Comprehensive Investigation of the Long-term Performance of Internally Integrated Concrete Pavement with Sodium Acetate

The research carried out in this study presents the effectiveness of using sodium acetate as a protective material for concrete pavement. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Additionally, the morphology of sodium acetate and its interaction with concrete were investigated by using Scanning Electron Microscope (SEM). Results demonstrated the effectiveness of sodium acetate in protecting concrete

Predictive model of asphalt mixes’ theoretical maximum specific gravity using gene expression programming

The theoretical maximum specific gravity of asphalt concrete (Gmm) is an imperative volumetric parameter for asphalt mix design. Many studies in the literature proposed predictive models of the Gmm, yet there is a lack of considering the effect of aggregate absorption in the models. This study introduces, for the first time, a simple and reliable model for predicting the Gmm by Gene expression programming (GEP). Four parameters that influence the Gmm measurements and have weak multi-collinearity are considered as input variables in the model: asphalt content (AC%), aggregate absorption (Ab%), the aggregates’ bulk specific gravity (Gsb), and the percentage of mineral fillers (F%) passing 0.075 mm sieve. The model proved its accuracy to predict the Gmm with a 97.6% coefficient of determination (R2) value. The model satisfied the standard ASTM and AASHTO precision limits for estimating the Gmm for both procedures of absorptive and non-absorptive aggregate mixtures. The model is sensitive to capturing the influence of each selected variable with respect to the predicted Gmm. The results showed that the Ab%, Gsb, and F% have a positive relationship with the Gmm values compared with AC% where a negative relationship is observed. These observations were consistent with the overall trends of results found in the literature. This study provides a simple and accurate empirical equation that can be adopted for asphalt mix design and quality control applications

Durability Enhancement of Concrete with Recycled Concrete Aggregate: The Role of Nano-ZnO

The replacement of virgin aggregate with recycled concrete aggregate (RCA) in concrete mixtures offers an eco-strategy to mitigate the environmental limitations linked with traditional recycling techniques of RCA. However, the inferior properties of RCA, in contrast to virgin aggregate, present an obstacle to efficiently proceeding with this approach. Therefore, the aim of this study is to enhance the characteristics of concrete that contains RCA using nano-ZnO particles. Virgin aggregate was replaced with RCA in 30 wt.% and 50 wt.% ratios, followed by the addition of 0.5 wt.% nano-ZnO. The performance of concrete mixtures was evaluated in terms of their physical, mechanical, and durability properties. The addition of nano-ZnO particles to concrete with RCA resulted in refining its pore structure and reducing its water absorption, where the impermeability of concrete with 30 wt.% and 50 wt.% treated RCA decreased by 14.5% and 18%, respectively. Moreover, nano-ZnO treatment increased the compressive strength of mixtures with 30 wt.% and 50 wt.% RCA by 2.8% and 4%, respectively. All mixtures underwent a reduction in their 28-day compressive strength after exposure to a 5% sulphuric acid solution, where concrete with 30 wt.% and 50 wt.% RCA showed 20.2% and 22.8% strength loss, respectively. However, there was a 17.6% and 19.6% drop in the compressive strength of concrete with 30 wt.% and 50 wt.% RCA and treated with nano-ZnO

Improvement of ornamental stone wastes as sand replacement in concrete using silane coupling agent

This study investigates the replacement of fine aggregates in concrete with untreated and silane-treated marble and granite waste (MGW) in different ratios of 3 wt.-%, 5 wt.-%, 10 wt.-% and 30 wt.-%. Fresh, mechanical, durability, microstructural, and synergistic properties of all concrete mixtures were assessed by conducting slump test, compressive strength test, water absorption test, and Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses, respectively. The results illustrated that mixtures with untreated MGW aggregates achieved a maximum reduction of 58 % in their water absorption when replacing sand with 3 wt.-% MGW, while a maximum reduction of 30 % in the water absorption of concrete was achieved when replacing sand with 30 wt.-% treated MGW. Moreover, all mixtures with MGW (treated and untreated) showed an improvement in their compressive strength at 28 days compared to the control, where a maximum increase of 20 % was achieved when replacing sand with 5 % silane-treated MGW. Microstructural and synergistic analyses revealed that mixtures with untreated MGW appeared to develop fewer microcracks, less distribution of hydration crystals (i.e., ettringite), and higher content of C–S–H than the control. In addition, as appeared in the SEM analysis, the incorporation of treated MGW into concrete resulted in the formation of microcracks that are more noticeable and prominent than the microcracks that were formed in concrete with untreated MGW