Karel Šeps

Cement Composite Reinforced with Synthetic Fibers: Comparison of Three-Point and Four-Point Bending Test Results

Presented article deals with the influence of PET fiber production on the bending strength of cement-based composite when incorporated into the fresh mortar, and comparison of results of 3-point and 4-point bending test. Cement paste samples were reinforced with 2 wt. % of primary or recycled PET fibers. The bending test was performed on prismatic samples with dimension of 40 × 40 × 160 mm. It was found that samples with recycled PET fibers, compared to primary ones, exhibit a decrease in bending strength. In the case of 4-point bending tests, the samples with recycled PET fibers exhibited higher bending strength than reference samples without any fibers. However, in the case of 3-point bending tests, the samples with recycled PET fibers had lower bending strength than the reference ones. The results suggest that recycled PET fibers could be used as an alternative to reinforce cement-based composites.

Composite Material from By-products and Its Properties

The paper shows an example of utilization of specific textile admixture – fluffs of torn textiles from waste cars in production of composite with aggregate consisting entirely of unsorted recycled concrete. The admixture in the mixture of recycled concrete and cement binder fills the pores and voids in composite. The elaborated composite has working title STEREDconcrete. In the article, basic mechanical-physical properties of the composite are presented also the fire resistance of STEREDconcrete, which was determined in tests.

Influence of Waste Crushed Limestone and Waste Micronized Marble Powder on Mechanical Properties of Cement Composite

For production of the samples were used several types of aggregate: the standard sand from Zalezlice, the standard sand from Gaza, waste crushed limestone, waste marble sludge and waste micronized marble powder. The Portland cement CEM I 42.5 R produced in Radotín was used as binder. Testing was carried at prismatic samples of dimension 40 × 40 × 160 mm. Another approach than previously used solutions consists primarily in micronization marble sludge with a high-speed mill, this modified micronized filler may also an impact on the final properties of composite materials based on cement. The micronized powder may have binding properties that are activated in this way. Dynamic modulus of elasticity, dynamic shear modulus, flexural strength and compressive strength were determined for the 28 days old samples.

Influence of Recycled Materials on Resulting Mechanical Properties of Cement Composites

This article presents the mechanical properties of composite materials based on recycled materials which differ in their composition – type of recycled materials. Dynamic modulus of elasticity was monitored during the first 28 days since manufacture by use of non-destructive testing (resonance method). Flexural strength and compressive strength were determined for the 28 days old specimens. The aim of this article was to determine the influence of type and amount of recycled material on the resulting mechanical properties. Mixtures with 3 different microground materials (recycled concrete, marble powder and silica sand) were tested. Microground materials were produced in the company Lavaris (Czech Republic) by use of high speed grinding. The results obtained from these materials were compared with reference material – cement mortar.