J. Forth

Laboratory tests were carried out to investigate the effect of steel fibres and recycled aggregate on the drying shrinkage and creep deformations of concrete. Steel fibres (Dramix 3D 65/35BG) were added to the mixes and washed construction and demolition wastes (CDW size 20mm) were used as a coarse recycled aggregate. The main variables of this study are the steel fibre contents; Vf = 0, 0.5 and 1.0% and the recycled aggregate replacement percentages; RP= 0, 50 and 100%. Small prisms (75×75×200mm) and bobbins (75×365mm) were cast (for 9 mixes), cured (for 28 days) and tested (for up to 90 days). A fine natural aggregate was used in all mixes and the amount of cement and the water-to-cement ratio was kept constant. The results showed that there are significant increments in drying shrinkage, compressive creep and tensile creep by 18%, 15% and 8% were recorded respectively when 50% of the recycled aggregate was used. However, when 100% of the recycled aggregate was replaced, the following results were achieved 38%, 29% and 15% respectively. In contrast, the effect of adding 0.5% of steel fibres content recorded reductions in these deformations (drying shrinkage, compressive creep and tensile creep) by 7%, 3% and 10% respectively. However, further reductions with percentages of 15%, 5% and 20% respectively were seen when 1.0% of fibre content was added. Interestingly, steel fibres had a significant effect on tensile creep and shrinkage, but little effect on compressive creep.

The applications of a mineral admixture, or a zinc coating to steel surface, or a combination of both are methods used for the corrosion prevention of ferrocement element in this study. Results of a study to evaluate many corrosion protection systems with metakaolin and/or galvanized steel mesh are presented in six U-shaped specimens. Specimens were built to simulate exposure conditions typical for marine environment. Laboratory data collected along duration of 40 weeks of exposure were used in modeling the cover depth as a function of time to corrosion initiation of the investigated corrosion prevention methods. Methods used to assess the condition of specimens included chloride concentration measurements, and corrosion rates. Model predictions show that the ferrocement specimen of high-performa nce mortar with metakaolin provides much better level of protection against moisture and chlorides than the conventional specimen, by delay rate of chloride ingress. Application of a galvan...

For the last few decades, research has been conducted to investigate the problem of corrosion in steel reinforced concrete. The outstanding of fibre reinforced plastics (FRP) suggests that these materials may be a possible solution to the problem of steel corrosion. In this investigation, some aspects of GFRP rebars were examined, namely flexural characteristics and micro-structural features such as porosity and pore size distribution. Mercury intrusion porosimetry (MIP) was used to show how the pores are distributed and connected to each other. Also, changes in both the flexural characteristics and the micro-structure of the material under high alkalinity and salinity solutions at high and moderate temperatures for different periods of aging up to 270 days were monitored. The results showed that GFRP material was very compacted, which improves its durability since the principal role of the resin matrix is to provide protection to the glass fibres and alkalinity at high temperature ...

As an outcome of recycling the mineral part of construction and demolition waste significant quantities of the fine fraction, particle size below 4 mm in Europe, are generated. A common feature of the produced fine recycled aggregates is the high content of cement paste that could impair its quality. With the recent advances on the processing technologies improvement on the characteristics of the fine fraction of C&DW can be envisaged and new perspectives to their application arise.

This paper describes laboratory experiments and presents results for the performances of cold-mix, cold-lay emulsion mixtures. The main objective of the experiments was to evaluate and improve the properties of the cold mixtures. The mixture properties evaluated were: volumetric properties, indirect tensile stiffness modulus (ITSM), repeated load axial creep and fatigue. These properties were compared with conventional hot asphalt mixtures not containing any waste/recycled materials. To optimise the performances of the mixtures, a target of ITSM value of 2000 MPa was selected. At full curing conditions, the stiffness of the cold mixes was found to be very similar to that of hot mixtures of the same penetration grade base bitumen (100 pen). Test results also show that the addition of 1–2% cement significantly improved the mechanical performance of the mixes and significantly accelerated their strength gain. The fatigue behaviour of the cold mixes that incorporated cement was comparab...