Utilization of Ceramic Waste Powder in Self-Compacting Concrete

TLDR: Rahhal et al. as discussed by the authors investigated the feasibility of utilizing ceramic waste powder (CWP) as filler material and examined the effect of using CWP on fresh concrete properties and mechanical properties of SCC.

Abstract: Self-compacting concrete (SCC) mixtures include high powder content (i.e. 450-600 kg/m) which is needed to maintain sufficient stability/cohesion of the mixture and hence improving segregation resistance. The use of high cement content to meet the need of high powder is not desirable as it will increase the cost and has other negative effects on concrete properties. The requirement for high powder content in SCC is usually met by using mineral admixtures such as slag, fly ash and/or less reactive filler materials such as limestone powder and granite powder. Ceramic waste powder (CWP) produced during the polishing process of ceramic tiles are dumped in landfills and can cause soil, air and groundwater pollution making a serious environmental problem. CWP is characterized by its fine particles’ size and chemical composition which is mainly SiO2 and Al2O3 (i.e. more than 80%). This makes CWP a very good candidate to be used as filler in SCC. Therefore, the utilization of CWP would achieve sustainable SCC with strong environmental incentives. In this study the utilization of CWP in making SCC is evaluated. The study involves two experimental phases. In the first phase; the main characteristics of the ceramic waste powder (i.e. chemical composition, specific surface area and scanning electron microscope) are examined. In the second phase; the effect of using CWP on fresh concrete properties and mechanical properties of SCC are investigated. It is found that CWP can be used to successfully produce SCC mixtures with improved fresh and hardened concrete properties. INTRODUCTION Sustainable waste management is an ongoing trend worldwide nowadays. This is accomplished through the utilization of recycled waste products in construction particularly concrete industry. This approach is considered an efficient way both economically and environmentally towards saving the exhausted landfills where huge amounts of industrial solid waste are being deposited annually. This waste management technique will also contribute towards reducing the carbon footprint on our ecological system produced from the great energy consumption used during cement manufacturing. It’s estimated that the production Fourth International Conference on Sustainable Construction Materials and Technologies http://www.claisse.info/Proceedings.htm of one ton of cement generates an equivalent amount of CO2 [Sadek et al. 2014]. The incorporation of industrial waste as alternative constituents in concrete industry will reduce the reliance on natural nonrenewable ingredients, and hence lower the quick depletion rate of raw minerals [Rahhal et al. 2014]. It will also help reducing the construction cost. Various industrial by-products have been widely used as less expensive cement substitutes and were proven to enhance the produced concrete properties both fresh and hardened [Uysal and Yilmaz 2011]. Self compacting concrete has been considered a great development in the construction field since it was first introduced in Japan in the late 20th century. This type of concrete inherits superior advantages over the traditional concrete. It is featured with high fluidity yet no segregation, and is placed under its own weight without the need for vibration. Large quantities of powder materials named generally as fillers or mineral admixtures are used to reduce the frequency of collision between particles and hence improve the flowability [Siddique and Kunal 2015]. Given the advantages SCC offers, many researchers have examined the role of different types of fillers both inert and reactive such as limestone powder, fly ash, and marble stone dust. For instance, [Pansesar and Aqel 2014] investigated the effect of replacing cement with limestone powder that resulted in higher compressive strength. Furthermore, a study conducted on marble powder [Alyamac and Ince, 2009] concluded that it had negligible effect on the flowability but can result in higher compressive strength compared to conventional concrete at a given w/c ratio. The ceramic products have been widely used in several applications in the building construction for a very long time. Unfortunately, the waste powder produced from the polishing process of the final ceramic products is generated in very large amounts and its disposal to landfills leads to great environmental problems. Therefore, the main aim of this study is to investigate the feasibility of utilizing ceramic waste powder (CWP) as filler material in self compacted concrete (SCC), and to examine its effect on both fresh and hardened properties. EXPERIMENTAL INVESTIGATION Materials. During the experimental work of this study, ordinary Portland cement Type I conforming to ASTM 150 was used. Natural coarse aggregates were obtained from Ras Al Khaima. The nominal maximum size, specific gravity, and absorption % of the used coarse aggregates were 10 mm, 2.65 and 1.0% respectively. While for the fine aggregates, two types were used namely: dune sand and crushed sand aggregates, with fineness modulus of 1.00 and 3.90 respectively. The specific gravity of the used fine aggregates was 2.63. Ground granulated blast furnace slag (i.e. slag) was used as filler in some of the mixtures with a specific surface area 432 m/kg and a specific gravity 2.93. Chemical analysis of CWP was conducted and showed that CWP is mainly composed of silica (SiO2) forming about 69.4% of the material. Furthermore, alumina also represents another major compound of CWP making about 18.2%. The total mix of silica and alumina oxides in CWP exceeds 80% of the total material weight. Other compounds included 3.19% Na2O, 3.53% MgO, 0.306% Cl, 1.89% K2O, 1.24% CaO, 0.617 TiO2, 0.83% Fe2O3, 0.266% ZrO2. Specific surface area (SSA) measurements using Blaine fineness method showed CWP to have SSA of 555 m/kg. The morphology of CWP was observed using scanning electron microscope (SEM) as shown in Figure 1. For both groups, polycarboxylic ether based superplasticizer (Glenium® sky 504) and a high molecular weight synthetic co-polymer viscosity modifying admixture (VMA) (RheoMATRIX ® 110) were used to improve the rheological properties of the mixtures. The optimum admixture dosages were chosen based on trial mixtures. The amount varied from 1.28% to 1.7% for the superplasticizer and from 0.29% to 0.33% for the VMA by weight of the binder content. Figure 1. SEM of Used CWP. Mix proportions. Tables 1 and 2 present the concrete mixture proportions. Two groups of mixtures were cast to investigate the addition of ceramic powder to the mixture and the replacement of cement by ceramic powder. In the first group the cement content in the control mixture (A-S-100) was 350 kg/m based on the preliminary mix design, which is below the value recommended by EFNARC-2005 specifications (i.e. powder content ≥ 450 kg/m). To meet the specifications’ requirements, slag was added as filler in the amount of 100 kg/m to fulfil the minimum powder content and to act as control mixtures. In mixes (A-S200 and A-S-300) the amount of slag was gradually increased to 200 and 300 kg/m respectively while maintaining the total powder content at 450 kg/m. Similarly, CWP was used in replacement of the slag (i.e. A-C-100, A-C-200 and A-C-300). For this group, the w/cm ratio used was (0.41). For the second group of mixtures, the initial cement content in the control mixture (R-0) was above the recommended value by EFNARC-2005 specifications without the need of any additional filler. The cement was partially replaced by the CWP in 20, 40 and 60% which are equivalent to 100, 200 and 300 kg/m respectively (R-100, R-200, and R-300). For this group, the w/cm ratio used was (0.35). The two groups were expected to yield compressive strength in the range of 60 to 80 MPa. MIXTURE PERFORMANCE EVALUATION Several tests were conducted to investigate the effect of CWP on both fresh and hardened properties of concrete. During the fresh stage, unconfined flowability of the produced SCC mixture was assessed by the slump flow test in accordance to ASTM C1611. The segregation resistance was evaluated through conducting the GTM segregation column test according to ASTM C1610. Correspondingly, strength was conducted at four different test ages (7, 28, 56, and 90 days) on three 100mm cubes at each test age and the average strength was calculated. Regarding the durability characteristics of the mixtures, it was examined through conducting the rapid chloride permeability test (RCPT) as per ASTM C1202. The RCPT was conducted on concrete disc (100mm diameter x 50 mm thickness) cut from the middle third of concrete cylinders. RCPT was performed on 2 specimens at two ages (28 and 90 days). Finally, Brunauer-EmmettTeller (BET) N2 measurement of porosity was performed on hardened cement pastes incorporating 0%, 20% and 40% CWP as replacement of cement representing concrete mixes R-0, R-100 and R-200. BET measurements aimed to determine the pore size distribution. The Barrett-Joyner-Halenda (BJH) analysis method was conducted to identify the change in cement paste porosity with incorporating CWP. Table 1. Mixture Proportions with Slag and CWP as Addition Mixture Ingredients Mixture Designation A-S-100 A-C-100 A-S-200 A-C-200 A-S-300 A-C-300 Cement (kg/m) 350 350 250 250 150 150 Slag (kg/m) 100 0 200 0 300 0 CWP (kg/m) 0 100 0 200 0 300 Water (Liters) 184 184 184 192 184 184 FA, Dune Sand (kg/m) 484 484 482 482 480.2 480.2 FA, Crushed Stone (kg/m) 484 484 482 482 480.2 480.2 CA 10-mm max. (kg/m) 792 792 771 771 785.7 785.7 Super Plasticizer (kg/m) 5.75 5.75 3 4.8 5.75 11.15* VMA (kg/m) 1.25 1.25 1.25 1.25 1.25 1.25 W/Cm 0.41 0.41 0.41 0.41 0.41 0.41 *high dosage of admixtures was used in this mix due to high casting temperature (40-45C). 1 Fine Aggregates 2 Coarse Aggregates Table 2. Mixture Proportions with CWP as Cement Replacement Mixture Ingredients Mixture Designation R-0 R-100 R-200 R-300 Cement (kg/m) 500 400 300 200 Slag (kg/m) 0 0 0 0 CWP (kg/m) 0 100 200 300 Wat