Concrete porosity with polypropylene fibres and silica fume

Purpose This research examines the effects of Type 1 and Type 2 synthetic polypropylene fibres in concrete, with and without silica fume, regarding porosity. The raison d’être for the research is to examine the porosity of fibre concrete where the concrete may be subject to a hydrostatic pressure from water. The use of silica fume defines the positive benefits that can be achieved by utilising a waste/by product in a concrete mix. Methodology The standard for determining the penetration depth of water under pressure (BS 12390: part 8 2009) in concrete was used with two types of synthetic fibre (Type 1 and Type 2) and plain concrete, with and without silica fume were subject to a water pressure test over 72 hours to determine the depth of water penetration. Findings The findings showed that synthetic fibres when added to a concrete mix increase the porosity of the concrete when compared to plain concrete, however when additional silica fume is used at a dry rate of 10% to the dry mass cement content or 20% slurry content, the porosity of the concrete is significantly reduced. Originality Designers and contractors use fibre reinforced concrete to create water retaining structures. Low permeability equates to more consistent and better stored water quality. This research demonstrates the effectiveness of silica fume, which improves the performance of the concrete with regard to porosity and mitigates the effects of the synthetic fibre inclusion. Low absorption in concrete equates to low life cycle costs and good sustainability credentials through the use of a by product

Sea shells used as partial aggregate replacement in concrete

Purpose – The purpose of this paper is to examine the use of a waste marine sea shell product incorporated into a concrete mix as an aggregate replacement. Utilising shells reduces the storage of shell waste, also reducing the need for quarried aggregate and has potential benefits of adding a different material to a design mix concrete mix design for improved performance. Design/methodology/approach – The test methods used to evaluate the concrete were, British Standard tests for compressive strength (BS EN 12390-3:2002) and porosity (BS EN 12390-8:2009). A paired comparison test was carried out examining two different partial replacement shell aggregate mixes against a plain concrete control sample. Findings – The results showed a reduction in compressive strength when 50 per cent of sea shells were used as an aggregate replacement, for both sand and gravel, compared to the control sample. Crushed and graded sea shells used in concrete displayed a lower porosity/permeability than plain concrete. Originality/value – Whilst there is existing work relating to the compressive strength of concrete using sea shells, the porosity of concrete using sea shells has not been widely addressed and the paper investigates this aspect of sustainable concrete research

Durability performance of concrete containing laterite aggregates

© 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. In Malaysia, concerns about the depletion of granite aggregates in the future and the availability of laterite aggregates locally have incentivized researchers to integrate laterite aggregate into the production of concrete. Studies found that the use of 20 to 30% of laterite aggregates, as partial replacement for coarse aggregates, results in concrete with the targeted strength. However, the effect of laterite aggregate content on the durability performance of this concrete is unknown. As such, the acid resistance and water absorption of concrete consisting of various percentages of laterite aggregates, integrated as partial replacement of coarse aggregates, are presented and discussed. Mixes consisting of varying amounts (0–50%) of laterite aggregates were prepared in the form of cubes (150 × 150 × 150 mm). After water curing for 28 days, the specimens were tested for the determination of compressive strength and durability against acid attack and water absorption. It was found that concrete with low water absorption can be produced through the integration of 50% of laterite aggregates. Similarly, the integration of laterite aggregates of up to 20% produces concrete that exhibits good durability against acid attack, chloride ion penetration, and water absorption