Improved fire resistance by using slag cements

2021

J Therm Anal Calorim

The effects of elevated temperatures on the properties of high-strength cement paste (HSCP) based on metakaolin (MK), silica fume (SF), and fly ash (FA) were studied in the current experimental research. The resistance of HSCP against elevated temperatures was evaluated as well. The new method is expressed by the total area under each curve of strength, known as “temperature resistance”, is adopted. Results of the HSCP mixtures containing MK, SF, and FA with replacements ratios of 9%, 6% and 15% have shown excellent temperature resistance at all levels of maximum temperatures, respectively. Properties added to HSCP by these supplementary cementitious materials (SCM) such as decreasing the amount of CaO and increasing the amounts of SiO2 and Al2O3 have minimized the harmful effects of the use of pure ordinary Portland cement (OPC) at elevated temperatures. The results have shown also that the grinding fineness of OPC influences the amount of optimum replacement of the used SCM on HSCP at elevated temperatures. Hence, the amount of optimum replacement of MK blended with CEM I 42.5 N was 9% whereas, the amount of optimum replacement of MK blended with CEM I 52.5 N shifted to 3%. Finally, the fineness of cement of 4500 cm2 g−1 has shown a better-elevated temperature resistance compared to the cement with a fineness of 4000 cm2 g−1 in case of using pure OPC.

Section: Impact Of Different Types Of Scm On Compressive Strength Resultsmentioning

confidence: 97%

Section: Impact Of Different Types Of Scm On Compressive Strength Resultsmentioning

confidence: 99%

The impact of metakaolin, silica fume and fly ash on the temperature resistance of high strength cement paste

Abdelmelek

2021

J Therm Anal Calorim

“…The third temperature range 600-900 °C has corresponded to the decomposition of C-S-H and calcium-carbonate (CaCO 3 ) [36]. The amount of Ca(OH) 2 and the amount of CaCO 3 on the HCP are the responsible for the deterioration of the strength [34,37]. As shown in Fig.…”

Section: Thermogravimetric Resultsmentioning

confidence: 99%

“…The ultra-fine particles of SF that contribute as excellent fillers and their pozzolanic reactions lead to the formation of a very dense microstructure in the HCP, resulting an HCP with a high capacity to resist elevated temperatures. Above 400 °C, the efficiency of SF in the HCP was increased significantly, this could be interpreted by decreasing the effect of decomposition of (Ca(OH) 2 ) by pozzolanic reaction [34].…”

Section: Effect Of Sf Amountsmentioning

confidence: 92%

Effects of Elevated Temperatures on the Properties of High Strength Cement Paste Containing Silica Fume

Abdelmelek

Period. Polytech. Civil Eng.

2021

Self Cite

High strength concrete (HSC) production is worldwide increased and gradually replacing the normal strength concrete (NSC). The cement matrix of concrete is the essential part that governs the behavior and strength of concrete. Several researchers have focused on the performance of hardened cement paste (HCP) at ambient temperature such as using different types of supplementary cementitious materials (SCM). However, the performance of HCP after exposure to elevated temperatures requires further evaluation. The present study investigates the influence of different replacements of silica fume (SF) to cement and different water/binder ratios (w/b) on the compressive strength of HCP before and after exposure to elevated temperatures. Eighteen mixes have been prepared and tested. Results of compressive strength tests at ambient temperature were ranged from 58 to 102 MPa depending on the difference of w/b. Furthermore, a new method has been adopted for comparing the responses of HCP at elevated temperatures "heat endurance". Results showed that using SF enhances the residual compressive strength of HCP after exposure to elevated temperatures due to the pozzolanic reaction and the filler contribution. Mixes containing 6%, 12%, and 15% of SF have shown the highest relative residual compressive strength values for 0.30, 0.35, and 0.40 w/b, respectively. Consequently, the results were significantly affected by changing the w/b ratio. Finally, different measurement techniques were provided to support the work, including Thermo-Gravimetric (TG), Computed Tomography (CT), and Scanning Electron Microscope (SEM) analysis to characterize the loss of mass, porosity, and micro-structure alteration of HCP.

“…Damage in concrete material can occur in reinforced concrete structures during fire, which may be due to various causes, i.e. different thermal expansion of the hardened cement paste and the aggregate; internal water vapor pressure; or different temperature in the cross-section as well as along the length of the element [4]. In some cases excessive cracking, decrease of bond and anchorage between the concrete and reinforcement or spalling of concrete cover can also occur during fire [5].…”

Section: Introductionmentioning

confidence: 99%

Fibers and fiber cocktails to improve fire resistance of concrete

Czoboly

Hlavicka

et al. 2016

J Therm Anal Calorim

Self Cite

Our study was directed to improve the residual flexural strength and the heat resistant properties of concrete exposed to high temperatures using different fiber cocktail loadings including steel, polymer or cellulose fibers. At first the morphology and the thermal properties of the fibers and the fiber/cement composites were investigated by SEM and TG/DTA-MS. Then the influence of fiber type and amount on residual flexural strength were tested after cooling back from 150, 500 or 800 °C temperature loadings. By adding steel, cellulose and polymer (polypropylene) fibers to cement, improvements both in post-cracking residual flexural strength and in insensitivity against explosive spalling were reached.