Development of Green Geopolymer Binders Based on Construction and Demoliton Wastes

This research focuses on the complete recycling of construction and demolition wastes (CDWs) to develop new green geopolymeric binders. An innovative mix design method based on (SiO2/Al2O3) and (Na2O/SiO2) chemical factors and liquids/solids (L/S) ratio was developed. The main focus was to optimize the compressive strengths of mixes incorporating mono, binary and ternary geopolymer systems of concrete waste (CW), red clay brick waste (RCBW) and ceramic tile waste (CTW). The effects of high temperature curing and the addition of supplementary cementitious materials (SCMs) were also investigated. Fresh properties comprising slump flow and setting time and mechanical characteristics including compressive strengths were investigated. Microstructural study was performed utilizing scanning electron microscopy (SEM), energy-dispersive X-Ray spectroscopy (EDS) and X-Ray Diffraction (XRD). This research proved the efficiency of the new mix design method in reaching high compressive strengths of mono-system of RCBW and CTW and all binary and ternary systems of geopolymer binders.

Development of Green Geopolymer Binders Based on Construction and Demoliton Wastes

This research focuses on the complete recycling of construction and demolition wastes (CDWs) to develop new green geopolymeric binders. An innovative mix design method based on (SiO2/Al2O3) and (Na2O/SiO2) chemical factors and liquids/solids (L/S) ratio was developed. The main focus was to optimize the compressive strengths of mixes incorporating mono, binary and ternary geopolymer systems of concrete waste (CW), red clay brick waste (RCBW) and ceramic tile waste (CTW). The effects of high temperature curing and the addition of supplementary cementitious materials (SCMs) were also investigated. Fresh properties comprising slump flow and setting time and mechanical characteristics including compressive strengths were investigated. Microstructural study was performed utilizing scanning electron microscopy (SEM), energy-dispersive X-Ray spectroscopy (EDS) and X-Ray Diffraction (XRD). This research proved the efficiency of the new mix design method in reaching high compressive strengths of mono-system of RCBW and CTW and all binary and ternary systems of geopolymer binders.

Strength Development and Pore Structure Characterisation of Binary Alkali-activated Binder Based on Tungsten Mining Waste

The mineralogical properties of tungsten mining waste mud (TMWM) make its valorisation and re-usage as an alumino-silicate source material to produce an alkali-activated binder without calcination is a challenge. Moreover, the dissolution of silicate and alumina species from TMWM is very slow. Despite the crystallinity of TMWM, this study demonstrates that its combination with other sources of the alumino-silicate source was the materials–such as red clay brick waste(RCBW),ground granulated blast furnace slag (GGBFS) and electric arc furnace slag (EAFS) – improved the compressive strength and the pore structure of the alkali-activated matrix.Thecombinedprecursors (90 vt.%TMWM+10 vt.%RCBW, 90 vt.%TMWM+10 vt.%GGBFS, and 90 vt.%TMWM+10 vt.%EAFS) were activated using a combination of alkaline activator solutions (sodium silicate and sodium hydroxide) with the ratio of 1:3(66.6wt.%sodiumsilicatecombined with 33.33 wt.% of NaOH 10M). The results show that the compressive strength increased from11.23MPa at 28 days to reach 24.98MPawhentheTMWMwaspartially replacedby10vt.%RCBW. In addition,this study shows that the interconnected porosity decreased where the critical pore size was reduced from 21.28 µm to 0.55 µm for the tungsten mining waste-based alkali-activated binder and the binary alkali-activated binder based on TMWM and RCBW. Keywords: Mining Waste, Alkali-activated, Microstructure, MIP, Metakaolin

Natural radioactivity and radiological hazard of red-clay brick produced in Shangluo, China

The radiological hazard of building materials originating from clay, rock and other mineral wastes has attracted more attention because they contain natural radionuclides (226Ra, 232Th, and 40K). The activity concentration of radionuclides in red-clay brick samples obtained from three different brickyards in Shangluo, China waHs measured. Various indexes, including radium equivalent activities, Raeq, external hazard index, Hex, internal hazard index, Hin, indoor air absorbed dose rate, D, and annual effective dose, AED, of the aforementioned radionuclides in the bricks were used to assess the radiation hazard for people. The average activity concentrations of 226Ra, 232Th, and 40K were respectively 34.5 ? 1.9, 62.5 ? 2.1, and 713.7 ? 19.8 Bqkg?1 for the studied red-clay bricks. The Raeq values of the red-clay brick samples varied from 167.0 to 184.7 Bqkg?1, which are lower than the limit of 370 Bqkg?1. Moreover, the activity concentrations of natural radionuclides in unfired brick, clay and coal were also determined and the results were compared with that in the red-clay brick samples. This study shows that the red-clay bricks produced in Shangluo, China can be used safely in construction industries.

Critical studies on bond strengths of masonry units

Performance of masonry is normally attributed to compressive strength of individual units, water absorption of individual units, strength of masonry mortar and the bond between mortar and individual units. Many researches in the past have contributed towards the bond strength and relevance of compressive strength of mortar in achieving good bonds. However, the quality of bricks available in India significantly vary from region the region. Thus, a need is felt in understanding bond strength of masonry. In this paper three types of mortars(total nine combinations), two types of bricks (red clay brick and fly ash brick) are considered, tests such as compressive strength, water absorption of the bricks, compressive strength of various mortar combinations, flexure bond strength and shear bond strength are presented. Failure patterns of the masonry units are also discussed. Results of the two tests show noticeable variation in bond strengths, however the shear bond strength has significant relationship with the compressive strength of mortar. The research outcome also points towards using bricks in saturated condition for achieving adequate performance.