EFFECT OF AGGREGATE GRAIN SIZE DISTRIBUTION ON PROPERTIES OF PERMEABLE CONCRETE

WOS: 000396673900020In this study, the effect of aggregate grain size distribution and water/cement (W/C) ratio on the mechanical properties of permeable concrete is investigated. The aim of this study is to prepare permeable concrete mixture with optimum properties in terms of strength and permeability. For this purpose, five different permeable concrete mixtures with 0.3 constant W/C ratio and containing different proportions of coarse aggregate which are 5-15 and 15-25 mm, but containing no fine aggregate are prepared. In addition, three different concrete mixtures with 0.35 W/C ratio and containing 20% (by weight) fine aggregate and different proportions of coarse aggregate which are 5-15 mm and 15-25 mm are prepared. Afterwards, some tests related to the compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity (UPV) and permeability of concrete mixtures are conducted. Test results demonstrate that permeability, strength and UPV of the mixtures increased upon using 20 wt% of fine aggregate instead of coarse aggregate and upon reducing coarse aggregate grain diameter though W/C ratio of mixtures increases from 0.3 to 0.35

Properties of self-consolidating concrete incorporating coarse recycled concrete aggregate [Wlasciwosci betonu samozageszczajacego sie zawierajacego kruszywo grube z odpadowego betonu]

In this study, the effect of recycled concrete coarse aggregate on properties of self-consolidating concrete was examined. This aggregate was replacing 25%, 50%, 75%, 100% of limestone coarse aggregates. RC aggregate was used in SCC mixtures after 24 hours water saturation and surface dry (SSD). The results have shown that replacement of limestone coarse aggregate with RC aggregate caused the compressive strength decrease. However, the effect on tensile splitting and flexural strength was lower. As a result of this study it was found that it is possible to produce SCC compatible with EFNARC 2002. Moreover; it was observed that the use of RC aggregate in SSD state positively affected the fresh properties of SCC. © 2017, Foundation Cement, Lime, Concrete. All rights reserved.213M485The financial support of Scientific and Technical Research Council of Turkey (TUBITAK) under grant no. 213M485 is greatly acknowledged. -

Effect of cement C3A content on properties of cementitious systems containing high-range water-reducing admixture

The effect of cement tricalcium aluminate (C3A) content on the properties of cement paste, mortar, and concrete mixtures containing high-range water-reducing (HRWR) admixture was investigated. Three commercial Type I cements prepared with the same raw material and same gypsum rock interground with clinker, but with different C3A contents (by changing mixture proportions), were used. The fresh state, rheological properties, and compressive strength of the mixtures were studied. Moreover, X-ray diffraction (XRD) patterns of 6-h-age paste mixtures from each cement were obtained. By reducing the C3A content of the cements, the fresh state, rheological, and consistency retention properties of the mixtures improved; however, the strength of the mixtures at early ages decreased. The difference between strength of the mixtures closed at later ages. The XRD analysis of the pastes revealed the formation of more ettringite in the paste prepared from high C3A content cement. © 2017 American Society of Civil Engineers

Effect of recycled concrete aggregate quality on properties of concrete

The possibility of the use of recycled aggregates from the construction industry in green concrete production is of increasing importance to reduce the negative environmental impact associated with construction and demolition wastes. The objective of this study is to investigate the effect of recycled concrete aggregate (RCA) quality on the properties of hardened concrete properties such as compressive strength, splitting tensile strength, density, water absorption capacity and porosity accessible to water. The RCA used in this study was obtained from the crushing of waste concrete with two different compressive strengths (LRCA obtained from the crushing of waste concrete having compressive strengths below 30 MPa and HRCA obtained from the crushing of waste concrete having compressive strengths above 30 MPa). The natural coarse limestone aggregate was 100% replaced with coarse LRCA and HRCA. As a result of the study, the use of 100% HRCA and %100 LRCA instead of limestone coarse aggregate in the concrete adversely affected its mechanical and physical properties. In addition, HRCA showed better performance in terms of compressive strength, tensile strength, water absorption and porosity compared to the use of LRCA. Furthermore, the percentage of adhered mortar on the surface of LRCA and HRCA was analyzed using a computerized micro tomography device, and it was found that the percentages of attached mortar and aggregates are 61% and 35.5% for LRCA, whilst the attached mortar and aggregate contents for HRCA are 45.9% and 53.7%, respectively. © 2020, College Publishing. All rights reserved

Effect of polymer/cement ratio and curing regime on polymer modified mortar properties

Cement is the most consumed building material in the world. However, cement manufacture is responsible for 5–7% of the world CO2 emissions. In this paper, cement was partially replaced by styrene-butadiene rubber (SBR) polymeric latex in order to reduce cement consumption. Besides, effects of SBR addition on the strength and physical properties of plain mortar exposed to three different curing regimes are presented. Three different curing regimes were applied to the 40 × 40 × 160 mm prismatic mortar specimens: (I): Specimens were cured in water until the test age (CW), (II): after demoulding, specimens were immersed in water for 2 days and kept in ambient temperature until the time of the test (2DWA) and (III) involved 2 days of water curing followed by 1 day in an oven at 50°C and subsequentely placing in ambient temperature until the test time (2W1OA). Results showed that combining 2 days of water curing followed by ambient temperature curing (2DWA) along with 3% SBR polymer content showed good performance in terms of compressive strength, water absorption and void content. Moreover, a good performance in terms of flexural strength was observed by combining 2W1OA curing regime with 2% SBR content. However, the detrimental effect of water curing regime (CW) in terms of compressive and flexural strength was also observed with the increase of SBR ratio. © 2020, College Publishing. All rights reserved

An investigation into strength and permittivity of compacted sand-clay mixtures by partial replacement of water with lignosulfonate

Strength and permeability of sand-bentonite mixtures are of main concern, particularly in liner design. This study presents the results obtained from an experimental investigation of strength and permittivity of compacted sand-bentonite mixtures in the presence of water-reducing admixture of lignosulfonate. For this, sand-bentonite mixtures containing 4, 8, 12, 16% of bentonite were subjected to standard Proctor tests, to obtain the optimum water content and maximum void ratio of the mixtures. Similar specimens were prepared by partially replacing 0.5, 1 and 2% of water in the mixture with lignosulfonate. Additional specimens containing 16% of bentonite were prepared with 5% deviation towards the wet and dry sides of optimum water content, which was partially replaced with lignosulfonate for evaluation of the effects of deviation from optimum moisture content during densification. It was observed that partial replacement of water with lignosulfonate slightly increases the strength and decreases the permittivity, and that this effect was more pronounced as the replacement level was increased. Additionally, test results reveal that lignosulfonate replacement was more effective on the dry side of optimum water content

Performance of steel micro fiber reinforced mortar mixtures containing plain, binary and ternary cementitious systems

Steel micro fibers provide strengthening, toughening and durability improvement mechanisms in cementitious composites. However, there is not much data in the literature regarding how the extent of their effectiveness changes depending on the type of matrix being reinforced. For clarifying this point, the influence of a constant volumetric ratio (1%) of 6 mm long steel micro fibers on the performance of 5 mortar mixtures was investigated and were prepared using plain, binary and ternary cementitious systems. A total of 10 mixtures were cast. The mineral admixtures used in the study include silica fume (SF), metakaolin (MK) and a Class C fly ash (FA). While the replacement levels of SF and MK were 10% by weight of the total mass of the binder, this ratio was chosen as 30% for FA. In addition to the behavior of the mixtures under compressive, flexural and impact loads, abrasion, water absorption, chloride ion penetration, freezing-thawing resistance and drying shrinkage characteristics of the mixtures were determined. Test results indicate that generally the refinement in the pore structure of the matrix provided by mineral admixtures and the increase in resistance against growth and coalescence of micro-cracks provided by fibers produce a synergistic effect and improve the investigated performances of the mixtures. © 2016, College Publishing. All rights reserved