Effect Of Recycled Coarse Aggregate Research Articles

Pengaruh Void Ratio dan Permeabilitas Beton Terhadap Kuat Tekan Beton Porous Dengan RCA

The infrastructure development raises the potential of old building destruction and demolition. This fact will results an environmental damage if construction waste is not being properly utilized. One type of construction waste that can be utilized is concrete waste. To apply sustainable development, concrete waste can be reused and recycled into aggregate in the form of RCA (Recycled Coarse Aggregate). Natural Coarse Aggregates (NCA) and RCA are processed into 0.5-1 cm, 1-2 cm, and 0.5-2 cm sizes and later mixed with cement paste into porous or pervious concrete. Porous concrete is a non-structural concrete which is water-permeable and has large pores. This study aims to determine the effect of RCA on the velue of concrete compressive strength, the most optimal concrete variation, and the influence of void ratio and permeability to the compressive strength of porous concrete. The result reported that RCA affects the compressive strength,, it can be proven that any variation of aggregate size, concrete variation with 0% RCA has the higher value than the 100% RCA one. The optimum concrete condition is in variation of 50% RCA at aggregate size 0.5-2 cm. The compressive strength value is 10.211 MPa. This is due to the more diverse aggregates affecting the concrete density. The larger the pores of the concrete (void ratio), the permeability value will be higher and the higher void ratio and permeability of concrete, the value of the compressive strength of porous concrete will be lower.

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

The present investigation aims to use recycled coarse aggregate (RCA) and ground granulated blast furnace slag (GGBFS) as replacement of natural coarse aggregate (NCA) and ordinary Portland cement (OPC) for developing sustainable concrete. Sixteen numbers of concrete mixes are prepared with 0%, 25%, 50% and 100% replacement of NCA by RCA for each 0%, 20%, 40% and 60% replacement of cement by GGBFS. The effects of RCA and GGBFS on fresh and hardened concrete properties such as workability, compressive strength, split tensile strength, flexural strength, rebound number, density, water absorption and volume of voids are experimentally investigated. The test results obtained in the present investigation show that the workability increases with the use of RCA or GGBFS or both of these two. The compressive, split tensile and flexural strength decrease with increase in the percentages of RCA or GGBFS or both. The reduction in split tensile and flexural strength of the concrete mixes containing RCA or GGBFS or both RCA and GGBFS is less pronounced unlike its compressive strength. The values of rebound number obtained from non destructive test (NDT) show the similar trend with the results of compressive strength. Water absorption and volume of voids of the concrete mixes increases with increase in RCA content. However, the use of GGBFS improves the quality of the concrete mixes by improving the ITZ and bond between mortar and RCA. The concrete mix with 50% RCA and 40% GGBFS achieves values of these properties closer to those of the concrete mix without RCA and GGBFS. Finally, the concrete mix with 50% RCA and 40% GGBFS is considered as the optimum mix which is satisfying the target mean strength of the mix design and producing sustainable concrete by saving 40% of cement and 50% of NCA and utilizing maximum waste products such as GGBFS and RCA.

Mechanical and durability properties of fly ash geopolymer concrete containing recycled coarse aggregates

Abstract This paper presents mechanical and durability properties of geopolymer concrete containing recycled coarse aggregate (RCA). The RCA is sourced from local construction and demolition (C&D) waste in Perth, Australia. The RCA is used as a partial replacement of natural coarse aggregate (NCA) in geopolymer concrete at 15%, 30% and 50% by wt. which corresponds to series two, three and four, respectively, while the geopolymer concrete containing 100% NCA is control and is considered as the first series. Class F fly ash is used as the source material for the geopolymer and 8 M sodium hydroxide and sodium silicate alkali activators are used to synthesise the fly ash geopolymer in this study. In all four series a constant alkali activator to fly ash ratio is used. Compressive strength, indirect tensile strength and elastic modulus of above geopolymer concrete are measured at 7 and 28 days, while sorptivity, immersed water absorption and volume of permeable voids of above geopolymer concrete are measured at 28 days. Relevant Australian standards are used to measure all the above properties except the sorptivity which is measured according to ASTM standard. Results show that the compressive strength, indirect tensile strength and elastic modulus of geopolymer concrete decrease with an increase in RCA contents, which is also true for both 7 and 28 days. Excellent correlations of compressive strength with indirect tensile strength and elastic modulus are also observed in geopolymer concrete containing RCA. Existing empirical models for cement concrete and geopolymer concrete containing NCA underestimate and overestimate the indirect tensile strength and elastic modulus, respectively of geopolymer concrete containing RCA. The measured durability properties such as sorptivity, water absorption and volume of permeable voids of geopolymer concrete were also adversely affected by the incorporation of RCA and these properties increase with an increase in RCA contents. The effects of RCA on the measured mechanical and durability properties of geopolymer concrete follow similar trend in cement concrete. Very good correlations of compressive strength with volume of permeable voids and water absorption of geopolymer concrete containing RCA are also observed, while the correlation between the compressive strength and the sorptivity is not that strong.

Properties of Self Compacting Concrete Using Recycled Coarse Aggregate

Abstract This paper presents the influence of different amounts of recycled coarse aggregate (RCA) obtained from a demolished Town Club building of Banki, N.A.C of Cuttack region, about 25 years old on the properties of self compacting concrete (SCC) and compared the results with normal vibrated concrete (NVC) containing 100% natural coarse aggregate (NCA). Important properties such as physical and mechanical properties of natural and recycled aggregates are carried out. NCA is partially replaced with RCA by an amount 10%, 20%, 30% and 40%. The effect of RCA on the properties of SCC in green state (e.g. Slump flow test, V-Funnel test and L-Box Test) and properties of concrete in hardened state (e.g. compressive strength, flexural strength, and Split tensile Strength) are studied. The mix design was carried out for M25 grade of concrete. The experimental results indicate that the compressive strength, flexural strength and split tensile strength of the SCC with 100% natural aggregate is less than the normal vibrated concrete (NVC) with 100% natural aggregate and the strength of SCC decreases with an increase in recycled aggregate (RA) replacement ratios. The present study recommends SCC marginally achieves required compressive strength up to 30% replacement of RCA.

Fresh Properties of Self-Compacting Concrete with Coarse Recycled Aggregate

In this paper, the fresh properties of self-compacting concrete (SCC) using recycled coarse aggregate (RCA) were evaluated. Five types of SCC mixtures were made, where the percentage of substitution of natural coarse aggregate by RCA was 0, 25, 50, 75 and 100%. The cement content, water to binder (W/B) ratio and Superplasticizer dosage were kept the same for all mixes. The effects of RCA on the key fresh properties such as filling ability, passing ability, and segregation resistance of SCC were investigated by conducting several fresh concrete tests included slump-flow, L-box, and sieve stability tests. The overall test results suggest that RCA can be used to produce SCC substituting up to 100% natural coarse aggregates without affecting the key fresh properties of concrete.