Compressive strength of geopolymer concrete modified with nano-silica: Experimental and modeling investigations

Geopolymers are novel cementitious materials that have the potential to replace conventional Portland cement composites completely. The production of geopolymer composites has a lower carbon footprint and uses less energy than the production of Portland cement. Recently efforts have been made to incorporate different types of nanoparticles (NPs) in geopolymer composites to enhance the properties of the composite with improved performances. Nanotechnology is one of the most active research areas with novel science and valuable applications that have gradually gained attention, especially during the last two decades. Many studies have been undertaken to date in order to understand better the impacts of NPs addition on the fresh, physical, mechanical, durability, and microstructure properties of geopolymer composites. In the current comprehensive review paper, the effects of different NP types on the most essential fresh, mechanical, durability, and microstructure characteristics of geopolymer paste, mortar, and concrete composites were reviewed, analyzed, and discussed in detail. In this regard, more than 280 published papers were used to create an extensive database that includes the main features of geopolymer composites modified with different NPs. In addition, the main mechanisms behind the influence of different NP types on the properties of geopolymer composites were examined. Past progress, recent drifts, current obstacles, and the benefits and drawbacks of these geopolymer composites enhanced with NPs were also highlighted. Based on the findings of this study, the addition of NPs has a promising future for developing high-performance geopolymer composites that the construction industry can efficiently implement due to significant improvements in strength, durability, microstructure by providing additional C–S–H, N-A-S-H, and C-A-S-H gels as well as filling nano-pores in the geopolymer matrix. 

The role of nanomaterials in geopolymer concrete composites: A state-of-the-art review

• A comprehensive review on the fresh, mechanical, and structural performances of GPC is presented. • Like traditional concrete, GPC has good fresh and mechanical properties. • The general behavior of the structural beam members is comparable to that of typical reinforced concrete structural elements. • Structural member design codes are applicable, but they are conservative in nature. The manufacture of ordinary Portland cement (OPC) produces a lot of CO 2 in the atmosphere. Researchers have recently focused on exploring the behaviour of geopolymer concrete (GPC) as an alternative to Portland cement concrete (PCC) in micro and macro dimensions. Geopolymers (GP) are innovative cement-based materials that could totally replace OPC composites. Geopolymer composites (GC) have a reduced carbon footprint and utilize less energy than OPC. The construction industry's main concerns are material characteristics and the performance of reinforced concrete (RC) structural components. Therefore, this review paper is going to look at some important material properties, like fresh characteristics, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity, as well as the evidence of the structural behaviour of GPC beams. According to the findings of this review, GPC offers similar or superior fresh and mechanical properties to conventional concrete composite. In addition, it was mentioned that GPC might be utilized to design GPC members securely in terms of their strength capabilities and standard codes of practice. Nevertheless, further study is suggested to include more detailed and cost-effective design methods for the potential use of GPC for large-scale field applications. 

Geopolymer concrete as a cleaner construction material: An overview on materials and structural performances

Geopolymer concrete is an inorganic concrete that uses industrial or agro by-product ashes as the main binder instead of ordinary Portland cement; this leads to the geopolymer concrete being an eco-efficient and environmentally friendly construction material. A variety of ashes used as the binder in geopolymer concrete such as fly ash, ground granulated blast furnace slag, rice husk ash, metakaolin ash, and Palm oil fuel ash, fly ash was commonly consumed to prepare geopolymer concrete composites. The most important mechanical property for all types of concrete composites, including geopolymer concrete, is the compressive strength. However, in the structural design and construction field, the compressive strength of the concrete at 28 days is essential. Therefore, achieving an authoritative model for predicting the compressive strength of geopolymer concrete is necessary regarding saving time, energy, and cost-effectiveness. It gives guidance regarding scheduling the construction process and removal of formworks. In this study, Linear (LR), Non-Linear (NLR), and Multi-logistic (MLR) regression models were used to develop the predictive models for estimating the compressive strength of fly ash-based geopolymer concrete (FA-GPC). In this regard, a comprehensive dataset consists of 510 samples were collected in several academic research studies and analyzed to develop the models. In the modeling process, for the first time, twelve effective variable parameters on the compressive strength of the FA-GPC, including SiO2/Al2O3 (Si/Al) of fly ash binder, alkaline liquid to binder ratio (l/b), fly ash (FA) content, fine aggregate (F) content, coarse aggregate (C) content, sodium hydroxide (SH)content, sodium silicate (SS) content, (SS/SH), molarity (M), curing temperature (T), curing duration inside ovens (CD) and specimen ages (A) were considered as the modeling input parameters. Various statistical assessments such as Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), Scatter Index (SI), OBJ value, and the Coefficient of determination (R2) were used to evaluate the efficiency of the developed models. The results indicated that the NLR model performed better for predicting the compressive strength of FA-GPC mixtures compared to the other models. Moreover, the sensitivity analysis demonstrated that the curing temperature, alkaline liquid to binder ratio, and sodium silicate content are the most affecting parameter for estimating the compressive strength of the FA-GPC.

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Systematic multiscale models to predict the compressive strength of fly ash-based geopolymer concrete at various mixture proportions and curing regimes.

M. Talha Ghafoor

Papers

Influence of alkaline activators on the mechanical properties of fly ash based geopolymer concrete cured at ambient temperature