Papers by Keyword: High Performance Concrete (HPC)

Abstract: This contribution is to verify the utilization of waste glass as partial replacement of fine aggregate for high performance concrete (HPC). Test results of fresh and hardened HPC will be presented. This study has been conducted through basic experimental research in order to analyze the possibilities of recycling waste glasses (grinding glass, milled glass powder from municipal waste) as partial replacement of silica powder for HPC.

Abstract: Some effects of self-curing on the mechanical properties of High Performance Concrete (HPC) are discussed in this paper. The matrix of HPC is very dense and it is very difficult to deliver the curing water into the cement matrix. Two different materials in different dosages were selected to examine self-curing. Polymer curing agent (PCA) was selected as the first, and 0.2% 0.4% 0.6% and 0.8% of PCA were added by weight of cement. This additive should allow the physicochemical binding of a larger portion of the mixing water and then release it slowly for better hydration without negative effects on the products. Pre-soaked slag of 0/4 mm was tested as another source of water for internal curing. The slag was also dosed in 10%, 15%, 20% and 30% volume of sand with the fraction 0/4 mm. Referential HPC was a high-dose cement that consumes a large amount of water for hydration. The water/cement ratio was 0.2. Metakaolin was added to improve the properties of fresh and hardened HPC.

Abstract: High performance concrete reinforced by technical textiles has found a wide range of applications in recent years. One of the most widespread is the use of this composite for the very thin facade panels of various shapes and technical solutions. This paper presents an unique way how to lighten the facade panels made of high performance concrete (HPC) reinforced by technical textiles, which are additionally equipped with LEDs, so that a sufficient distance can be watch programmed based image displays.

Abstract: This paper presents a model of small experimental facade panel using four-point bending test. The facade panel with dimensions 100 x 360 mm and thickness approximately 18 mm was slightly reinforced using two layers of impregnated technical fabric from AR-glass roving. The amount of reinforcement in cross-sectional area of the concrete element is small and it is a reason of plastic joints initiation under the loading supports. The purpose of this experiment was validation of all used material parameters from the previous research in the program for nonlinear analysis of concrete and reinforced concrete Atena Engineering. For slightly reinforced concrete elements are monitored parameters better visible especially interaction between reinforcement and used concrete. The load transfer to the concrete element from the testing machine is typically modeled using some small steel plate. This paper shows the difference in results if we insert another flexible plate between the steel plate and the concrete element with a small defined stiffness.

Abstract: Concrete as the one of the most used material in civil engineering has also a very high negative environmental impact. In recent years’ environmental parameters of all building materials become the most important aspect. Especially reduction of concrete is becoming a very hot topic around the word because it can lead to the reduction of environmental impacts especially the consumption of primary energy, primary non-renewable materials and CO₂ production. Textile reinforced concrete (TRC) is one of the possibilities to reduce amount of concrete in the structures. It is possible to design very thin structures because of non-corrosive properties of textile reinforcement and thus distinctly reduce the thickness. Combination with high performance concrete (HPC) allows to creating construction with mechanical properties on a required high level. This paper presents mechanical and economical comparison of different types of AR-glass reinforcement for HPC facade elements with the same amount of concrete.

Abstract: This article deals with optimal dosage of metakaolin as addition in high performance concrete. The main criteria for assessing the optimal dosage of metakaolin was compressive strength, rheological behaviour and economic benefits. Metakaolin was added to the mixture of high performance concrete in the range from 0 to 25% weight of cement. The comparison of metakaolin and microsilica, which is often used by concrete producers due to its excellent properties, is also performed in this article. The experiments showed that using metakaolin as addition in high performance concrete affects the compressive strength and rheological behaviour positively. While the compressive strength increases especially at lower doses of metakaolin and at higher doses remained unchanged, changes in rheological behaviour were most obvious at the higher doses. From this point of view, it is possible to recommend a higher dose of metakaolin.

Abstract: Technology of High-Performance Concrete (HPC) presents one of advanced concrete technologies. In comparison to common concrete, HPC is characterized by much better qualitative parameters both for fresh and hardened concrete. However, utilization of adequate materials as well as specific processes of both the production and handling of fresh concrete is required to achieve the above standard parameters of concrete. Currently, limited possibility of utilization of local source materials with applicable parameters curtails wider production of HPC within the building practice. Results of experimental approval of HPC properties which was prepared from local aggregates are presented in the paper. Used aggregates have not appropriate parameters for application into HPC on its face. Therefore the achieved results show the potential of its applied utilization.

Abstract: The effect of high temperature load on mechanical properties and porosity of a newly designed Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is studied. The hybrid reinforcement of UHPFRC is based on a mixture of polypropylene and steel fibers. In order to identify influence of high temperature exposure on UHPFRC, its residual mechanical parameters such as compressive strength, flexural strength and Young’s modulus of elasticity are accessed. Moreover, residual bulk density, matrix density and total open porosity are examined and related to the monitored structural changes. Simultaneous Thermal Analysis (STA) is employed in order to describe transformation processes during high temperature loading. The conducted tests provide practical information for controlled regulation of water vapor transport in a low permeable cementitious composite in order to decrease risk of spalling.

Abstract: The aim of this work is to study the influence of carbon nanotubes in the cement matrix of high performance concrete (HPC) on flexural and compressive strength. This paper describes the samples preparation for the flexural and compression experimental tests. In order to understand the effect of carbon nanotubes in the cement matrix, a scanning electron microscope (SEM) analysis was carried out. It was reported after experimental tests that an improper dispersion of nanoparticles can have a negative influence on the mechanical properties. The dispersion of carbon nanotubes in the cement matrix is the most important aspect in order to attain the predicated influence on the mechanical properties.

Abstract: After more than fifty years from the opening of the largely discussed “Autostrada del Sole” Highway in 1964, the infrastructure system in Italy appears marked by the passing of time, similarly to what observed in several other countries worldwide. The great heterogeneity of the Italian landscape has determined a great variety of construction types, such as large span concrete bridges over the northern rivers and large arch concrete bridges over the valleys of the central region. Increment of vehicle traffic and new seismic regulations are setting new requirements to adapt the existing infrastructure, which should be otherwise replaced. Moreover, reinforced concrete (RC) aging and deterioration have led to structural and material degradation, including severe cracking and corrosion. Specialized materials such as High Performance Concrete (HPC) could represent a viable convenient solution for repairing, strengthening and retrofitting of RC structures as both structural capacity and durability can be refurbished. However, alongside high mechanical performance, HPC is characterized by a high cracking sensitivity at very early age, due to its high stiffness and shrinkage. Restrained shrinkage cracking, particularly significant in repaired structures where the existing concrete generates a considerable restraint against the free movement of the repair material, may represent a limit to the effective application of these materials. For this reason, shrinkage compatibility of HPC with the existing concrete substrate needs to be experimentally and numerically assessed. A study is herein presented where, based on experimental tests, different numerical models are developed and compared to assess and eventually minimize the risk of shrinkage cracking in bridge piers strengthened with HPC.