Preparation and mechanical properties of red mud-based geopolymer recycled concrete

An experimental program was carried out to investigate the usability of recycled coarse aggregate (RCA) concrete with and without ground granulated blast furnace slag (GGBFS). The RCA was derived from concrete having compressive strength of 47.6 MPa. Twelve concrete mixtures having various RCA (0–25–50–100%) and GGBFS (0–30–60%) replacement levels were designed with a water-to-binder (w/b) ratio of 0.50. Fresh concrete properties were observed through workability and slump loss. Compressive strength, tensile splitting strength, bond strength, ultrasonic pulse velocity, water absorption and density of hardened concretes were also determined at 7 and 28 days and the relations between physical properties and mechanical properties of RCA concretes with/without GGBFS were investigated. The RCA content significantly improved the tensile splitting strength of the concrete according to the compressive strength and the use of 60% GGBFS content in RCA concrete had a marginal increasing effect on the tensile splitting strength. The mixes containing 100% RCA was found to be noticeably beneficial in terms of the bond strength and the highest bond strengths were obtained with the use of 60% GGBFS content in RAC for all series at 28 days. However the lowest density and the greatest water absorption was obtained for RAC and an inverse relationship between the density and the water absorption ratio was determined.

Development of sustainable concrete using recycled coarse aggregate and ground granulated blast furnace slag

Bond, durability and microstructural characteristics of ground granulated blast furnace slag based recycled aggregate concrete

Fly ash, GGBS, and silica fume based geopolymer concrete with recycled aggregates: Properties and environmental impacts

PurposeThe purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing.Design/methodology/approachM25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na2SiO3) of 1:1.5, subjected to 90°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio.FindingsThe workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing.Research limitations/implicationsThe scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study.Originality/valueThe replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

Effects of elevated temperatures on properties of concrete containing ground granulated blast furnace slag as cementitious material

Service life prediction and environmental impact evaluation of recycled aggregate concrete with supplementary cementitious materials

A variety of ashes used as the binder in geopolymer concrete such as fly ash (FA), ground granulated blast furnace slag (GGBS), rice husk ash (RHA), metakaolin (MK), palm oil fuel ash (POFA), and so on, among of them the FA was commonly used to produce geopolymer concrete. However, one of the drawbacks of using FA as a main binder in geopolymer concrete is that it needs heat curing to cure the concrete specimens, which lead to restriction of using geopolymer concrete in site projects; therefore, GGBS was used as a replacement for FA with different percentages to tackle this problem. In this study, Artificial Neural Network (ANN), M5P-Tree (M5P), Linear Regression (LR), and Multi-logistic regression (MLR) models were used to develop the predictive models for predicting the compressive strength of blended ground granulated blast furnace slag and fly ash based-geopolymer concrete (GGBS/FA-GPC). A comprehensive dataset consists of 220 samples collected in several academic research studies and analyzed to develop the models. In the modeling process, for the first time, eleven effective variable parameters on the compressive strength of the GGBS/FA-GPC, including the Activated alkaline solution to binder ratio (l/b), FA content, SiO2/Al2O3 (Si/Al) of FA, GGBS content, SiO2/CaO (Si/Ca) of GGBS, fine (F) and coarse (C) aggregate content, sodium hydroxide (SH) content, sodium silicate (SS) content, (SS/SH) and molarity (M) 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 ANN model better predicted the compressive strength of GGBS/FA-GPC mixtures compared to the other models. Moreover, the sensitivity analysis demonstrated that the alkaline liquid to binder ratio, fly ash content, molarity, and sodium silicate content are the most affecting parameter for estimating the compressive strength of the GGBS/FA-GPC.

Effects of combined usage of GGBS and fly ash on workability and mechanical properties of alkali activated geopolymer concrete with recycled aggregate

Extensive use of cement in the construction industry increases CO2 emissions and has a negative impact on the environment. In this work, recycled coarse aggregate (RCA) from construction and demolition wastes (C&DW) was used to fabricate sustainable pervious concrete (PC). In order to mitigate the environmental hazards of excess cement waste and to improve the engineering properties of PC, silica fume (SF) and ground granulated blast-furnace slag (GGBS) were added. The effects of SF and GGBS on the compressive strength, permeability coefficient, porosity, and abrasion resistance of recycled aggregate pervious concrete (RAPC) were investigated. The results show that the incorporation of GGBS and SF effectively improves the compressive strength of RAPC but reduces the permeability coefficient and porosity. Moreover, due to the filling effect and pozzolanic activity, the incorporation of GGBS and SF significantly enhances the abrasion resistance of RAPC. Furthermore, the relationships between the compressive strength, permeability coefficient, porosity, and abrasion resistance of RAPC are clarified. The optimum replacement is achieved when the SF content is 7%, and the GGBS content is 20%, respectively, which results in the highest compressive strength (28.9 MPa) and the lowest permeability coefficient (1.2 mm/s) at 28 days, and the lowest mass loss rate (12.1%) after the Cantabro abrasion test.

This study used waste concrete as a recycled coarse aggregate and added an appropriate proportion of groundgranulated blast-furnace slag (GGBFS) to formulate recycled concrete. Based on the recycled coarse aggregate and GGBFS content, 24different mixture ratios were formulated, and then an experimental study of the slumpand compressive strength of the mixtures was conducted. The results showed that because slag can improve the physical and mechanical properties and performances of ordinary concreteand can compensate for certain natural deficiencies occurring in recycled coarse aggregate,GGBFS and recycled coarse aggregate can form recycled aggregate green concrete with a slump of 170mm and a 28-day compressive strengthof 50MPa.

This paper investigates the cement hydration, and the slag reaction contributes to the compressive strengths of mortars mixed with ground river sand (GRS) and ground‐granulated blast furnace (GGBF) slag with different particle sizes. GRS (inert material) and GGBF slag (reactive material) were ground separately until the median particle sizes of 32 ± 1, 18 ± 1, and 5 ± 1 micron and used to replace Portland cement (PC) in large amount (40–60%) by weight of the binder. The results showed that, at the early age, the compressive strength obtained from the cement hydration was higher than that obtained from the slag reaction. The results of compressive strength also indicated that the GGBF slag content and particle size play important roles in the slag reaction at the later ages, whereas cement hydration is more prominent at the early ages. Although the results could be expected from the use of GGBF slag to replace PC in mortar or concrete, this study had presented the values of the compressive strength along with ages and the finenesses of GGBF slag that contributed from cement hydration and from GGBF slag reaction.

Interaction of various parameters on the properties of semi-dry gypsum-based blocks produced by compression forming method

Evaluation of graded layer in ground granulated blast furnace slag based layered concrete

Performance of fly ash/GGBFS based geopolymer concrete with recycled fine and coarse aggregates at hot and ambient curing