Assessment of the durability performance of fiber-cement sheets

According to standards, the durability performance of fiber-cement sheets must be evaluated by comparing the modulus of rupture (MOR) before and after durability tests (freeze-thaw, soak-dry, and warm water) are completed. This paper investigated the MOR of two different fiber-cement sheets samples before and after durability tests as well as its ductility and toughness. Results showed no significant difference between the MOR of control specimens and that of the specimens submitted to durability tests except in the case of the freezing and thawing test where after 100 cycles, a 7–9% decrease was observed. The differences between the MOR of the control specimens and that of the specimens submitted to durability tests were negligible and acceptable in accordance to the requirements of the standard. However, toughness and ductility decreased considerably in specimens of sample 1 by 25, 35, and 15%, respectively, when exposed to soak-dry (25 and 50 cycles) and warm water conditions. In turn, the reduction in toughness and ductility for specimens of sample 2 exposed to soak-dry (50 cycles) and warm water conditions were of 40 and 7%, respectively. The results of this investigation suggest that ductility and toughness should also be considered to assess the durability performance of fiber-cement sheets

Evaluation of adhesion in polymeric fibre reinforced cementitious composites

In this study adhesion of some polymeric fibres to a cement matrix was evaluated both by a theoretical and by an experimental approach. In common methods adhesion of the fibres to the cementitious materials is determined by pull-out test. This test evaluates the energy failure during the fibre drawing out. This paper analyzes the adhesion theory for fibre reinforced cementitious composites to separate the share of the chemical and mechanical adhesion expressing new parameters, which are effective in the adhesion behaviour. Explanations about how the different fibres, matrix properties, test factors and environmental conditions can affect the adhesion results are given. It was found that for fibre/cement composites the fracture energy due to the interfacial interactions is for several orders of magnitude smaller that the polymeric fibre losses function. By employing adhesion theory, fibre/cement interac- tions are better described by a simple relationship of their surface free energy. Determination of the loss function (energy dissipation) leads us to predict the fibre behaviour in the cement matrix and the selection of the appropriate reinforcement

Design for Clean Technology Adoption: Application of Discrete Choice Analysis and the Theory of Planned Behavior for Development Engineering

Clean technologies can address multiple challenges associated with climate change, environmental protection, and human health. However, the impact desired by introduction of such technologies is achievable only if new options effectively replace inefficient, conventional practices. This ‘design for adoption’ requires understanding of user motivations, associated beliefs, context of use, and technology’s performance. To address this need, this work develops an integrated methodology that links the Theory of Planned Behavior to predict behavior intentions with Discrete Choice Analysis to systematically incorporate users’ behavioral intentions into the engineering design process. Drawing on a case study of improved biomass cookstove projects in Honduras and Uganda, the developed framework provides insight into consumer attitudes both before and after trial phases of a given technology, and then simulates the long-term community-scale adoption behavior based on the influences of social networks using Agent Based Modeling. Results can inform technology designers and international development programs on key attributes to consider to optimize technology design and intervention strategies and ultimately improve the long-term adoption rate of clean cookstoves in a given target market. These methods are expected to be extensible to other sectors as well, where the uptake of clean technologies can benefit from a systematic understanding of the multitude of behavioral, social, and technology design attributes that are relevant in different settings

Cementitious composites reinforced with polypropylene, nylon and polyacrylonitile fibres

This paper compares the adhesion strength between three polymeric fibres (polypropylene (PP), nylon66 (N66) and polyacrylonitrile (PAN)) embedded in a cement paste. The specimens were prepared at a water to cement ratio (w/c) of 0.5, and tested after 7, 14 and 28 curing days. It was found that although the adhesion between the polymeric fibres to the cement matrix is an important factor, the energy absorption capacity or energy dissipation ability of the fibres plays a more important role in the improvement of the cementitious composites fracture toughness. Scanning electron micrographs was used to characterize the fibres surface before and after the Pullout tests

Influence of acrylic fibers geometry on the mechanical performance of fiber-cement composites

This article analyses the influence of acrylic fibers shape on the flexural behavior of cement composite. The fibers differ in their cross-sectional shapes due to the spinning process (wet-spun and dry-spun). The fibers were characterized by optical microscopy, and the shape factors were calculated on the basis of their geometric characteristics. Results showed that both types of acrylic fiber remarkably improved the flexural performance of the composites. Wet-spun acrylic fibers lead to high flexural strength and toughness. It was found that by increasing the fibers’ shape factor by a factor of 10%, flexural strength and toughness increase to 26% and 23%, respectively

A monte carlo platform for characterization of x-ray radiation dose in ct imaging

Background: Computed tomography (CT) is currently known as a versatile imaging tool in the clinic used for almost all types of cancers. The major issue of CT is the health risk, belonging to X-ray radiation exposure. Concerning this, Monte Carlo (MC) simulation is recognized as a key computational technique for estimating and optimizing radiation dose. CT simulation with MCNP/MCNPX MC code has an inherent problem due to the lack of a fan-beam shaped source model. This limitation increases the run time and highly decreases the number of photons passing the body or phantom. Recently, a beta version of MCNP code called MCNP-FBSM (Fan-Beam Source Model) has been developed to pave the simulation way of CT imaging procedure, removing the need of the collimator. This is a new code, which needs to be validated in all aspects. Objective: In this work, we aimed to develop and validate an efficient computational platform based on modified MCNP-FBSM for CT dosimetry purposes. Material and Methods: In this experimental study, a setup is carried out to measure CTDI100 in air and standard dosimetry phantoms. The accuracy of the developed MC CT simulator results has been widely benchmarked through comparison with our measured data, UK�s National Health Service�s reports (known as ImPACT), manufacturer�s data, and other published results. Results: The minimum and maximum observed mean differences of our simulation results and other above-mentioned data were the 1.5, and 9.79, respectively. Conclusion: The developed FBSM MC computational platform is a beneficial tool for CT dosimetry. © 2021, Shriaz University of Medical Sciences. All rights reserved