THE EFFECT OF CELLULOSE FIBER ON THE PROPERTIES AND STRUCTURE OF HARDENED CEMENT PASTE

The article analyses the effect of cellulose fiber on the properties and structure of hardened cement paste. Nine batches of concrete were mixed: one batch for the control sample without cellulose fiber, and eight batches with cellulose fiber introduced at the rate from 0.25% to 2 %. The modification of hardened cement pastes with cellulose fiber showed that the addition of cellulose fiber at 2 % caused a 5.4% drop in the heat of hydration, which increases the workability of concrete mix and has a positive effect on concrete manufacturing. The cellulose fiber obtained from waste paper has a positive effect on the microstructure of hardened cement paste as it bonds well to the cement matrix in mortars containing 1 % of cellulose fiber. The flexural strength of hardened cement paste was found to increase with higher cellulose fiber content. The control sample without cellulose fiber had the flexural strength of 3.24 MPa and the sample modified with 2% of cellulose fiber had the flexural strength of 6.89 MPa, which is more than twice the value of the control sample. Thus, cellulose fiber can be added up to 1 % in the production of modified concrete products subjected to flexural force during operation

THE EFFECT OF CRUSHED GLASS AND METAKAOLIN WASTE IN THE PROPERTIES OF MODIFIED CONCRETE

This paper examines the possibility of using waste crushed glass as a substitute for sand, and waste from the production of foaming agent - metakaolin as a substitute for cement in the production of modified concrete. Concrete mixes were formulated with different amounts of metakaolin (M) replacing cement at 5 %, 10 %, 15 % and 20% and 25% crushed glass (TS) replacing sand. From the results of the research, it can be said that crushed glass waste and metakaolin waste can be used in the production of modified concrete, while reducing the amount of cement and sand. The optimal amounts of waste to replace part of cement and sand is 10% of metakaolin waste and 25% of crushed glass waste, with which concrete mix increase density, ultrasonic pulse velocity (UPV), compressive strength, frost resistance cycles, absorption decreases. Thus, using metakaolin waste 10% (replacing Portland cement) and 25% crushed glass waste (replacing sand) in concrete mixes results in more durability concrete can be used in building structures

THE EFFECT OF A POZZOLANIC BY-PRODUCT CONTAINING GLASS POWDER AND METAKAOLIN ON THE PROPERTIES AND AAR RESISTANCE OF MORTAR INCORPORATRING CRUSHED GLASS

The paper presents the research into the effect of an integrated pozzolanic addition containing glass powder and metakaolin on the physical and mechanical properties and the resistance to an alkali aggregate reaction in mortars incorporating crushed glass. Six batches of specimens were made for the tests. Sand was replaced with 25% of crushed waste glass in all the specimens. Cement was replaced with 5% of glass power (GP) and 5%-25% of metakaolin (MK) by weight. Specimens containing 20% of the compound pozzolanic addition were found to have better physical and mechanical properties and higher resistance to alkali aggregate reactions compared to the reference specimens without the addition. Additional hydration products were observed in X-ray and microstructure tests. The formation of new products confirms the results of the tests of the physical and mechanical properties and resistance to alkali aggregate reactions. Mortars incorporating crushed glass were found to be suitable for applications in potentially corrosive environments when modified with a 20% of a compound pozzolanic addition consisting of 5% waste glass powder and 15% waste metakaolin

THE EFFECT OF WASTE FROM MINERAL WOOL MANUFACTURING ON THE PROPERTIES OF CONCRETE

The article analyses the effect of the residues from mineral wool manufacturing (mineral dust) on the properties of concrete. Concrete mixes were made of cement, sand, gravel, superplasticiser, water and mineral dust generated as a residue stream in the manufacture of stone wool. Different compositions of concrete mix were designed where cement was replaced by mineral dust at 0 %, 2.5 %, 5 %, and 7.5 % by weight of cement. Tests were made to determine the following characteristics of concrete modified with different amounts of mineral dust: density, compressive strength, ultrasonic pulse velocity, water absorption rate, resistance to cyclic freeze-thaw action. The evaluation of physical and mechanical properties of the tested concrete revealed that modification of concrete with 5 % of mineral dust leads to higher density, ultrasonic pulse velocity, compressive strength and resistance to cyclic freezing and thawing and lower water absorption rate. Concrete modified with up to 5 % of mineral dust by weight of cement in the mix is durable concrete that can be used in engineering structures

THE EFFECT OF POZZOLANIC WASTE OF DIFFERENT NATURE ON THE HYDRATION PRODUCTS, STRUCTURE AND PROPERTIES OF HARDENED CEMENT PASTE

The paper analyses the effect of different pozzolanic waste - ground waste glass, metakaolin and addition made of ground waste glass and metakaolin, on cement hydration and physical-mechanical properties of hardened cement paste. Four batches of specimens were made for the tests. Cement (C) in the cement matrix was replaced with 5% of ground waste glass (5S), 15 % of metakaolin and mixed pozzolanic was addition (MIX 20) made of 5% of ground waste glass and 15 % of metakaolin. The best improvement of mechanical properties after 90 days of curing was observed in the specimens modified with the mixed pozzolanic addition. X-ray, TGA tests and microstructure analysis revealed that the improvement of mechanical properties is caused by the higher content of hydration products and a strong contact zone between glass particles and foam glass splinters present in metakaolin waste addition. The formation of C-S-H hydrates on the surface of glass foam splinters and in the pores was also observed. This kind of microstructure formation has a positive effect on cement matrix microstructure and physical-mechanical properties of hardened cement paste

IMPACT OF NATURAL ZEOLITE ON THE PROPERTIES AND RESISTANCE TO ALKALI SILICA REACTION OF MORTAR

This research investigates the effect of the amount (from 2.5 % to 15 %) of natural zeolite on the alkali silica reaction resistance (ASR), density, ultrasonic pulse velocity and mechanical properties of mortar. Research revealed that physical and mechanical characteristics of mortar mix improve with higher amount of natural zeolite, however, the appropriate zeolite amount must be selected because overdosing leads to deterioration of mortar mix properties. The impact of natural zeolite and the amount used on the expansion of mortar specimens was tested using Rilem AAR-2 method. Altered composition mortar specimens were tested using SEM and X-ray structure analysis, their mineral composition was determined. Dependence between natural zeolite amount in mortar mix, mineral composition of hardened mortar and expansion was determined. Test results revealed that alteration of mortar composition by natural zeolite not only improves physical and mechanical properties of the mix but also increases alkali silica reaction resistance (ASR) of mortar. The tests revealed that alteration of mortar composition with 15 % of natural zeolite (replacing cement mortar mix) increases durability and resistance to alkaline silica reaction

THE EFFECT OF POZZOLANIC WASTE AS CEMENT SUBSTITUTE ON THE PROPERTIES OF CEMENT MORTAR AND RESISTANCE TO ALKALI-SILICA REACTION

The article analyses the effect of pozzolanic waste on the properties of cement mortar. Seven batches of specimens were made for the tests: control specimens without any pozzolanic waste, three batches of specimens where cement was replaced with 5%, 10%, and 15% of wood fly ash, and three batches of specimens where cement was replaced with 5%, 10%, and 15% of ground glass. The replacement of 5% of cement with pozzolanic waste in the mix increased the density, the ultrasonic pulse velocity, compressive and flexural strengths of the mortar. A further increase of pozzolanic waste content degraded the values of physical and mechanical properties, as the lower amount of cement did not ensure a strong bond between the aggregate and the cement matrix. The alkali-silica reaction tests revealed that the expansion of the specimens containing 5% of pozzolanic waste as cement replacement does not the permissible limit of 0.1%. With the increase of pozzolanic waste content up to 15%, the expansion of specimens modified with wood fly ash continues decreasing down to the limit of 0.01%, whereas the expansion of the specimens modified with ground glass starts increasing to the limit of 0.05%

THE IMPACT OF RUBBER ADDITIVE CONTENT ON THE PROPERTIES OF CEMENT COMPOSITE

This paper analyses the impact of rubber additive content on the properties of cement composite. It describes the materials and the test methods used to determine various parameters of the composite mix and the cured composite. The properties of the cured composite were tested and compared. The effect of the amount of rubber additive on the following properties of cement composite was tested and analysed: slump flow, density, ultrasonic pulse velocity, compressive and flexural strengths, thermal conductivity, water absorption, and resistance to freeze-thaw cycles. The cement composite was produced by using crushed waste tyre granules as fine aggregate, i.e. sand was replaced with crushed tyre granules from 0 % to 10 %. The tests showed that the rubber additive used as sand replacement had little impact on the properties of the cement composite: density, ultrasonic pulse velocity, flexural and compressive strengths of the modified composite decreased, but resistance to freeze-thaw cycles increased. According to the test results and their analysis, 10 % is the optimal rubber additive content to be used as sand replacement in cement composite, which would have higher frost resistance and a lower coefficient of thermal conductivity

THE EFFECT OF A COMPLEX POZZOLANIC ADDITIVE CONSISTING OF MILLED GLASS AND METAKAOLIN ON THE DEGRADATION OF A CEMENTITIOUS COMPOSITE WITH GROUND WASTE GLASS CAUSED BY ALKALI-SILICA REACTION

This paper investigates the effect of partial replacement of cement by milled glass (MS), metakaolin (MK), and their mixture and partial replacement of sand by crushed glass (TS) on the physical and mechanical properties of a cementitious composite, as well as on the resistance of the composite to degradation caused by alkali-silica reaction (ASR). After 28 and 56 days of curing, the highest improvement in the mechanical properties was observed in the batches of specimens with the MS, MK and their mixture. The physical and mechanical properties of specimens with partially replaced sand to TS also deteriorated the least (the lowest expansion 0.02 %) with the application of the MS and MK mixture after 56 days of exposure to alkaline attack. XRD and microstructural analyses have shown that the reduction in expansion is due to the higher content of hydration products, as well as to the denser contact zone between the aggregate and the cementitious matrix

THE EFFECT OF CRYSTALLIZING ADMIXTURE ON THE PROPERTIES AND SHRINKAGE OF CONCRETE

This study investigates the effect of the amount (from 0.6 % to 1.4 %) of crystallizing admixture (CA) on the shrinkage, density, porosity and mechanical properties of concrete specimens. A higher content of CA increased the total porosity of concrete from 10.6 % to 11.15 %. In contrast to the specimens containing 0.8- 1.0% of CA, the lowest amount of closed pores and highest total porosity was observed in the specimens containing 1.2 %-1.4 % of the CA. Compared to the control specimen, concrete specimens containing 1.4 % of CA showed a 5.4 % decrease in flexural strength and a 13.6 % decrease in compressive strength after 28 days of curing. The specimens containing 0.9 %-1.0 % of CA demonstrated the lowest shrinkage in the period of 190 days. The shrinkage of these specimens reduced 4.8 %-4.9 % compared to the control specimen. Higher content of CA had an opposite effect on the shrinkage, a short-term expansion of specimens was observed after 28-56 days. Taking into account all the properties of the concrete specimen, the optimum amount of CA, which could prevent cracks in the structures is 1.0% of the cement mass