Key Engineering Materials Vol. 857

Abstract: This paper presents a study (experimentally) for strengthening reinforced concrete (RC) beams with Near-Surface-Mounted (NSM) technique. The use of this technique with CFRP strips or rebars is an efficient technology for increasing the strength for flexure and shear or for repairing damaged reinforced concrete (RC) members. The objective of this research is to study, experimentally, RC beams either repaired or strengthened with NSM CFRP strips and follow their flexural behavior and failure modes. NSM-CFRP strips were used to strengthen three RC beam specimens, one of them was initially strengthened and tested up to failure. Four beam specimens have been initially subjected to preloading to 50% and 80% of ultimate load. Two of the specimens were either repaired or strengthened with NSM-CFRP strips. All the repaired/strengthened pre-damaged beams have been tested up to failure by using compression-testing machine. An appropriate-scale model was adopted. All the specimens have a cross-sectional dimension of 150 mm with an effective span of 110 mm. Depends on the experimental results, a better performance of the strengthened concrete specimens was obtained in both strength and serviceability. As a comparison with the control beam specimen, all the repaired specimens show a very good increase of about 40% in the load-carrying capacity and a high improvement in resistance to cracking of about 120% in NSM. On the other hand, the test results of NSM CFRP-strengthened concrete specimens with a preloading of 50% and 80% of the ultimate load show an increase of about 9% to 20% in the load-carrying capacity, for 50% and 80% pre-loading, respectively an improvement in deflection of about 2% to 27% in NSM, for 80% and 50% pre-loading, respectively.

Abstract: This research is concerned with a new type of ferrocement characterized by its lower density and enhanced thermal insulation. Lightweight ferrocement plates have many advantages, low weight, low cost, thermal insulation, environmental conservation. This work contain two group experimental : first different of layer ferrocement, second different of ratio aggregate to cement. The experiments were made to determined the optimum proportion of cement and lightweight aggregate (recycle thermestone ). A low W/C ratio of 0.4 was used with super plasticizer conforming to ASTM 494 Type G. The compressive strength of the mortar mixes is 20-25 MPa. The work also involved the determination of thermal properties .Thermal conductivity value of this ferrocement plate is between (0.6-0.45)W/m.K.

Abstract: Reactive Powder Concrete (RPC) could be considered as the furthermost significant modern high compressive strength concrete. In this study, an experimental investigation on the impact of micro steel fiber volume fraction ratio and gamma ray irradiation duration influence upon the compressive strength of RPC is presented. Three volume fraction ratios (0.0, 1.0 and 1.5) % was implemented. For each percentage of the adopted fiber ratios, six different irradiation duration was considered; these are (1, 2, 3, 4, 5 and 6) days. Gamma source (Cs-137) of energy (0.662) MeV and activity (6) mci was used. In a case of zero volume fraction ratio, the experimental results showed that gamma ray had a significant influence on the reducing of the compressive strength varies between (1.2-8.6)% for a period of (1-6) days, respectively. Although there was a decrease in the compressive strength for a state of non-zero volume fraction ratio (1 and 1.5) % varies between (1.0-3.1 and 0.4-1.6) %, respectively, the attained results indicated that gamma ray had no significant effect to reduce the compressive strength of the RPC that’s included micro steel fibers as a volume fraction.

Abstract: This study evaluates the influence of utilizing silica fume as a stabilizer to the filler on the behavior of asphalt mixes. The investigation of the properties of asphalt mixes was conducted by using different percentages of Silica Fume (0, 3, 6, and 9% by filler weight). Results indicate that, the OAC is 4.7% and it achieves the best results in the Marshall tests. Marshall Stability is increased by about 27.5% and the flow is decreased by about 20.2 %. In this study the implementation of 9% of silica fume in the asphalt concrete mix showed a considerable excess in the resistance to moisture damage of 28% when compared to the original mix. A great decrease in the tensile strength of asphalt concrete mixes, in a range from (4-15)% could be noticed following the moisture damage process for both the reference and silica fume adjusted mixes. Six percent of it was the optimum percent that had developed the tensile characteristics of the hot asphalt concrete mixes. The moisture sensibility of the asphalt concrete was reduced with an increase in the silica fume content. Following the moisture damage process, Silica fume of 9% was the optimum percent that had developed the punching shear characteristics of asphalt concrete. It exhibited a positive effect of 20%, while 6-9% of silica fume exhibited a positive effect of 5-9% on the development of the tensile characteristics of asphalt concrete.

Abstract: Thermal conductivity is one of the most important properties of construction materials due to change the structure and the chemical composition of these materials particularly in hot weathers. Thermal conductivity testing of building materials in situ provides useful database about of temperature, moisture and conditions of storage. In this paper, thermal conductivity of Huston sand has been investigated for dry and saturation status by transient technique. TP02 Hukseflux probe used to calculate thermal conductivity of Huston sand. TP02 Hukseflux probe has been calibrated by Glycerol and compare with results from art-of-literature. The results showed that the value of thermal conductivity during the saturation is more than the dry state. This is identical to reality as the parameter is strongly influenced by presence of water. Comsol Multiphysics® simulation has been used to validate the experimental test. Slightly difference is marked between the experimental and theoretical results

Abstract: Reactive Powder Concrete (RPC) can be incorporate as a one of the most important and progressive concrete technology. It is a special type of ultra-high strength concrete (UHSC) that’s exclude the coarse aggregate from its constitutive materials. In this research an experimental study had been carried out to investigate the effect of using three types of materials (porcelain aggregate) and others sustainable materials (glass waste and granular activated carbon) as a partial replacement of fine aggregate. Four percentages had considered (0, 10, 15 and 20) % to achieve better understanding for the influence of these materials upon the compressive strength of RPC. Four curing ages had included in this study, these are; 7, 28, 60 and 90 days. The outcomes of the experimental works improved that using porcelain aggregate as a partial replacement had an advanced effect on the compressive strength for all the adopted percentages and for all the studied curing ages. The maximum modification that’s obtained in case of porcelain aggregate was (24.14) % at age (90) days for 20% replacement. Using glass waste caused an increase in the overall values of the compressive strength for all the adopted replacements with less efficient than porcelain to reached (20.69) % at age (90) days for 20% replacement. Regarding the granular activated carbon, only (10%) replacement had a positive influence on the compressive strength to reached (13.16) % while the others caused a reduction in the compressive strength reached to (29.13)% for 20% replacement.

Abstract: Al-Hadba minaret is one of the ultimate minarets in beauty and excellence that belonged to the constructions of Zankid dynasties in Syria and upper Mesopotamia. The minaret was built during the 12^th entury, it is located in the center of old Mosul city-Northern Iraq. This minaret is the most famous in the Middle East, since it has a significant curvature (banana shape) that threatens its integrity. Unfortunately, the main parts of this monument were destroyed during the last military operations in 2017. Nowadays, there are serious attempts to reconstruct the minaret. The objective of this study is to characterize the original bricks, one of the main building materials of the minaret, in an attempt to complete planning preparations for returning to Mosul its historic value. In this research, the ancient bricks were characterized under different laboratory tests including the determination of skeletal density, porosity, free water absorption, forced water absorption, water retention capacity, capillarity parameters and uniaxial compressive strength. It is expected that the information obtained from this study can be helpful in providing the important knowledge for selecting the suitable and compatible material for the future reconstruction and maintenance works.

Abstract: This paper deals with the problem of a flexible pipe with internal diameter of 110 mm buried in laboratory soil box facilities for this study. The box is filled with sand reinforced by geogrid layer of different widths to investigate the effect of geogrid width layer on the performance of buried pipe subjected to static load. Two type of reinforcement used (geogrid and geocell). The geogrid location is kept constant at a depth of 0.5d (do is o the pipe o diameter) below the loading plate. The results show that the reduction in crown strain in loose sand, when the geogrid width equals 1B iso13% in comparison with results of tests excluding geogrid, this percent reduces to 11% when the geogrid width equals 2B, while the reduction percent in medium sand becomes 14% and 12% when the geogrid width was B and 2B, respectively and becomes in dense sand 15 % and 11% when the width of geogrid change from B to 2B.

Abstract: Many experimental and numerical works are attempting to predict the elastic properties of Lightweight Aggregate Concrete (LWAC). The purpose of this paper is to estimate the Young’s modulus of Lightweight Aggregate Concrete utilizing two-phase composite models. However, results of experimental data published in the literature were used as a platform, upon which, two-phase composite models had been utilized. The outcomes of this comparative analysis show that neither of the two-phase analytical models could be directly utilized for predicting Young’s modulus of LWAC. The Hashin-Hansen composite model provides a good prediction of experimental Young’s modulus of all LWAC tested with a maximum error percentage equal to 16.94%. This model provides an upper bound whereas the Counto2 model provides the lower bound of experimental Young’s modulus of LWAC.