Reference Concrete Specimens Research Articles

Eco-friendly concrete with waste glass powder: A sustainable and circular solution

Waste glass is a significant concern in India, and management solutions seek. Finely ground waste glass (GP) presents pozzolanic properties, which make it potential for concrete applications as cement replacement. The main feature of the present work lies in the simultaneous incorporation of two GPs with different fineness, generated from consumer scrap in India, as cement replacement in equal proportions, from 0 to 40 %, in two concrete grades, M30 and M40. An experimental programme was carried out, including fresh, shrinkage, mechanical and durability properties. GP concrete specimens showed compressive strength and a slight improvement for both concrete grades compared to reference concrete specimens (0 % GP incorporation). The durability indicators, namely, water absorption, sorption, chloride-ion penetration and moisture movement in GP concrete, improved with the increase of GP content. The drying shrinkage increased with the rise in GP content; however, the results still fit the permissible standard limits. Optimal concrete mixtures were selected to further study GP incorporation in concrete paver blocks. Four concrete paver block types were produced, including M30 and M40 with no GP (0 %GP) and M30 and M40 with 30 % GP as cement replacement (15 % GP1 + 15 % GP2). The compressive strength of the concrete paver blocks with GP significantly improved. Thus, the concrete with 30 % partial cement replacement by GP is a potential option for the construction industry while providing a management waste solution and contributing to a circular economy.

Behavior of strengthened Timber Concrete Composite under axial loads

The research study focuses on different strengthening techniques for timber concrete composites (TCC) using different types of wire and wire mesh integrated with a layer of epoxy on a timber core embedded in concrete using experimental and analytical procedure. The impact of TCC on axial compression performance, modulus of elasticity, failure mode and post failure behavior and ductility were compared to reference concrete specimens. Different types of wire and wire mesh used in strengthening of the timber core, timber core size and reinforcement in the concrete cylinder were all parameters considered in this study. Timing of application of the epoxy on the wire strengthened timber core was very important. For structural applications, where the weight reduction and ductility as well as post failure endurance are essential, the development of this composite is recommended. The ratio of the ductility index to the weight is discussed. The light weight of the timber composite, and the increased ductility were noted in this study. An equation to estimate the axial compression capacity of the strengthened timber concrete composite was developed in this study. This study will pave the way for further applications for timber concrete composite aiming at reducing dead weight of concrete and the reducing the amount of concrete and steel in construction.

Experimental Study on the Tensile Properties of Short-cut Basalt Fiber Concrete

Improving the tensile, flexural, and shear strength of concrete is always the focus of research because the poor tensile property of concrete is relatively poor. Base on the mechanical performance test of short-cut basalt fiber concrete, the influence of fiber content and fiber length on split tensile strength, flexural strength, and shear strength of basalt fiber concrete were discussed in this paper. With the increase of short-cut basalt fiber content, the split tensile strength and flexural strength were respectively increased by 13.3% and 16.9%, but the shear strength of basalt fiber concrete specimens was lower than reference concrete specimens. With the same fiber content, the monofilament length of short-cut basalt fiber was increased, the shear strength recovered to the level of reference concrete. When the fiber content was 0.1% and the length of the fiber concrete specimens was 12mm, the split tensile strength of the fiber concrete specimen was 13.3% higher than that of the reference concrete specimens. According to the test results, increasing the content and length of fibers could effectively improve the tensile properties of concrete materials.

Mechanical Performance of High-Strength Sustainable Concrete under Fire Incorporating Locally Available Volcanic Ash in Central Harrat Rahat, Saudi Arabia.

This study investigated the effect of elevated temperatures on the mechanical properties of high-strength sustainable concrete incorporating volcanic ash (VA). For comparison, control and reference concrete specimens with fly ash (FA) were also cast along with additional specimens of VA and FA containing electric arc furnace slag (EAFS). Before thermal exposure, initial tests were performed to evaluate the mechanical properties (compressive strength, tensile strength, and elastic modulus) of cylindrical concrete specimens with aging. Additionally, 91 day moist-cured concrete specimens, after measuring their initial weight and ultrasonic pulse velocity (UPV), were exposed up to 800 °C and cooled to air temperature. Subsequently, the weight loss, residual UPV, and mechanical properties of concrete were measured with respect to exposure temperature. For all concrete specimens, test results demonstrated a higher loss of weight, UPV, and other mechanical properties under exposure to higher elevated temperature. Moreover, all the results of concrete specimens incorporating VA were observed before and after exposure to elevated temperature as either comparable to or slightly better than those of control and reference concrete with FA. According to the experimental results, a correlation was developed between residual UPV and residual compressive strength (RCS), which can be used to assess the RCS of fire-damaged concrete (up to 800 °C) incorporating VA and EAFS.

Some properties of green concrete with glass and plastic wastes

This study focusses on the flexural strength, flexural toughness, thermal conductivity, and failure modes under flexural for concrete containing 15% glass powder waste as partial replacement of cement by weight and 25, 50, 75, 100% plastic waste as volumetric replacement of natural coarse aggregate at 60 days.The results show an increase in flexural strength and thermal conductivity when 15% glass powder waste was used, while there is a significant decrease with the use of plastic waste relative to reference specimens (without wastes). It can be observed a significant increase in total flexural energy when the content of plastic waste coarse aggregate is increased.The incorporation of plastic waste aggregate in concrete with 15% glass powder changes the failure behavior of concrete specimens from a brittle to a more ductile failure. The failure in reference concrete specimens without coarse plastic waste aggregate occurs in matrix, through coarse aggregate, and around the aggregates in interfacial transition zone (ITZ). On the other hand, in concrete containing HDPE (high density polyethylene) plastic waste aggregate with 15% glass powder, the failure occurs mainly around plastic particles.

A Study of the Impact Resistance of Rubber Concrete at Low Temperatures (−30°C)

In the present study, the impact resistance of rubber concrete at low temperatures (−30°C) was examined. The initial and ultimate crack impact times and the ductility indexes were evaluated. This study’s specimens were prepared by adding two different sizes of rubber particles (20 mesh and 50 mesh) in different ratios (0%, 5%, 10%, 15%, and 20%) at both 25°C and −30°C. The concrete specimens were evaluated using a drop hammer weight test method. The results showed that the initial and ultimate crack impact times and ductility indexes of the rubber concrete specimens had decreased at −30°C. Also, the decrease amplitudes were determined to be lower than those of the reference concrete specimens. Consideration was given in this study to the large variations in the impact values, and a two‐parameter Weibull distribution method was adopted in order to analyze the obtained experimental data. The results had demonstrated that the impact times of the rubber concrete specimens could be described using the two‐parameter Weibull distribution method results.

Assessment the thermal properties lightweight concreteproduced by using local industrial waste materials

In this research study of the thermal properties of light weight concrete produced from using two locally industrial wastes materials, to evaluate the thermal insulation, and some physical properties like strength of concrete (compressive and flexural tensile strength and variation of density of light weight concrete. Two types of wastes admixtures were used in this study, (chopped rubber, and wood sawdust) with (5%, 10%, 15% and 20%) percent of each one. Thermal conductivity, compressive strength, flexural tensile strength and variation of density have been examined for each specimen at all percentages of admixtures, and compare with the reference concrete specimens. Experimental test results indicated that using these types of wastes as replacement of fine aggregate in concrete significantly affects the thermal conductivity, compressive strength, flexural tensile strength (rise or fall out), especially at (5%) of adding materials, as well as utilization of additives in concrete to produce low density mixture with wood sawdust or as high density concrete when using rubber chopped in the concrete mixture.

Mechanical Properties of Fiberous High Performance Lightweight Aggregate Concrete

Structural lightweight aggregate concrete solves weight and durability problems in buildings and structures. Recent advanced in material technology have accelerated the development of high performance concrete using lightweight aggregate. The main objective of this research is to produce high performance lightweight aggregate concrete reinforced with polypropylene and to study the mechanical properties of this type. The effect of various factors such as type of fiber and volume fraction of fibers also has been investigated. The experimental work included the use of pumice as coarse and fine lightweight aggregate, superplasticizer and silica fume to produce high performance lightweight concrete. Several trial mixes were examined to determine the proper proportion of the concrete constituent. Three types of polypropylene with different volume fraction were used. The procedure also includes studying the compressive strength, splitting tensile strength, flexural strength and static modulus of elasticity. The test results shows that the addition of all types of polypropylene fiber results in significant improvement in most mechanical properties compared with reference concrete specimens at different ages except compressive strength it was improved at Vf =0.25% and decrease at Vf =0.75%.

Experimental study on modulus of elasticity of steel tube-confined concrete stub columns with active and passive confinement

This study presents the results of an experimental investigation on the initial and reloading elastic modulus of steel tube-confined concrete (STCC) stub columns with active and passive confinement. Here, a new method was used to create an active confinement in the STCC columns, in which the fresh concrete was compressed by applying an external pressure and subsequently the steel tube was pretensioned in the circumferential direction. The prestressed steel tube-confined compressed concrete (PSTC) was produced in two ways: long- and short-term pressure to reach high and low prestressing levels, respectively. A total of 135 confined concrete specimens including non-prestressed steel tube-confined concrete (NPSTC), short-term prestressed steel tube-confined compressed concrete (SPSTC), and long-term prestressed steel tube-confined compressed concrete (LPSTC) along with 45 reference concrete specimens in 15 experimental groups were tested to investigate the effect of reference concrete strength, diameter to thickness ratio of the steel tube, and prestressing level on the initial and reloading modulus of elasticity. The results showed that prestressing the STCC specimens by the present method significantly enhanced the initial modulus of elasticity between 46% and 184% for the SPSTC and between 51% and 280% for the LPSTC. Moreover, the reloading elastic modulus increased considerably compared with the first loading elastic modulus for the passive specimens while the opposite trend was observed for the active specimens. Finally, by separating the contribution of prestressing to increasing the elastic modulus of the active specimens from that of compressing the fresh concrete, a significant contribution of prestressing was indicated.

Mechanical and thermal characterization of concrete with incorporation of microencapsulated PCM for applications in thermally activated slabs

Evolution towards sustainable building design is a current goal worldwide, shaping codes and policies, to achieve such goal the construction industry and sector requires new energy saving concepts and building materials. The objective of this study is to quantify the influence of microencapsulated phase change material (PCM) over the concrete mechanical and thermal properties. The experimental tests on concrete with PCM yielded resistance loss up to 66% and 52% for compression and bending strength respectively, comparatively with the reference concrete specimens, without PCM.Thermal performance of concrete incorporating PCM was also evaluated. The results showed that the incorporation of PCM can contribute to reduce the energy demand in buildings.

Mechanical Properties of High Performance Concrete Containing Waste Plastic as Aggregate

The world's population growth and the increasing demand for new infrastructure facilities and buildings , present us with the vision of a higher resources consumption, specially in the form of more durable concrete such as High Performance Concrete (HPC) . Moreover , the growth of the world pollution by plastic waste has been tremendous. The aim of this research is to investigate the change in mechanical properties of HPC with added waste plastics in concrete. For this purpose 2.5%, 5% and 7.5% in volume of natural fine aggregate in the HPC mixes were replaced by an equal volume of Polyethylene Terephthalate (PET) waste , got by shredded PET bottles. The mechanical properties (compressive, splitting tensile, and flexural strength ) evaluated at the ages of (7 ,28, 56 and 91) days while the static modulus of elasticity tested at (28 and 91) days . The results indicated that HPC containing PET-aggregate presented lower compressive strength and static elasticity . The splitting strength displayed an arising trend at the initial stages, however, they have a tendency to decrease after a while. On the other hand, flexural strength results gave better modulus of rapture at all ages of curing , as compared with reference concrete specimens.

Investigation of durability properties of concrete pipes incorporating blast furnace slag and ground basaltic pumice as fine aggregates

In this study, the effects of using blast furnace slag, ground basaltic pumice and blast furnace slag + ground basaltic pumice as fine aggregates, on the durability of concrete pipes, were investigated. Blast furnace slag, ground basaltic pumice, and equal amounts of blast furnace slag and ground basaltic pumice were used at 5%, 10% and 15%, by weight, in place of fine aggregate, in mixes. The durability of concrete pipes has been tested, according to standard procedures. The sulfate resistance and permeability of the reference specimen and the specimen with admixtures were investigated. It was observed that the ultimate load of specimens depends on the type and percentage of admixtures. The maximum ultimate load was obtained in concrete specimens containing 5% blast furnace slag and 5% ground basaltic pumice, which was 20% larger than that of the reference concrete specimens. Furthermore, concrete specimens with 10% ground basaltic pumice were found to have the highest sulfate resistance.

Influence of mortar rendering on chloride penetration into concrete structures

Abstract This experimental work studied the influence of mortars used as external rendering on chloride transport in concrete. Prismatic concrete specimens were cast with dimensions of 80 × 80 × 80 mm and water to binder ratio of 0.55. Three different mixtures of mortar were used to cover these specimens, after making a thin layer of spatter dash treatment. Reference concrete specimens were also cast. After a curing period in wet chamber and in laboratory environment, five of the six faces of the specimens were coated with epoxy resin to simulate unidirectional flux of chloride during the test. The specimens were subjected to natural diffusion tests for 49 days and, afterwards, samples were extracted and analysed to obtain chloride profiles. Results show that mortar renderings directly influence chloride penetration into concrete and this influence is more pronounced for mortars with higher contents of cement and less porosity. This shows that, although mortars have higher porosity than concrete, they can provide an additional protection to concrete structures, delaying chloride penetration into bulk concrete.

Lateral load response of high performance fiber reinforced concrete beam–column joints

Six beam–column (B–C) joints were constructed according to the existing practice in Jordan and tested under cyclic lateral loading to determine the effect of using high performance steel fiber reinforced concrete (HPFRC) in place of conventional concrete in the joint region. The properties of ultimate strength, ductility, energy dissipation capacity, and joint stiffness of the reference concrete specimens were compared with those containing different amounts of brass-coated (BCSF) or hooked steel fibers (HSF). It was determined that the steel fiber concrete specimens exhibited three times higher load levels, 20 times larger energy dissipation, and two times slower stiffness degradation compared to the reference concrete specimens. Using hooked steel fibers showed a significant increase (three times) in the maximum load carrying capacity and in the initial secant stiffness compared to reference specimens.