No abstract

Nano ferrite/cement composites (NFCC) have been prepared by adding different weight ratios of Nano ferrite (N.F) ranging from (1 up to 4%) cement. This study is aimed to evaluate the effect of addition of N.F on the mechanical behavior of NFCC and study the performance of cement pastes and cement mortars mixed with Nano ferrite (N.F) when exposed to elevated temperatures of 200 oC and 400 oC, for firing period of two hours. Compressive strength test showed valuable enhancement in mechanical properties of NFCC with increasing N.F loading ratio. The obtained minerals of Cu-Zn ferrites nanoparticles were identified by using X-ray diffraction (XRD) and the morphology of N.F was determined using transmission electron microscopy (TEM). The microstructure of the NFCC was characterized by means of scanning electron microscope (SEM) analysis. The addition of N.F by about 1% enhanced the compression strength to about 52 % for cement paste and1% enhanced the compression strength to about 35% for cement mortar. The results indicated that cement pastes and cement mortars mixedwith N.F are more able to resist elevated temperature than pure cement pastes.

Ultra Cellulose Fibers are hydrophilic fibers which can hold most of their weight water when it is mixed into concrete, after concrete is hardened, these fibers will slowly release this water to unhydrated cement during the critical early phases of curing which assist in more complete hydration, this internal self curing action results in more completely hydrated cement which contributes to more strength development and more control of internal microcracking, particularly when normal curing is not adequate. Also, these fibers can be used easily in ready mixed concrete batch plants and in hot weather environments. The results indicated clear improvements in both the shrinkage and compressive strength of all cement paste mixes contained these fibers in comparison with control ones in both normal and aggressive curing conditions.

In recent years, an emerging technology termed high-performance concrete (HPC) has become popular in construction industry. The constituent materials of HPC depend on the desired characteristics and the availability of suitable local economic alternatives. One of these alternatives is steel slag waste material. It is an industrial by-product waste particles resulted from reinforcing steel bars manufacture, its production is very huge; total quantity produced from all steel rebars manufacture factories in Egypt is nearly million tons/year. HPC made with steel slag aggregate (SSA) is considered as green concrete, using of steel-slag as a coarse aggregate increases the probability of consuming such large accumulations of slag (in HPC industry) which they represent as a waste and polluted material in environment. A total of eight under, balanced and over reinforced concrete beams were fabricated and tested. RC beams were made with HPC having compressive strength of 58.1 and 75.6 MPa and tensile reinforcement ratio in the range of 0.90 to 4.3%. Data presented concentrated on the chemical, physical, and mechanical properties of the used new material (SSA) and the flexural behavior of reinforced high-performance concrete beams made with steel slag coarse aggregate (RHPC-SSA) beams. It was observed that the RHPC-SSA beams can give satisfactory structural performance according to the American and Egyptian Building Codes.

ExtEndEd AbstrAct:The aim of this work is to study the effect of nanomaterials on the properties of cement paste, the experimental program included three parts: a-two types of nanosilica, locally produced NS1 and imported NS2, b-nanoclay (NC) and c-Hybrid nanoparticles (NS1 & NC). In each part, cement paste was used with different percentages of nanoparticles. Compressive strength and drying shrinkage tests were applied in each part on the cured and uncured samples. The results showed that the compressive strength improved in the cement paste mixtures in the cured condition, the optimum percentages was 1% for NS1, 1% for NS2, 5% for NC, and 5% (0.5%NS1 & 4.5%NC) for hybrid nanoparticles. The drying shrinkage increases with adding nanosilica and hybrid nanoparticles, while it decreases when adding NC. key words: nanosilica, nanoclay, hybrid nanomaterials. THE RESULTS OF THE SPECIALISTS' AND SCIENTISTS' RESEARCHESMAchinE-rEAdAblE inforMAtion on cc-licEnsEs (htMl-codE) in MEtAdAtA of thE pApEr