The author details the reactions of various concretes on steel reinforcement. Although portland cements, slag cements and high alumina cements are all hydraulic binders, each possess special properties which are examined. The discussion of causes and methods of preventing the corrosion of steel reinforcement covers such aspects as galvanised steel reinforcement, effects of concrete composition, corrosion of steel reinforcments in concrete and prestressed reinforcement. It is concluded that the most significant influences on the corrosion of prestressing wire in concrete are: the presence of chloride; the presence of nitrates; the composition of the concrete; the degree of carbonation of the concrete; concrete compaction and, chlorides and sulphates should be used as far as possible when steel is embedded. (TRRL)

Corrosion of steel by concrete

Mix design and properties assessment of Ultra-High-Performance Fibre Reinforced Concrete (UHPFRC)

This paper addresses the development of an eco-friendly Ultra-High Performance Concrete (UHPC) with efficient cement and mineral admixtures uses are investigated. The modified Andreasen & Andersen particle packing model is utilized to achieve a densely compacted cementitious matrix. Fly ash (FA), ground granulated blast-furnace slag (GGBS) and limestone powder (LP) are used to replace cement, and their effects on the properties of the designed UHPC are analyzed. The results show that the influence of FA, GGBS or LP on the early hydration kinetics of the UHPC is very similar during the initial five days, while the hydration rate of the blends with GGBS is mostly accelerated afterwards. Moreover, the mechanical properties of the mixture with GGBS are superior, compared to that with FA or LP at both 28 and 91 days. Due to the very low water amount and relatively large superplasticizer dosage in UHPC, the pozzolanic reaction of FA is significantly retarded. Additionally, the calculations of the embedded CO2 emission demonstrate that the cement and mineral admixtures are efficiently used in the developed UHPC, which reduce its environmental impact compared to other UHPCs found in the literature.

/pdf/development-of-an-eco-friendly-ultra-high-performance-3fud7qno8j.pdf

Development of an eco-friendly Ultra-High Performance Concrete (UHPC) with efficient cement and mineral admixtures uses

Effect of different superplasticizers and activator combinations on workability and strength of fly ash based geopolymer

Synthesis of heat and ambient cured one-part geopolymer mixes with different grades of sodium silicate

U radu su pregledno prikazani postupci ispitivanja, mogucnosti primjene i reoloske osnove ponasanja svježeg samozbijajuceg betona. Prikazane su preporucene metode ispitivanja i zahtjevi za samozbijajuci beton u svježem stanju. U radu su također prikazani rezultati vlastitih laboratorijskih ispitivanja svojstava samozbijajuceg betona. Dane su preporuke za projektiranje sastava kako bi se postigla zahtijevana svojstva samozbijajuceg betona za određenu namjenu.

/pdf/mix-design-for-self-compacting-concrete-47z4sbneee.pdf

Mix design for self compacting concrete

Active thermography methods enable structural investigations of reinforced concrete elements taking into account many different testing problems. The goal of this review is to provide an overview on the state-of-the-art regarding the use of active infrared thermography (IRT) for detection and characterization of defects in reinforced concrete. The paper will provide the physical background, equipment being used, as well as post-processing methods that are used to analyse sequences of thermograms. This work also presents the fields of applicability of IRT with a focus on the aspects related to reinforced concrete structures, as well as the advantages, limitations and potential sources of errors of IRT employment. Additionally previous non-destructive testing (NDT) studies that employed thermography techniques with natural excitation are briefly presented. A review of the future trends of thermal imaging are also included in this work. It can be concluded that while IRT is a useful tool for the characterisation of defects in the building sector, there is great prospect for the development of more advanced, effective and accurate approaches that will employ a combination of thermography approaches.

https://www.mdpi.com/2313-433X/2/2/11/pdf

Review of Active IR Thermography for Detection and Characterization of Defects in Reinforced Concrete

Hygrothermal Performance Of Ventilated Prefabricated Sandwich Wall Panel From Recycled Construction And Demolition Waste – A Case Study

This paper examines the possibility of using crushed brick and recycled concrete as a partial replacement of natural aggregates in a production of prefabricated wall panels used for constructing nearly zero-energy buildings. Replacement ratios of natural aggregates by 40%, 50% and 60% were investigated. Mechanical, durability and thermal properties of recycled aggregate concrete were tested. The test results indicate the possibility of manufacturing concrete with recycled concrete aggregates and recycled brick aggregates, which can find wide use in the building construction process. In addition, energy efficiency and sustainability parameters of recycled aggregate concrete can be coupled with an exigent need to improve energy performance of the building stock in the European Union and neighbouring countries. It is shown in this paper that around 46% of embodied energy and around 39% of embodied carbon per panel can be saved for a life span of 50 years, compared to conventional structural concrete insulate...

Recycled Aggregate Concrete for Nearly Zero Energy Buildings

Although using various innovative materials for ventilated facade systems positively contribute to the energy efficiency of buildings, the application of such materials can also pose a certain risk of fire propagation through the facade. In the last decade, medium and large-scale tests, as well as numerical analysis have been performed to assess the impact of fire barriers on fire propagation through ventilated facades. However, the number of fire barriers and their specific positions can also have an effect on the fire safety of facades, which has not been studied. Consequently, the question arises whether real fire exposure on a facade can be adequately simulated and analysed in sufficient detail, by using large-scale testing methods. This paper aims to conduct a parametric analysis on a broader range of large-scale samples by using the procedure given in the standard BS 8414-1:2015 + A1:2017. To understand better the impact of the number and position of cavity barriers for different types of insulation materials (stone wool/PIR/phenolic foam) used in modern facade systems with non-combustible cladding (ACM-A2). Seven tests were carried out in Croatia between October 2017 and April 2018. In the case of combustible insulation, two horizontal barriers were insufficient in preventing fire propagation. Temperatures accumulated above 600°C, reaching 840°C in PIR insulation and 979°C in phenolic foam insulation. For the same sample designed with non-combustible insulation, the maximum temperature measured was 133°C. Facades with combustible insulation passed the test only when four horizontal barriers were used. The existence of vertical barriers had a positive impact on preventing the fire propagation because the insulation on the left side of the chamber, behind the vertical barrier, remained undamaged. Vertical barriers on the right side of the chamber delayed the horizontal fire propagation from the main wall to the wing wall depending on the type of insulation. The results from these tests can serve as a basis for future research on the effects of fire barriers on fire propagation.

/pdf/influence-of-horizontal-and-vertical-barriers-on-fire-2c191odt0d.pdf

Ivana Banjad Pečur

Papers

Mix design for self compacting concrete

Review of Active IR Thermography for Detection and Characterization of Defects in Reinforced Concrete

Hygrothermal Performance Of Ventilated Prefabricated Sandwich Wall Panel From Recycled Construction And Demolition Waste – A Case Study

Recycled Aggregate Concrete for Nearly Zero Energy Buildings

Influence of Horizontal and Vertical Barriers on Fire Development for Ventilated Façades