Analysis of the geometrical imperfections of a dry-stacked masonry block based on Miscanthus

in Construction and Building Materials (2021)

Machine learning in mix design of Miscanthus lightweight concrete

in Construction and Building Materials (2021)

Overcome of bed-joint imperfections and improvement of actual contact in dry-stacked masonry

in Construction and Building Materials (2020)

Several researchers studied dry-stacked masonry walls (DSM) and inferred that the actual contact surface between the different block rows and the compressive strength in such walls are reduced by bed ... [more ▼]

Several researchers studied dry-stacked masonry walls (DSM) and inferred that the actual contact surface between the different block rows and the compressive strength in such walls are reduced by bed-joint imperfections as well as by height differences between different masonry blocks leading both to high stress concentration. This paper concentrates on the first type on imperfections. Through experimental tests, it analyses the influence of bed-joint roughness on the load bearing capacity and investigates a strategy to improve the load-bearing capacity of DSM by placing an additional horizontal layer on the top face of raw masonry blocks. First, different contact layers using conventional and auxetic materials were applied. Then 20 dry-stacked masonry prisms built with raw and improved masonry blocks were tested under axial compressive load until failure. Prescale Fujifilm strips were used to measure the actual contact in the bed-joints. Experimental tests show that the use of a contact layer with well-defined material properties enables firstly to increase the actual contact area in the bed-joints from 23% to 98% of the nominal contact area and secondly to increase the load-bearing capacity by 14 to 97%. In addition, the contact layer with an auxetic material shows a significant capacity in altering the lateral expansion in the block units. The outcomes show that although the bed joint roughness influences the stress distribution in a dry-stacked masonry block, a contact layer with well-defined material properties enables to overcome the roughness induced by the bed-joint imperfections. [less ▲]

Basic mechanical behaviours and deterioration mechanism of RC beams under chloride-sulphate environment

in Construction and Building Materials (2018)

This paper investigates the basic mechanical behaviour of reinforced concrete (RC) beams using chloride corrosion-damaged steel reinforcements and subjected to sulphate ions environment. To this end, ten ... [more ▼]

This paper investigates the basic mechanical behaviour of reinforced concrete (RC) beams using chloride corrosion-damaged steel reinforcements and subjected to sulphate ions environment. To this end, ten RC beams were studied which contained 5% sodium chloride and implemented by a series of drying-immersion cycling (15% sodium sulphate immersion solution). Test results indicated that the flexural capacity, ductility, and stiffness of the beams were improved at early stage of the corrosion. This was attributed to the fact that concrete strength and steel-concrete interfacial bond were enhanced. The former is for the filling effects of micro-expansive Ettringite and gypsum sulphate, while the latter is due to the slight surface corrosion pits of steel bars at the stage. However, the mechanical properties of the beams decreased subsequently for the deteriorations in the concrete strength due to excessive expansion of Ettringite and gypsum sulphate, and the degradation of self-property of reinforcement and its interface bond with the concrete. Based on the study, the deterioration mechanism of RC beams under chloride-sulphate environment was discussed and its main determining factors at different stages were analysed. [less ▲]

3D meso-scale modelling of foamed concrete based on X-ray Computed Tomography

in Construction and Building Materials (2018), 188

Foamed concrete has been widely used in infrastructure construction and poses new challenges to design and modelling. This paper investigates the behaviour of foamed concrete with the help of X-ray ... [more ▼]

Foamed concrete has been widely used in infrastructure construction and poses new challenges to design and modelling. This paper investigates the behaviour of foamed concrete with the help of X-ray Computed Tomography (XCT), which is capable of characterising the microstructure of foamed concrete. An in situ compressive test-XCT scan is carried out to observe the failure mechanism of foamed concrete by XCT when subjected to compression load. A meso-scale simulation based on XCT images is conducted to simulate the behaviour of foamed concrete. An algorithm that directly reconstructs the meso-scale model from XCT images is developed. The experimental and numerical results show that foamed concrete exhibits a significant change in mechanical behaviour; it is less brittle compared to the response of dense samples. However, the reduction in the level of brittleness is accompanied by a significant decrease in compressive strength. Failure development inside samples is successfully captured by the XCT scan and the meso-scale modelling. The topology of foamed structures, in particular the chain of interconnected pores, influences the failure mechanism of foamed concrete. The combination of XCT scan and meso-scale modelling provides a comprehensive framework to understand the mechanical behaviour of foamed concrete. [less ▲]

Influence of the sheet profile design on the composite action of slabs made of lightweight woodchip concrete

in Construction and Building Materials (2017), 148C(September 2017), 887-899

The trend for using renewable materials in construction to create sustainable and robust buildings is currently gaining in popularity. Therefore, in this work, the applicability of dense lightweight ... [more ▼]

The trend for using renewable materials in construction to create sustainable and robust buildings is currently gaining in popularity. Therefore, in this work, the applicability of dense lightweight woodchip concrete in constructive engineering is investigated. Here, the material is used as a top concrete layer on composite floors with profiled sheets and is analysed with regard to its load-bearing behaviour and composite action. One specific concrete mixture which fulfils the requirement for minimum strength of LC 20/22 is used for the test series. The scale of the study comprises 22 plate elements in total. The varied parameters are the shear spans, profiled sheet types and sheet thicknesses. Each examined sheet has an undercut profile with additional embossment. On the basis of experimental results, the influences of the varied parameters and profile forms on the load-bearing and composite behaviour are discussed. This study provides important key findings which show that dense lightweight woodchip concrete can transfer sufficient longitudinal shear forces to the composite joint. [less ▲]

Steel fibres as only reinforcement for flat slab construction

in Construction and Building Materials (2011)