Shear capacity prediction of slender reinforced concrete structures with steel fibers using machine learning

Shear failure in reinforced concrete beams poses a critical safety issue since it may occur without any prior signs of damage in some cases. Many of the existing shear design equations for steel fiber reinforced concrete (SFRC) beams include significant uncertainty due to failure in reflecting the phenomenology of shear resistance accurately. Given these, adequate reliability evaluation of shear design provisions for SFRC beam is of high significance, and increased accuracy and minimisation of variability in the predictive model is essential. This contribution proposes machine learning (ML) based methods - Gaussian Process regression (GPR) and the Random Forest (RF) techniques - to predict the ultimate shear resistance of SFRC slender beams without stirrups. The models were developed using a database of 326 experimental SFRC slender beams obtained from previous studies, utilising 75% for model training and the remainder for testing. The performance of the proposed models was assessed by statistical comparison to experimental results and to that of the state-of-practice existing shear design models (fib Model Code 2010, German guideline, Bernat et al. model). The proposed ML-based models are in close alignment with the experimentally observed shear strength and the existing predictive models, but provide more accurate and unbiased predictions. Furthermore, the model uncertainty of the various resistance models was characterised and investigated. The ML-based models displayed the lowest bias and variability, with no significant trend with input parameters. The inconsistencies observed in the predictions by the existing shear design formulations at the variation of shear span to effective depth ratio is a major cause for concern; reliability analysis is required. Finally, partial resistance safety factors were proposed for the model uncertainty associated with the existing shear design equations

Reinforced concrete deterioration caused by contaminated construction water: An overview

Over the years, there were cases of building failures in most developing countries of the world that have led to the loss of lives and property. Yet, most investigations conducted on the causes of building failures have suggested poor design, inadequate supervision, and the use of inferior materials as the factors responsible for the failures. However, not so much emphasis has been placed on concrete mixing water as a contributing factor to the failures. Therefore, this review summarizes the effect of the type and composition of mixing water on the properties of concrete. Different sources of water that can be used to mix concrete were explored, alongside with the effect on fresh and hardened properties of concrete. The fresh properties of concrete, such as setting time and slump, were examined, while the hardened properties focused on the strength and durability of the concrete. A brief statement on the available regulation and standards for mixing water was also reported. This review shows the viability of using water from different sources, such as wastewater, to mix concrete successfully. However, the treatment of some types of water might be required to ensure that excellent strength and durability properties are achieved while preventing any threat to human life and the environment. Area for future research was also suggested, which, among other procedures, could help proffer solutions to the challenge of building failures in developing countries

Alkali-activated materials: advances on accelerated and long-term durability assessment and methodologies—a short review

Developments in material testing have brought about the invention of some durability assessment methodologies for alkali-activated materials. This study reported advances in accelerated and long-term durability assessment and methodologies for alkali-activated composites (AAC). For both alkali-activated materials (AAM) and ordinary Portland cement (OPC)-based composites, the common methods such as increased acid concentration, standard non-accelerated test, wetting and drying cycling, brushing were assessed. The study assessed common methods: increased acid concentration, standard non-accelerated test, wetting and drying cycling, and brushing. The discussion also identified the limitations associated with the accelerated and long-term durability assessment in AAM composite. Some limitations include concrete pore solution concentration, precursor type, and admixture. In AAMs, pore size is within ranges > 1 μm and < 20 nm, which is an indication of insignificant porosity. Also, the compressive strength coefficient of AAM mortars was better than the cement mortar after 75 cycles. Finally, the study revealed the most appropriate mechanism for measuring the durability of AAM composite, which could be well utilized in the construction field

Modelling the edge breakout shear capacity of single anchors using gene expression programming

The use of soft computing techniques is becoming more common in providing solutions to complex engineering problems such as the concrete breakout strength of anchor. Available techniques include semi-empirical equations that are known to over or underpredict and some soft computing techniques that is incapable of generating predictive equations. This study proposes a gene expression programming (GEP)-based mathematical model to predict the concrete edge breakout capacity of single anchors loaded in shear. In doing so, an experimental database compiled by the American Concrete Institute (ACI) Committee 355, containing 366 samples, was used for the model training and testing. The independent variables considered in the model development are the edge distance, anchor diameter, embedment depth and concrete strength. Moreover, the predictive performance of the developed model was compared to that of the existing models proposed in ACI 318 and the Eurocode 2 (EC2) design standards. The assessment showed that the proposed GEP-based model provided a much more uniform and accurate prediction of the actual strength than the models in the existing design standards. The proposed mathematical model is simple and robust and is expected to be very useful for evaluating the concrete breakout shear capacity of single anchors in pre-planning and pre-design phases; that is, towards inclusions in design standards

A review of the engineering properties of metakaolin based concrete: towards combatting chloride attack in coastal/ marine structures

Changing human lifestyle and increasing urbanisation are contributory factors to the high demand for concrete construction materials across the globe. With the imminent developments in the unpopulated marine/coastal zones, higher installation of concrete facilities is still expected. However, poor design and construction procedures coupled with inadequate materials selection and exposure to aggressive environmental conditions, such as chloride laden environments, often result in the reduced aesthetic and structural performance of concrete. Deterioration of reinforced concrete structures located in a coastal/marine setting can influence the safety, economic, and sustainability aspects of society. Hence, there is an increased need for alternate binder systems with the ability to reduce the effects of chloride attack in concrete. 1is paper presents a critical review of the engineering properties of metakaolin (MK) based concrete exposed to chloride attack. 1e key advantages and limitations of using MK for concrete production purposes were outlined and evaluated. Areas for future research were also highlighted in this paper. Based on the favourable 28-day compressive strength (73–84 MPa) and durability performance documented across the numerous past year studies that were reviewed, it can be concluded that MK is a viable alternate binder material for combatting chloride attack in coastal/marine concrete structures. 1is, in conjunction with its lack of chemical CO2 emissions, proves that MK can be used to improve the serviceability and sustainability states of marine structures. 1e viewpoint of this review will guide concrete constructors and researchers on a possible framework for the utilisation of metakaolin for enhancing durability concrete in aggressive environments

Mechanical and durability properties of recycled aggregate concrete with ternary binder system and optimized mix proportion

tThis study aimed to investigate the mechanical and durability properties of recycled aggre-gate concrete with a ternary binder system and optimized mix proportion. Two concretebatches were developed using a densified mix design approach (DMDA) to evaluate therequired mix proportions. Batch I have GGBS content varied at 0%, 10%, 20%, 30%, 40% and50% at constant w/b ratio of 0.45, while batch II concrete mix have varied water/binder ratios:0.3, 0.35, 0.4, 0.45 and 0.5 at constant GGBS replacement level of 30%. The fine aggregate(river sand) of the two batches was blended with fly ash at optimum loose packing density(FA + Sand) and superplasticizer (SP) was incorporated in the mix at a constant level of 1.4%.A control mix comprising of natural aggregate was also developed. The results obtainedshowcased the feasibility of producing structural concrete with recycled aggregates usingGGBS and fly ash. The mechanical and durability properties were best at 30% GGBS content and 0.35 water/binder ratio. The DMDA for mix proportion adopted for RAC contributed sig-nificantly to improving its properties when compared to NAC, especially at the optimumobserved RAC mix with compressive strength of 52 MPa. Also, the mix demonstrated goodpermeability resistance in terms of chloride-ion ingress and capillary water absorption

Engineering performance of metakaolin based concrete

The sustainable development goal (SDG) 14 of the 2030 Agenda for Sustainable Development aims at protection, conservation, and management of coastal ecosystems and resources, including by strengthening their resilience, to avoid significant adverse impacts. Coastal/marine structures are exposed to aggressive environmental con- ditions, such as chloride laden environment. Deterioration of reinforced concrete structures located in a coastal/ marine setting can influence the safety, economic and sustainability aspects of the society. Hence, there is an increased need for sustainable materials with the ability to reduce the effects of chloride attack in concrete. This experimental study aims to investigate the engineering properties of metakaolin (MK) based concrete exposed to chloride attack. The investigation was conducted for different w/b ratios of 0.54–0.61. The MK, utilised as cementitious material, was varied from 0 to 20% with an increment of 5% and ages of concrete from 7 to 56 days were considered. The effects of the above-mentioned parameters on the various properties of concrete such as workability, compressive and flexural strength, durability, resistance to chloride attack and microstructure properties of the concrete samples were investigated. From the favourable strength and durability results that were observed during the experimental study (optimum compressive strength of 49.8 MPa for 10% MK and optimum flexural strength of 8.35 MPa for 5% MK), it can be concluded that MK is a feasible supplementary cementitious material for combatting chloride attack in coastal/marine concrete structures. The obtained results, in combination with the lack of carbon dioxide CO2 released during the MK manufacturing process, further highlights the positive influence of MK on improving the serviceability and sustainability states of coastal/marine structures

Utilization of millet husk ash as a supplementary cementitious material in eco-friendly concrete: RSM modelling and optimization

The environment has been greatly impacted by the increase in cement consumption. However, a huge quantity of energy is consumed and large amount of poisonous gases releases into the atmosphere during the cement production, which harms the environment. In order to decrease not only cement manufacturing but also energy usage and to aid in environmental protection, scientists are attempting to introduce agricultural and industrial waste materials with cementitious characteristics. Therefore, millet husk ash is used as supplementary cementitious material (SCM) in the concrete for producing sustainable environmental. The main purpose of this investigation is to check the workability, compressive strength, splitting tensile strength, flexural strength and drying shrinkage of concrete incorporating 0 %, 5 %, 10 %, 15 % and 20 % of MHA as SCM in concrete. A total of 165 concrete samples was made with mix proportion of 1:1.5:3 and cured at ages of 7, 28, and 90 days. The investigational outcomes displayed that there was an improvement in compressive strength, tensile strength, and flexural strength by 11.39 %, 9.80 %, and 9.39 %, correspondingly, at 10 % of MHA replacement of cement. Also, the water absorption reduced as MHA content increased after 28 days. There was also a reduction in drying shrinkage of concrete as the MHA increased after 28 days. Though, the workability is declined as the proportion of MHA increased in concrete. Moreover, the embodied carbon is declined while the content of PC substituted with MHA rises in concrete. In addition, response prediction models were built and validated using ANOVA at a 95 % significance level. R2 values for the models varied from 87.47 to 99.59 percent. The study concludes that the accumulation of 10 % MHA in concrete has a favourable effect on the characteristics of the concret

Experimental Findings and Validation on Torsional Behaviour of Fibre-Reinforced Concrete Beams: A Review

Fibres have long been utilized in the construction sector to improve the mechanical qualities of structural elements such as beams, columns, and slabs. This study aims to review the torsional behaviour of various forms of fibre reinforced concrete to identify possible enhancements and the practicability of concrete structural beams. Concrete reinforced steel fibre, synthetic fibre, and hybrid fibre are examples of fibre reinforced concrete. The review found that the mixing, orientation, and volume of fibres, the size of coarse particles, the aspect ratio of fibres, and the stiffness of fibres all affect the torsional strength of fibre reinforced concrete. Nevertheless, the application of fibres to recycled self-consolidating concrete of various forms needs to be explored and studied to ascertain its feasibility to facilitate greener concrete. Thus, with the results compiled in this review paper, it was possible to delimit advances and gaps on the effect of editing reinforcement fibres in relation to the torsion of structural element

Evaluation of pozzolanic reactivity of maize straw ash as a binder supplement in concrete

Cementitious materials, irrespective of their sources, play a vital role in cement hydration reaction in concrete. Hence, it is critical to understand how each supplement affects the early and later age properties of concrete. Maize Straw Ash (MSA), being a material with minimal consideration as a pozzolan for partial replacement of cement, was evaluated based on different researcher’s reports. A range of outcomes involving the use of maize straw ash as replacement materials in concrete were examined based on their impact on concrete in the early and later stages, and the findings were presented in addition to assisting in their future use. The impact of pozzolanic material on both mechanical and durability property were analysed, and how certain treatment methods influence the property of concrete in the early and later period. The data revealed that maize straw ash has comparable behaviour when given the same treatment technique before use, ability to increase strength over a long duration compared with other Agricultural waste (agro) materials, and likewise act as a void filler when concrete hardens to improve durability, with the usage of these materials for optimal strength not exceeding 20% replacement, shrinkage control not exceeding 30%, and 10–15% for good workability. At (500–800 °C calcination heat), the pozzolanic reaction produces good results