This paper presents quality control charts techniques usually applied in quality control of compressive cement strength. Nonlinear regression model useful for the prediction of compressive cement strength at 28 days was proposed. Combining the prediction and quality control tools, a PI (Proportional Integral) controller useful for the regulation of 28 days compressive cement strength around a target (39 Mpa) was constructed. Results of the one-year prediction of quarterly compressive cement strength aligned with the values of the historical data obtained from a leading Cement Company in Nigeria for the years, 2011-2015.
Assessment of Bahariya Hematite – Barite Ore as a Heavy Weight Concrete Mix For Subsea Pipeline Cladding (Published)
Heavy aggregates of iron ore were imported by petroleum companies in Egypt, for utilization as a major constituent of concrete mix used for coating of offshore petroleum pipelines as a heavy coat for pipeline stability on sea bed and mechanical protection against anchor damages. The hematite -barite heavy aggregates form the main constituents 75% of the concrete mix, with sea water cements and specific water-cement ratio desired to achieve required compressive strength, water absorption and dry density. In earlier studies, author was succeeding to found the Egyptian Ilmenite and Ferro – manganese ores adequate for concrete heavy weight coating of subsea pipelines. This study deals with another substitute of high density aggregates not utilized as economic ore for other valuable purposes, the hematite-barite ore mined and produced by Steel Manufacture Company and not used in steel manufacture due to containing barite ore and low iron content. The laboratory and field tests conducted for the hematite – barite aggregate to ensure that the physical, chemical and mechanical properties complying with coating specification and standards. The hematite – barite heavy aggregate have 3.9 – 4.2 g/cm³ specific gravity, well graded hematite-barite aggregate, chemically free from detrimental matter. Heavy concrete mix composed from hematite-barite aggregate, sea water cement and fresh water mixed together to produces a concrete mix of 180 -185 pcf (2880 -2964 Kg/m3), minimum dry density and compressive strength varying from 40-47 N/mm² (400-470 kg/cm²), which satisfied the standard specification of submarine pipeline coating.
This paper studies the influence of shredded rubber from waste tyres on concrete strength .These shredded particles from waste tyres were used to replace the 20mm size aggregate in different percentages (5%, 10% and 15% in volume). Concrete mixtures without these additives were also tested. The experimental results show a reduction of the compressive strength as the percentage of rubber particles increases. Four point bending test conducted on six samples of each specimen also unveil a reduction in the flexural strength and bending capacity of concrete as the rubber content increases. Deflection at failure of the rubberized concrete is more than that of the plain concrete which unveils the ability of the rubberized concrete to withstand larger deformations than the plain concrete.
An experimental study on the effect of inclusion of three different types of fillers on mechanical properties of concrete is carried out. This paper presents the results of laboratory tests of 72 concrete cylindrical specimens of 10 cm diameter and 20 cm length with inclusion of Vf=10% of steel fillers, cast iron fillers and stone powder fillers in the concrete mix. Permeability, Compressive strength and splitting tensile strength are investigated by comparing the density of different types of concrete. Test results demonstrated that the stone powder fillers significantly improve mechanical properties of concrete while the cast iron fillers decline.
The interaction that occurs when combining surfactants is more than the sum of the properties of each surfactants. These interactions can either enhance or detract from the action of these surfactants as air entraining agents. In an attempt to understand these interactions of some surfactants used as air entraining agents, the effect of several air-entraining agents was compared, in addition to two mixtures of them. The results show that CABP surfactants can be used lonely and in conjunction with other surfactant groups, taking into consideration that the compatibility of betaines with anionic surfactants is better than that with cationic surfactants. Higher compressive strength and less pore size appeared when using LM solo and in mixes which demonstrates the positive impact of using LM in these mixes
Masonry components of Historic building in Bagamoyo, Tanzania have suffered considerable deterioration in a variety of forms, and close examination indicates that the root cause of the deterioration of the structure is mainly due to masonry mortar joint failure because of chemical and physical degradation of the material. This paper examines the colours, physical and mechanical properties as well as chemical composition of the mortar; thus its replacement carefully matches the historic in chemical composition, strength and texture as determined by a laboratory analysis. In terms of colour, the mortars were divided into three groups of colours namely light grey, light brown and light yellowish brown. Point counting by microscopical study indicated that the hard mortar has higher binder content and composed of a homogenous hydraulic matrix and a heterogeneous coarse fraction with moderate voids while the moderate hard mortar contained modest binder and soft and friable lime mortar contained little hydraulic binder. The results of chemical composition indicated that the stones composed of high amount of Calcium Oxide (CaO) while the mortar contained low percentage of CaO indicating that the mortar is not pure hydraulic lime but hydrated lime (air-hardening lime).