Ozgur Ekincioglu

Effect of TiO2 Addition on the Properties of Macro Defect Free Cement-Polymer Composites

Macro-defect free (MDF) cement is a cement-polymer composite with superior flexural strength although produced by mixing cement with small amounts of polymer and water. Special production technique and the crosslinking occurred between cement and polymer are important factors for obtaining such high strengths. However, MDFs lose considerable strength when exposed to water. The objective of this study was to explore the effects of TiO2 addition on flexural strength and water sensitivity of MDF. In this study, MDF cements were produced by adding up to 4 % TiO2 by weight of cement. Biaxial flexural test as well as Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) tests were conducted in order to investigate the effect of TiO2 addition. TiO2 addition improved the water resistance of MDF cements in some batches, especially with 2 % addition possibly due to the CPVA–O–Ti–O–CPVA bond and this cross-linking mechanism together with CPVA–O–Al–O–CPVA bonds cause a more stable polymer network.

Effect of Epoxy Resin Addition on the Moisture Sensitivity of Macro Defect Free Polymer-Cement Composites

Macro-defect-free (MDF) cements are cement-polymer composites and were developed by Birchall et al. three decades ago. The composites are produced by mixing small amounts of polymer and water with cement. However, they have a different production method than that of cement pastes, which was inspired by rubber production. Mixtures of cement, polymer and water are processed by using a two-roll mill. The composites are known with their high flexural strengths. Unfortunately, there are not any known commercial products using MDF cements because of their poor durability under moisture. In this study, MDF cements were prepared by using poly(vinyl alcohol--vinyl acetate) PVA, calcium aluminate cements and two different types of epoxy resins. Epoxy resins were a diglycidyl ether of bisphenol A and a mixture of a diglycidyl ethers of bisphenol A and F. Durability performance was compared with respect to biaxial flexural strengths, contact angle and atomic force microscopy (AFM) for the specimens stored in water.

Evaluation of Interface Shear Strength Between Interlocked Geofoam Blocks and Cast-in-Place Concrete

Expanded polystyrene (EPS) block (geofoam block) roadway embankment typically involves the construction of cast-in-place reinforced Portland cement concrete (PCC) slab as a traffic load distribution layer since it reduces live load stresses and also provides lateral confinement of the overlying unbound pavement layers. Therefore, in addition to the geofoam block to geofoam block and geofoam block to bedding sand, interface properties of geofoam block to cast-in-place concrete slab should also be investigated for the stability calculations regarding transitional sliding failure mode. In order to enhance the traditional geofoam block to cast-in-place concrete interface shear strength, previously introduced interlocked geofoam block concept has been utilized. Flat-surfaced traditional geofoam blocks were trimmed by a hot-wire to form interlocked geofoam blocks with ledges along their contact surface with the cast-in-place concrete. EPS19 with a minimum density of 18.4 kg/m3 was used in the experimental program. Four different types of interlock configurations (blocks with one- and four-square ledges and blocks with one- and four-triangle ledges) were used to investigate the effect of interlocked geometry and number of ledges in the shear plane. In addition, interface friction properties of traditional geofoam block and cast-in-place concrete surface was also quantified to highlight the improvement provided by the interlocking mechanism. The adhesion bond between traditional geofoam blocks and cast-in-place concrete was close to that of internal shear strength of geofoam blocks. Regardless of the shape, the interface adhesion bond was slightly improved by the number of ledges when compared to that of traditional geofoam and cast-in-place concrete.