increase the self-healing capability. For that, a healing agent was encapsulated into a tubular healing fiber made with polyvinylidene of fluoride resin (PVDF). Then, the healing fiber was combined with steel fibers to align both fibers together parallel to the direction of an intended splitting tensile stress when subjected to a magnetic field in a cylindrical cementitious composite. The alignment method and the key point through which the alignment of the healing fibers could efficiently improve autonomic self-healing were investigated. Since the magnetic field is known to be able to drag steel to an expected direction, steel fibers were combined with the healing fibers to form a hybrid fiber that aligned both fibers together. The required mixture workability was investigated to avoid the sinking of the healing fibers into the mixture. The healing efficiency, according to the orientation of the healing fibers in the composite matrix, was evaluated through a permeability test and a repetitive splitting tensile test. The aligned healing fibers performed better than the randomly distributed healing fibers. However, according to the healing efficiency with aligned healing fibers, it was deduced that the observed decreasing effect of the container’s alignment on the specimen’s mechanical properties was low enough to be neglected.

Tensile Behavior of Self-Compacting Steel Fiber Reinforced Concrete Evaluated by Different Test Methods

Due to the mechanical properties related closely to the distribution of steel fibers in concrete matrix, the assessment of tensile strength of self-compacting steel fiber reinforced concrete (SFRC) is significant for the engineering application. In this paper, seven groups of self-compacting SFRC were produced with the mix proportion designed by using the steel fiber-aggregates skeleton packing test method. The hooked-end steel fibers with length of 25.1 mm, 29.8 mm and 34.8 mm were used, and the volume fraction varied from 0.4% to 1.4%. The axial tensile test of notched sectional prism specimen and the splitting tensile test of cube specimen were carried out. Results show that the axial tensile strength was higher than the splitting tensile strength for the same self-compacting SFRC, the axial tensile work and toughness was not related to the length of steel fiber. Finally, the equations for the prediction of tensile strength of self-compacting SFRC are proposed considering the fiber distribution and fiber factor, and the adaptability of splitting tensile test for self-compacting SFRC is discussed.

The Effect of Pumice Sand as Fine Aggregate on Tensile Strength of Precast Concrete

In this study, a cylinder with a size of 15 cm x 30 cm totaling 10 pieces for the splitting tensile test. 5 pieces cylinder were used for the normal splitting tensile test and the other 5 pieces cylinder were used for the joint splitting tensile test were used. Two tests have been carried out, namely the normal splitting tensile strength (control) and the joint splitting tensile strength. In testing the tensile strength of the test object, the applied tool to provide the load is the Compression Testing Machine. The splitting tensile strength test was carried out on 10 test objects in the form of concrete cylinders with an age of 28 days. 5 test objects were used in the normal splitting tensile strength (control). Meanwhile, the other 5 test objects were used in the joint splitting tensile strength. The test objects were given the load gradually until the test objects experienced cracks or reaching maximum load.

The Application of Dynamic Shock Mechanics Test in Engineering Blasting

With the continuous advancement of China's infrastructure construction to the west, according to the geographic situation in the southwest region, such as mountainous areas and complex terrain, the road construction process is inevitably accompanied by earth and rock blasting. To improve the quality and safety of the project, this paper addresses the problems of land and rock blasting faced in the construction of mountain road projects, taking the research of rock dynamic mechanics test as the starting point, and using a combination of theoretical analysis and experimental research methods. The specific research content includes the following parts: dynamic impact compression test (SHPB), dynamic splitting tensile test, and stress-strain curve analysis of the test results, which provides the theoretical basis and numerical parameters for the numerical simulation of future engineering blasting.

Mechanical behaviour and permeability of geopolymer mortars

Geopolymers may be considered as an alternative materials to Portland cement ones, providing an opportunity to exploit industrial wastes or co-products with promising short and long-term performances in the construction field, f.ex. for reparation issues. However, these materials are porous and consequently their durability depends on the risk of intrusion of aggressive agents. In order to assess their durability, we propose to investigate in this study gas permeability of sound and mechanically loaded specimens. Loading is performed using a splitting tensile test driven by a crack opening displacement up to a level of 50 microns. Tests are performed on four types of blended fly-ash (FA) and ground granulated blast furnace slag (GGBFS) geopolymer mortars, containing four different levels of GGGBF slag in the binder: 0%, 10%, 30% and 50% wt. Results show a positive effect of blending with slag in terms of modulus of elasticity and tensile and compressive strength, as well as the permeability. However, permeability recovery after cracking is the lowest when blending is the highest.

A COMPARISON OF TESTING METHODS FOR DETERMINATION OF SPRAYED CONCRETE TENSILE STRENGTH

Sprayed concrete is important construction material in tunnelling. Primary lining is essential in NATM where the sprayed concrete can be loaded by tension due to bending moments. The tension is common reason of failure because concrete has a relatively low tensile strength. The tensile strength is usually determined by splitting tensile test in laboratory. However, the results can be distorted because the specimen is not loaded by pure tension in this case. The paper compares results of concrete tensile strength determined by two methods: indirect by the splitting tensile test and direct by the modified tensile test.