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Conflicting claims have been made in relation to the effects of polypropylene fibres on the compressive strength of concrete. The purpose of this paper is to examine the effects on compressive strength of various dosages of monofilament polypropylene fibres when used in concrete. Compressive strength is widely used as the key indicator of concrete quality and therefore needs accurate determination. Monofilament fibres and air entrainment provide a similar function in that they provide freeze/thaw protection, they are both compared against a plain concrete sample to determine relative strength and density.

Two different concrete design strengths (medium and high) were examined with varying amounts and types of polypropylene fibre fraction/volume to establish a common link between fibre additions and reduced final compressive strength.

The findings from the test programme showed a linear reduction in strength which was observed as being directly related to fibre inclusion in concrete. Density was also found to be reduced with the addition of fibres in a similar degree to that of air entrainment.

The lower density of concrete with polypropylene fibre additions was not scientifically explained and this aspect currently forms part of a long term freeze/thaw research programme, which will examine pore spacing and void formation compared to plain concrete.

This paper is of interest to clients, concrete manufacturers, concrete additive manufacturers, designers, surveyors and specifiers who need to know what effect polypropylene fibre additives have upon the final compressive strength.

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.

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.

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.

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.

From recent laboratory research monofilament and fibrillated polypropylene fibres were used in structural concrete and have been tested against 150 freeze/thaw cycles. The findings show monofilament fibres to play a significant role in protecting the concrete matrix against the forces encountered. External cube integrity was shown to be a poor indicator of structural condition. A significant aspect of the work is the range of tests applied to the freeze/thaw concrete cubes against the control sample. Strong evidence of condition was obtained from ultrasonic, compressive strength and weight loss. Surface scaling was not a satisfactory indication of the structural condition of the concrete.

The paper aims to propose a rate‐dependent model of structural concrete in combination with the kinematics of condensed water.

First, the paper proposes the coupling model of water versus cracked concrete with a mathematical completeness of equilibrium and deformational compatibility. The proposed model deals with anisotropy of structural performance and of permeability, which is a particular issue of concrete caused by cracks. The governing equation for saturated concrete in this study is based on Biot's theory that deals with particle assembly as a two‐phase composite. Second, the paper shows the possible reduction of the fatigue life of real‐scale bridge RC decks owing to the water residing in structural cracks under moving wheel‐type loading.

The paper shows that the existence of water possibly has an influence on the rate‐dependency of structural performance. The comparison of transition of pore pressure and principal strain indicates that damage to the concrete skeleton is accelerated by internal stress caused by high pore pressure. It suggests that the existence of water can reduce the fatigue life of bridge decks, especially when the upper layer is saturated.

This paper clarifies the effect of pore water on structural concrete by using numerical model considering kinematics of water.

Nowadays, circular concrete-filled tubular (CFT) columns are largely used in construction because of structural and architectural advantages such as high load bearing capacity and aesthetic appearance. The behavior of CFT columns at ambient and high temperatures is good; however, there are problems related to their behavior in fire when inserted in a real building structure, as for example, the influence of the restraining to thermal elongation that have to be addressed in order to improve their design. This study aims to present the results of a numerical study on the behavior of CFT columns with restrained thermal elongation in case of fire.

The parameters tested in the numerical simulations included column slenderness, load level, surrounding structure stiffness and steel reinforcement ratio. A sequentially coupled thermal stress analysis was carried out. The numerical model was validated with results from a large series of fire resistance tests carried out at Coimbra University, in Portugal. From these, simple equations to evaluate CFT column critical times were derived.

The results were also compared with the ones obtained from the current EN 1994-1-2:2005 simplified calculation and tabulated data methods. For the analyzed cases, it was verified that, while the simplified calculation method led to safe results on the evaluation of the fire resistance of CFT columns with restrained thermal elongation, the tabulated data method led, in certain cases, to unsafe results. This research showed also lower critical times than those from literature on similar type of columns.

The influence of the stiffness of the surrounding structure on the behavior of CFT columns subjected to fire was not yet clear in the major part of the studies already carried out. So, this paper has the originality to consider this parameter in the numerical simulations of this type of columns.

The use of recycled aggregates (RA) has been explored to lead to a more sustainable future. The paper investigates on a sustainable concrete mix incorporating steel fibres (SF) and RA to provide an alternative to traditional natural aggregate concrete for structural applications. This paper aims to explore the feasibility of combining RA and SF in structural applications in terms of strength, cost and industry perspectives.

A mixed research approach is established with two phases. Phase 1 aims to identify an optimum material combination that satisfies the structural strength requirements and to identify the costs in its optimum combination. Phase 2 involves qualitative interviews with key industry parties to explore their perspective and identify various enablers and barriers for this material.

The optimum combination of 30 per cent RA replacement and 0.3 SF volume content has been identified through laboratory testing. It was noted that there would be a direct additional cost because of SF addition. However, when other benefits such as reduction in transportation costs and landfill dumping fees were considered, an overall cost saving could be achieved. Consequently, the key industry practitioners’ perspectives for this material have been gathered through qualitative interviews. Several enablers and barriers were identified through these interviews.

Even though, there are various research attempts on improving RA for structural purpose by adding different additives, a holistic study that incorporate cost effects and the industry perspectives was lacking and is addressed in this current study. In particular, industry perspectives lead to refocus research directions and get closer to the realisation of a sustainable construction industry.

A new roller compacted concrete dam of Fengman hydropower station was determined to be built in the toe of the old dam which had been identified as a dangerous dam. The new dam during construction would be impacted by the high‐speed flow discharged from the old dam. This is an important problem met for the first time in China, which would affect the whole project construction. The purpose of this paper is to describe a series of erosion experiments of the new dam material.

A kind of high‐speed flow erosion test apparatus was developed for erosion experiment of the new dam material. The maximum jet velocity was up to 40 m/s and the section area of the nozzle was 25 cm². In the process of experiments, the equipment showed its good performance. Erosive wear tests of two types of materials used in the new dam, a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30‐35 m/s.

Erosion parameters and erosion laws of the two types of concretes with different ages were obtained, and a general relationship had been found between erosion rate and flow velocity: with velocity exponent between 3.33 and 3.93. It was also concluded that the erosion resistance of the distorted concrete was better than that of the roller compacted concrete and the mechanics properties of the concretes of over 14 days age was influenced slightly by water impacted.

The test results would play a practical technique guide role for the safety of this project during construction in the flood season.

Steel-reinforced concrete-filled steel tubular (SRCFST) columns have been increasingly popular in engineering practice for the columns' excellent seismic and fire performance. Significant design progress guidance has been made through continuous numerical and experimental research in recent years. This paper tested and analysed the residual loading capacity of SRCFST columns under axial loading after experiencing non-uniform ISO-834 standard fire.

The experimental research covered the main parameter of heating conditions, 1-side and 2-side fire, through two specimens. Two specimens were heated and loaded simultaneously in the furnace for 240 min. After cooling, the columns were moved to the hydraulic loading system and loaded to failure to determine the columns' residual capacity.

The experimental results indicated that the non-uniform heating area plays an essential role in the overall performance of SRCFST columns, the increasing heating area of columns results in lower residual loading capacity and stiffness. The SRCFST columns still had a high loading capacity after heating and loading in the fire.

The comparison of experimental data against design results showed that the design method generated a 16% safety margin for S2H4 and a 39% safety margin for S1H4.

This study aims to enhance the understanding of fiber-reinforced polymer (FRP) applications in partially confined concrete, with a specific focus on improving economic value and load-bearing capacity. The research addresses the need for a more comprehensive analysis of non-uniform vertical strain responses and precise stress–strain models for FRP partially confined concrete.

DIC and strain gauges were employed to gather data during axial compression tests on FRP partially confined concrete specimens. Finite element analysis using ABAQUS was utilized to model partial confinement concrete with various constraint area ratios, ranging from 0 to 1. Experimental findings and simulation results were compared to refine and validate the stress–strain model.

The experimental results revealed that specimens exhibited strain responses characterized by either hardening or softening in both vertical and horizontal directions. The finite element analysis accurately reflected the relationship between surface constraint forces and axial strains in the x, y and z axes under different constraint area ratios. A proposed stress–strain model demonstrated high predictive accuracy for FRP partially confined concrete columns.

The stress–strain curves of partially confined concrete, based on Teng's foundation model for fully confined stress–strain behavior, exhibit a high level of predictive accuracy. These findings enhance the understanding of the mechanical behavior of partially confined concrete specimens, which is crucial for designing and assessing FRP confined concrete structures.

This research introduces innovative insights into the superior convenience and efficiency of partial wrapping strategies in the rehabilitation of beam-column joints, surpassing traditional full confinement methods. The study contributes methodological innovation by refining stress–strain models specifically for partially confined concrete, addressing the limitations of existing models. The combination of experimental and simulated assessments using DIC and FEM technologies provides robust empirical evidence, advancing the understanding and optimization of FRP-concrete structure performance. This work holds significance for the broader field of concrete structure reinforcement.

S. R. Pandey, Superintending Engineer (SE), Rural Roads Department, Bihar wanted to have a meeting of all the agencies involved, including his other engineers, the contractors to discuss his village road-making project in Pradhan Mantri Gram Sadak Yojona (PMGSY). This case discusses how the concept of work breakdown is used to subdivide all the activities of road-making into different sub activities (earthwork, bridgework, roadwork and other miscellaneous activities) in different levels.