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Structures made from recycled aggregate concrete are exposed to high temperatures during fire scenarios which degrade their mechanical properties. Hence, this study investigated the residual mechanical properties of recycled aggregate concrete (RAC) containing ground granulated blast furnace slag (GGBS) after exposure to elevated temperatures. 21 experimental runs for design mix of RAC considering recycled coarse aggregate (RCA) replacement of natural coarse aggregate at 50, 75, and 100%, GGBS replacement of cement at 0, 20, 40, and 60% and water to binder ratio at 0.4 and 0.5 levels were used. The residual mechanical properties of RAC including compressive strength, splitting tensile strength, and elastic modulus were determined through laboratory experimental tests at room temperature (about 25°C) and after exposure to elevated temperatures of 200, 400, 600, and 800°C. Experimental results showed that residual mechanical properties of RAC decreased with increasing temperatures but their resistance to degradation was significantly enhanced with the addition of GGBS at 40% GGBS content. The novel model developed for the prediction of residual compressive strength of RAC has high prediction accuracy based on the performance metrics used to evaluate the model performance. The model has p-values less than 0.0001, a high R² value of 0.9781, a low root mean square error (RMSE) of 1.456 and mean absolute percentage error (MAPE) of 0.2287. Overall, the study contributed immensely to the knowledge of RAC as a sustainable alternative to normal concrete in areas prone to exposure to high temperatures which will significantly aid the effective fire safety design of structural members produced with recycled aggregate concrete.

Recently, sugarcane bagasse ash (SBA), generated in boilers after combustion of sugarcane bagasse for cogeneration has been basically accepted as a pozzolanic material. In this study, SBA, which was first sieved through the No. 100 sieve (SBA-s) before burning at 600 °C, 700 °C, 800 °C for 1 h as post-treatment (denoted as SBA-600, SBA-700, SBA-800) was sequentially used as a partial replacement for Portland cement (i.e. 5%, 10%, 15%, 20% by weight) in casting blended mortars. Performance in fresh and hardened states of these mixes were examined and compared to that of the cement mortar (cement: sand of 1:2.75 and water-to-cement ratio of 0.57). The results indicate that the SBA-systems required more mixing water than Portland cement; whereas, blended pastes with a part of re-burnt ash manifested an acceleration of setting time compared to that with SBA-s. In addition, mortars prepared with SBA-700 or SBA-800 at replacement rates of 5% and 10% for cement showed the lowest porosity, the best both of mechanical strength and durability (in terms of sulphate resistance, surface resistivity). SEM analysis verifies that a dense phase was observed for the matrix of blended mortars contained 5–10% SBA-700 or SBA-800. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse ash (SBA) is a by-product generated from cogenerations in sugar industries. This study is aimed at investigating on performance of alkali-activated binder using SBA and ground blast furnace slag (GBFS). The proposed mixtures were developed by changing GBFS/SBA ratios in blends (i.e. 100/0, 90/10, 80/20, 70/30, and 60/40) and silicate moduli (Ms = 0.6, 0.8, 1.2). Several results are highlighted: (1) alkali-activated GBFS/SBA pastes perform a quick hardening with an increase in Ms; (2) testing specimens cured in room–air ambient have the 28-day compressive strength beyond 110 MPa; and the 90/10 one shows the highest mechanical strength and manifested the best sulfate resistance and the lowest water absorption; (3) magnitude of drying shrinkage is smallest for 80/20 sample and following by the 90/10 sample. In summary, with balance of fresh behavior, strength, and shrinkage, a substitution up to 20% SBA could be appropriate to manufacture a sustainable binder. [ABSTRACT FROM AUTHOR]

This study presents the analytical models to predict the compressive strength of roller-compacted concrete pavement (RCCP) containing steel slag aggregate and fly ash. Based on the experimental results, three models were established in this study including multiple regression analysis (MRA), artificial neural networks (ANN) and fuzzy logic (FL). In the RCCP mixtures, cement was partially substituted by fly ash at four levels: 10%, 20%, 30%, and 40%; natural coarse aggregate was replaced by steel slag aggregate at ratio of 50% and 100%. The compressive strength was determined at 3-, 7-, 28-, 56- and 91-day ages. 75 sets of testing data were collected to build the target values set. With same seven input variables, the MRA model is less reliable than the ANN model in terms of predicting the compressive strength of RCCP. Besides, the use of triangular membership functions with three input variables (fly ash content, steel slag aggregate content and age) in the FL algorithm is sufficient to obtain accurate results. The performance of the FL model is as good as the ANN model. Additionally, a total of 33 fuzzy rules found for building the FL model can be applied to predict the compressive strength of RCCP. Highlights MRA, ANN, and FL were used to construct the models for predicting the compressive strength of RCCP containing steel slag aggregate and fly ash. The ANN model and FL model created reliable results in predicting the strength of RCCP. The MRA model is less reliable than the ANN and FL models in terms of predicting of RCCP compressive strength. The best model is the FL model because of its friendly and efficiency. [ABSTRACT FROM AUTHOR]